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.