Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 182001
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
301 PM EST Wed Jan 18 2017

.SYNOPSIS...
High pressure will build toward the region tonight before
settling overhead Thursday. A warm front will move into the area
Friday and stall out nearby through Saturday. Low pressure will
affect the area to start the new week.

&&

.NEAR TERM /THROUGH THURSDAY/...
Relatively quiet weather expected through Thursday. At present,
cold front has cleared the area and the upper low is also heading
east away from us. Instability caused by the cold pool of the low
passing overhead is waning and clouds are starting to diminish.
Pressure gradient and mixing will gradaully wane through tonight
allowing winds to also relax. However, it does not completely go
away, so we should still have enough of a breeze to keep fog from
developing. Upslope flow may keep a few snow showers going along
the Allegheny Front, but otherwise dry conditions expected with
lows mostly in the 30s.

On Thursday, high pressure moves right overhead. Sounds look quite
dry so high clouds may be minimal through the day, though some
puffy low cumulus or stratocumulus may develop. Temperatures aloft
will remain mild for January so surface temps should rise back
into the 50s in most of the area thanks to rather plentiful
sunshine. Winds will be fairly light under the high.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Warm front starts to lift back north towards us on Thursday night
and enters southern Virginia before stalling out on Friday. Warm
advection surge with the front will result in increasing clouds
Thursday night, with a period of rain looking definite starting
mid-late morning and lasting into early afternoon Friday. That
rain should leave the area late in the afternoon, though lingering
low level moisture and light southeast flow may result in patchy
fog and/or drizzle which could linger through Friday night. Lows
Thursday night will be in the 30s with highs Friday afternoon in
the mid to upper 40s generally. Lows Friday night will drop back
into the lower 40s with plenty of clouds and the potential for
fog/drizzle.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Weak high pressure will be overhead Saturday into Saturday night.
Temperatures will stay mild throughout the period. A separate area
of high pressure over New England could aid in some cloud cover
with an upslope flow. A few rain showers can`t be ruled out,
mainly Saturday night.

A storm system will develop over the Mississippi Valley and
deepen as it pivots northeastward Sunday and Sunday night. This
low could send additional energy into our region Sunday into
Sunday night, bringing rain showers to the region.

On Monday, the main low will move to the northeast a little
further. The threat for showers and perhaps a rumble of thunder
exist Monday into early Monday evening. Temperatures will remain
mild. Drier air will push in behind the departing storm system
Monday overnight.

High pressure will usher in cooler and drier air Tuesday and
Tuesday night. Clouds will break for sun, except for clouds and
upslope rain and/or snow showers in the Potomac Highlands
possible.

An upper level trough of low pressure will sag from the Great
Lakes region toward the mid-Atlantic Wednesday. A return of mild
air from the south will evolve ahead of the trough with some
sunshine giving way to some clouds.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
VFR thru the next 36 hours at all TAF sites. High pressure
building in from the west is producing a gusty wind of 20-25 knots
right now, but this should diminish after sunset. Clouds with 3-5k
ft bases should also gradually dissipate overnight. Light winds
with limited clouds on Thursday. Cigs redevelop and begin to lower
later THursday night with a period of rain and sub-VFR, if not
sub- MVFR conditions looking likely on Friday. IFR looking
possible with lingering clouds, drizzle and fog behind the system
Friday night.

Vfr conditions Saturday. Mvfr conditions Saturday night with a
chance of a few rain showers, mainly at the CHO terminal. Winds
light and variable Saturday. Winds easterly around 5 knots
Saturday night.

&&

.MARINE...
Gusty northwest wind reaching SCA criteria as high pressure
builds in this evening should diminish overnight. Not quite sure
how quickly gusts die down given the air is not that cool and is
blowing over relatively cool water, so mixing may be minimal after
sunset. Extends SCA a few hours to cover potential for early
evening mixing and will let evening shift re-evaluate if SCA needs
to go any further. SHould be sub-SCA for Thursday with high
pressure overhead. Warm front approaches from south on Friday with
rain and mist, but winds should stay sub-SCA. Drizzle and mist may
linger Friday night, but still sub-SCA winds expected.

No marine hazards Saturday and Saturday night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 PM EST this evening for
     ANZ530>543.

&&

$$
SYNOPSIS...RCM
NEAR TERM...RCM
SHORT TERM...RCM
LONG TERM...KLW
AVIATION...RCM/KLW
MARINE...RCM/KLW


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