Posts by Sig Silber

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sat Jan 18 2025
Valid 12Z Sat Jan 18 2025 – 12Z Mon Jan 20 2025

…Winter storm to bring moderate to heavy snow to the Mid-Atlantic and
Northeast Sunday…

…Snow showers with moderate accumulations continue Saturday through the
central Rockies and adjacent central/southern High Plains…

…Arctic front brings dangerous cold to much of the nation this weekend…

Moisture lifting northward ahead of a storm system/cold front pushing
through the eastern U.S. will bring wintry precipitation to the north and
rain and thunderstorms to the Southeast Saturday. A light to moderate
wintry mix is expected to move from the Great Lakes into the Appalachians
and interior Northeast, with mostly light rain showers elsewhere in the
Ohio Valley/Southeast and along the East Coast. An enhanced flow of Gulf
moisture over northern Florida will bring some more intense showers and
thunderstorms Saturday night with locally heavy rainfall and the risk for
some isolated flash flooding. A changeover to snow is expected Saturday
night for the Ohio/Tennessee Valleys following cold frontal passage,
though accumulations should generally remain light. Then, an upper-level
shortwave traversing the southern U.S. will help to encourage the
development/deepening of an area of low pressure as it moves off the coast
of the Mid-Atlantic. This will lead to an enhanced swath of snow to the
northwest of the low track beginning early Sunday morning across the
Appalachians and continuing into the day Sunday from the northern
Mid-Atlantic to New England. The swath of heaviest snow (5-8″+) will
likely stay just to the north and west of the I-95 corridor. However, 3-6″
of snow with locally higher amounts is expected from northern Maryland
through Boston. Lake-effect snow will also continue this weekend for
favorable locations downwind of the Great Lakes with strong northwesterly
flow in place following the frontal passage.

Elsewhere, snow showers will continue Friday for portions of the Rockies
and adjacent central/southern High Plains in post-frontal upslope flow.
Moderate totals of 3-6″ are possible in vicinity of the Raton Mesa.
Otherwise, the rest of the central/western U.S. will be mostly dry this
weekend.

Besides the impactful winter weather, dangerously cold temperatures
spreading across much of the Lower 48 this weekend and into next week will
be the other big weather story. Arctic air will plunge southward Saturday
over the Rockies, Plains, and Midwest following the cold frontal passage,
and will reach the East Coast Sunday night as the front moves off into the
Atlantic. Forecast highs by Sunday range from below zero to the single
digits in the northern Plains/Upper Midwest, the teens and 20s across the
central Plains and Midwest, the 20s and 30s for the southern Plains and
Lower Mississippi Valley, and the 40s along the western and central Gulf
Coast. These temperatures will spread to the East Coast for highs Monday,
just beyond the forecast period. Dangerously cold wind chills of 30-55
degrees below zero are expected across the Rockies, northern Plains, and
Upper Midwest Sunday and continuing into next week. This will pose a
life-threatening risk of hypothermia and frostbite to exposed skin. Wind
chills below zero will reach as far south as Oklahoma and the Tennessee
Valleys. Temperatures will remain near average west of the Rockies, with
30s and 40s for the Interior West/Pacific Northwest, the 50s and 60s in
California, and the 60s and 70s in the Desert Southwest.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Fri Jan 17 2025
Valid 12Z Fri Jan 17 2025 – 12Z Sun Jan 19 2025

…Arctic front begins to bring hazardous cold to much of the nation this
weekend…

…Wintry mix for the Midwest/Northeast and rain for the Southeast Friday
into Saturday…

…Snow showers with some moderate accumulations expected through the
Northern/Central Rockies and adjacent High Plains…

A clipper system will move quickly across the northern Plains into the
Midwest Friday and the Northeast by Saturday, bringing a wintry mix of
rain and snow showers ahead of a sweeping cold front. Precipitation totals
should remain on the lighter side for most locations through Saturday,
with only some light snow accumulations expected for some of the higher
elevations of the Appalachians. More moderate totals are expected where
post-frontal flow across the Great Lakes will lead to some lake-effect
snow showers for favorable downwind locations, especially along the Upper
Peninsula of Michigan and east of Lake Ontario. Some potentially more
impactful snow is becoming more likely for the Northeast on Sunday just
beyond the current forecast period. Further South, moist return flow from
the Gulf of Mexico will lead to heavier rain showers ahead of the trailing
cold front through the Middle Mississippi/Ohio Valley and the Southeast
late Friday and into early Saturday. Some wintry precipitation will be
possible following the frontal passage for the Ohio/Tennessee Valleys on
Saturday. Showers and thunderstorms will continue ahead of the front as it
passes into northern Florida by Saturday evening, with more potent locally
heavy downpours and isolated flash flooding possible.

