Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191953
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
253 PM EST Sun Feb 19 2017

.SYNOPSIS...
High pressure will build from the west through tonight. A
backdoor cold front will enter the area Monday into Tuesday. A
weak disturbance will cross the area Tuesday night. High
pressure will be located off the southeast coast of the United
States for the second half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure extends from the Great Lakes to the central Gulf
coast this afternoon. The bulk of cloud cover has moved out of
the area, with stratus banked along the west side of the
Appalachians. Temperatures have risen into the 60s and 70s in
most locations. Wind gusts have been somewhat spotty, but with
occasional gusts over 20 mph. These gusts will subside with
sunset.

For tonight, the high will edge eastward while a mid-level
trough digs over New England. Western areas may have a better
chance of decoupling, and 30s will be more likely there.
Elsewhere will remain in the 40s. Only some scattered mid and
high level clouds are expected.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A backdoor cold front will slip southwestward on Monday. Latest
guidance hasn`t deviated significantly in the temperature
forecast, but the ultimate gradient may be much tighter than
currently in the grids between lower to mid 50s in northeast MD
and around 70 in central VA. Clouds should remain limited to
the mid and high level variety during the day. An
upslope/overrunning component will develop by Monday night,
which could lead to some lower cloud development over the
mountains. Expect Monday night to be one of the cooler nights
this week as drier air seeps in with light winds and few clouds.

Ridge axis aloft will move over the area Tuesday morning while
the surface high extends along the coast. Despite developing
southerly flow, mixing will be poor, and thus Tuesday is still
expected to be the coolest day this week. Of course that is
relative, with high temperatures still running at least 10
degrees above normal. Clouds will begin to increase through the
day. A shortwave trough will approach Tuesday night. However,
that`s where the bulk of the forcing and moisture will be
located, with only a hint of a surface trough reflection.
Computer models are a little more aggressive with QPF than last
night`s system as the narrow ribbon of forcing/moisture
traverses the area, but still only looking at less than a tenth
inch where rain does fall. The highest chances will be
north/west of DC. Clouds should keep lows in the 40s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Upper-level ridging will traverse the area Wednesday into early
Thursday as surface high pressure remains stationed off the
southeast coast. Continued southwesterly flow will keep temperatures
quite mild by late February standards, and perhaps near record
levels (especially for warm lows and/or in the IAD area; see
Climate section below).

As strong low pressure develops over the central Plains late
Thursday into Friday, a warm front will develop and push to the
north of the area, but may also lead to increasing clouds and
potential bouts of rain. The low will track across the Great Lakes
Friday night into Saturday bringing a cold front through the area.
Most of the forcing will likely be just north and west of the area,
but showers are still possible, as are thunderstorms if the front
crosses near peak heating Saturday (exact timing still in question).

Temperatures will cool closer to seasonable levels by the second
half of the weekend behind the front.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR flight conditions will continue to prevail across the
terminals through the TAF period. Occasional gusts to 20 kt will
subside with sunset. Relatively clear and calm tonight. LAMP
guidance suggests fog at CHO, but am not seeing much other
support to include anything in the TAF now. Winds will become
more northerly Monday and northeast Monday night. Do not
anticipate gusty winds, though.

Clouds will be sparse until Monday night. Some lower VFR or
MVFR cigs could develop at or near the western terminals (MRB,
CHO, IAD), but confidence is low. No issues expected Tuesday. A
weak trough will cross the area Tuesday night. Any showers
appear to be scattered and light and thus do not anticipate
widespread cig/vsby issues.

Patchy MVFR possible Wed AM mainly near outlying
terminals...then mainly VFR expected through Thursday. Flow
generally SWLY AOB 10 kts.

&&

.MARINE...
Despite morning indications of efficient mixing of 20 kt gusts
nearshore and on the narrower waterways, such gusts have been
very sporadic into this afternoon. Will allow SCA to continue
with occasional gusts ongoing, but it may be able to be
cancelled early. Winds aloft increase this evening, but models
suggest a sharp low level inversion by that time.

High pressure builds from the west tonight into Tuesday.
Overall winds should be light, although there may be periods
with 10-15 kt during the daytime hours. The direction will be
veering to north Monday, northeast Monday night as a subtle,
backdoor cold front settles across the waters, and perhaps
southerly by late Tuesday as high pressure moves east.

With high pressure ridging across the region Wednesday into
Thursday and non-channeling flow of mild air over cooler waters,
winds will likely stay below Small Craft Advisory criteria.

&&

.CLIMATE...
Unseasonably mild temperatures are being observed across
the region today, and are forecast again later in the week.

Below is a list of record daily warm temperatures for today
and the next potential near-record warm spell later this week.

February 19th
Site   Record High  Record Warm Low
DCA    74 (1939)    52 (1981) SAFE: low this morning was 49
BWI    72 (1997)    47 (1976)
IAD    71 (1997)    46 (1981)

February 22nd
DCA    77 (1874)    60 (1874)
BWI    74 (1874)    51 (1874)
IAD    71 (1991)    52 (1981)

February 23rd
DCA    78 (1874)    51 (1922)
BWI    78 (1874)    52 (1874)
IAD    73 (1985)    51 (1975)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ530-
     531-535-536-538-542.

&&

$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...DFH
AVIATION...ADS/DFH
MARINE...ADS/DFH
CLIMATE...DFH



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