Posts by Sig Silber

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Mon Jul 01 2024
Valid 12Z Mon Jul 01 2024 – 12Z Wed Jul 03 2024

…Dangerously hot conditions will continue across the southern Plains and
lower Mississippi Valley, while simmering heat builds throughout
California’s Central Valley starting Tuesday…

…Heavy rain and flash flooding likely across parts of the Southeast
coastline today…

…Severe thunderstorm and heavy rain threat situated over northern Plains
and Midwest early this week…

July kicks off with anomalous and potentially dangerous heat impacting the
south-central U.S. and portions of the West Coast. As of this morning,
over 50 million residents are under heat-related watches, warnings, and
advisories. The upper-level pattern throughout the next few days
responsible for the summer heat consists of ridging just off the West
Coast and over the lower Mississippi Valley, while an upper trough
situates over the northern Rockies and northern Plains. For the central
U.S., high temperatures are forecast to soar into the upper 90s and low
100s across the southern Plains through midweek. When combined with
elevated humidity levels, heat indices are forecast to rise into the 110s
across the lower Mississippi Valley and Gulf Coast. Excessive Heat
Warnings and Heat Advisories currently span from Kansas to the Gulf Coast
States. After enjoying a refreshing start to the workweek, the Midwest and
East Coast can expect a gradual return to muggy summer warmth by Wednesday
as surface high pressure reorients itself off the East Coast and ushers in
southerly flow. Extreme heat building throughout the West Coast and more
specifically interior California this week will also be particularly
dangerous for those without effective cooling. High temperatures away from
the immediate coastline are forecast to reach into the 100-110F range,
which could break numerous daily records in the San Joaquin and Sacramento
valleys on Tuesday and Wednesday. Excessive Heat Warnings, Watches, and
Heat Advisories go into effect as early as Tuesday and span from southern
Oregon to the low desert of southeast California. The duration of this
heat wave is concerning as the current forecast keeps scorching conditions
in place through at least the end of the week. This level of heat could
pose a danger to the entire population if proper heat safety is not
followed. This includes staying hydrated, out of direct sunlight, and in
properly air-conditioned buildings. Additionally, it is very important to
check on vulnerable friends, family, and neighbors to confirm their safety.

A cold front sliding down the East Coast today is forecast to slow its
southerly motion as it intersects the Southeast coastline, with developing
thunderstorms along the boundary. Some storms are expected to contain
intense rainfall rates and slow propagation, which creates the threat for
flash flooding. Parts of the South Carolina coastline, including the city
of Charleston, has been highlighted as having a Moderate Risk (level 3/4)
of Excessive Rainfall today. Areas most at risk for flooding are locations
with poor drainage, where heavy rainfall coincides with the afternoon high
tide, and in urbanized communities. Be sure to remain weather aware and
always remember to never drive through flooded roads.

Additionally, a storm system exiting the northern Rockies this morning is
anticipated to create some pre-Independence Day fireworks across the
northern Plains and Midwest through midweek as the threat of heavy rain
and severe weather slides eastward with time. Severe thunderstorm chances
are centered over Nebraska South Dakota today, with neighboring states
included in the potential for potent thunderstorms capable of containing
damaging wind gusts and sporadic hail. Of potentially greater concern
throughout the upper Mississippi Valley is the prospect for more heavy
rainfall over saturated soils and swollen rivers. As approaching frontal
boundaries provide a focus for several clusters of thunderstorms, areas of
intense rainfall rates are possible throughout the northern Plains and
upper Midwest today before sliding gradually eastward on Tuesday, but
still remaining centered over the Midwest. Probabilities for at least 1
inch of rain are high (70-90%) for much of Iowa, eastern Nebraska,
southern Minnesota, central/southern Wisconsin, and far northwest Illinois
through Tuesday. This next round of heavy rain could create instances of
flash flooding as well as exacerbate ongoing river flooding across areas
still recovering from last weeks heavy rainfall.

