Atmospheric Rivers

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Wed Aug 28 2024
Valid 12Z Wed Aug 28 2024 – 12Z Fri Aug 30 2024

…Record heat for the Mid-Atlantic today but the heat will last a couple
more days for the Ohio and Tennessee Valleys into the interior Southeast…

…Active thunderstorms will bring the threats of heavy rain, flash
flooding and severe weather across the northern Plains tonight and then
the upper Midwest Thursday through early Friday…

…Strong to severe late afternoon thunderstorms possible across the
east-central U.S for today and Thursday…

…First snowflakes of the season expected for the high elevations of
northwestern Montana today while fire weather threat blankets portions of
the northern Rockies…

A cold front has brought relief to the heat across the northern Plains
while triggering clusters of strong thunderstorms across the Midwest this
morning. As the front continues to push east and southeastward, a day of
record heat is expected to impact the Mid-Atlantic states where high
temperature could reach 100 degrees around the nation’s capital. This
heatwave will be relatively short-lived for the Mid-Atlantic as a much
cooler and damp air mass associated with a Canadian high pressure system
will quickly settle southward across the Great Lakes/New England into the
Mid-Atlantic by Thursday. However, much of the Ohio and Tennessee Valleys
will feel a couple more days of high temperatures topping into the upper
90s at the hottest locations as the next low pressure system marching
across the northern Plains will cease the southward progress of the cool
air and keep the heat in place for these areas. As the cold front
approaches, the hot air will be lifted and help trigger lines of
thunderstorms which can become severe along with locally heavy downpours
and very gusty winds. The highest threat for severe weather will be later
today into this evening from Ohio eastward across the northern
Mid-Atlantic near/after the time of maximum heating in the afternoon.
Some more strong thunderstorms could form Thursday afternoon farther
southward into the Mid-Atlantic on Thursday. Very cool air will then
blanket the entire Northeast on Thursday.

Meanwhile, the strong cold front associated with the next low pressure
system is marching across the northern Rockies. Sharply colder air behind
the system will likely bring the first snowflakes of the season for the
high elevations of northwestern Montana today while fire weather threat
blankets portions of the northern Rockies. The strong frontal system will
move steadily across the northern and central Plains on Thursday where the
threat of severe weather will be highest from Wednesday night across North
Dakota, then shifting east across a large chunk of the Midwest and upper
Midwest Thursday to Thursday night.

Farther south in Texas, an upper low had moved inland from the Gulf of
Mexico since yesterday. The instability has continued to help trigger
scattered thunderstorms across southern Texas. Meanwhile, deep southerly
flow to the east of the upper low has directed tropical moisture northward
from the Gulf toward the western Gulf Coast region, where some heavy
rainfall could develop in the vicinity during the next couple of days.
Elsewhere, while monsoonal moisture has become not as active and
widespread over the southern Rockies today, more focused activities across
southwestern New Mexico could lead to heavy rainfall. By Thursday, the
trailing cold front across the Plains will likely push the rain farther
east into the southern Plains where strong to severe storms are possible
by later in the day.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Tue Aug 27 2024
Valid 12Z Tue Aug 27 2024 – 12Z Thu Aug 29 2024

…A brief spell of record heat expected to spread from the Midwest to the
East Coast…

…Active showers and severe thunderstorms this morning across the
northern Plains and upper Midwest/Great Lakes will shift eastward into the
northern Mid-Atlantic/southern New England by late Wednesday into early
Thursday…

…First snowflakes of the season could reach the higher elevations of
northwestern Montana on Wednesday followed by a chance of severe
thunderstorms across North Dakota Wednesday night/early Thursday…

The closed upper high currently centered over the mid-Mississippi Valley
will be expanding eastward over the next two days, spreading into large
portions of the East Coast from the Mid-Atlantic southward. This will
send a quick spell of potentially record high temperatures from the
Midwest into the Ohio Valley, Tennessee Valley, southern to central
Appalachians and into the Mid-Atlantic. The combination of hot
temperatures in the mid to upper 90s to near 100 degrees together with
high humidity levels will produce maximum daily heat indices of between
105 and 115 degrees across these regions, with heat risks reaching major
to extreme levels today across the Midwest into lower Great Lakes.
Excessive Heat Warnings and Heat advisories are currently in effect across
the mid to upper Mississippi Valley, the Midwest and southern New England,
affecting nearly 61 million people, with further expansion of these
warnings and advisories possible into portions of the Mid-Atlantic for
Wednesday. This spell of record heat will be relatively short-lived as a
cool high pressure system settling into southern Canada is forecast to
send a cool and damp air mass into the Great Lakes on Wednesday and will
quickly overspread New England Wednesday night, reaching into the
Mid-Atlantic by Thursday morning behind a sharp cold front.

