Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 221852

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
252 PM EDT Sat Oct 22 2016

Surface high pressure will build south of the area through the
remainder of the weekend as low pressure pulls away into the
Canadian Maritimes. A reinforcing cold front will move through
Monday with cool high pressure to follow for mid week. A low
pressure system will approach from the west late in the week.


Deepening low pressure is located over Maine this afternoon as
high pressure builds over the southern MS Valley. The tight
pressure gradient has been resulting in strong winds. The few
hours of 40 kt wind gusts during late morning/midday may have been
the peak, as KLWX VWP shows 40 kt winds now located around 7kft.
This evolution generally agrees with forecast soundings. However,
will leave Wind Advisory in effect for now as gusts near 40 MPH
are still notable. Low level winds are expected to
strengthen/lower this evening, although nocturnal stabilization
should prevent stronger gusts from reaching the surface. It will
still be a breezy night (except perhaps in sheltered valleys).
Ridgetops will remain windy, but low confidence on magnitude since
CAA pattern will be reversing.

Within our CWA, we have only received one reports of flurries in
Grant County, although favorable upslope areas are likely still
seeing off and on rain and snow showers. This activity should
diminish by this evening as moisture, lift and wind direction
become less favorable.

Lows tonight will be in the 40s for most with lower to mid 30s in
higher elevations.


Main trough axis lifts to the northwest for Sunday and Sunday
night which will allow for dry weather. Since we will still be in
the gradient with low pressure to the NE and high pressure to the
SW, it will still be breezy with 20-35 MPH gusts during the day.
Under weak warm advection, temperatures should recover 5-8

A reinforcing cold front will drop south into the area on Monday.
It will be moisture starved though, with only a small chance of
showers in the highlands. High temperatures will depend on the
timing of frontal passage, with southern areas standing the best
chance to see highs reach the 70+. The wind will still be
noticeable as well with gusts of 20-30 MPH. High pressure will
build from the west Monday night with lows returning to the 30s
and 40s.


Long term starts out with a big closed low over Atlantic Canada and
fast northwest flow on its southwestern flank over our region. This
low will very slowly shift east out into the Atlantic so that by
early Thursday a weak ridge is located over our region. This will
quickly be followed by a sharp trough which will move in Thursday
night. After that uncertainty grows with some guidance pushing the
shortwave through but leaving the longwave trough in place...while
other guidance cuts off a deep low over the region aloft.

For our sensible weather at the surface, this translates to high
pressure slowly building in with diminishing northwest winds
Tuesday. While the surface high doesn`t build directly overhead, it
will be close enough such that we could have a good radiational
night on Tuesday night, perhaps enough to bring frost into suburbs
again. High pressure remains to our north influencing our weather on
Wednesday into Wednesday night, but by Thursday, the next surface
low pressure will be approaching from the west with increasing
clouds and rain chances. Depending on the progress of the system,
the rain may continue into Friday or even Friday night, or end
fairly quickly. This is still pretty uncertain.

Overall, temps will stay below normal, with the coolest period
likely Tuesday with a little warming possible just ahead of the
front on Thursday.


The primary aviation impact for the TAF period (and to some extent
through Monday) will be the wind. NW gusts to 35 kt will remain
possible through late afternoon. They will abate some tonight, but
westerly gusts of 20-30 kt are expected on Sunday. Otherwise, VFR
conditions are expected with only some cumulus clouds around

A cold front will pass through Monday, with winds becoming NW
again with gusts 20-25 kt.

VFR overall Tuesday through Wednesday night outside of any early
morning fog, which would mainly CHO/MRB/IAD. Sub-VFR cigs/vis
possible Thursday on as a storm system brings rain back to the


NW gales continue through the afternoon. Should see the more
sheltered waters decrease to Small Craft Advisories by late
afternoon, with other waters not following suit until late
tonight. For now, have allowed a decrease in winds for the upper
Potomac and Patapsco tonight, but this is not certain. Otherwise
Small Craft conditions will likely continue through Monday night
(westerly Sunday, then northwest again Monday with a frontal
passage), especially on the wider parts of the Bay. Will allow
future headlines to be refined as near-term headlines become

Overall looking like winds will diminish through Tuesday with sub-
SCA likely by Tuesday night. Southerly channeling could bring
winds back to SCA levels Wednesday night or Thursday, but this is
still highly uncertain.


DC...Wind Advisory until 5 PM EDT this afternoon for DCZ001.
MD...Wind Advisory until 5 PM EDT this afternoon for MDZ003>006-011-
VA...Wind Advisory until 5 PM EDT this afternoon for VAZ025>031-
WV...Wind Advisory until 5 PM EDT this afternoon for WVZ051>053-055-
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Sunday for
     Gale Warning until 2 AM EDT Sunday for ANZ531>534-539>541-543.
     Small Craft Advisory from 6 PM this evening to midnight EDT
     tonight for ANZ535-536-538.
     Gale Warning until 6 PM EDT this evening for ANZ530-535>538-
     Small Craft Advisory from 6 PM this evening to 8 PM EDT Sunday
     for ANZ530-537-542.


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