956
FXUS61 KLWX 220215
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
915 PM EST Thu Nov 21 2024

.SYNOPSIS...
Low pressure will loop counterclockwise over the northern Mid-
Atlantic through Friday night, then depart toward New England and
the Canadian Maritimes this weekend. High pressure will briefly
build across the area late in the weekend, then another frontal
system will likely approach early next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Snow showers/squalls along and west of the Allegheny Front will
continue overnight. The frequency will decrease later tonight
toward sunrise Friday. Snowfall totals will be between 2 and 4
inches with locally higher amounts on the western facing slopes
above 2500 feet. Winter Storm Warnings remain in effect across
the Allegheny Front, with Winter Weather Advisories for western
Mineral/extreme western Allegany. Overnight lows will be in the
20s west of the Blue Ridge with 30s further east.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Winter Storm Warnings continue for the western slopes of the
Alleghenies through Friday night. Winter Weather Advisories get
reissued for western Allegany County and western Mineral County
Friday into Friday evening.

Previous discussion...
Upper-level low pressure will rotate counterclockwise just to
the north of the area Friday morning before drifting toward the
New England coast late Friday into Saturday. Multiple pieces of
shortwave energy will pivot around the upper-level low Friday
morning into Friday afternoon and again Friday night into
Saturday. Each piece of shortwave energy will supply a
reinforcing shot of wind, cold temperatures, and enhanced
upslope mountain snow.

The steadiest and heaviest upslope mountain snow shower activity
looks to occur late Friday morning through Friday evening. This
is when the strongest piece of shortwave energy pivots through
as the cutoff upper low progresses north and east toward New
England. Latest deterministic and ensemble guidance continues
to hint at snowfall rates of 1-2"/hr with persistent
banding/squalls working over the warning areas.

Storm total snow of 6-12 inches with localized amounts of 1 to 2
feet along western facing slopes above 2500 feet are expected
along and west of the Allegheny Front, with 3 to 6 inches for
elevations above 1500 feet just east of the Alleghenies in
western MD down into western Mineral County WV.

Outside of the significant snow accumulation, blowing and
drifting will become a problem. This is due largely in part to
increasing winds Friday afternoon into Saturday as the shortwave
disturbance lifts out of the region. Gusts will be close to
Wind Advisory criteria (up to 50 mph) along the higher ridges
with 30 to 40 mph gusts down below. This will yield wind chills
in the teens and 20s on both Friday and Saturday across the
higher elevations.

Areas further east will likely experience a band of rain/snow
showers, especially near/east of I-81 and near/north of
I-66/US-50. Across the Catoctins and perhaps Parr`s Ridge over
north-central MD, as much as 3 inches of snow is possible
Friday as the deformation axis wrapping around the low pivots
overhead. Most other locations across a large chunk of central
Maryland into Northeast Maryland near the Mason-Dixon line will
receive a coating to as much as 2 inches.

Snow shower activity will begin to decrease Saturday morning into
Saturday midday as the shortwave trough kicks east and the upper
level low exits off coastal New England. A period of freezing
rain or drizzle is possible Friday night into Saturday morning
along the higher elevations of the Allegheny Front as deeper
moisture vacates halting ice crystal formation. By Saturday
afternoon, the shortwave will pivot east and heights begin to
rise. This will result in pretty rapid drying out across the
mountains into the afternoon/evening. Elsewhere, Saturday
remains dry with gusty northwesterly winds of around 25 to 35
mph, with gusts up to 40 mph, mainly on the ridges and over the
open waters.

High temperatures will range from below freezing over the mountains
to mid to upper 40s and low 50s further east Friday. Lows Friday
night into Saturday morning will fall into the 30s and 40s. By
Saturday, temperatures warm back above freezing in the mountains
with upper 40s and low to mid 50s further east toward the metros.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Sunday into Monday look to remain mostly dry as high pressure
returns to the region. Sunday will see highs around the mid 50s,
then increasing to around the low 60s on Monday.

Meanwhile, low pressure over the central U.S. will track north
and east into the Great Lakes late Monday into Tuesday. This may
bring some showers to the region during this time along with a
cool down into Wednesday as high pressure builds to our north.
High temperatures on Tuesday reach the mid to upper 50s, while
highs drop into the 40s by Wednesday.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected at most terminals through Saturday.
Some brief periods of MVFR are possible Friday into Friday
night as a potent piece of upper-level energy pivots through. A
few mixed rain/snow/graupel showers may be possible at times,
but the vast majority of the time should remain dry. Friday
brings a slightly higher chance of precipitation for the
terminals north of KCHO.

Wind will likely be the biggest impact to aviation later
overnight through Saturday. Expect sustained speeds of 10-20
kts with gusts 20 to 30 knots Friday and Saturday. Highest
winds look to occur late Friday into early Saturday.

Gusty W/NW winds around 15 to 20 kts will be the main threat to
the terminals on Sunday. VFR conditions are expected. Winds on
Monday will taper off and turn southerly around 6 to 12 kts. VFR
conditions will continue.

&&

.MARINE...
High end SCAs are likely to continue through Saturday night
with frequent gusts of 20 to 30 kts expected across all waters.
Gale-force gusts are possible over the open waters of the
Chesapeake Bay and lower tidal Potomac River late Friday into
early Saturday as winds surge behind a departing shortwave
trough.

Gusty winds out of the W/NW will continue into Sunday in the
wake of the frontal passage, with SCAs likely to continue for
much of the waters. Winds then turn out of the south on Monday
as high pressure moves quickly offshore. Winds may channel up
the Chesapeake Bay and result in continued SCAs over the wider
waters.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 7 AM EST Saturday for MDZ008.
     Winter Storm Warning until midnight EST Friday night for
     MDZ001.
     Winter Weather Advisory until 10 PM EST this evening for
     MDZ501.
     Winter Weather Advisory from 6 AM to 6 PM EST Friday for
     MDZ501.
VA...Winter Storm Warning until 6 AM EST Saturday for VAZ503.
     Wind Advisory from noon Friday to 6 AM EST Saturday for VAZ503-
     504-507-508.
WV...Winter Weather Advisory until 10 PM EST this evening for
     WVZ503.
     Winter Weather Advisory from 6 AM to 6 PM EST Friday for
     WVZ503.
     Winter Storm Warning until 6 AM EST Saturday for WVZ501-505.
     Wind Advisory from noon Friday to 6 AM EST Saturday for WVZ505-
     506.
MARINE...Small Craft Advisory until 7 AM EST Saturday for ANZ530-535-
     536-538.
     Small Craft Advisory until 4 PM EST Friday for ANZ531>534-537-
     539>543.
     Gale Warning from 4 PM Friday to 7 AM EST Saturday for
     ANZ531>534-537-539>543.

&&

$$

SYNOPSIS...DHOF
NEAR TERM...KLW/DHOF
SHORT TERM...DHOF
LONG TERM...CJL
AVIATION...KLW/DHOF/CJL
MARINE...KLW/DHOF/CJL