Posts by Sig Silber

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Tue Dec 24 2024
Valid 12Z Tue Dec 24 2024 – 12Z Thu Dec 26 2024

…Heavy rain and mountain snow returns to the West Coast region Wednesday
night…

…Showers and thunderstorms developing over portions of the south-central
states…

…Relatively mild conditions across the majority of the country leading
up to Christmas…

An active weather pattern is expected to continue across the West Coast
region as an energetic storm track across the eastern Pacific brings in
multiple rounds of precipitation. The next in a series of atmospheric
river events is arriving across northern California and western Oregon
late tonight and continuing into Tuesday afternoon. Although the storm
system will be progressive overall, there will be a deep surge of moisture
ahead of the cold front that will intersect the coastal terrain and the
western slopes of the northern Sierra Nevada. Rainfall totals on the
order of 2-4 inches, and locally higher, are likely across this region
through Tuesday evening. Snow levels will be initially high, but should
fall some once the front passes. The heaviest snow from this event should
affect the highest terrain of the central Sierra Nevada, with up to a foot
of accumulation possible, affecting travel through the mountain passes.
Winter weather advisories and winter storm warnings are currently in
effect for this event. After a brief break on Christmas Day, the next
round of moisture moves in towards the West Coast and brings another
substantial round of rain and mountain snow, along with windy conditions
as the pressure gradient tightens in response to a very intense surface
low off the coast of British Columbia.

A relatively weak low pressure system crossing the Northeast U.S. region
on Tuesday will produce light to occasionally moderate snow from the
central Appalachians to New England, increasing the odds of a White
Christmas across this region, especially when combined with existing snow
cover from recent snowfall. This system quickly exits offshore by Tuesday
evening. Farther to the south across Texas, a separate surface low
develops, and increasing southerly flow from the western Gulf of Mexico
ahead of that system will fuel the development of scattered to numerous
showers and some thunderstorms, mainly from eastern Texas northward across
much of Arkansas and into southern Missouri through Christmas morning.
Some locations may get over an inch of rainfall with this event, and thus
a Marginal Risk of excessive rainfall is valid for these areas.

Much of the East Coast region will have a moderation trend in the cold
temperatures going into Christmas Eve, as the arctic surface high moves
offshore and milder air from the Ohio Valley advects eastward across the
region. The remainder of the country should enjoy generally above average
temperatures by late December standards, particularly across the central
and southern Plains where daytime highs could be 15-20 degrees above
average. This would equate to highs well into the 60s and 70s for much of
Texas.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Mon Dec 23 2024
Valid 12Z Mon Dec 23 2024 – 12Z Wed Dec 25 2024

…Heavy rain and mountain snow returns to the West Coast region Monday
night…

…Showers and thunderstorms developing over portions of the south-central
states…

…Relatively mild conditions across the majority of the country leading
up to Christmas…

An active weather pattern is expected to continue across the West Coast
region as an energetic storm track across the eastern Pacific brings in
multiple rounds of precipitation. After a brief respite Monday, the next
atmospheric river event arrives across northern California and western
Oregon late Monday night and into Tuesday. Although the storm system will
be progressive overall, there will be a deep surge of moisture ahead of
the cold front that will intersect the coastal terrain and the western
slopes of the northern Sierra Nevada. Rainfall totals on the order of 2-4
inches, and locally higher, are likely across this region through Tuesday
evening. Snow levels will be initially high, but should fall some once
the front passes. The heaviest snow from this event should affect the
highest terrain of the central and northern Sierra Nevada, with up to a
foot of accumulation possible.

A low pressure system crossing the Great Lakes region on Monday will
produce a corridor of mixed wintry precipitation from southern Minnesota
to southern Lower Michigan, and mainly light to moderate snow to the north
across northern Wisconsin and into northern Michigan. Winter weather
advisories are currently in effect for those areas. This low reaches the
Northeast U.S. Christmas Eve, with light snow mainly for interior
portions. Farther to the south across Texas, a separate surface low
develops, and increasing southerly flow from the western Gulf of Mexico
ahead of that system will fuel the development of scattered to numerous
showers and some thunderstorms from eastern Texas northward across much of
Arkansas and into southern Missouri through Tuesday.

