Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 131906

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
306 PM EDT Tue Mar 13 2018

Intense low pressure east of Cape Cod will move northeastward
in to the Canadian Maritimes tonight. High pressure will build
southward into the central U.S. through Wednesday and move over
the southeastern U.S. on Thursday. A weak cold front will sweep
through the area Thursday with Canadian high pressure building
over the region through the first half of the weekend.


Unseasonably chilly temperatures and blustry northwesterly
winds gusting to 35 mph along with upslope snow in the western
mountains are the main weather factors elements that are
impacting are region this afternoon. Cyclonic flow aloft around
the associated upper level low over PA-NY tonight will continue
to keep winds gusty most of the night.

12Z models including the HREFv2, along with satellite data,
show an upper level vort will dive down from the Great Lakes
into the Tennessee Valley overnight. The best potential for
upslope snow continues to be focused tonight mainly on where we
have the advisory up for western Pendleton- Grant and Mineral
counties. So far this afternoon, our COOP observer in Bayard had
only picked up 1.5" of upslope snow. But with the upper level
vort colder temperatures aloft and energy rotating around, snow
accumulation totals should increase later this evening and
continue into the overnight. Later shift might want to look at
adding western Highland into the advisory.


On Wednesday into Wednesday night, we continue to be caught between
deep low pressure over the Canadian maritimes and high pressure
building over the central U.S. Expect continued gusty northwest
winds on Wednesday with continued unseasonably chill conditions
over the region and upslope snow in the western mountains.

Models continue to show a weak low dropping southeast out of
the Great Lakes area on Wednesday night and bringing a weak cold
front across the area on Thursday. Other than some increase in
clouds, it will be a dry front with perhaps some upslope snow
showers in the western mountains.


A boundary will be to our south on Friday as upper level trough
slides eastward. A few showers possible west of the Allegheny
Front and dry conditions expected elsewhere. High pressure
builds into our area from the north on Saturday into Sunday as a
wave of low pressure tracks east along the front and passes to
our south. Guidance suggests mainly dry condtions Saturday night
into Sunday but showers, mainly over our southern counties,
cannot be ruled out. Dry conditions will continue Sunday night
into Monday before another low pressure system affect us Monday
night into Tuesday, increasing PoPs over our area.


NW winds gusting 25-30 kt through 00Z will lose some of the
gustiness tonight except perhaps at MTN winds gust to near 20 kt
all night. On Wednesday...NW winds will gust 20 to perhaps 25 kt
after 12Z but not quite as blustry as today.VFR conditions
expected at all terminals through Thursday.

Expect mainly VFR conditions Friday into Sunday over the terminals
as high pressure will be in control. Breezy conditions on Friday,
gusting to 25 kts. Maybe a passing shower could affect the
terminals Saturday night into Sunday.


Have extended the small craft advisories through Wednesday
afternoon on all waters. Gradient btwn the departing nor`easter
and high pressure building to our west will continue to keep NW
winds up tonight and will continue to meet SCA criteria on
Wednesday. As the high builds on late Wednesday expect winds to
marginally meet SCA levels possibly extending into Thursday, but
confidence is low on SCA on Thursday.

Wind gusts will be above the small craft advisory criteria on
Friday, therefore, expecting advisories for this day. Winds will
decrease on Saturday and remain below criteria into Sunday. &&

WV...Winter Weather Advisory from 9 PM this evening to 9 AM EDT
     Wednesday for WVZ501-503-505.
MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ530>543.


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