This sweeping cold front will begin to usher in a frigid Arctic airmass
that will be one of the main national weather stories this weekend and
into the next week. Temperatures will plunge by 30-40 degrees Saturday
after above average conditions on Friday. Forecast highs Saturday range
from the single digits and teens in the northern Plains/Upper Midwest, the
teens and 20s for the central Plains and Midwest, and the 30s and 40s into
the Southern Plains/northern Texas. Wind chills upwards of 20-30 degrees
below zero are expected for the northern Plains. Unfortunately, this is
only just the tip of the iceberg, as even colder temperatures will expand
in coverage beyond the current forecast period. Conditions will be at or
above average ahead of the front along the East Coast and the Southeast
through Saturday, with highs the next couple of days in the 30s and 40s
for the Northeast, the 40s and 50s from the Ohio Valley east through the
Carolinas, and the 60s and low 70s for the Southeast.

Upslope flow following the passage of the front along the Rockies will
lead to some scattered snow showers with light to moderate accumulations
for the northern Rockies/High Plains Friday and the central and southern
Rockies/High Plains Friday into Saturday. Gusty winds are also expected
across portions of the Plains and along the Front Range of the Rockies.
This may lead to some blowing snow in the northern Plains. Dry conditions
are expected for the Great Basin and West Coast, with high temperatures
generally around average. Forecast highs range from the 30s and 40s in the
Great Basin, the 40s for the Pacific Northwest, the 50s and 60s in
California, and the 60s to low 70s in the Desert Southwest.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Thu Jan 16 2025
Valid 12Z Thu Jan 16 2025 – 12Z Sat Jan 18 2025

…Improvement in fire weather conditions across southern California…

…A brief moderation of temperatures across the central U.S. before an
arctic front plunges into the northern U.S. on Friday…

…Lake effect snow expected on Thursday and snow also expected for the
central Appalachians…

There will be a few things making weather headlines through Friday night
across the country. Lake effect snow is expected in the wake of a
shortwave passage, and the heaviest snowfall will be downwind of Lake Erie
across western New York on Thursday, where lake effect snow warnings are
now in effect. Moderate to heavy snow is also on the way for the central
Appalachians with moist upslope flow leading to 5-10 inches of
accumulation across the higher terrain of West Virginia into south-central
Pennsylvania, where winter storm warnings are in effect.

A pattern change will evolve across the Central U.S. and the Rockies going
into Friday and especially into early Saturday. After a brief moderation
in temperatures across the north-central U.S. on Thursday, an abrupt
change to reality is coming by Friday as a pair of strong cold fronts
heralds the arrival of frigid temperatures and brutally cold wind chills.
This will continue well beyond the short range forecast period, and the
Weather Prediction Center has Key Messages regarding this arctic blast.
This could also be accompanied by some snow showers and a few snow squalls
across the northern Rockies and western High Plains going into Friday and
Friday night, resulting in mainly light accumulations but accompanied with
poor visibilities and gusty winds.

For the Eastern U.S., a gradual moderation trend in the recent very cold
conditions is on the way to conclude the work week with readings returning
to near seasonal averages for the East Coast, and above average for much
of the Southeast states. A developing low pressure system over the Deep
South Friday night will likely lead to increasing showers and perhaps a
few thunderstorms near the central Gulf Coast region by Saturday morning,
but this region should remain dry until then.

Things are starting to look better in terms of the forecast across
California and the areas that have been devastated by the ongoing
wildfires. Even though no rain is in the forecast, the winds are expected
to switch to a more onshore flow late Thursday and into Friday, bringing
higher relative humidities and less chaotic wind flow, thus helping to
mitigate the wildfire threat compared to recent days.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Tue Jan 14 2025
Valid 12Z Tue Jan 14 2025 – 12Z Thu Jan 16 2025

…Extremely critical fire weather conditions will continue across coastal
Southern California today…

…Much below average temperatures from the Midwest to the central
Appalachians through Wednesday but warming into the central U.S. on
Thursday…

…Locally heavy lake effect snow showers downwind of the Great Lakes
through Wednesday…

Overall, the weather pattern across most of the lower 48 through Thursday
will feature a lack of precipitation with a warming trend later in the
week. This will be a reflection of broad upper level troughing over the
eastern two thirds of the nation and ridging over the Pacific Northwest,
forecast to migrate eastward through Thursday.

