Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 241317
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
917 AM EDT Mon Jul 24 2017

.SYNOPSIS...
A cold front will approach the area today before passing through
tonight. High pressure will build into the area Tuesday before
moving offshore Wednesday. Another cold front will approach the
area Thursday before passing through Friday into Friday night.
High pressure may return for the weekend.

&&

.NEAR TERM /TODAY/...

Low pressure over PA with an attendant cold front over WV. The
front will move across the region late this afternoon and
evening. A mix of sun and clouds is expected into the afternoon.
Temperatures expected to rise back into the upper 80s and low
90s, and with dew points from the mid 60s to low 70s. We`ll see
heat indices back into the mid to upper 90s, perhaps locally
near 100F along the I-95 corridor.

As the cold front moves across the region, additional scattered
showers and thunderstorms are possible. Storm Prediction Center
has placed portions of the region in a Marginal Risk for severe
thunderstorms. With surface westerly flow developing today
leading to dew points a bit lower than previous days, and weak
mid-level lapse rates, environment is not as conducive for
widespread activity. That being said, MLCAPE is still progged to
reach 1000 J/kg or so, with 35-40 knots of 0-6km overlaid, and
with a cold front serving as a focus for convective activity,
there is certainly a risk for isolated to scattered severe
thunderstorms, with linear segments and localized wind damage
being the primary threat.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

Quieter, cooler, and drier weather is expected beginning
tonight and lasting through Wednesday night.

The aforementioned cold front will continue pushing
southeastward and clear the area by Tuesday morning. This will
usher in relatively cooler and drier air with dew points falling
through the 60s overnight. Lows overnight from the mid 60s to
low 70s.

High pressure building in behind the front will move from the
Great Lakes into the northeastern US Tuesday, leading to
northerly surface flow across our region. A mix of sun and fair
weather cumulus clouds expected for Tuesday with highs in the
80s and dew points in the low to mid 60s, which will be a
noticeable difference. Quiet weather continues Tuesday night
with the caveat that there may be some patchy fog and low clouds
around early Wednesday morning. Lows Tuesday night in the 60s
to near 70F.

The high will slide offshore Wednesday with the low level flow
turning easterly and then southeasterly. Should see mostly dry
conditions, although an isolated shower or thunderstorm can`t be
ruled out. Highs will likely actually be a bit below normal for
late July, in the low to mid 80s. Potential will exist again for
some patchy fog and low clouds Wednesday night into early
Thursday morning, but otherwise quiescent weather expected
Wednesday night with lows in the 60s to around 70F.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A cold front and its associated upper-level trough will approach
the area Thursday into Thursday night before passing through
Friday. Warm and humid conditions are expected ahead of the
front Thursday. Showers and thunderstorms are possible ahead of
the cold front...especially late Thursday into Friday.

High pressure may build into the region behind the
front...bringing dry...cooler and less humid conditions.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
VFR is expected today. There may be some isolated to scattered
showers and thunderstorms later this afternoon and evening.
Primarily VFR is then expected overnight through Wednesday
night, although we`ll have to monitor for patchy fog and low
clouds both Tuesday night and Wednesday night with onshore flow.

Showers and thunderstorms are possible ahead of a cold
front...mainly late Thursday into Friday.

&&

.MARINE...
Small Craft Advisory is in effect through 4 pm across the
lower tidal Potomac and portions of the central Chesapeake for
gusty southwesterly winds. These winds will diminish late this
afternoon with mainly sub-SCA winds expected for the rest of
today and through Wednesday night.

There may be some isolated to scattered showers and
thunderstorms this afternoon and evening. Special Marine
Warnings may be necessary.

A cold front will approach the waters Thursday into Thursday
night before passing through Friday. Showers and thunderstorms
are possible ahead of the front...especially late Thursday into
Friday. A Small Craft Advisory may be needed for portions of the
waters Thursday and Friday. High pressure may return for the
weekend.

&&

.TIDES/COASTAL FLOODING...
Coastal Flood Advisories in effect for the District of Columbia
this morning. No other tidal issues expected at this time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 11 AM EDT this morning for DCZ001.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ534-
     537-543.

&&

$$
UPDATE...WOODY!
PREVIOUS...MJM/BJL


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