Around the peripheries of the above mentioned upper high, precipitation is
likely to be active along the Gulf Coast and from portions of the
Southwest, northeastward into the Central Plains, upper Mississippi
Valley, upper Great Lakes into northern New England in this “ring of
fire”. In these regions, moisture values are forecast to remain above
average, supporting the potential for areas of active thunderstorms, heavy
rains and flash flooding. Active showers and severe thunderstorms this
morning across the northern Plains and upper Midwest/Great Lakes could
result in areas of heavy rains and flash flooding. Some of these
thunderstorms are expected to shift eastward into the northern New England
by early Wednesday, before some additional strong to severe thunderstorms
and heavy rain possible across portions of the upper Ohio Valley, central
Appalachians and into the Mid-Atlantic later on Wednesday into early
Thursday ahead of the sharp cold front.

While much above to record high temperatures dominate portions of the
central to eastern U.S. into mid week, another strong front will be
pushing inland into the Pacific Northwest followed by the northern Rockies
and into the northern High Plains by this evening. Much below average
temperatures in the wake of this front will likely spread across the
Pacific Northwest for today and into the northern Rockies/northern High
Plains on Wednesday with high temperatures 10 to 20 degrees below average.
There is not expected to be a lot of precipitation with this front over
the Northwest, but the falling temperatures could bring the first
snowflakes of the season for the higher elevations of northwestern Montana
on Wednesday. By Wednesday night into early Thursday, a chance of severe
thunderstorms will be moving eastward across North Dakota ahead of the
strong cold front.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Aug 26 2024
Valid 12Z Mon Aug 26 2024 – 12Z Wed Aug 28 2024

...A couple of days of intense heat and humidity expected to impact the
Midwest…

…Severe storms and isolated flash flooding possible across the Northern
Plains/Upper Midwest today and the Great Lakes on Tuesday…

…Daily monsoonal thunderstorms shifting eastward into the southern
Rockies/High Plains…

A couple of days of intense heat and humidity are expected to impact the
Midwest as deep southerly flow behind an intensifying upper-level high
unleashes the heat from the southern Plains. Forecast highs in the
mid-90s to near 100 combined with high humidity will send heat indices
into the 105-115 degree range, with widespread heat-related advisories and
warnings in place. Morning lows will also remain very warm, in the mid-
to upper 70s, providing little relief from the heat overnight. Numerous
record-tying/breaking highs will be possible both over the Midwest as well
as into portions of the Southeast on Tuesday. Those without efficient
air-conditioning or who must spend time or effort outdoors will be at a
heightened risk of heat-related illness. Remember to drink plenty of
water and seek out relief from the heat. An approaching cold front and
increased storm coverage will help to bring relief to portions of the
upper Midwest on Tuesday. While the southern Plains will see some relief
from the record heat that has plagued the region, conditions will still be
hot with highs generally in the mid to upper 90s.

Meanwhile, as upper-level shortwaves eject out of the northern Rockies and
interact with a low pressure wave tracking along a couple of fronts across
the northern Plains, multiple rounds of showers and thunderstorms are
expected to impact portions of the northern Plains into the upper Midwest.
The hot temperatures and plentiful moisture ahead of the front will
contribute to strong to extreme instability leading to the potential for
rapid development of severe thunderstorms. The Storm Prediction Center is
forecasting an enhanced risk of severe weather from eastern South Dakota
through southern Minnesota into central Wisconsin today into tonight as
the center of the low pressure wave tracks just to the south. Very large
hail, widespread and potentially significant damaging winds with any
organized lines of storms, and a few tornadoes will all be possible. A
broader Slight Risk covers portions of the Upper Midwest and
northern/central Plains for some more isolated instances of large hail and
damaging winds. The upper-level shortwaves will help to erode the
upper-high over the Great Lakes on Tuesday mainly across the Great Lakes.
In addition to severe weather, the plentiful moisture and high instability
will support areas of intense downpours which could organize into more
widespread heavy rain coverage at times, leading to the risk of some
isolated flash flooding each day.

