Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 161855
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
255 PM EDT Thu Mar 16 2017

.SYNOPSIS...
High pressure will gradually build east from the
mid-Mississippi valley through early Friday. A warm front will
move into the area Friday night into early Saturday before a
cold front passes through Saturday afternoon. High pressure
builds over the area for the second half of the weekend into
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure will continue to approach from the west. A
blustery northwest wind will continue with frequent gusts around
25 to 35 mph through late this afternoon. Drier air has allowed
for more sunshine...which will cause max temps to be a bit
milder compared to Wednesday but still below climo. Max temps
will range from the 20s in the mountains to the upper 30s and
lower 40s near Washington and Baltimore...to the middle 40s in
central Virginia.

High pressure will settle just to our south tonight...but it
should be close enough to allow for mainly clear skies and light
winds. Radiational cooling will allow for more unusually cold
conditions this time of year. Leaned toward the colder guidance
due to the favorable setup for radiational cooling.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
High pressure will move offshore Friday and low pressure will
track into the western Great Lakes during this time. The warm
front associated with the low will approach the region Friday
before moving overhead Friday night. Clouds will increase ahead
of the warm front through midday. A period of rain and snow will
likely develop later Friday afternoon and last into Friday
night. The best chance for snow will be across northern
Maryland...extreme northern Virgina...eastern West Virginia and
for locations along and west of the Allegheny Front. However...a
southerly flow ahead of this system will allow for surface temps
to get above freezing during the day Friday. Therefore...any
accumulation should be light and confined to grassy surfaces.
The one exception will be for locations along and west of the
Allegheny Front where 1-3" inches are most likely with surface
temps near or even below freezing.

Warmer air will work its way in aloft later Friday evening into
overnight...causing most of the precipitation to fall as rain
during this time. However...surface temps may be near freezing
right along the Mason Dixon Line. A few pockets of freezing rain
cannot be ruled out but confidence is low. Any freezing rain
would most likely be on elevated surfaces with most paved
surfaces being wet due to the warmer conditions preceding this
on Friday.

Upper-level low pressure will dive south toward our area
Saturday while a cold front also moves through the area. A dry
slot will allow for much of the day to be dry...but there should
be enough instability for a few showers. Snow showers are
possible in the mountains as colder air filters in Saturday
afternoon behind the front. Saturday will turn out to be much
milder compared to recent days for the valley locations as well
as the Washington and Baltimore Metropolitan areas.

The upper-level low will slowly pass through our area Saturday
night. Blustery and chillier conditions will return along with a
few rain and snow showers possible. The best chance for snow
showers will be in the mountains and across northern Maryland.
Accumulating snow is likely along/west of the Allegheny Front.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Cold and breezy conditions expected Sunday as upper
level low moves away from the Mid-Atlantic coast. High
temperatures  in the 40s and 50s over our CWA, feeling around
10 to 15 degrees cooler. High pressure builds over our region
Sunday night into Monday night, before a weak cold front moves
across our area early on Tuesday. High pressure returns behind
the front and into Thursday. High temperatures Monday and
Tuesday will be in the 50s for most of our CWA, and then
reaching the 40s and 50s for Wednesday and Thursday.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected through midday Friday. Gusty
northwest winds will diminish early this evening. A period of
rain and snow is likely later Friday afternoon and Friday night.
The best chance for snow will be across KMRB with rain more
likely elsewhere. SubVFR conditions are possible during this
time.

A cold front will pass through Saturday and northwest winds will
return later Saturday afternoon through Saturday night. A few
rain and snow showers are possible during this time.

Cold and breezy conditions Sunday, some showers
possible as front moves through. VFR conditions Sunday night
into  Monday night before another front moves across early on
Tuesday. High pressure returns later on Tuesday.

&&

.MARINE...
Gusty northwest winds will gradually diminish tonight. A Small
Craft Advisory remains in effect for all of the waters through
early this evening...and for portions of the waters tonight.
High pressure will move off the coast Friday. A return flow will
develop...and a Small Craft Advisory is in effect for portions
of the waters Friday night when the gradient strengthens.

A cold front will pass through Saturday and high pressure will
approach Saturday night. A Small Craft Advisory may be needed
for portions of the waters during this time.

Cold and breezy conditions Sunday, some showers
possible as front moves through. Dry conditions Sunday night
into Monday night before another front moves across early on
Tuesday. Winds increase as high pressure builds over later on
Tuesday. Small craft advisory possible Sunday.

&&

.CLIMATE...
Record low maximum temperatures were set at IAD and
BWI yesterday. See RERs for those two airports.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ530>534-537-
     539>541-543.
     Small Craft Advisory until 8 PM EDT this evening for ANZ535-
     536-538-542.
     Small Craft Advisory from 8 PM Friday to 6 AM EDT Saturday for
     ANZ532>534-537-540-541-543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...IMR
AVIATION...BJL/IMR
MARINE...BJL/IMR
CLIMATE...LFR



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