Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191843

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
243 PM EDT Thu Apr 19 2018

An unseasonably strong area of high pressure will migrate across
the Great Lakes and into the northeastern U.S. Friday into the
weekend, then move offshore early next week as low pressure
approaches from the lower Mississippi River valley.


A surface cold front has passed east of the area. Gusty west to
northwest winds are being observed in its wake, with snow
showers west of the Allegheny Front. Snow showers are forecast
to linger into the overnight hours with accumulation totals of a
coating to an inch expected over the highlands.

A Freeze Warning has been issued for much of the area between
I-95 and I-81. Winds likely stay up for most areas tonight (10
knots or so), but 925 mb temperatures drop to -3 to -5 C which
should correspond to surface temperatures at or a little below
freezing at the surface.


Canadian high pressure will build north of our area from the
Great Lakes on Friday. Sunny and breezy conditions are expected
with wind gusts generally in the 20 to 30 mph range. Winds will
diminish in the evening as high pressure moves closer and the
gradient relaxes.

Light winds and clear to mostly clear conditions are expected Friday
night. May need to watch temperatures again for possible
freezing conditions, mainly over the Shenandoah Valley and
northern Maryland.

Pleasant but somewhat cooler than normal conditions are expected
Saturday into Saturday night as the high slowly moves by to the
north of the area.


High pressure centered over the eastern Great Lakes/Northeast
will continue to dominate our weather on Sunday bringing dry
conditions and slightly below normal temperatures to the region.

By Sunday Night, models have a cutoff upper-level low and associated
surface low tracking through the Deep South. Deterministic models
diverge significantly with the handling of this system. The
deterministic GFS moves this system up the east coast and into our
CWA by Monday Night. The GEFS support the operational GFS solution,
suggesting that a period of rainfall may be possible Monday Night
through Tuesday with this system. This differs significantly from
the 00z Euro, which keeps the system stalled out to our south until
Wednesday, when it is picked up by a trough approaching from the
Midwest. The 00z European ensembles showed a wide range of
solutions, suggesting that uncertainty is high with this event.

Generally speaking, Monday appears to be mostly dry and an unsettled
period of weather will be likely sometime in the Tuesday through
Wednesday period. However, exact timing and details remain up in
the air. Regardless of what happens with the upper-level cutoff,
it appears as though some precipitation will be possible on
Wednesday as an upper-level trough swings in from the Midwest.


VFR through Saturday. Likely SKC after midnight tonight as high
pressure builds to the north from the Great Lakes. Gusty NW flow
(20 G 35) will persist into early this evening, then gradually
diminish tonight through Friday, then light N Saturday.

VFR conditions are expected for the weekend into Monday. Sub-
VFR conditions are possible Monday Night through Wednesday as
an area of low pressure approaches the region from the south.


A Gale Warning is currently in effect into this evening. A Small
Craft Advisory follows into Friday. Winds are expected to fall
below Small Craft Advisory criteria Friday night and remain
light through the weekend.

Sub SCA conditions are forecast to persist into early next week
as a ridge of high pressure should keep winds light.


MD...Wind Advisory until 6 PM EDT this evening for MDZ501.
     Freeze Warning from 2 AM to 9 AM EDT Friday for MDZ003>006-
VA...Wind Advisory until 6 PM EDT this evening for VAZ503-504-507-
     Freeze Warning from 2 AM to 9 AM EDT Friday for VAZ025>031-
WV...Wind Advisory until 6 PM EDT this evening for WVZ501-503-505-
     Freeze Warning from 2 AM to 9 AM EDT Friday for WVZ051>053.
MARINE...Small Craft Advisory from 11 PM this evening to 6 PM EDT
     Friday for ANZ530>533-537-539>541.
     Gale Warning until 11 PM EDT this evening for ANZ530>533-537-
     Small Craft Advisory from 8 PM this evening to 6 PM EDT Friday
     for ANZ535-536-538-542.
     Gale Warning until 8 PM EDT this evening for ANZ535-536-538-
     Small Craft Advisory from 6 AM to 6 PM EDT Friday for ANZ534-
     Gale Warning until 6 AM EDT Friday for ANZ534-543.


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