Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 230856
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
356 AM EST Thu Nov 23 2017

.SYNOPSIS...
High pressure will build over the area through Friday. Another
cold front will approach overnight Friday into Saturday before
passing through Saturday night. High pressure returns for Sunday
and Monday before moving offshore Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Temperatures around the region at 08Z were generally in the
mid-to-upper 20s in well mixed boundary layer, except those
areas directly adjacent to tidal Potomac and western shore of
Chesapeake Bay. NW winds have diminished over the land areas but
still gusting up to 20kts on the water. Satellite shows high
clouds across southern Maryland, and all other areas clear.

Today winds will become light as high pressure maintains across
the region. The area will be under the influence this afternoon
by the entrance region of an upper level jet as evidenced by the
00Z GFS H4 wind speed. This feature, coupled with mid-level
moisture advection will develop a scattered mid cloud deck that
will traverse west-to-east across the CWA, primarly north of
Interstate 66/US Route 50 from late this afternoon through
midnight tonight.

Temps for this period will be generally 5-10 degrees below
normal, but dewpoints tonight will be about 10 degrees warmer
than current, taking away some of the crispness of the air.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Friday and Friday night will have seasonable fair weather under
the continued influence of high pressure, with very light
winds.

Saturday will start out with partly sunny skies, but quickly
become overcast as cold front moves through the region,
bringing chance of rain showers, with diminshing chances the
further east as deep westerly winds will promote downsloping
and associated drying. Most likely scenario brings scattered
showers Shenandoah Valley and points west, with sprinkles at
higher elevations along the Blue Ridge, and mid-deck along and
east of Interstate 95. Cold air advection with strong winds
behind the front for Saturday night, with snow showers
developing in favored upslope regions.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
High pressure will build overhead Sunday through
Monday...bringing dry and seasonably chilly conditions. The high
will move offshore Tuesday and a southwest flow around the
departing high will usher in milder conditions...and it will
remain dry.

A cold front will approach the area Tuesday night and it may
pass through Wednesday or Thursday. Confidence in how far south
the front makes it is low at this time due to divergence in the
long range guidance. Leaned toward the SuperBlend for
temperature forecasts during this time...which keeps temps near
or above climo. This makes sense this far out since there will
be an anomalous subtropical ridge over the southeastern
CONUS...and this would favor the front being slower and weaker.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR for all terminals through 36 hours. Gusty winds develop
Saturday night behind cold front.

VFR conditions are expected Sunday through Tuesday as high
pressure controls the weather pattern.

&&

.MARINE...
At 08Z, winds continue to gust to SCA criteria on Chesapeake
south of Annapolis. Winds will continue to blow at small craft
threshold through mid-morning Thanksgiving in big water
Chesapeake Bay from Smith Pt to Drum Pt and Tangier Sound. Small
Craft is expected to return Saturday night and continue through
Sunday.

High pressure will build overhead Sunday through Monday. A Small
Craft Advisory may be needed for portions of the waters Sunday
ahead of the building high.

&&

.COASTAL FLOOD...
Used a 50-50 blend of ESTOFS/ETSS for total water level grids.
No evidence of coastal flood advisory through 96 hours.

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EST early this morning for
     ANZ531>533-537-539>541.
     Small Craft Advisory until 10 AM EST this morning for ANZ534-
     543.

&&

$$

SYNOPSIS...BJL
NEAR TERM...Lee
SHORT TERM...Lee
LONG TERM...BJL
AVIATION...BJL/Lee
MARINE...BJL/Lee
COASTAL FLOOD...Lee


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