Continued sufficient moisture content over the Southwest and southern
Rockies will also aid in daily showers and thunderstorms capable of
producing localized instances of flash flooding. Regions most likely to be
affected by scattered downpours include Arizona, New Mexico, and
southwestern Colorado, with burn scars and sensitive terrain the most at
risk for flash flooding.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sun Jun 30 2024
Valid 12Z Sun Jun 30 2024 – 12Z Tue Jul 02 2024

…Dangerously hot conditions will continue for the Southeast through the
end of the weekend, while simmering heat builds across the southern Plains
and California’s Central Valley early this week…

…Severe thunderstorm and heavy rain threat for the East Coast today…

…Showers and thunderstorms for the Four Corners/Southwest over the next
few days; wet weather returns to the upper Midwest by Monday…

The transition to July will continue to feature areas of potentially
dangerous heat throughout parts of the southern U.S. and California. At
the upper levels, higher pressure over the southern Plains and lower
Mississippi Valley will focus much of the heat over the south-central U.S.
over the next few days before ridging begins to build toward the West
Coast by Tuesday. This equates to high temperatures in the mid-to-upper
90s today from the Mid-Atlantic to the southern Plains. This level of heat
and the potential for maximum temperatures into the low 100s are expected
to remain throughout the south-central U.S. through at least Tuesday,
while much of the Southeast and Mid-Atlantic cools off behind a cold
front. Overnight temperatures are expected to be quite warm over the
southern Plains and not offer much time for relief after scorching daytime
temperatures. In fact, several daily warm minimum temperature records
could be broken/tied over the next few days in this region. Excessive Heat
Warnings and Heat Advisories currently stretch from Texas to New Jersey.
For California, a dangerous and long-duration heat event is forecast to
begin on Tuesday as high temperatures soar into the triple digits, which
has prompted Excessive Heat Warnings and Watches to be posted. These
readings will impact interior valley locations and areas away from the
immediate coastline. Residents and visitors are urged to follow proper
heat safety as this level of heat could be deadly for anyone without
effective cooling.

Thunderstorms and instances of heavy rain are forecast to impact parts of
the East Coast, Midwest, and Four Corners/Southwest over the next few
days. A potent cold front ushering in a comfortable airmass to the Great
Lakes and Midwest today will continue to trek towards the East Coast while
sparking numerous showers and thunderstorms. A few storms could turn
severe between Maine and the Carolinas, with damaging wind gusts the
primary weather hazard. Heavy rain could also lead to isolated flash
floods between New England and the Southeast. This same frontal boundary
is anticipated to focus additional thunderstorm chances on Monday across
the Southeast. The flash flood threat is expected to be highest across
coastal South Carolina and southeast Georgia, where slow-moving storms
could produce a few inches of rainfall in a very short period of time.

The other notable weather system impacting the Lower 48 at the midway
point of the year is forecast to push from the Intermountain West to the
upper Midwest by early this week. Lingering rainfall chances and the
potential for flash flooding is expected to continue as the upper trough
traversing the western U.S. maintains a fresh flow of moisture-rich air
into the Southwest and southern Rockies. Flash Flood Watches remain in
effect across parts of New Mexico, Colorado, and Utah. On the dry side of
the system, gusty winds and low relative humidity are anticipated to
create Critical Fire Weather across parts of the central Great Basin
today. Meanwhile, areas of robust thunderstorms could turn severe by this
evening throughout the northern High Plains as an area of low pressure
develops. This low pressure system is then forecast to spread unsettled
weather into the northern Plains and Upper Midwest on Monday. Scattered
severe thunderstorms are possible, with an elevated threat for tornadoes,
damaging wind gusts, and large hail over parts of central Nebraska. For
the upper Midwest, any heavy rain will be unwelcome as ongoing river
flooding impacts the region. Any additional rainfall could exacerbate
flooding concerns, with the potential for numerous thunderstorms creating
an increasing flash flood risk for this part of the country. As the system
continues to progress eastward on Tuesday and an attached cold front slows
its forward progress over the Midwest and central Plains, additional
chances for severe weather and heavy rain are expected to continue.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sat Jun 29 2024
Valid 12Z Sat Jun 29 2024 – 12Z Mon Jul 01 2024

…Severe thunderstorm and heavy rain threat enters the lower Great Lakes
and northern Mid-Atlantic today before sliding to the East Coast on
Sunday…

…Unsettled weather remains throughout parts of the southern Rockies and
Southwest over the next few days, while wet weather returns to the upper
Midwest by Monday…

…Dangerously hot conditions will continue from parts of the southern
Plains to the Southeast this weekend…

