Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 111528
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1028 AM EST Sat Nov 11 2017

.SYNOPSIS...
High pressure will dominate the region through Sunday. Low
pressure will affect the region Sunday night into Monday,
followed by another area of high pressure by Tuesday. Another
front may impact the region midweek.

&&

.NEAR TERM /THROUGH TONIGHT/...
Strong high pressure will remain overhead through the rest of
today. This will lead to light winds and dry weather. High
clouds will gradually increase through the day today associated
the jet stream and warm air advection aloft. Highs today will be
well below normal, generally within a few degrees of 40F.

Light winds expected tonight with high pressure still around -
however, high clouds may make their way overhead, and temps
aloft will be starting to rebound. So, all in all, not quite as
cold.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Approaching trough with weak surface low will be moving into the
Ohio Valley Sunday. As this occurs, a secondary low is expected
to start developing east of the mountains, with an energy
transfer to this low on Monday. As this low develops,
clouds will become common Sunday, and precipitation looks more
likely to break out across the region Sunday night. Right now,
given some moderation Sunday with warm advection aloft and a
light east flow at the surface, most of the region should see
rain. However, cold air damming could allow a period of mixed
precip west of I-95 and north of I-66 in western Maryland,
eastern West Virginia and far northwestern Virginia on Sunday
night. For now have included likely rain and chance
snow/sleet/freezing rain given high uncertainty, but may need to
put out advisories should the odds of freezing rain increase
significantly.

This system pulls out during the day Monday, with decreasing
clouds on a west wind during the afternoon. This should allow
even more moderation, particularly since the air mass behind the
system has more of a Pacific influence to it. This also means
that Monday night, despite some clearing, should not be as cold
as tonight, but some places could still drop below freezing.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
High pressure will pivot across the area Tuesday into Wednesday
bringing seasonable conditions. As the high moves offshore, a
weakening cold front will approach from the Ohio Valley. Upper-
level support will be weakening and lifting north during this
time, so the best chance of showers (albeit somewhat scattered)
will likely be confined to northwestern portions of the CWA.

A stronger upper trough/surface frontal system will approach
late in the week likely bringing more widespread chances for
precipitation, which looks to be mainly rain at this time given
the fact that the Mid-Atlantic will be solidly in the warm
sector.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
VFR through Sunday. Winds dropping below 10 knots and staying
light through Sunday.

Sub-VFR possible Sunday night as a storm system brings a period
of light rain, which could possibly be mixed with ice or snow
at MRB. Returning to VFR by Monday afternoon.

Mainly VFR Tuesday-Wednesday. Light flow under high pressure.

&&

.MARINE...
Winds will gradually diminish through today, with sub-SCA winds
for this afternoon and tonight. Generally expecting sub-SCA
Sunday through Monday night, though will need to watch a
strengthening coastal low late Monday. Winds could pick up
enough to reach SCA levels as the low pulls away.

No marine hazards expected Tuesday-Wednesday under high
pressure.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...RCM
NEAR TERM...MM/RCM
SHORT TERM...RCM
LONG TERM...DFH
AVIATION...MM/RCM/DFH
MARINE...MM/RCM/DFH



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