Much of the East Coast region will have a very cold start to the holiday
week on Monday, with an arctic surface high slowly moving east across the
region. The coldest morning of the season thus far is expected for most
of the Mid-Atlantic and Northeast states, followed by another chilly day
on Monday, albeit slightly milder compared to what was observed on Sunday.
A further moderation trend is expected going into Christmas Eve as the
surface high moves offshore and milder air from the Ohio Valley advects
eastward across the region. The remainder of the country should enjoy
generally above average temperatures by late December standards,
particularly across the central and southern Plains where daytime highs
could be 15-20 degrees above average. This would equate to highs well
into the 60s and 70s for much of Texas.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sun Dec 22 2024
Valid 12Z Sun Dec 22 2024 – 12Z Tue Dec 24 2024

…Periods of moderate to heavy rainfall for the Pacific Northwest and
northern California as systems move in from the North Pacific…

…Record warmth possible across parts of the Southwest on Sunday…

…More winter weather from the northern Plains through the Great Lakes
and the Northeast from Sunday into Tuesday morning…

The general flow pattern becomes more zonal with time, with systems of
Pacific origin moving eastward and reforming downstream across the
Plains/Midwest. The consequence of this pattern will be rainfall/elevation
snows near the Pacific Northwest & northern California, decreasing warmth
across the West, and by Monday decreasing cold across portions of the
East. Starting out West, weakening fronts move eastward out of the
Pacific into the Great Basin, pushing batches of rainfall into and through
the Pacific Northwest, northern Intermountain West, and northern
California, with snowfall expected at higher elevations through Tuesday
morning. The heaviest precipitation is expected in and near northern
California Monday night and Tuesday, which carries some risk of excessive
rainfall/flash flooding, particularly in burn scars. Some periods of high
winds are expected on Sunday — wind advisories are in effect for areas of
northern California and southern Oregon. Across the Southwest, high
temperatures should rise 60s to 70s on Sunday, threatening daily record
high temperatures in and near southern Arizona and southern California.
As one of the Pacific disturbances aloft moves east of the Rockies, a low
pressure system develops across the Upper Midwest and Great Lakes Sunday
into early Monday, which is expected to bring freezing rain to portions of
northeast Montana and northwest North Dakota — winter weather advisories
are in effect — then snowfall which increases in coverage and intensity
with time from North Dakota eastward through Michigan into the Northeast.
This system should weaken as it moves through the Northeast.

A seasonably strong and cold high pressure system migrates through the
East into the Western Atlantic on Sunday and Monday, continuing the cold
in the eastern United States. Cold Weather Advisories are in effect
across portions of eastern Upstate New York and northeast Pennsylvania,
while freeze warnings and frost advisories are out for portions of
southeast Georgia and North Florida for Sunday morning. As the flow over
the Great Lakes becomes more anticyclonic with time, Lake Effect Snows
should continue to fade on Sunday. For some areas of the East, Sunday
should be the coldest day thus far this winter. Once the high moves
offshore on Monday, temperatures should begin to moderate closer to late
December averages.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sat Dec 21 2024
Valid 12Z Sat Dec 21 2024 – 12Z Mon Dec 23 2024

…Periods of moderate to heavy rainfall near the Pacific Northwest and
northern California…

…Record warmth possible across parts of the West Saturday and Sunday…

The general flow pattern favors an upper level trough across the eastern
Pacific ocean, ridging aloft in the West, and troughing aloft in the
eastern United States. The consequence of this pattern will be some
rainfall along the West Coast, warmth across the Intermountain West, and
cold across portions of the East. Starting out West, skirmishes of rain
along the West Coast are expected Saturday as low pressure systems move
northward offshore the West Coast. On Saturday and Sunday, weakening
fronts move eastward, pushing a couple batches of rainfall into the
through the Pacific Northwest, northern Intermountain West, and northern
California, with snowfall expected at higher elevations. Some periods of
high winds are expected — high wind warnings are in effect for areas of
northern California and southern Oregon. High temperatures across
northern portions of the West will rise into the 40s and 50s, high enough
to threaten record high temperatures on Saturday. Across the Southwest,
high temperatures should rise into the 70s to 80s Saturday and 60s to 70s
on Sunday, threatening daily record high temperatures in and near southern
Arizona and southern California.

Mid-continent, a seasonably strong and cold high pressure system migrates
from the Great Lakes into the East, bringing below average temperatures
near and to its east. For some areas of the East, it should be the
coldest temperatures thus far this winter. Freeze Watches and Cold
Advisories have been posted for sections of northern Florida and southeast
Georgia for the incoming cold. When combined with cyclonic flow around a
low moving offshore the East Coast, lake effect snowfall is expected near
the Great Lakes, portions of the Appalachians, northern Mid-Atlantic
States, and New England which slowly fades Saturday and Sunday. Winter
weather advisories are in effect in patches across the eastern Great
Lakes, Central/Southern Appalachians, northern Mid-Atlantic States, and
coastal New England with a very localized Winter Storm Warning is in place
for portions of Downeast Maine through midday Saturday to help advise on
the moderate to heavy snowfall expected. A low pressure system developing
across the Upper Midwest and Great Lakes Sunday into early Monday is
expected to lead to snowfall which increases in coverage and intensity
with time from North Dakota eastward into Michigan.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Thu Dec 19 2024
Valid 12Z Thu Dec 19 2024 – 12Z Sat Dec 21 2024