A surface low pressure system currently crossing the upper Great Lakes and
anticipated to swing through southeast Canada this weekend will help push
a cold front into the lower Great Lakes by tonight. This cold front is
expected to spark scattered strong to severe thunderstorms from the Ohio
Valley to the lower Great Lakes and northern Mid-Atlantic, with damaging
wind gusts and a few tornadoes the most likely weather hazards,
particularly from eastern Ohio to central Pennsylvania. Heavy rain may
also lead to instances of flash flooding throughout this region and into
the interior Northeast. As the cold front nears the East Coast on Sunday,
another round of robust thunderstorms are possible between the Southeast
and New England, with some storms containing frequent lightning and gusty
winds. This same frontal boundary will also be responsible for isolated to
widely scattered thunderstorms extending westward across the
mid-Mississippi Valley, central/southern Plains, and southern Rockies this
weekend. The slow-moving nature of thunderstorms over the sensitive
terrain of the southern Rockies and Southwest will create additional daily
chances for flash flooding through at least early next week. More
specifically, parts of northern New Mexico, southern Colorado, and
southeast Arizona are most likely to be dealing with thunderstorms
producing intense rainfall rates this weekend.

The next upper-level trough to traverse the Intermountain West is forecast
to spark thunderstorms across the northern High Plains on Sunday prior to
spreading rainfall chances into the upper Midwest on Monday. Heavy rain is
not welcome for much of the upper Mississippi and middle Missouri valleys
as ongoing river flooding continues. However, the threat for another round
of organized thunderstorms capable of containing intense rainfall rates
and severe weather has prompted a Slight Risk (level 2/4) of Excessive
Rainfall to be issued for much of the region on Monday.

Dangerously high heat and humidity is forecast to continue across the
south-central and southeastern U.S. through the start of July. High
temperatures into the mid-to-upper 90s and low 100s can be expected, with
heat index values up to 110 degrees throughout the lower Mississippi
Valley and parts of the southern Plains. Overnight temperatures will not
offer much relief and only dip into the low 80s and upper 70s. In fact,
the warm overnight temperatures are forecast to break dozens of daily
records and potentially a few June monthly records from the southern
Plains to Mid-Atlantic. Much cooler weather and below average temperatures
are forecast to follow high pressure as it builds southward from the
northern Plains today to the Midwest and Great Lakes on Sunday.
Comfortable high temperatures in the 70s with mostly sunny skies can be
anticipated across these locations.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Valid 00Z Fri Jun 28 2024 – 00Z Sun Jun 30 2024

…Severe thunderstorms and flash flooding expected across portions of the
northern/central Plains today and into the Midwest Friday…

…Dangerously hot conditions will continue for parts of the South and
Southeast…

…Monsoon-like conditions persist today in the Four Corners region…

A strong upper level trough is swinging across the Pacific Northwest today
and pushing a surface frontal system southeast across the Intermountain
West into the northern and central Plains. Conditions will be supportive
of severe thunderstorm development this afternoon and evening across the
Plains, and the Storm Prediction Center has highlighted portions of the
northern and central Plains with an Enhanced Risk (level 3/5) of severe
thunderstorms today. Potential severe storm hazards will include very
large hail, significant damaging winds, and a few tornadoes. Locally heavy
downpours may lead to scattered instances of flash flooding across
portions of the Plains, especially where soils are saturated from recent
heavy rains. The WPC Excessive Rainfall Outlook includes two Slight Risk
areas (level 2/4) in the northern and central Plains where flash flooding
will be most likely.

The Excessive Rainfall Outlook for today also highlights a Slight Risk
area (level 2/4) over the Four Corners region where persistent
monsoon-like rains are ongoing. Precipitation chances will decrease on
Friday for the Four Corners region as the frontal system approaches from
the north, but the front is forecast to stall and lift back northwards as
a warm front over the weekend. This will allow moisture to stream into the
Southwest ahead of the front, continuing rain chances in portions of
Arizona and New Mexico through the weekend.

The frontal system will push across much of the Central U.S. and lift a
warm front north across the Lower Mississippi Valley on Friday.
Precipitation chances will spread east as the system progresses, expanding
the severe thunderstorm and flash flooding threats into portions of the
Midwest. The Storm Prediction Center has a Slight Risk (level 2/5) of
severe thunderstorms from the central Plains towards the Middle/Upper
Mississippi Valley on Friday, and WPC has a Slight Risk (level 2/4) of
Excessive Rainfall for this area as well. Potential storm hazards will be
large hail, damaging winds, a couple tornadoes, and locally heavy rain.

