985
FXUS61 KLWX 050901
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 AM EST Wed Feb 5 2025

.SYNOPSIS...
High pressure briefly builds to the north while an area of low
pressure approaches from the west tonight into Thursday.
Another area of low pressure may potentially impact the area
this weekend. A coastal system could affect the region sometime
during the early to middle portions of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
The latest surface analysis places the early week cold front
down along the North Carolina/South Carolina border. At the same
time, high pressure centered over the arrowhead of Minnesota
extends eastward across the Great Lakes into interior New
England. Locally, the influence of this anticyclone is being
felt through the dry northerly winds. Current observations are
largely in the upper 20s to 30s, but with dew points in the mid
teens to low 20s. The extent of low-level dry air actually
extends further up the column with aircraft soundings near KBWI
showing a sub-saturated layer up to 650-mb. Any saturation is
largely confined to the 600-475 mb layer.

With that in mind, local WSR-88D radar imagery shows an enhanced
area of 15 to 20 dBZ echoes stretching along and north of I-70
in central to northeastern Maryland. However, given the
extensive dry air noted in the aircraft sounding, none of this
is likely reaching the ground. Have introduced isolated snow
flurries in this pocket if any snowflake happens to reach the
surface. Otherwise, the radar is devoid of echoes elsewhere
underneath a mixture of mid to high clouds.

Through the day, expect a continued thickening of the mid/high
clouds streaming in from the Ohio Valley. High-resolution model
guidance is somewhat all over the place in any wintry
precipitation during the first half of the day. Of note, the 00Z
FV3 solution shows that swath of light snow mainly north of the
D.C. metro area this morning. This seems to follow rather close
to the ongoing trends on the radar mosaic. Elsewhere, some very
light freezing rain is possible over Highland and Pendleton
counties. As such, winter headlines go into effect at 7 AM this
morning for these locations. Elsewhere, any impactful wintry
precipitation holds off until the evening hours.

Although temperatures are forecast to be marginal for any winter
threats, the continued dry air mass in place will support ample
wet-bulbing effects to carry temperatures to around to below
freezing. Today`s high temperatures are largely confined to the
mid/upper 30s, with upper 20s to near freezing in the mountains.
Wind fields will mainly be out of the east to southeasterly
direction which is often not the most favorable for cold
advection. However, as mentioned, the expectation of wet-bulb
effects should mitigate any concerns, particularly as continued
precipitation helps saturate the column.

The overall forecast remains on track with a mixture of all
wintry precipitation types to impact the area this evening
through the night and into the early morning hours. Although the
onset could consist of a brief period of light snow, a warm nose
around 850-750 mb continues to expand as noted in forecast
soundings. At some point, the maximum temperature in this layer
could near 6-8C. Given the extent of such warming aloft,
freezing rain will certainly prevail at times, especially after
midnight. Before that, thermal profiles are more favorable for
sleet with perhaps up to a quarter to half inch of accumulations
possible for areas north of I-66. The impacts of ice accretions
from freezing rain could be much higher for those in the eastern
West Virginia panhandle, western to central Maryland, and over
the mountains. Ice Storm Warnings are in place where at least a
quarter inch of ice accretions are expected. Elsewhere, forecast
ice amounts are lower with Winter Weather Advisories in effect
over a bulk of remaining areas. Continuing to monitor the need
to expand such advisories over the area spanning I-64 to I-95 in
central Virginia, and across southern Maryland.

Overnight temperatures will be confined to the freezing mark and
below given the ongoing wintry mix.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
With the cold air damming (CAD) signature continuing into
Thursday, the expectation is surface temperatures should remain
supportive of mixed wintry precipitation into portions of the
morning. Such a threat gradually winds toward the lunch hour on
Thursday. Some shift over to rain is expected thereafter before
conditions dry out into the late evening/overnight period. A
warm front attempts to lift northward across the Mid-Atlantic
area. However, such warm frontal passages can be challenging as
the mentioned CAD wedge will likely be stubborn to erode.
Consequently, the forecast continues to favor colder
temperatures on Thursday with highs in the mid/upper 40s north
of I-66, with low/mid 50s off to the south. The true warm spot
could be west of I-81 where mid 50s to low 60s are in the
forecast. Given the notable temperature spread in the guidance,
could see these forecast numbers drop a bit, particularly with
statistical guidance being colder. Heading into Thursday night,
most spots will be in the mid/upper 30s, accompanied by upper
20s to mid 30s across mountain locales.

A cold front sweeps across the Mid-Atlantic region overnight on
Thursday with a brief period of tranquil weather on Friday.
Winds will be gusty at times, especially along the Alleghenies
where gusts up to 35 to 45 mph are possible. This dry
downsloping wind will help raise temperatures into the 50s for
areas south of I-66 and into the Shenandoah Valley. Temperatures
will be cooler closer to the Mason-Dixon Line as well as over
the higher terrain. After a mostly sunny start to the day, skies
cloud up later on in response to the next system in the chain.
Like the preceding one, this also has implications of a mixed
wintry precipitation event. Before the warm nose arrives, a
period of light snow is possible. Low temperatures will stay
mainly in the mid/upper 20s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The long term period will feature an active stretch of weather
locally, with multiple chances for wintry precipitation.
Synoptically speaking, this period will feature predominantly zonal
flow across the CONUS, with several fast moving, low amplitude
disturbances progressing through the waveguide. A strong north-south
temperature gradient will be maintained across the CONUS, which will
provide opportunities for warm advection/overrunning driven
precipitation as each passing upper disturbance interacts with the
low-level temperature gradient in place.