…Clipper system to bring periods of heavy snow to the Upper Midwest
Thursday with some light to moderate accumulations for the
Appalachians/Interior Northeast Friday…

…Well above average temperatures and mild conditions continue across the
West…

…Frontal passages will bring colder temperatures to much of the eastern
U.S. through the end of this week and into the weekend…

A clipper system dropping east-southeasterly through the northern Plains
and into the Upper Midwest/Great Lakes will bring periods of heavy snow
along a path from central Minnesota through northern Wisconsin and into
the UP/northern LP of Michigan today. Winter Storm Warnings are in effect
for snow totals generally between 3-6″, locally higher. Gusty winds may
lead to periods of blowing snow and hazardous travel conditions. Although
snow has come to an end to the west over the northern Plains, very gusty
winds will continue through this afternoon. The clipper system will
continue quickly southeastward across the Ohio Valley, Appalachians,
Northeast, and off the East Coast Friday, bringing wintry precipitation to
the interior and some rain showers to the coast. Some moderate snow
accumulations will be possible across the central Appalachians and
downwind of Lake Erie, with lighter amounts more broadly over the Interior
Northeast.

Elsewhere, a few lingering showers and storms may occur over South Florida
Thursday, with conditions drying out into Friday. An upper-level shortwave
dropping southeastward over the northern Plains may lead to some renewed
light snow chances Friday. An active storm track over the Pacific will
also bring some periods of lower elevation/coastal rain and perhaps some
mountain snow to the Pacific Northwest/northern California the next couple
of days, though totals should remain much lighter than earlier this week.

Temperatures across the West will remain well above average by 10-20
degrees for most locations to end the week as upper-level ridging remains
in place. Forecast highs generally range in the 40s and 50s across the
Interior West, Pacific Northwest, and northern California with 60s to low
80s for southern California and the Desert Southwest. A cooling trend is
expected for much of the eastern half of the country following a cold
frontal passage off the East Coast this morning and an additional cold
front dropping southward with the clipper system. Very cold temperatures
in the teens are forecast for the northern Plains/Upper Midwest today.
Highs will drop into the 20s and 30s in the Midwest, the 30s and 40s in
the Mid-South and central Plains, and the 50s and 60s in Texas by Friday.
Highs along the East Coast range from the 20s to 40s in New England, the
30s and 40s in the Mid-Atlantic, and the 50s and 60s in the Southeast.
Much colder temperatures are expected along the East Coast by this
weekend.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Wed Dec 18 2024
Valid 12Z Wed Dec 18 2024 – 12Z Fri Dec 20 2024

…Clipper system to bring periods of moderate to heavy snow and gusty
winds to the northern Plains and Upper Midwest/Great Lakes the next couple
of days…

…Showers and storms continue into the day Wednesday for the
Ohio/Tennessee Valleys with some locally heavy rainfall and isolated flash
flooding possible…

…Well above average temperatures continue for much of the lower 48…

Lower elevation/coastal rain and higher elevation snow will linger into
the early morning hours Wednesday over the Pacific Northwest and northern
Great Basin/Rockies as an upper-level wave departs the region. The wave
will then pass over the northern High Plains, leading to lee cyclogenesis
and the organization of a clipper system that will drop east-southeastward
over the Plains and Midwest the next couple of days. Strengthening moist
southerly flow over colder air to the north will bring an intensifying
band of snow to the northern Plains Wednesday evening and into the
overnight hours. Winter Storm Watches have been issued for northern and
eastern North Dakota and northwestern Minnesota where 3-6 inches of snow,
locally higher, can be expected. A wintry mix will be possible to the
south of the heaviest snow with some snow and light ice accretions
possible from eastern Montana southeastward through western North Dakota
and into eastern South Dakota. In addition, very strong, gusty winds are
expected across the northern Rockies and High Plains Wednesday into
Thursday. This will lead to blowing snow and low visibility where snow is
either falling or remains on the ground. The system will pass through the
Upper Midwest/Great Lakes Thursday, bringing some moderate to locally
heavy snowfall, particularly across portions of northern Wisconsin.

Showers and thunderstorms continue this morning ahead of a cold front
stretching from the Ohio Valley southwest through the Tennessee/Lower
Mississippi Valleys and into the southern Plains. Some locally heavy
rainfall is expected across the Ohio and Tennessee Valleys where storm
motions more parallel to the slow moving front will lead to a few repeated
rounds of storms. Isolated flash flooding will be possible particularly
across the Tennessee Valley where local soil conditions are more
saturated. The boundary will become more progressive by Wednesday
afternoon and sweep eastward across the Southeast and to the East Coast
into Wednesday evening, with some more isolated storms possible. Moist
flow along a warm front lifting northward ahead of the system will also
bring moderate rainfall to the coastal Northeast as well as the potential
for some accumulating snow for higher elevations of the interior Northeast
Wednesday afternoon through the early morning hours Thursday.
Precipitation should come to an end for all but Florida by Thursday
afternoon as the front pushes into the Atlantic.