This weekend, the broad frontal system will push into the eastern U.S.
while the back end lifts north across the Intermountain West.
Precipitation chances will extend from the Northeast down across the
Mid-Mississippi Valley to the central/southern Plains and Southwest. The
potential for severe weather will decrease as the upper level energy
becomes less organized, and the Storm Prediction Center has only a small
Slight Risk (level 2/5) of severe thunderstorms for much of Ohio and
western Pennsylvania. The risk for flash flooding will decrease as well,
and only isolated instances of flash flooding are anticipated along the
frontal system.

Temperature-wise, dangerously hot conditions will persist across parts of
the South and Southeast through the weekend. High temperatures near 100
degrees will be common across the southern Plains and Texas, and high
temperatures will likely reach above 90 degrees each day in much of the
Southeast. High humidity will make these temperatures feel even hotter,
and heat indices may reach as high as 105-110 degrees. Daily summertime
convection will bring some relief to the Southeast, but mainly dry
conditions are forecast across Texas through the weekend. Overnight lows
will also remain above average in the 70s and 80s, providing little relief
from the heat.

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

…Flash flooding and severe weather threat across portions of the
northern/central Plains Thursday expands into the Midwest Friday…

…Dangerously hot conditions continue over portions of the southern
Plains…

…Monsoon-like conditions persist for the Four Corners Region…

An upper-level trough passing over the Pacific Northwest and the Rockies
will begin to overspread the northern/central High Plains Thursday
afternoon. Lee cyclogenesis will lead to a deepening surface low over the
northern High Plains, with strengthening wind fields helping to reinforce
a warm front lifting northeastward across the High Plains and a trailing
cold front extending southwest into the Rockies. Scattered thunderstorm
development is expected Thursday afternoon in the presence of moist,
upslope flow. Ample instability and strengthening wind fields will promote
some more intense storms, with the Storm Prediction Center issuing an
Enhanced Risk of severe weather (level 3/5) for the threat of very large
hail and a few tornadoes. Storms will likely increase in coverage into the
evening given enhanced forcing along the cold/occluded front, with a line
of storms expected to propagate eastward with a threat for significant
damaging winds. Some locally heavy downpours will also be possible given
anomalously high moisture available. A Slight Risk of Excessive Rainfall
(level 2/4) extends east through North Dakota as more widespread storms
and heavy rainfall are expected with the eastward moving convective
system, and some scattered flash flooding is possible. A similar scenario
exists further south as more widespread, heavy downpour producing storms
are expected to organize and grow upscale along and ahead of the
northeastward moving warm front. Another Slight Risk of Excessive Rainfall
is in place for northern Kansas and southern Nebraska to cover the threat
for some scattered flash flooding here as well.

The upper-level trough/surface frontal system will continue eastward on
Friday, bringing storm chances to the Upper/Middle Mississippi Valley and
Great Lakes region back southwest along the cold front through the central
Plains. Initial storm focus will be ahead of the northeastward lifting
warm front over the Middle Mississippi Valley, with the chance storms to
the west overnight Thursday persist across the region. Then, later in the
afternoon, a renewed round of storms is expected along the increasingly
east-to-west oriented cold front. Storm motions relatively parallel to the
boundary will bring a higher threat for heavier rain totals as storms
repeat over the same regions, with a Slight Risk of Excessive Rainfall
extending from the Upper/Middle Mississippi Valley west through the Middle
Missouri Valley. More sensitive conditions over the area due to recent
heavy rainfall will increase the risk for flash flooding. In addition,
there is another Slight Risk of severe weather (level 2/5) over the same
region and west to the central High Plains with large hail, damaging
winds, and a few tornadoes all anticipated.

