Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 120202
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1002 PM EDT Wed Oct 11 2017

.SYNOPSIS...
An area of low pressure will track along a front and push the
front well to our south tonight and Thursday. High pressure
will build north and east of the area later Friday through
Saturday before moving offshore Sunday. A stronger cold front
will pass through the area early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A nearly stationary boundary remains over the Potomac Highlands
into central Virginia this evening. The boundary separates
cooler marine air to the north and east vs. warm and humid air
to the south and west. More shortwave energy will pass by to
the north over the next few hours. More showers and drizzle are
expected through the night, with the primary cause being
convection upstream which is overrunning the boundary.
Therefore...moderate to locally heavy rain is possible, but it
should be brief.

The boundary will move south and west as a cold front overnight
as the shortwave energy moves off to the east. The onshore flow
will cause low clouds along with areas of rain and drizzle/fog.
Min temps will be in the 50s and 60s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
High pressure will along the New England coast will extend
southwest into our area Thursday through Friday before building
overhead Friday night. An onshore flow is expected during this
time while warm and moist air overruns the marine air in place.
Therefore...plenty of clouds are expected along with areas of
rain and drizzle/fog. Cooler conditions will persist during this
time with max temps in the 60s and min temps in the 50s/60s. Fog
may be locally dense...especially along the ridge tops.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Large area of high pressure will drift eastward into the
northwestern Atlantic over the weekend. A front will drop in
from the northwest early next week but weaken as it does so.
Some scattered showers are possible with this front, but
significant rain is not expected due to an overall lack of
moisture. Long term guidance has been reasonably consistent with
timing the frontal passage late Monday. High pressure and more
fall-like weather returns behind the front for the middle of
next week.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
A stationary boundary will remain to the south and west of all
the terminals overnight. An easterly flow to the north and east
of the boundary will cause low clouds along with areas of
drizzle, while showers will move in from the west. MVFR to IFR
conditions will continue. Should generally trend towards IFR as
we head towards morning. Showers are moving in at present as
shortwave energy passes through, but they will likely
diminish/move away toward morning.

The boundary will drop south and west as a cold front late
tonight. An onshore flow behind the boundary will cause more low
clouds and some fog along with areas of rain and drizzle.
Mainly IFR conditions are expected late tonight through Friday
night.

Sub-VFR possible in low clouds/fog Sat and Sun AM. Otherwise,
mainly VFR this weekend. Light flow.

&&

.MARINE...
An onshore flow will strengthen overnight as a stationary
boundary drops south as a cold front and high pressure builds
toward the area from the north and east. A Small Craft Advisory
is in effect for the Bay and lower Tidal Potomac River tonight.
A pressure surge is expected Thursday and a Small Craft Advisory
is in effect for all of the waters. The strongest winds are
expected Thursday across the middle portion of the Bay and lower
Tidal Potomac River with gusts around 25 to 30 knots likely.

The gradient will subside a bit for Thursday night and
Friday...but a Small Craft Advisory continues for portions of
the waters overnight Thursday and it may need to be extended
into Friday evening as well.

Generally light winds expected over the waters this weekend
as high pressure drifts eastward.

&&

.TIDES/COASTAL FLOODING...
E/SE flow will keep water levels elevated with a persistent
threat for minor flooding into the weekend.

&&

.EQUIPMENT...
The NWS 88D Sterling radar (KLWX) will be down during the day
from 7 AM through 5 PM through Saturday this week. This is for
nationally scheduled maintenance on the radome. Our surrounding
88D radars as well as FAA terminal radars will continue to scan
our skies during this downtime.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ531>534-537-
     539>541-543.
     Small Craft Advisory from 6 AM Thursday to midnight EDT
     Thursday night for ANZ535-536-538-542.
     Small Craft Advisory until midnight EDT Thursday night for
     ANZ530.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL/RCM
SHORT TERM...BJL
LONG TERM...DFH
AVIATION...BJL/DFH/RCM
MARINE...BJL/DFH/RCM
TIDES/COASTAL FLOODING...BJL
EQUIPMENT...LWX



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