Monsoonal thunderstorm chances today are shifting a bit eastward into the
southern Rockies and High Plains, with similar activities returning later
on Tuesday. Some locally heavy downpours remain possible along with the
threat of isolated flash flooding especially across terrain-sensitive
areas along steeper hills/mountain ranges and over burn scars. Some
post-frontal showers and storms are expected into the northern Rockies
through this evening as well. Temperatures over portions of the West will
remain well below average following a frontal passage and under the
influence of an unseasonably strong upper-trough. Forecast highs in the
70s will be common over the northern/central Rockies and eastern Great
Basin. More seasonably warm temperatures will return by Tuesday with highs
back up into the 80s. However, a cold front moving into the Pacific
Northwest will drop highs into the 60s and 70s along with the arrival of
showers and embedded thunderstorms on Tuesday mainly over western
Washington.

Elsewhere, instability associated with an upper-level trough dipping into
New England will bring shower and storm chances through this evening with
some moderate to possibly locally heavy rainfall. Some severe storms will
also be possible, with a Slight Risk over southern New England for the
potential of some large hail and damaging winds. Plenty of clouds will
help to keep temperatures cool here compared to elsewhere in the eastern
U.S., with highs in the 70s and low 80s. Daily showers and storms are also
expected over Florida and along the Gulf Coast into south Texas with a
lingering frontal boundary in the region as an upper-level low tracks
westward into southern Texas.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sun Aug 25 2024
Valid 12Z Sun Aug 25 2024 – 12Z Tue Aug 27 2024

…Record heat relents over the Southern Plains as the heat shifts
northward into the central/northern Plains and Midwest…

…Severe storms and isolated flash flooding possible for the Northern
Plains/Upper Midwest Sunday-Monday…

…Daily monsoonal thunderstorms continue across the Four Corners region,
shifting eastward into the southern Rockies/High Plains...

As the cool upper trough pushes farther inland across the western U.S.,
the heatwave over portions of the Southern Plains will gradually relent
during the next couple of days. Meanwhile, deep southerly flow ahead of
the upper trough will direct the heat farther north into the central and
northern Plains today before spreading into the Midwest on Monday, then
reaching into the Great Lakes on Tuesday. The area of major HeatRisk
today will expand well to the north across much of the central and
northern Plains into the upper Midwest. By Monday into Tuesday, extreme
HeatRisk is forecast to overspread the Midwest and toward lower Michigan
where maximum heat indices are forecast to reach well into the 90s to the
mid-100s in the afternoon, prompting widespread heat-related advisories
and warnings. Extra caution should be observed by those without effective
air conditioning and anyone who must be outdoors should remain adequately
hydrated.

A cold front marking the leading edge of a large dome of cool air over the
western U.S. will reach into the Northern Plains on Monday, bringing
relief to the heat into the region. However, the cold front will also
bring a period of inclement weather across the northern Plains on Monday,
followed by the possibility of severe thunderstorms by Monday night into
Tuesday toward the upper Midwest. This is in response to strong
upper-level dynamics ahead of the upper trough interacting with a low
pressure system that is forecast to form along the cold front over the
northern Plains. The Storm Prediction Center highlighted an area of
enhanced risk for severe weather across the northern Plains toward the
upper Midwest from Monday into early Tuesday, with a chance for
potentially larger hail and significant damaging winds. Some locally
heavy rainfall and isolated flash flooding will also be possible. By
early Tuesday, the severe weather threat is forecast to shift east into
the Great Lakes with areas of heavy rain farther north from the upper
Midwest to the upper Great Lakes as the low pressure system passes to the
south.

