917
FXUS61 KLWX 220224
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
924 PM EST Sat Feb 21 2026
.WHAT HAS CHANGED...
Recent computer model runs have not provided a compelling enough
consensus to change any of the winter weather headlines. Will
continue to monitor for changes in position of inverted trough
and western edge of the higher coastal precipitation. Light rain
is already approaching the western CWA border late this
evening. Additionally, a Small Craft Advisory has been filled in
for areas not under a Gale Warning Sunday night.
&&
.KEY MESSAGES...
-1) A Winter Storm will move across the area Sunday into early
Monday, resulting in locally significant impacts.
-2) Multiple fronts will cross the area mid to late next week
amidst a general warming trend.
&&
.DISCUSSION...
KEY MESSAGE 1...A Winter Storm will move across the area Sunday
into early Monday, resulting in locally significant impacts.
Synoptic overview: Over the next 24 hours, a complex upper
trough with several embedded shortwave disturbances is forecast
to dig southward into the Ohio/Tennessee Valleys and Lower Great
Lakes. In response, an area of low pressure is expected to
develop along a stalled frontal boundary to our south in the
vicinity of the Carolinas, and then rapidly deepen as it tracks
off the Delmarva and up the East Coast, eventually reaching just
southeast of Cape Cod by midday Monday. This system will bring
a mixture of rain and snow to region Sunday through early Monday
morning, leading to locally significant impacts.
Forecast details: Precipitation is expected to break out from
west to east across the region late tonight into early tomorrow
morning as large scale ascent ahead of the approaching upper
trough gradually overspreads the area. Precipitation should
begin as a mixture of light rain and snow for most, with all
snow above around 1500 feet. Surface temperatures will initially
be in the mid to upper 30s at lower elevations, and should hold
in the mid 30s through mid-afternoon. As a result, much of the
region will experience several hours of mixed rain and snow that
won`t accumulate and will largely be unimpactful other than
making the roads wet. However, snow will accumulate across the
higher elevations above 1500 feet throughout the day.
As we move into the late afternoon and evening, a combination of
factors will enable temperatures to start to fall. First, we will
start to lose solar insolation as the sun angle drops and the
sun eventually sets. Second, low-level cold advection will
increase as the upper trough approaches from the west and the
coastal low intensifies offshore, drawing colder air into the
region within northerly flow. Finally, increasing large scale
lift ahead of the upper trough and to northwest of the
developing coastal will act to dynamically cool the column. This
will result in a gradual changeover to all snow from higher to
lower elevations through the late afternoon and evening hours as
temperatures fall from the middle to lower 30s.
The heaviest precipitation locally is expected Sunday evening
through the first half of Sunday night as the coastal low tracks
off the Delmarva and the upper axis trough moves overhead. Two
locally enhanced areas of precipitation are expected within a
much broader precipitation shield that will encompass most of
the forecast area.
The first area of enhanced snowfall rates will be close to
Chesapeake Bay, where mid- level frontogenetic forcing to
northwest of the coastal low will be strongest. There is a bit
of uncertainty about how just far west this area of heavier snow
gets, but most solutions show it only impacting the counties
immediately adjacent to Chesapeake Bay in our forecast area (St.
Mary`s northward through Cecil). Snowfall rates could approach
an inch per hour at times in this area between roughly 6 PM and
2 AM.
The second area of enhanced snowfall rates will be along an
inverted trough axis (sometimes referred to as a Norlun trough)
that will extend north to south through north-central portions
of the forecast area. Dynamically, this will occur along a low-
level trough axis (in the 900-700 hPa layer) where northeasterly
winds in response to the developing coastal low offshore
converge with northwesterly winds advancing beneath the upper
trough. Model guidance is in very good agreement that such a
feature will occur, but there is still some uncertainty with
respect to the positioning. Such features typically are very,
very narrow in width (likely only 10-20 miles from west to
east), and are notorious for producing very heavy snowfall
rates. Most guidance shows hourly QPF values of around 0.1-0.2
inches, which would translate to 1-2 inches per hour of snow.