The first of these disturbances will rapidly track from the Central
Plains to the Northeastern states over the course of Saturday into
Saturday night, causing an attendant surface low to track from
northern Oklahoma to near Boston during that same timeframe. Warm
advection in advance of this system will result in a wintry mix of
precipitation across the area Saturday into Saturday night.
Precipitation looks to be relatively light, but even light amounts
of ice or snow could lead to travel disruptions. At this juncture,
most guidance favors much of the precipitation falling as sleet and
freezing rain, with a changeover to plain rain Saturday night before
precipitation ends. A little snow could also potentially mix in
toward onset.

This first system will depart off toward the northeast by Sunday.
Dry conditions and gusty northwesterly winds are expected on Sunday,
with high temperatures reaching into the 40s and 50s for most (30s
mountains). Temperatures should drop back into the 20s Sunday night.

Additional weak upper level disturbances will move through on both
Monday and Tuesday, potentially leading to periods of warm advection
driven overrunning precipitation both days. 00z guidance showed a
marked increase in probabilities for precipitation on Monday,
especially to the south of I-66/US-50. With this forecast package,
we`ve trended up probabilities for precipitation to 30-50 percent on
Monday, but further increases may be needed if trends continue. Most
of the guidance favors precipitation on Monday falling mainly in the
form of snow if it were to occur, but some mixing with ice or rain
can`t be ruled out.

A very small lull in the precipitation may occur Monday night
(assuming it does precipitate Monday), before a more substantial
push of warm advection driven precipitation occurs on Tuesday. Many
deterministic 00z models (such as the GFS, Canadian, and ICON) show
this largely falling in the form of snow. However, there was a
notable northward shift in both the EPS (probabilistically
speaking), and also with the deterministic run of the Euro, which
now shows mainly ice to the northwest of I-95, with rain further
southeast.

With several fast moving, low amplitude disturbances moving through,
forecast uncertainty (in terms of both precipitation amount and
precipitation type) remains high during the Monday/Tuesday
timeframe. At this juncture, at least one and maybe two wintry
precipitation events appear possible during that time, with
substantial accumulations at least a possibility. We`ll continue to
monitor this potential over the upcoming days, and refine the
forecast as uncertainty slowly decreases.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected through the day and into the
early/mid-evening hours. However, the approaching winter storm
will lead to a lowering of ceilings and visibility as mixed
wintry precipitation falls from the sky. All locations should
see periods of sleet and freezing rain from this evening through
the overnight and into early Thursday morning. As a warm nose
expands aloft, it could become more of a freezing rain event
during the latter half of the night.

IFR conditions persist overnight into a good portion of
Thursday. This does come with a shift to rain after the morning
hours. Improvements do not really come until late Thursday
behind the passing cold front. Friday should yield VFR
conditions with a gusty northwesterly wind. Gusts during the
afternoon could push into the 20 to 25 knot range. The next
system with implications of wintry precipitation arrives late
Friday into the first half of the weekend.

Sub-VFR conditions appear likely on Saturday in association with low
ceilings and wintry precipitation. Rain, freezing, sleet, and snow
may all be possible during that time. Improvement back to VFR
conditions is expected on Sunday. Winds will be light out of the
east to southeast on Saturday, before turning gusty out of the
northwest on Sunday.

&&

.MARINE...As high pressure moves from the Great Lakes toward
New England, initial northerly winds will give way to east-
southeasterlies through tonight. Mixed wintry precipitation
overspreads the waters later this evening through the night and
into portions of Thursday morning. An eventual shift to
southerlies is expected which introduces some need for Small
Craft Advisories. Winds remain elevated into the night and
Friday. A cold front sweeps across the waters late
Thursday/early Friday which will likely necessitate Small Craft
Advsiories given the gusty northwesterlies on Friday.

Sub-SCA east to southeasterly winds are expected on Saturday, along
with a wintry mix of precipitation. SCA conditions appear likely in
northwesterly flow on Sunday, with a few low-end Gale gusts not
entirely out of the question.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Winter Weather Advisory from 9 PM this evening to 10 AM EST
     Thursday for DCZ001.
MD...Winter Weather Advisory from 9 PM this evening to 10 AM EST
     Thursday for MDZ008-011-013-014-504-506-508.
     Ice Storm Warning from 7 PM this evening to noon EST Thursday
     for MDZ001-003-501-502.
     Winter Weather Advisory from 9 PM this evening to noon EST
     Thursday for MDZ004>006-503-505-507.
VA...Winter Weather Advisory from 9 PM this evening to 10 AM EST
     Thursday for VAZ038-039-050-051-053-054-502-527.
     Ice Storm Warning from 7 PM this evening to noon EST Thursday
     for VAZ028-031-507.
     Winter Weather Advisory from 9 PM this evening to noon EST
     Thursday for VAZ040-501-505-506-526.
     Winter Weather Advisory from 7 PM this evening to noon EST
     Thursday for VAZ025>027-029-030-508.
     Ice Storm Warning from 7 AM this morning to 7 AM EST Thursday
     for VAZ503.
     Winter Weather Advisory from 7 AM this morning to 7 AM EST
     Thursday for VAZ504.
WV...Ice Storm Warning from 7 PM this evening to noon EST Thursday
     for WVZ050>053-055-501>504.
     Ice Storm Warning from 7 AM this morning to 7 AM EST Thursday
     for WVZ505.
     Winter Weather Advisory from 7 AM this morning to 7 AM EST
     Thursday for WVZ506.
MARINE...Winter Weather Advisory from 9 PM this evening to 10 AM EST
     Thursday for ANZ530.

&&

$$

SYNOPSIS...BRO
NEAR TERM...BRO
SHORT TERM...BRO
LONG TERM...KJP
AVIATION...BRO/KJP
MARINE...BRO/KJP