To the south, temperatures will remain dangerously hot over the southern
Plains under the influence of an upper-level high over the
Southwest/south-central U.S. Forecast highs Thursday will range from the
upper-90s to low-100s from central/northern Texas west through the
southern High Plains. Higher humidity over portions of central/northern
Texas into southern Oklahoma have prompted Heat Advisories as Heat Index
values may reach as high as 110. Hotter temperatures will flow back
northward following the warm front on Friday, with highs in the upper 90s
to low 100s reaching up into portions of the central Plains. Very warm
lows in the upper 70s to lower 80s will provide little relief overnight.
An upper-level shortwave dipping down into the Southeast and interacting
with a quasi-stationary frontal boundary will bring shower and storm
chances as well as some relief from the intense heat to most of the Lower
Mississippi Valley and Southeast. Forecast highs will remain in the upper
80s to low 90s over the next couple of days. However, areas of coastal
Georgia north through the Carolinas to the southeast of the boundary will
stay hot, with highs in the mid-90s and heat indices potentially reaching
into the low 100s. Unfortunately, upper-level ridging expanding over the
southern tier of the country will begin to bring more widespread heat back
to the region this weekend.

Monsoon-like conditions will persist over the Four Corners region Thursday
with the upper-level high overhead continuing to steer tropical moisture
northward. The upper-level trough arriving from the west will help to
encourage scattered thunderstorms with the threat for locally heavy
downpours. A Slight Risk of Excessive Rainfall covers portions of western
New Mexico north through western Colorado and far eastern Utah for the
risk of some flash flooding. The trough will help to break down the
upper-high as it moves eastward on Friday, helping to reduce the influx of
moisture and keep the highest storm chances and risk for some isolated
flash flooding limited to southeastern Arizona.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Valid 00Z Tue Jun 25 2024 – 00Z Thu Jun 27 2024

…Heat wave focus shifts to the Southeast, Mid-South, and
central/southern Plains into midweek…

…Severe storms and flash flooding possible for portions of the Upper
Midwest into Monday night, shifting a bit south Tuesday…

…Monsoon-like conditions persist for the Southwest/Four Corners Region…

A broad upper-level ridge building over the west-central U.S. will
continue to produce potentially hazardous heat over the next few days.
Forecast high temperatures will continue to soar into the upper 90s across
much of the Plains and Mississippi Valley and into southeastern parts of
the Lower 48, with low 100s possible over the central Plains. When
combined with the humidity, heat index values may reach as high as 110,
prompting Heat Advisories and some embedded Excessive Heat Warnings.
Meanwhile, low temperatures will mostly remain in the mid- to upper 70s,
bringing little relief from the heat overnight. The arrival of this more
intense heat early in the Summer season leads to a higher level of
heat-related stress, especially for those outdoors and without reliable
air conditioning available. While the north-central U.S. can expect some
relief from the heat Tuesday and especially Wednesday behind a cold front,
the Southern Plains to Mid-South to Southeast will maintain potentially
dangerously hot conditions through the period, with a brief period of heat
returning to the Middle Mississippi/Ohio Valleys on Tuesday and
Mid-Atlantic on Wednesday.

To the north, an upper-level shortwave and accompanying surface frontal
system will move along the northern tier of the central U.S. towards the
Upper Midwest. Deep moisture flowing northward ahead of the system will
bring increasing storm chances through tonight. Hot temperatures along
with the plentiful moisture will lead to strong to extreme instability,
prompting an Enhanced Risk of severe weather (level 3/5) from the Storm
Prediction Center. Tornadoes and large hail are possible with the storms,
but the primary threat is a corridor of very high wind across southern
Wisconsin and surrounding states. Additionally, a Marginal to Slight Risk
of excessive rainfall causing flash flooding is in place for portions of
the Upper Midwest with locally heavy downpours. The low system will
continue eastward on Tuesday, with a cold front pushing southeastward into
the Midwest/Great Lakes region. Storms developing along and ahead of the
front could tend to repeat over the same areas as storm motions become
more parallel to the increasingly east-to-westward oriented front. This is
prompting a larger Slight Risk of flash flooding for portions of the
Middle Mississippi Valley with a Slight Risk of severe weather aligned in
a similar area for Tuesday into Tuesday night. By Wednesday, the
southeastward progression of the front will produce thunderstorm chances
from the Lower/Middle Mississippi Valley into the Tennessee and Ohio
Valley to the Mid-Atlantic and Northeast.