This feature will likely be either stationary or very slow
moving over several hours tomorrow evening into early tomorrow
night. A narrow band of 6-12 inches could occur as a result. Due
to position uncertainty, we spread this enhancement in
precipitation out over a slightly wider location than will
likely occur in reality. American model guidance (GFS, NAM,
HRRR, 3 km NAM, WRF-ARW, FV3, WRF-NSSL) have this feature
occurring roughly from Hancock, MD southward through Winchester
toward Front Royal, while most other guidance (Euro, Canadian,
ICON, most EPS members) have it occurring from near Hagerstown
southward into Loudoun County. Our current forecast hedges the
placement slightly more toward the eastern solution (Hagerstown
to Loudoun County), but has an enhancement over that broader
region. This is also why the Winter Storm Warning extends
southward and wraps around the DC Metro area.
The immediate DC Metro will likely fall within a relative min
between these two areas of precipitation enhancement, but will
still experience several hours of accumulating snow tomorrow
evening into tomorrow night. Another localized minimum will be
between the inverted trough and the Allegheny Front. Very little
in the way of snow may end up falling in the shadow of the
mountains just to the east of the Allegheny Front and also in
the Central Shenandoah Valley.
Across the entire forecast area, snow totals will be heavily
elevation and snow rate dependent. With such marginal
temperatures in place, a lot of the snow will be lost to melting
at lower elevations with surface temperatures above freezing,
while higher elevations have lower temperatures and accumulate
more efficiently. The aforementioned heavier snowfall rate areas
(closer to the low and near the inverted trough) will help to
drive dynamic cooling through strong lifting in the column,
thereby bringing cooler temperatures down to lower elevations,
and making snowfall accumulate more efficiently.
In terms of specific accumulation amounts, a general 2-4 inches
is expected in the DC Metro, although there could be locally
lower totals at the lowest elevations if warmer temperatures
and lighter precipitation rates verify. 4-6 inches is expected
along the Bay shore from St. Mary`s northward through Baltimore
City, with higher totals of 6-12" from Carroll eastward toward
Cecil. Higher totals of 8-16 inches are expected in the
Catoctins, where snow will accumulate more efficiently
throughout the event. Snow will also accumulate efficiently
southward along the Blue Ridge, where a general 6-10 inches of
snow is expected. To the west of the Blue Ridge, snow totals
will be heavily elevation dependent, with 3-6 inches expected at
higher elevations between the Allegheny Front and Blue Ridge,
while lower elevations in the Central Shenandoah Valley and
Potomac Highlands see little in the way of accumulation. A
general 1-3 inches is expected at lower elevations along the
I-70 corridor to the west of the Blue Ridge, with the exception
of near Hagerstown, where they could receive significantly more
snow under the inverted trough. For now, that inverted trough
area which extends southward from near Hagerstown into Frederick
and Loudoun is forecast to receive around 3-6", but as
mentioned before, the gradient will likely be tighter than
depicted, and the max there will likely be between 6 and 12
inches. In the Alleghenies Winter Storm Warnings are in effect.
Snow will linger much longer there through the day Monday within
upslope flow behind the departing low. Snowfall accumulations
there are expected to reach 6-12 inches by Monday evening.
Elsewhere, snow should wind down late tomorrow night through
mid-morning Monday. For more details on the storm, including
exact placement of Winter Weather Advisories and Winter Storm
Warnings, see www.weather.gov/lwx/winter.
KEY MESSAGE 2..Multiple fronts will cross the area mid to late next
week amidst a general warming trend.
Temperatures will remain below normal Tuesday and Tuesday night
amidst broad troughing in the eastern US. A clipper type system will
move into the Great Lakes Tuesday night into Wednesday morning. The
warm advection portion of this system could bring some snow to the
Allegheny Mountains. Some guidance has a little precipitation
spilling to the east across northern portions of the area, but this
is more uncertain. Southerly flow behind the warm front will usher
in warmer conditions for Wednesday and Thursday. Model spread
increases during this time with respect to forcing features, but
eventually a cold front may reach the area Thursday or Friday. Any
precipitation with this front would likely be rain, although there
are some solutions that push the front through earlier with a second
wave of low pressure potentially bringing wintry weather to the
Alleghenies. In the end, cold advection won`t be too strong with
this front, and near to above normal temperatures will likely end
the week
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR conditions and light east to northeasterly winds are
expected through the first half of tonight. Thereafter, ceilings
will begin to lower and precipitation will move into the area
from west to east. Ceilings will likely drop to IFR by mid-
morning on Sunday, and then remain IFR or lower through the
first half of Sunday night. Gradual improvement to MVFR and then
VFR is expected through the day Monday. Precipitation likely
starts off at all terminals as light rain late tonight. Snow
will start mixing in from north to south through the day Sunday,
although accumulations will likely be minimal through mid
afternoon. Precipitation type should switch over to all snow
later Sunday afternoon, with the bulk of the accumulating snow
occurring Sunday evening through Sunday night. CHO will likely
have the least impacts from snow. LIFR to VLIFR visby will be
possible at times in snow bands Sunday evening through the first
half of Sunday night, but have broadbrushed the TAF for now due
to lack of confidence in mesoscale features. Snow will taper off
Monday, although it is somewhat uncertain how quickly it moves
out of the metro terminals. Winds will also pick up out of the
north to northwest Sunday night, and remain gusty out of the
northwest on Monday. Gusts to around 30-35 knots appear likely
within northwesterly flow during the day Monday.