Across the Southwest, daily monsoonal thunderstorm chances will continue,
initially focusing over the Four Corners region today before shifting east
to mainly across the southern Rockies for Monday and Tuesday. Deep
moisture and moderate instability will lead to some more intense
thunderstorms with locally heavy downpours along with some isolated flash
flooding especially for terrain sensitive areas such as burn scars.
Besides the rainfall, the big story across the West the next few days will
be the much below average temperatures expected behind a strong cold
front. Widespread high temperatures in the 60s and 70s will be common
across the Pacific Northwest, northern Rockies, Great Basin, and northern
California, with near record low maximum values for some locations. Lows
are dipping into the 40s and even 30s this morning for much of the
interior Pacific Northwest and Great Basin where Frost Advisories are in
effect in portions of Nevada. Some post-frontal showers and storms over
portions of the Great Basin will expand across the northern Rockies into
the northern High Plains tonight into Monday, and then across the northern
Plains later on Monday into early Tuesday. Elsewhere, some showers and
storms with moderate to locally heavy rainfall will be possible Monday
into Tuesday over New England when a back-door upper-level wave passes
over the region. Daily showers and thunderstorms will also be possible for
Florida and along the Gulf Coast with a lingering frontal boundary in the
region. Over the Pacific Northwest, showers associated with the next
system from the Pacific are forecast to arrive Monday night into early
Tuesday.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sat Aug 24 2024
Valid 12Z Sat Aug 24 2024 – 12Z Mon Aug 26 2024

…Monsoonal thunderstorms across the Four Corners this weekend will edge
east toward southern Rockies by early next week producing locally
excessive rainfall…

…Record heat relents over the Southern Plains as record cool
temperatures envelop California to the Great Basin…

…Critical Fire Risk and Red Flag Warnings in effect across much of the
Great Basin…

An anomalously amplified weather pattern across North America will
continue to bring sharply contrasting weather conditions across the U.S.
for the next couple of days. This weather pattern will feature a warm
upper high over the southern Plains sandwiched in between two deep and
cold upper lows/troughs on either side of the West and East Coasts. An
unstable channel of moist southwesterly flow between the ridge and the
upper low near the Pacific Northwest will continue to support monsoonal
showers and embedded thunderstorms across the Four Corners region today,
shifting only slightly east toward the southern Rockies by Monday when the
flash flooding threat dwindles further as the upper high begins to give
way to the upper low moving inland across the western U.S. Farther north
across the northern High Plains, a couple of new low pressure systems are
forecast to form one after another and move toward southern Canada through
the next couple of days, bringing gusty winds but only modest amounts of
rainfall. Some of the thunderstorms could become severe near the Canadian
border of Montana early this morning ahead of the first low pressure
system. Meanwhile, critical fire weather danger is forecast for the Great
Basin under blustery and dry conditions behind a cold front.

The large upper low dipping into the Pacific Northwest will continue to
provide very cool and damp conditions into the West Coast today. In fact,
record cool high temperatures can be found once again today across
California and into the Great Basin. The anomalous cool conditions will
penetrate farther inland and overspread much of the western U.S. by
Sunday. In contrast, the heatwave across the southern Plains is showing
signs of relenting as the cool air from the western U.S. begins to erode
the upper ridge. Nevertheless, another afternoon with triple digit high
temperatures are forecast for today over a large portions of Texas into
the central Plains behind a warm front and associated low pressure center.
With relatively little moisture to work with, the low pressure system
will produce generally light amounts of rain. However, some heavy
rainfall can be expected to associate with localized clusters of strong
thunderstorms across the Midwest this weekend.

Meanwhile, cool mornings, increasingly warm afternoons and abundant
sunshine will prevail across much of the eastern U.S. under a cool upper
trough together with a cool high pressure system at the surface. A gradual
warming trend will continue across the eastern half of the country through
the next couple of days as the high pressure system begins to slide off
the East Coast. Afternoon high temperatures will recover to the lower 90s
by Sunday afternoon for some urban locations along the East Coast.
Meanwhile, high temperatures well into the 90s will be common across the
northern and central Plains ahead of a warm front lifting across the
mid-section of the country and ahead of a cold front in advance of the
cool air over the western U.S.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Fri Aug 23 2024
Valid 12Z Fri Aug 23 2024 – 12Z Sun Aug 25 2024

…Monsoonal thunderstorms could lead to excessive rainfall for much of
the Four Corners region today and into the weekend…

…Record heat begins to relent over the Southern Plains this weekend but
near record cool in the eastern U.S. and California…

…Critical Fire Risk and Red Flag Warnings in effect across much of the
Great Basin…

An anomalously amplified weather pattern across North America will
continue to bring sharply contrasting weather conditions across the U.S.
as we head into the weekend. This weather pattern will feature a warm
upper high over the southern Plains sandwiched in between two deep and
cold upper lows/troughs on either side of the West and East Coasts. A
deep and unstable southwesterly flow between the ridge and the upper low
near the Pacific Northwest will support monsoonal showers and
thunderstorms across the Four Corners region through the next few days,
especially early this morning when severe thunderstorms are advancing
farther downstream into the central Plains. Slot canyons and burn scars
are particularly vulnerable to flash flooding. The flash flooding threat
dwindles a bit heading into the weekend as the upper-ridge shifts slightly
eastward and the main energy associated with the upper low will be
directed farther north toward the northern High Plains where a new low
pressure system is forecast to form by Saturday night. Meanwhile,
critical fire weather danger is forecast for the Great Basin under gusty
and dry conditions behind a cold front.