Daily shower and thunderstorm chances continue over portions of the
Southwest/Four Corners Region as an influx of ample tropical moisture
brings monsoon-like conditions. Some locally intense downpours are
possible and may lead to isolated instances of flash flooding, for broad
Marginal Risks in the Excessive Rainfall Outlook (ERO). Through Monday
evening, more focused rainfall may be possible in southeast Arizona, which
may cause more scattered instances of flash flooding especially for urban
areas around Tuscon. Then by Wednesday, rainfall may be particularly
concerning over portions of New Mexico that are sensitive to additional
rainfall due to recent burn scars, prompting an embedded Slight Risk there
in the Day 3 ERO. The higher moisture, cloud cover, and storms will keep
temperatures around average, with 80s and 90s in the Four Corners region
and 100s to 110 for the Southwest. Forecast high temperatures are
generally above average by 5-10 degrees elsewhere in the West, with 60s
and 70s along the immediate Pacific Coast, 70s and 80s in the Pacific
Northwest, and low to mid-90s for the Great Basin. Highs in the low to
mid-100s for portions of interior central California and the 110s for the
western Mojave/Sonoran Deserts have prompted heat-related advisories and
warnings.

Elsewhere, areas of showers and storms may continue into this
evening/tonight in the vicinity of a surface low slowly pushing away from
northern New England. Farther south, additional storms are possible ahead
of a cold front over portions of the Southeast. Diurnal sea breeze-related
storms are also expected over Florida Monday and Tuesday. Welcome relief
from the weekend’s heat is present in the Mid-Atlantic, with highs
generally in the 70s and 80s. Temperatures will gradually rise across the
Eastern Seaboard Tuesday and Wednesday, with highs in the upper 80s to
90s.

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

…Heat wave focus shifts to the Southeast, Mid-South, and
central/southern Plains early this week…

…Severe storms for portions of the Upper Midwest on Monday, with an
increasing flash flooding threat for the Midwest Tuesday…

…Monsoon-like conditions persist for the Southwest/Four Corners Region…

As an upper-level trough moves over the northeastern U.S., bringing relief
from the heat over the weekend, a broad upper-level ridge will build over
the central/western U.S., shifting the focus for the ongoing heat wave to
the Southeast, Mid-South, and central/southern Plains early this week.
Forecast high temperatures will continue to soar into the upper 90s over
the region, with low 100s possible over the central Plains. When combined
with the humidity, heat index values may reach as high as 110, prompting
widespread Heat Advisories. Meanwhile, low temperatures will mostly remain
in the mid- to upper 70s, bringing little relief from the heat overnight.
The arrival of this more intense heat early in the Summer season leads to
a higher level of heat-related stress, especially for those outdoors and
without reliable air conditioning available.

To the north, an upper-level shortwave and accompanying surface frontal
system will move along the northern tier of the central U.S. towards the
Upper Midwest during the day Monday. Deep moisture flowing northward ahead
of the system will bring increasing storm chances by later Monday
afternoon and into Monday evening. Hot temperatures along with the
plentiful moisture will lead to strong to extreme instability, prompting a
Slight Risk of severe weather (level 2/5) from the Storm Prediction
Center. Very large hail and significant damaging winds can be expected
with any storms, and possibly a tornado. A potentially higher threat of
damaging winds exists if enough storms develop and evolve into an
organized convective system. Locally heavy downpours can also be expected,
with an isolated risk of flash flooding especially if storms are able to
become more organized and widespread. The system will continue eastward on
Tuesday, with a cold front pushing southeastward into the Midwest/Great
Lakes region. Storms developing along and ahead of the front will tend to
repeat over the same areas as storm motions become more parallel to the
increasingly east-to-westward oriented front. This will bring a greater
chance of flash flooding compared to Monday, with a Slight Risk of
Excessive Rainfall (level 2/4) in effect. Some severe storms will again be
possible, with a Slight Risk in place for the threat of large hail and
damaging winds.

Daily shower and thunderstorm chances continue over portions of the
Southwest/Four Corners Region as an influx of tropical moisture brings
Monsoon-like conditions. Some locally intense downpours are possible and
may lead to isolated instances of flash flooding. The highest confidence
in storm coverage exists over portions of southeast Arizona where a Slight
Risk of Excessive Rainfall is in effect. A few more scattered instances of
flash flooding will be possible here, especially for urban areas around
Tuscon. The higher moisture, cloud cover, and storms will keep
temperatures around average, with 80s and 90s in the Four Corners region
and 100s to 110 for the Southwest. Forecast high temperatures are
generally above average by 5-10 degrees elsewhere in the West, with 60s
and 70s along the immediate Pacific Coast, 70s and 80s in the Pacific
Northwest, and low to mid-90s for the Great Basin. Highs in the low to
mid-100s for portions of interior central California and the 110s for the
western Mojave/Sonoran Deserts have prompted heat-related advisories and
warnings.

