Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 260218 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
918 PM EST Fri Nov 25 2016

.SYNOPSIS...
Low pressure will track across Virginia tonight and move out to
sea early Saturday. High pressure builds over the region for the
weekend into early next week before another storm system
approaches for the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

Objective analysis reveals surface low to our south over VA
moving offshore...while expansive high pressure from the midwest
into the middle CONUS is shifting eastward into the area. As this
occurs...increasing pressure gradient will led to breezy NW winds,
with gusts 15-20 mph possible after midnight. Otherwise...quiet
weather east of the Allegheny Front.

Upslope component through a shallow moist layer could lead to
some light drizzle across the western slopes of the Allegheny
Front. This would turn to freezing drizzle as temperatures
throughout the column fall into the U20s/L30s overnight. Depth of
moist layer will be important in determining hydrometeor type...as
some IP/needles/graupel are also possible if depth of low-level
moisture is greater than forecast. Road temperatures are currently
in the U30s/L40s across the area and will take some time to cool
overnight...which would help limit any accretion from freezing
drizzle on road surfaces. Overall...QPF is expected to be very
light...with less than a hundredth of an inch anticipated
overnight.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
A shortwave trough will cross the region Saturday morning and any
freezing drizzle will likely transition to snow showers Saturday
morning. Little to no accumulation is expected. NW winds will
increase Saturday and 10-15 mph with gusts up to 25 mph.
Temperatures will range from the 40s north-west of the metros and
50s elsewhere. Snow showers will taper off by Saturday evening.

High pressure continues to move eastward and northwest winds will
continue Saturday night through Sunday. High pressure moves
overhead Sunday night and temperatures will drop into the 20s/L30s
Sunday night.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
High pressure along the East Coast will move offshore Monday. Also,
a strong storm system over the Upper Midwest U.S. will strengthen.
The difference in pressure between the high and the storm system
will provide an increased southerly flow late Monday through
Tuesday.

There is a chance for a few rain showers along a warm front
Monday night. The likelihood of rain showers will become imminent
Tuesday as a cold front approaches the region.

There could be brief break in the rainfall activity Tuesday night
into Wednesday morning as a weak area of high pressure slides east
across the Mason-Dixon Line.

A second storm system could develop over the Southern Appalachians
along the first storm`s slow-moving cold front Wednesday morning.
This next storm system could ride northeast along the eastern slopes
of the Appalachian Mountains. Additional rain showers may develop
and overspread the region through the day Wednesday into Wednesday
evening.

High pressure could build in behind the departing storm system
and bring drier and cooler air into the region late Wednesday
night into Thursday.

An upper level trough of low pressure is expected to sag southward
into the region from the Eastern Great Lakes Thursday night. There
may not be a lot of moisture available to fuel any showers with the
trough. Additional cloud cover may be the only story here.

High pressure is expected to build in behind the trough of low
pressure Friday.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions expected through the TAF period. Pressure gradient
increases overnight as high pressure gradually shifts into the
area, bringing an onset of northwesterly winds. NW winds will
continue through Sunday, with the strongest period during the
day Saturday (G20-25 kt). Any clouds should be VFR.

VFR conditions expected Monday. Mvfr conditions possible at any
one of the terminals with a few rain showers in the area. Winds
southeast around 5 knots Monday. Winds southeast 5 to 10 knots
Monday night.

&&

.MARINE...

Pressure gradient increases after midnight as high pressure
gradually works its way into the area...with increasing NW flow.
Guidance continues to indicate that current SCA headlines are in
good shape...with winds increasing to near SCA by 6z for the main
portion of the Chesapeake Bay...and shortly afterwords for upper
portions of Potomac and bay inlets. Winds peak during the day
Saturday...with SCA conditions continuing. SCA headline continues
Saturday night for all but the upper Potomac...though winds may
lessen some. Winds become light by Sunday night as high pressure
builds overhead.

No marine hazards expected Monday and Monday night. Winds
southeast 5 to 10 knots Monday. Winds southeast 10 to 15 knots
Monday night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 1 AM Saturday to 6 AM EST Sunday for
     ANZ530>534-537>543.
     Small Craft Advisory from 1 AM to 6 PM EST Saturday for ANZ535-
     536.

&&

$$
SYNOPSIS...HSK/MSE
NEAR TERM...HSK/MSE
SHORT TERM...HSK
LONG TERM...KLW
AVIATION...HSK/MSE/KLW
MARINE...HSK/MSE/KLW



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