The large upper low dipping into the Pacific Northwest will continue to
provide very cool and damp conditions into the West Coast today. In fact,
record cool high temperatures can be found today across California. The
anomalous cool conditions will penetrate farther inland during the
weekend, overspreading much of the western U.S. by Sunday morning. In
contrast, another afternoon of record high temperatures are forecast for
portions of Texas into Oklahoma under the warm upper high where 110s are
possible in portions of Texas Panhandle into nearby Oklahoma. This
heatwave is showing signs of relenting by this weekend as the cool air
from the western U.S. upper trough begins to erode the upper ridge.
However, heat indices are forecast to reach into the upper 90s to the mid
100s during the weekend while the heat begins to spread northward into the
central Plains.

Meanwhile, very cool and pleasant weather for August will continue to
prevail across much of the eastern U.S. under the cool upper trough
together with a cool high pressure system at the surface. In fact, record
cool temperatures are possible this morning across portions of the
Mid-Atlantic, central Appalachians, and interior Southeast with
temperatures dipping as cold as the 40s. A gradual warming trend is
expected through the weekend for the eastern half of the country as the
high pressure system begins to slide off the East Coast.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Thu Aug 22 2024
Valid 12Z Thu Aug 22 2024 – 12Z Sat Aug 24 2024

…Record heat continues into the end of the week across the Southern
Plains…

…There is a Slight Risk of excessive rainfall over parts of the
Southwest, Great Basin, and Central/Southern Rockies on Thursday…

…Record cold develops across California Friday into Saturday…

…There are Excessive Heat Warnings and Heat Advisories over parts of the
Southern Plains…

A front over the Pacific Northwest Coast will move slowly eastward to the
Northern High Plains to the Great Basin and then into Southeastern
California by Saturday. The boundary will be on the leading edge of an
upper-level trough, bringing colder temperatures in the mid-70s to
California. The associated upper-level low will develop rain over parts of
the Pacific Northwest and Northern California through Saturday.

Furthermore, monsoonal moisture and upper-level energy will aid in
producing showers and thunderstorms with heavy rain over parts of
southeastern Utah, northern Arizona, southwestern Colorado, and
northwestern New Mexico. Therefore, the WPC has issued a Slight Risk
(level 2/4) of excessive rainfall over parts of the Southwest, Great
Basin, and Central/Southern Rockies through Friday morning. The
associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, small streams, low-lying areas, narrow
canyons/gullies, and burn scars the most vulnerable.

The threat of excessive rainfall will decrease slightly over the Four
Corners Region on Friday. However, there will still be a threat of heavy
rain. Therefore, the WPC has issued a Marginal Risk (level 1/4) of
excessive rainfall over parts of the Southwest, Great Basin, and
Central/Southern Rockies from Friday into Saturday morning. The
associated heavy rain will create localized areas of flash flooding,
affecting low-lying areas, narrow canyons/gullies, and burn scars that
experience rapid runoff with heavy rain.

Additionally, a second front extending from the Northern Plains to the
Great Basin will move northward as a warm front over the Northern Tier
States by Saturday. On Thursday, the boundary will produce showers and
thunderstorms over parts of the Northern/Central Plains into parts of the
Upper Mississippi Valley. The showers and thunderstorms will expand into
parts of the Upper Great Lakes and Middle Mississippi Valley on Friday.

Moreover, another upper-level low over the Northeast will help create rain
with an embedded thunderstorm over parts of the Northeast through late
Thursday night. Further, an area of upper-level energy moving into the
Southeast will develop a weak upper-level low by Thursday evening. With
ample moisture over the area and a lingering boundary, showers and
thunderstorms will develop over parts of the Southeast through Saturday.

Additionally, upper-level energy trapped under an upper-level high and
moisture moving northward off the Gulf of Mexico will create scattered
showers and thunderstorms over parts of the Southern Plains through
Saturday.

