Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 301959
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
259 PM EST Mon Jan 30 2023

.SYNOPSIS...
A cold front will pass through from the northwest through Tuesday
morning. Multiple waves of low pressure will impact parts of the
area through Tuesday night. High pressure returns on Wednesday
before a strong cold front passes through Thursday night and build
in well below normal temperatures for Friday and into the weekend
with high pressure nearby.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Cold front is situated off to the west of the area early this
afternoon. High clouds have mostly dissipated east of the Blue
Ridge and allowed for increased sunshine for the time-being.
This has allowed for temperatures to increase into the upper 50s
to even localized low 60s across portions of central/northern
VA. The front will slowly track further east this evening and
into tonight. Some light rain showers are possible east of the
Blue Ridge, especially across portions of central/north-east MD.
Thermal gradients may allow for a brief rain/snow mix for areas
right along the Mason-Dixon where temperatures may be favorable
for a short period of time overnight.

The Allegheny Front will likely see some light wintry precipitation
through tonight. Sounding profiles and latest CAMs/global guidance
suggests that there may be a light ice accretion possible right
along the Allegheny Front. As confidence increased over the
last 6-8 hours, a Winter Weather Advisory was hoisted for
Garrett County, MD as well as Grant and Pendleton counties in
West Virginia for the potential for a light glaze of ice. Timing
wise, precipitation should begin to funnel down into Garrett
County, MD between 7 and 9 PM tonight and slowly move south into
the 2 remaining western zones a few hours later. Given this, do
expect some localized slick spots for the Tuesday morning
commute across those areas.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
As the front continues to slowly sag south, low pressures along the
front will allow for increased moisture availability, particularly
across the southern half of the area (central VA/southern MD). With
high pressure pushing down from the north allowing colder air to
build in, there may be enough cold air to allow for a rain/snow mix
across much of the forecast area. Confidence remains higher for
general precipitation chances further south, closer to the frontal
boundary. Most areas aside from the mountains are not expected to
see any accumulation during the day on Tuesday in terms of wintry
precipitation. QPF of a few hundredths of an inch are expected for
areas along and south of I-66. For the central/northern Blue Ridge
zones as well as some higher elevations further west will see
another opportunity for a light glaze of ice accumulation beginning
Tuesday afternoon and continuing into the overnight hours before
dissipating. Confidence at this point is not high enough to hoist an
advisory just yet but additional headlines may need to be addressed
leading up to the event.

With cold temperatures in place Tuesday night into Wednesday coupled
with increased moisture availability, there will be an opportunity
for widespread snow to rain/snow mix across the area. Overall
accumulations are expected to be generally less than one-half inch
out west and just a few hundredths further east if possible. Most
snow accumulation will be on grassy surfaces. As the Arctic front
passes further to the south, precipitation chances decrease by
daybreak on Wednesday. High pressure builds in during the day on
Wednesday and into Wednesday night with only a few showers possible
across central VA where the frontal disturbance will continue to
linger briefly.

A much colder airmass is expected Tuesday and Wednesday, with highs
only reaching the 30s and 40s (20s/30s for the mountains) for
most.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
On Thursday, a deep upper trough is expected to descend into the
Northeast, with a souther stream upper low near the southern Plains
progressing east and degrading the subtropical high over the
Caribbean.

Surface ridging will accompany the deep upper trough moving into the
area, bringing in a bitter cold Arctic air mass. This should also
limit precipitation in the area from the system to the south, with
mostly dry conditions expected outside of southern parts of the
area.

The most impactful aspect of the extended period will be the cold
temperatures and wind chills, with Friday night into Saturday
morning being the coldest. The mountains can expect the coldest
daytime temperatures Friday (teens into 20s), while outside of the
mountains daytime temperatures will be coldest Saturday (highs in
20s to 30s). Friday night/Saturday morning, low temperatures will be
in the teens for most of the area and single digits in the mountains
and along the MD-PA border. Strong winds will bring the apparent
temperature down even further, into the negatives in the mountains
and around 0 elsewhere.

By Sunday, an upper trough is expected to move into the Ohio River
Valley from the Plains, returning the area to near normal
temperatures and bringing the next chance of precipitation.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
VFR conditions likely for the remainder of today. A
cold front will impact the terminals later tonight and into Tuesday
morning. Brief gusty northwest winds will follow along and just
behind the front Tuesday morning, with gusts 15 to 20 knots
possible. MVFR ceilings will be possible overnight and into Tuesday
with the possibility of a rain/snow mix across most of the
terminals. Confidence in precipitation is higher across the southern
terminals for Tuesday into Tuesday night(CHO/IAD/DCA). High pressure
returns Wednesday into Wednesday night.

VFR conditions are expected Thursday and Friday with high pressure
building into the region from the north. Winds initially out of the
south on Thursday shift northwesterly and increase to 10-15 kts
(gusts 20-25 kts) on Friday.

&&

.MARINE...
Sub-SCA winds expected the remainder of today. A cold front will
cross the waters late tonight and into Tuesday morning which will
bring brief gusty northwest winds of 15 to 20 knots. An SCA has been
hoisted to account for this 3 to 5 hour window for increased winds
through the late morning hours.

Winds should remain lighter Wednesday into Wednesday night as high
pressure influences the area.

SCAs will likely be needed late Thursday night through Friday with
strong winds out of the N/NW. Gales cannot be ruled out at this
time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Winter Weather Advisory from 7 PM this evening to 7 AM EST
     Tuesday for MDZ001.
VA...None.
WV...Winter Weather Advisory from 10 PM this evening to 7 AM EST
     Tuesday for WVZ501-505.
MARINE...Small Craft Advisory from 3 AM to noon EST Tuesday for
     ANZ530>532-535-538>540.
     Small Craft Advisory from 6 AM to noon EST Tuesday for ANZ533-
     534-536-537-541>543.

&&

$$
SYNOPSIS...ADM
NEAR TERM...ADM
SHORT TERM...ADM
LONG TERM...CAS
AVIATION...ADM/CAS
MARINE...ADM/CAS


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