Northwest wind gusts in excess of 20 kt will likely continue into
Tuesday. A warm front may bring sub-VFR ceilings and low
precipitation chances Wednesday.
&&
.MARINE...
Sub-SCA level winds are expected over the waters through Sunday
morning. Winds start to increase gradually starting Sunday
afternoon, reaching SCA levels within northerly flow. Winds will
then increase to Gale level to the south of the Bay Bridge on
the Bay and across the Lower Tidal Potomac Sunday night within
north to northwesterly flow as low pressure strengthens
offshore. Gale Warnings are in effect for all waters within
northwesterly flow on Monday as low pressure tracks off to our
north and east. SCA conditions likely linger within
northwesterly flow through Tuesday.
Winds will be lighter Tuesday night, shifting to the south.
Southerly winds will increase Wednesday, potentially nearing
advisory criteria later in the day.
&&
.TIDES/COASTAL FLOODING...
As strong low pressure moves off the coast, northwesterly gales
will cause a sharp drop in water levels Monday. Some locations
could approach low water thresholds, although the latest
forecast is not quite that low.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Winter Weather Advisory from 5 PM Sunday to 10 AM EST Monday
for DCZ001.
MD...Winter Storm Warning from 3 PM Sunday to 10 AM EST Monday for
MDZ003>006-008-011-014-017-018-503-505>508.
Small Craft Advisory from 6 PM Sunday to 6 AM EST Monday for
MDZ008.
Gale Warning from 6 AM to 6 PM EST Monday for MDZ008.
Winter Weather Advisory from 5 PM Sunday to 10 AM EST Monday
for MDZ013-016-504.
Winter Weather Advisory from 4 AM Sunday to 6 PM EST Monday
for MDZ501.
Winter Weather Advisory from 10 AM Sunday to 7 AM EST Monday
for MDZ502.
Winter Storm Warning from 1 AM Sunday to midnight EST Monday
night for MDZ509-510.
VA...Winter Storm Warning from 3 PM Sunday to 10 AM EST Monday for
VAZ031-505-506.
Winter Weather Advisory from 5 PM Sunday to 10 AM EST Monday
for VAZ053-054-501-526-527.
Winter Weather Advisory from 10 AM Sunday to 7 AM EST Monday
for VAZ027>030.
Winter Storm Warning from 1 AM Sunday to midnight EST Monday
night for VAZ503.
Winter Weather Advisory from 6 PM Sunday to 10 AM EST Monday
for VAZ040-051-055>057-502.
Winter Storm Warning from 6 AM Sunday to 7 AM EST Monday for
VAZ507-508.
WV...Winter Storm Warning from 3 PM Sunday to 10 AM EST Monday for
WVZ051>053.
Winter Weather Advisory from 4 AM Sunday to 6 PM EST Monday
for WVZ503.
Winter Weather Advisory from 10 AM Sunday to 7 AM EST Monday
for WVZ050-055.
Winter Storm Warning from 1 AM Sunday to midnight EST Monday
night for WVZ501-505.
MARINE...Winter Storm Warning from 3 PM Sunday to 10 AM EST Monday for
ANZ530.
Small Craft Advisory from 6 PM Sunday to 6 AM EST Monday for
ANZ530-531-535-536-538-539.
Gale Warning from 6 AM to 6 PM EST Monday for ANZ530-531-535-
536-538-539.
Gale Warning from 6 PM Sunday to 6 PM EST Monday for
ANZ532>534-537-540>543.
Small Craft Advisory from 10 AM to 6 PM EST Sunday for ANZ533-
534-537-541-543.
&&
$$
DISCUSSION...ADS/KJP/EST
AVIATION...ADS/KJP
MARINE...ADS/KJP
NWS LWX Office Area Forecast Discussion