Meanwhile, the upper-level high over the Southern Plains will allow high
temperatures to be in the upper 90s and low 100s, with dew points in the
upper 60s and low 70s, prompting Excessive Heat Warnings and Advisories
over parts of the Southern Plains. Additionally, with low temperatures in
the lower 80s and upper 70s, little relief from the heat will occur
overnight. Therefore, people spending more time or effort outdoors or in a
building without cooling in areas with heat warnings are still at an
increased risk of heat-related illness.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Wed Aug 21 2024
Valid 12Z Wed Aug 21 2024 – 12Z Fri Aug 23 2024

…There is a Slight Risk of excessive rainfall over parts of the
Southwest and Great Basin on Wednesday and expanding into parts of the
Central/Southern Rockies on Thursday…

…There is a Slight Risk of severe thunderstorms over parts of the
Northern High Plains on Wednesday…

…There are Excessive Heat Warnings and Heat Advisories over parts of the
Southern Plains…

A front over the Northern Rockies will move slowly eastward to the
Northern Plains by Friday. The boundary will produce showers and severe
thunderstorms over northeastern Montana and northwestern North Dakota.
Therefore, the SPC has issued a Slight Risk (level 2/5) of severe
thunderstorms over parts of the Northern High Plains through Thursday
morning. The hazards associated with these thunderstorms are frequent
lightning, severe thunderstorm wind gusts, hail, and a minimal threat of
tornadoes. However, there is an increased threat of severe thunderstorm
wind gusts 65 knots or greater.

In addition, an upper-level low over the Northeast will help create rain
with an embedded thunderstorm over parts of the Northeast through
Thursday. Moreover, upper-level energy over the Middle Mississippi Valley
will move southeastward to the Southeast, developing a weak upper-level
low by Thursday evening. With ample moisture over the area, showers and
thunderstorms will develop over parts of the Southeast through Friday.

Furthermore, monsoonal moisture and upper-level energy will aid in
producing showers and thunderstorms with heavy rain over parts of Arizona
and southern Utah. Therefore, the WPC has issued a Slight Risk (level
2/4) of excessive rainfall over parts of the Southwest and Great Basin
through Thursday morning. The associated heavy rain will create mainly
localized areas of flash flooding, with urban areas, roads, small streams,
low-lying areas, narrow canyons/gullies, and burn scars the most
vulnerable.

On Thursday, the monsoonal moisture will extend farther northward over the
area. Likewise, the upper-level energy and monsoonal moisture will produce
showers and thunderstorms with heavy rain over parts of southeastern Utah,
northern Arizona, southwestern Colorado, and northwestern New Mexico.
Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive
rainfall over parts of the Southwest, Great Basin, and Central/Southern
Rockies from Thursday through Friday morning. The associated heavy rain
will create mainly localized areas of flash flooding, with urban areas,
roads, small streams, low-lying areas, narrow canyons/gullies, and burn
scars the most vulnerable.

Moreover, as the front over the Northern High Plains moves eastward on
Thursday, showers and strong to severe thunderstorms will develop over
parts of the Northern/Central Plains and the Central High Plains.
Therefore, the SPC has issued a Marginal Risk (level 1/5) of severe
thunderstorms over parts of the Northern/Central Plains and the Central
High Plains from Thursday into Friday morning. The hazards associated with
these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a minimal threat of tornadoes.

Elsewhere, as upper-level low moves southward along the Northwest Coast
will develop rain over parts of the Pacific Northwest through Friday.

Meanwhile, an upper-level high over the Southern Plains will allow high
temperatures to be in the upper 90s and low 100s, with dew points in the
upper 60s and low 70s, prompting Excessive Heat Warnings and Advisories
over parts of the Southern Plains. Additionally, with low temperatures in
the lower 80s and upper 70s, little relief from the heat will occur
overnight. Therefore, people spending more time or effort outdoors or in a
building without cooling in areas with heat warnings are still at an
increased risk of heat-related illness.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Tue Aug 20 2024
Valid 12Z Tue Aug 20 2024 – 12Z Thu Aug 22 2024

…Severe thunderstorms possible across the central to northern High
Plains through Wednesday with flash flood potential continuing over the
Southwest…

…Record breaking heat continues across Texas…

After several days of active and unsettled weather, the cold front across
the eastern U.S. has finally largely cleared the coast, aside from coastal
Maine where a few lingering showers will remain possible through this
morning. Otherwise, sprawling high pressure will encompass much of the
Great Lakes region through the East, bringing much drier conditions and
generally below normal temperatures for the next couple of days. High
temperature departures of 10 to nearly 20 degrees for mid-August are
expected for Great Lakes and Northeast. Plan on highs only in the 60s and
70s for many areas from the Midwest to northern Mid-Atlantic and
Northeast. This high pressure is expected to dominate the weather story
for the region through at least mid-week, from the Mississippi River to
the Appalachians.

