Snow Squall Warning 2, NWS Baltimore/Washington

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
338 AM EST Wed Jan 8 2020

.SYNOPSIS...

A cold front approaching from the Great Lakes will move
southeastward across the Mid-Atlantic today. High pressure will
follow Thursday and Thursday night, before a frontal system
slowly approaches from the central United States late this week
into this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...

Clouds will be on the increase this morning in advance of a
shortwave-trough dropping southeast from the eastern Great Lks.
Sct-nmrs snow showers are expected now through late morning
ahead of trof axis and associated cold frontal passage generally
north of I-70 and west of Route 15 south to Big Meadows. Snow
squall parameter is showing some decent CAPE values along the
Mason Dixon line, so some brief intense squalls are possible
and Snow Squall Warnings may be required for some areas later
this morning. The other concern is the strengthening winds in
the tightening gradient and subsidence behind shortwave-trof
axis late this morning into mid afternoon hours. 850-mb winds
are around 40 kt today with the best mixing in the 16Z-22Z time
frame. Have issued a Wind Advisory for much of the area today.

Clear and very cold tonight as winds diminish as strong 1040 mb sfc
high pressure builds in.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...

Chilly on Thu with sfc high overhead and increasing high clouds.
Fair weather Thu-Thu night under influence of sfc high and
building ridge. Warming trend begins Fri as winds turn southerly
as sfc high moves offshore. Rain chances begin to increase late
Fri-Fri night as warm advection pattern strengthens well ahead
of a slow moving frontal zone.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...

A strong upper level trough will dig down into the Texas and the
southeastern US on Saturday. A surface allow associated with the
upper level trough will move through the midwestern US. The warm
front associated with the surface low will move to our north early
on Saturday. As the warm front moves to our north, our region will
move into the warm sector ahead of the surface low and cold front.
Strong warm air advection will leading rising temperatures up into
the mid to upper 60s with some area potentially reaching the 70s.
The upper level low will tap into the Gulf of Stream leading to
increasing moisture into our region. The combination of increasing
temps and moisture will lead to the threat for convective showers
ahead of the stratiform rain associated with the cold frontal
passage on Saturday.

The cold front is currently forecast to move through our region late
Saturday through Sunday afternoon. There remains some uncertainty on
the exact timing of the frontal passage with the GFS being about 6
hours quicker than the Euro model. A lot of moisture is associated
with this frontal passage which suggest that this could be a large
rain producer capable of dropping locally heavy rain. We will need
to continue to monitor the trend of the front and upper level setup
to determine exact timing and magnitude of the rain. Since
temperatures will hover in the 60s, there will be no threat for snow
with this system.

The cold front will fully move through our region by Sunday evening
and is forecast to stall to the south of our region. The question is
how far does the front go before it stalls and whether we will
experience any precipitation from this boundary. Some models have
continue chances for precipitation through Tuesday. A weak upper
level low is forecast to move to our north Tuesday into Wednesday
next week. As the upper level disturbance moves through, the
boundary that remains to our south is forecast to shift northeastward
over the Atlantic Ocean. This shift could lead to further showers
over our region late Tuesday into early Wednesday. A lot of
uncertainty remains for the system next week. Overall it will be a
continued pattern for unsettled weather and mild temperatures.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...

Gusty NW winds up to 40 kt the main concern today mainly in the
16Z-22Z time frame. Winds diminish quickly early this evening.

A cold front will lead to the potential for MVFR conditions during
the day with MVFR conditions likely Saturday evening and into
Sunday. IFR/LIFR conditions will be possible during periods of
moderate to heavy rain Saturday evening into early Sunday. The
system is expected to exit our region Sunday afternoon with VFR
conditions returning Sunday afternoon and evening.

&&

.MARINE...

Gale Warning today 13Z-23Z with SCA conditions lingering through
tonight. Light winds Thu-Thu night before winds strengthen again
Friday into the weekend.

A strong cold front will move through the waters late Saturday and
into Sunday. Strong winds associated with this boundary will be
possible over the waters Saturday afternoon through Sunday morning.
Small Craft Advisories are likely Saturday into Sunday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Wind Advisory from 11 AM this morning to 5 PM EST this
     afternoon for DCZ001.
MD...Wind Advisory from 8 AM this morning to 5 PM EST this
     afternoon for MDZ003-501-502.
     Wind Advisory from 11 AM this morning to 5 PM EST this
     afternoon for MDZ004>006-011-013-014-503>508.
VA...Wind Advisory from 8 AM this morning to 5 PM EST this
     afternoon for VAZ025>031-503-504-507-508.
     Wind Advisory from 11 AM this morning to 5 PM EST this
     afternoon for VAZ040-052>054-501-505-506.
WV...Wind Advisory from 8 AM this morning to 5 PM EST this
     afternoon for WVZ050>053-055-501>506.
MARINE...Small Craft Advisory until 9 AM EST this morning for
     ANZ532>534-537-540>543.
     Gale Warning from 9 AM this morning to 6 PM EST this evening
     for ANZ530>543.

&&

SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...JMG
AVIATION...LFR/JMG
MARINE...LFR/JMG

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