Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 170024
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
824 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 /UNTIL 7 AM FRIDAY MORNING/...
High pressure will continue to build in from the west tonight,
cresting near the region early Friday morning. This will lead to
slackening winds, clear skies, and radiational cooling.
Temperatures will once again be quite cold for mid March, with
lows from the upper teens in the coldest locations to upper
20s in the urban centers.

&&

.SHORT TERM /7 AM FRIDAY MORNING 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 /00Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected through midday Friday. Any lingering
gusts out of the northwest this evening will dissipate overnight.
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. Sub-VFR 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 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 again 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 from 8 PM Friday to 6 AM EDT Saturday for
     ANZ532>534-537-540-541-543.

&&

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



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