A nearly stationary front will settle to its south across the Gulf Coast
region and then extending northward across the High Plains, along the
western periphery of the high pressure axis. This boundary, along with
interactions with another passing weather system passing through the
Northern Rockies, will bring threats for severe thunderstorms to much of
the central and northern High Plains through Wednesday. The Storm
Prediction Center is advertising a Slight Risk (Level 2 of 5) for severe
weather including damaging winds and large hail.

Meanwhile, deep monsoonal moisture persistent over the Southwest U.S. will
bring a daily threat of localized and isolated flash flooding. Slow moving
but intense rainfall producing thunderstorms are possible across portions
of Arizona, Utah, Colorado, and New Mexico. For today, the threat appears
to be fairly localized, a greater threat will exist for Wednesday across
northern Arizona where a Slight Risk (Level 2 of 4) of excessive rainfall
and flash flooding exists.

Finally, underneath a strong upper level ridge, record breaking heat will
continue for at least a couple more days across portions of Texas and
southern Oklahoma. Excessive Heat Warnings and Heat Advisories remain in
effect and many daily record high temperatures will be possible as
temperatures soar into the 90s and triple digits. Combined with the
oppressive humidity, daily maximum heat indices up to 110F will be
possible. This will create a dangerous situation for some groups,
particularly anyone spending large amounts of time outdoors. They will be
at a heightened risk of heat-related illness. Some of the heat is expected
to spread into eastern New Mexico by the middle/end of the week.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Mon Aug 19 2024
Valid 12Z Mon Aug 19 2024 – 12Z Wed Aug 21 2024

…There is a Slight Risk of excessive rainfall over parts of New England
on Monday…

…There is a Slight Risk of severe thunderstorms over parts of the
Central High Plains on Monday…

…There are Excessive Heat Warnings over parts of the Southern Plains and
Heat Advisories over parts of the Southern Plains and Lower Mississippi
Valley…

A front extending from the Northeast Coast across the
Mid-Atlantic/Southeast Coast and then across the Gulf Coast State will
move off most of the Eastern Seaboard while lingering over the Southeast
by Wednesday. The boundary will produce showers and thunderstorms with
heavy rain over parts of New England as a plume of moisture feds into the
area. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive
rainfall over parts of New England through Tuesday morning. The
associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, small streams, and low-lying areas the
most vulnerable.

Moreover, showers and thunderstorms will develop along the front from the
Mid-Atlantic to the Southeast and the Gulf Coast State. Showers and
thunderstorms will also develop over parts of the Central Appalachians and
Ohio Valley on Monday.

In addition, on Monday, upper-level energy over the Central Rockies will
interact with ample amounts of moisture to produce showers and severe
thunderstorms over parts of eastern Colorado. Therefore, the SPC has
issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the
Central High Plains through Tuesday morning. The hazards associated with
these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a minimal threat of tornadoes.

Furthermore, monsoonal moisture and daytime heating will create showers
and thunderstorms over parts of the Southwest, Eastern Great Basin, and
Northern/Central Rockies from late afternoon into late evening on Monday.
On Tuesday, the showers and thunderstorms will be over a much smaller area
over the Southwest and adjacent regions. Additionally, disorganized
upper-level energy will aid in triggering showers and thunderstorms over
parts of the Northern/Central Plains. Further, on Tuesday, an upper-level
low will move over parts of the Northeast, creating rain over parts of the
area. Additionally, showers and thunderstorms will also develop over parts
of Florida.

As the quasi-stationary front moves southward over the Southern Plains and
Lower Mississippi Valley, the areas under Excessive Heat Warnings and Heat
Advisories have reduced to parts of the Southern Plains and Lower
Mississippi Valley. Moreover, people spending more time or effort outdoors
or in a building without cooling in the areas of heat warnings are still
at an increased risk of heat-related illness.