Coastal southern California will continue to see extremely critical fire
weather conditions through at least today with localized wind gusts near
70 mph focused across Ventura and Los Angeles counties. Very dangerous
conditions will continue into Wednesday for many of these same locations
with a broader, though not as extreme, threat extending along most of the
Transverse and Peninsular Ranges. Winds are expected to oscillate in
magnitude over the next 48 hours but the environment is expected to be
remain extremely dangerous, favorable to very rapid fire growth if a fire
does start.

After the passage of a cold front on Monday night across the eastern U.S.,
another surge of modified Arctic air will move across the Midwest today.
High temperatures will be 10 to 20 degrees below average for many
locations from the Upper Midwest through the Ohio Valley today, with the
cold continuing for the Ohio Valley on Wednesday. A change in wind
direction from northerly/northwestelry to westerly will accompany a warm
front on Wednesday across the north-central U.S. which will have the
effect of significant warming for the region. In fact, high temperatures
are forecast to jump about 20 degrees higher on Wednesday compared to
Tuesday for the north-central U.S., moving high temperatures from below
average to above average. The warmer weather will expand south and east
for Thursday but the East Coast will still remain a little below average.

The other consequence of the cold weather will be heavy lake effect snow
showers on the southeast and eastern shores of the Great Lakes. While
local wind direction will vary over the next couple of days, moving narrow
bands of heavy snow north or south, the heaviest accumulations of 1 to 2
feet (locally higher) are expected east of Lake Erie and Lake Ontario,
especially into the Tug Hill Plateau.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Mon Jan 13 2025
Valid 12Z Mon Jan 13 2025 – 12Z Wed Jan 15 2025

…Extremely dangerous fire weather conditions to develop across coastal
southern California early this week…

…Locally heavy lake effect snow showers downwind of Lakes Erie and
Ontario as renewed surge of arctic air moves through into the upper
Midwest and Ohio Valley…

The weather pattern across the lower 48 will feature upper level ridging
from the northeastern Pacific into the northwestern U.S., while upper
level troughing dominates much of the remaining area of the country. Below
average moisture across much of the lower 48 will result in a lack of
rain/snow for many areas of the lower 48 through Tuesday with the
exception of lake effect snow showers and scattered snow showers in and
around the northern/central Rockies into the High Plains.

The passage of a weak surface low and cold front through Florida today
will bring a gradual end to rainfall across portions of the southeastern
U.S. Meanwhile, another cold front, moving through the Ohio Valley this
morning, will be followed by another surge of Arctic air which will reach
the Midwest today and into the Mid-Atlantic and Northeast for Tuesday. The
cold front will be accompanied by snow showers today across the Northeast
with potential for isolated snow squalls which could result in hazardous
travel from sudden reduced visibilities, gusty winds and quick minor
accumulations of snow. High temperatures will be 10 to 20 degrees below
average today from the Upper Midwest to lower portions of the Ohio Valley.
The airmass will be modifying/losing vigor as it reaches the East Coast,
but will still be responsible for below average temperatures by Tuesday
for the Eastern Seaboard. Heavy lake effect snow showers are expected to
develop later today as the colder air moves across the Great Lakes, with
localized snowfall accumulations of 1-2 feet for isolated locations which
experience persistent banding through Tuesday night, mainly east of Lake
Erie and Lake Ontario.

The lack of precipitation across the CONUS will also include southern
California which has experienced a number of high profile wildfires over
the past week. Upper troughing aloft and increasing surface pressures over
the Great Basin will again lead to strong gusts across the typically
favored areas across coastal southern California today with winds peaking
between 40-50 mph. Conditions are expected to worsen for these locations
by Tuesday morning as wind gusts near 70 mph will be possible. When
combined with low relative humidities and a lack of recent rainfall (dry
fuels), a Particularly Dangerous Situation Red Flag Warning has been
issued for Santa Barbara, Ventura and Los Angeles Counties from Monday
night through Wednesday morning. These locations will be under a high risk
for large fires with potential for very rapid spreading of any fires that
may develop.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sun Jan 12 2025
Valid 12Z Sun Jan 12 2025 – 12Z Tue Jan 14 2025

…Critical fire weather conditions will continue for southern California
into early this week…

…Clipper system to bring snow showers to the Great Lakes along with
renewed surge of Arctic air to the Upper Midwest and Ohio Valley…

…Rain for the central Gulf Coast today and Georgia/Florida on Monday…

Snow showers that were ongoing early Sunday morning from the northern
Great Basin into the northern and central Rocky Mountains will begin to
taper off today as a surface low tracks toward the Great Lakes region.
Snow showers will linger through Monday from parts of Montana into the
High Plains near a strong frontal boundary but snowfall intensity will be
decreased compared to what occurred Saturday/Saturday night.