Elsewhere, thunderstorms remain in the forecast for South Florida
Wednesday with some very heavy downpours and isolated flooding possible
for urban areas. Extreme to Critical Fire Weather conditions have also
been outlined by the Storm Prediction Center in the Los Angeles vicinity
as gusty winds and dry conditions remain in place. Precipitation chances
will return to the Pacific Northwest by Thursday evening as another
Pacific system approaches the region. Much of the lower 48 will continue
to see well above average temperatures over the next couple of days, with
highs running 10-20 degrees above average for the Southeast Wednesday
(60s-70s), the south-central U.S. Thursday (60s-70s), and the West through
Thursday (40s-50s interior, 60s-70s West Coast and Deserts). The Northeast
will be more seasonable with highs in the mid-30s (interior) to low 50s
(coast). One region that will see much colder temperatures will be the
Northern Plains/Upper Midwest, where highs will mainly be in the teens and
20s and gusty winds will lead to even colder wind chills. The northern
High Plains will see some relief Thursday as downsloping winds bring
warmer temperatures.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Tue Dec 17 2024
Valid 12Z Tue Dec 17 2024 – 12Z Thu Dec 19 2024

…Another Atmospheric River to bring heavy coastal rains and high
elevation mountain snow to the Northwest…

…Unsettled, wet weather expected for most of the eastern U.S.
Wednesday…

…Periods of snow for the Northern Plains through mid-week with heavier
accumulations most likely Wednesday night…

…Much above average temperatures expected for most of the lower 48 into
mid-week…

Yet another Pacific system will help to usher in a wave of Pacific
moisture/Atmospheric River into the Pacific Northwest and inland over the
northern Great Basin/Rockies Tuesday. A more northerly track will help to
focus the heaviest lower elevation rainfall along the coastal ranges of
northern Oregon and Washington State, with heavy high elevation mountain
snow for the northern Cascades. Some moderate snow accumulations will also
be possible into the northern Great Basin and northern/central Rockies,
aided in part by a leading wave departing the region early this morning.
Lower elevation inland locations can expect a wintry mix of rain and snow,
with some freezing rain possible to the east of the Cascades in
Washington. Precipitation chances should come down through the day
Wednesday for the Pacific Northwest while lingering longer in the northern
Rockies.

A lingering frontal boundary will help to trigger some showers and
thunderstorms over portions of the Southern Plains east into the Lower
Mississippi, Tennessee, and Ohio Valleys through the day Tuesday. An
approaching upper-level wave will help to reinforce the boundary overnight
Tuesday and enhance moist, southerly flow from the Gulf, leading to
increasing storm coverage and locally heavy rainfall. The boundary will
push eastward as a cold front towards the East Coast through the day
Wednesday spreading showers and storms into the Southeast and coastal
Northeast. Colder air in place to the north over the interior Northeast
will lead to snow showers with some light to moderate accumulations for
higher mountain elevations.

A quick moving upper-level wave will bring some snow showers to portions
of the Northern Plains/Upper Midwest today with some light accumulations
possible, especially from central South Dakota east through southern
Minnesota. These light snow showers will spread eastward into the Great
Lakes Wednesday. Then, another more potent wave will approach from the
west during the day Wednesday leading to lee cyclogenesis over the
northern High Plains and helping to consolidate/strengthen a surface
frontal system. This will lead to enhanced lift over the Northern Plains
and a quick developing and potentially intense band of snowfall by
Wednesday evening. Snow totals of 2-4″ can be expected with locally
heavier amounts possible through Thursday morning. Some mixed
precipitation with light ice accumulations will be possible as well.

Elsewhere, persistent shower and thunderstorm chances will continue for
Florida, particularly along the Atlantic Coast. Some intense downpours
will be possible Tuesday with an isolated threat of some flooding in the
urban areas of South Florida. Most of the country will continue to see
well above average temperatures through at least mid-week. Forecast highs
Tuesday range from the 40s and 50s in the interior West and New England;
the 50s and 60s for the West Coast, central Plains, Ohio Valley, and
Mid-Atlantic; and 60s and 70s for the Southwest, southern Plains, and
Southeast. A cold front will bring some cooler, more seasonable
temperatures to the Plains Wednesday as highs fall into the 40s and 50s.
One region that will remain much colder will be the Northern Plains/Upper
Midwest, with most highs only into the teens and 20s.