Elsewhere, areas of showers and storms will continue in the vicinity of a
surface low and cold front pushing through Upstate New York and New
England into early Monday afternoon. Storm chances should taper off as the
system clears the coast Monday evening. Further south, additional storms
will be possible ahead of a cold front over portions of the Southeast.
Diurnal sea breeze-related storms are also expected over Florida Monday
and Tuesday. Welcome relief from the heat will come to the Mid-Atlantic,
with highs generally in the 70s and 80s. Temperatures will return closer
to average Tuesday, with highs in the upper 80s to low 90s.

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

…Heat wave focus shifts from the Mid-Atlantic to portions of the
Southeast/Southern Plains by Monday…

…Widespread storms will bring the threat of flash flooding, damaging
winds, and tornadoes to New England Sunday…

…Severe storms for portions of the Upper Midwest on Monday…

…Monsoon-like conditions persist for the Southwest…

Broad long-wave upper-level ridging over the East Coast and western U.S.
Sunday will keep hot Summer temperatures in the forecast for much of the
country. Highs are forecast into the upper-90s from the Mid-Atlantic to
the Southeast/Lower Mississippi Valley/Southern Plains and west through
the High Plains into the Great Basin and California. Humidity helping to
push heat index values into the low 100s as well as warm low temperatures
generally in the mid-70s, providing little relief from the heat overnight,
will make this heat most dangerous for portions of the Mid-Atlantic,
Southeast, Lower Mississippi Valley, and Southern Plains, with
heat-related advisories and warnings in effect for some areas. Numerous
record-tying/breaking highs are possible for the Mid-Atlantic. In the
West, heat-related advisories/warnings are also in effect where
temperatures will push past 100 over northern Utah and portions of
central/southern interior California. An approaching upper-level
trough/surface cold front later Sunday will bring temperatures down closer
to average Monday for the Mid-Atlantic, while the Southeast/Lower
Mississippi Valley/Southern Plains continue to simmer. The upper-level
ridge over the West will also begin to move eastward over the central
U.S., bringing highs into the upper 90s and low 100s more broadly over the
Central/Southern Plains.

The noted upper-level trough and accompanying surface low pressure/frontal
system pushing eastward will bring storm chances from New England
southwestward through the Mid-Atlantic into the Upper Ohio/Tennessee
Valleys Sunday with moderate to locally heavy rainfall possible. The
greatest chance for some potentially more significant rainfall will fall
ahead of the surface low track over northern New England where anomalously
high moisture values and strong forcing could lead to downpours upwards of
2″/hour. A Slight Risk of Excessive Rainfall (level 2/4) is in effect for
the risk of some scattered instances of flash flooding. In addition,
strengthening upper-level and low-level winds as well as strong
instability given the high moisture and warming temperatures will promote
some more intense thunderstorms. The Storm Prediction Center has added an
Enhanced Risk of severe weather (level 3/5) over central New England where
these conditions are most favorable for the threat of damaging winds and a
few tornadoes. A broader Slight Risk (level 2/5) is in place across the
region and southwest through the northern Mid-Atlantic into the Upper Ohio
Valley for a more isolated threat of damaging winds. The system is
expected to reach the coast by Monday morning, bringing drier conditions
into the day Monday, though some storms may linger over northern New
England.

To the West, an upper-level shortwave/surface frontal system moving
eastward along the northern tier of the West/southern Canada Sunday will
approach the Upper-Midwest by Monday afternoon. Warm, moist air flowing
northward ahead of the system will help to lead to the chance for some
storms along and ahead of an eastward moving cold front. A Slight Risk of
severe weather remains in place for portions of northern
Minnesota/Wisconsin for the threat of some damaging winds and large hail.
The chance for some more widespread/organized convection and locally heavy
downpours may lead to an isolated instance or two of flash flooding as
well. Monsoon-like conditions will persist over the Southwest through at
least Monday, with daily shower and thunderstorm chances. Anomalously high
moisture over the region will lead to some locally heavy downpours and an
isolated risk for flash flooding. Daily storm chances will also persist
over Florida and south Texas.