The surface low moving into the Great Lakes will have a trailing cold
front that will sweep across the Ohio Valley by Monday morning, bringing a
renewed surge of Arctic air in its wake. High temperatures that are only
in the single digits and teens will affect the northern Plains today with
the cold, clipper-like system continuing eastward through Tuesday morning
with high temperature departures of 10 to 20 degrees from normal following
in its wake, reaching the Midwest on Monday and East Coast for Tuesday.
Snow showers will likely track with the front as it moves east across the
Upper Ohio Valley into the Northeast on Monday, briefly reducing
visibilities.

Fire weather concerns will remain across coastal locations of southern
California today with winds gusting between 30-50 mph early this morning.
Weakening winds are expected into this afternoon/evening as the pressure
gradient weakens across the region. However, a resurgence of gusty winds
is forecast Sunday night into Monday across southern California as
mid-level impulses sink south across the western U.S., allowing for a
re-tightening of the surface pressure gradient and gusty
downslope/offshore winds.

For the Gulf Coast, an area of low pressure will form along a remnant
frontal boundary over the open Gulf waters Sunday night and track toward
the central Gulf Coast. Rain will increase in coverage late this morning
across the upper Texas coast into southern Louisiana and steadily move
east through Sunday night. By Monday morning, rain will be affecting the
Florida Panhandle into portions of southern Alabama/Georgia but rainfall
intensity will diminish throughout the day on Monday. While some light
rain may continue over Florida near a frontal boundary Tuesday morning,
much of the U.S. will see relatively quiet weather.

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Sat Jan 11 2025
Valid 12Z Sat Jan 11 2025 – 12Z Mon Jan 13 2025

…A return to dangerous fire weather concerns for southern California
beginning later today…

…Moderate to locally heavy snow for the parts of the northern to central
Rockies…

…Below average high temperatures for much of the lower 48 this weekend
after departure of southern Mid-Atlantic winter storm…

A significant winter storm that brought widespread impacts to much of the
South over the past couple of days will quickly move away from the East
Coast this morning, leaving light snow showers in its wake for the central
Appalachians and New England. High pressure and quieter weather will
settle into locations east of the Mississippi River through Sunday morning
but more rain is expected for the central Gulf Coast Sunday into Monday as
low pressure organizes in the Gulf of Mexico, sending anomalous moisture
northward. Temperatures will be cold today for the southern/southeastern
U.S. with high temperature departures running 10 to 20 degrees below
average. Below average temperatures will also extend into the Midwest,
Ohio Valley and Northeast but Maine will be close to average for
mid-January. Some moderation of the cold temperatures will occur for
Sunday for the South and East, except for New England which will be near
to above average.

Out West, an upper level trough will continue to advance eastward from the
central Rockies today with moderate to locally heavy snow showers
continuing through Saturday night for northern sections of the Great Basin
and northern/central Rockies in its wake via northwesterly to northerly
flow behind the upper trough axis. Snow will continue near a strong
frontal boundary in central Montana on Sunday but subside elsewhere across
much of the West. By Monday morning, localized snowfall accumulations of 1
to 2 feet are expected for portions of central and southern Montana into
the Big Horn Mountains of Wyoming.

High Temperatures across the West will generally be below average this
weekend while temperatures along the West Coast remain near average
through the weekend. The exception to colder than average high
temperatures for the lower 48 will be in and around the Upper Great Lakes
which will lie on the warm side of low pressure tracking across the
north-central U.S. with colder air filtering into the region behind the
low on Monday.

In southern California, a return to heightened fire weather conditions
will return later today after a brief lull from Friday night. High
pressure will increase across the Great Basin today as a surge of colder
air moves into the region behind a cold front which is forecast to move
into Mexico Sunday morning. Gusty offshore winds along the coast of
southern California support a Critical Risk area for Saturday as
highlighted by the Storm Prediction Center, with these dangerous
conditions continuing into Monday.