Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 260112
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
912 PM EDT Mon Jul 25 2016

.SYNOPSIS...
A cold front will drift into the region from the north tonight.
This front will stall across the region during the middle of the
week. Another cold front is expected at the end of the week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Boundary has sunk southward near the region this evening. Earlier
convection has dissipated for the most part. Most concentrated
areas of activity are across the Philly Metro area and back across
portions of northern West Virginia. Still could see some
additional showers/thunderstorms develop out ahead of the
boundary, especially across parts of eastern Maryland near
established convective line and areas from the DC Metro on
southward where considerable MLCAPE remains. Can`t rule out an
additional pulse severe storm, but threat of organized severe
weather is waning.

Otherwise...patchy fog possible, especially where rain has fallen
today. Lows in the 70s to near 80F.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The front will become stalled across Virginia, likely toward the
southern half of the area, for Tuesday and Wednesday as it becomes
parallel to the upper level flow. Thunderstorm chances will
largely be diurnally based each day, but with the front in the
area and potential for subtle shortwave troughs to be moving
across the area, it will be tough to pinpoint any dry periods. For
Tuesday afternoon, bulk shear will again be in the 25-30 kt range
in the midst of strong destabilization over the southern portions
of the forecast area, so a Marginal Risk of severe weather has
been introduced. Wednesday afternoon and evening will need to be
monitored as well as the pattern changes very little. High PWAT
will mean heavy rain is also a threat.

Temperatures will lower a little for the next two days, generally
in the low to mid 90s. However, heat indices will approach 100 yet
again, especially Tuesday, with the highest values over the far
southern areas. Due to values near 105...have issued a Heat
Advisory again for Tuesday for Nelson, Albemarle, Orange, and
Spotsylvania Counties. Overnights will remain in the 70s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Main story Thursday through the weekend will be persistent above
normal temperatures (though not too extreme) and the potential for
showers and thunderstorms (some of which could be heavy at times).

Front will linger near the area Thursday, which will keep chances
for at least isolated afternoon thunderstorms in the forecast. Mid
90s temperatures coupled with upper 60s dewpoints yields heat index
values in the upper 90s Thursday.

Heights begin to fall late Thursday as shortwave approaches. While
timing differences exist among long term guidance, the best chance
for precipitation will occur as this feature crosses the area late
Thursday into Friday. Depending on the track, there could be some
heavy rain across parts of the area.

While uncertainty exists with next weekends forecast, general
consensus is for above normal temperatures to continue, with at
least isolated afternoon thunderstorm chances.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
Mainly VFR expected. Could still be a few showers/thunderstorms
this evening and into tonight, but coverage will be lessening.
Some patchy fog possible as well, but will leave out of TAFs for
now due to limited coverage. Some isolated to scattered additional
showers/thunderstorms possible as well Tuesday and Wednesday.

Nearby frontal boundary will allow for isolated afternoon
thunderstorms Thursday. Better chance for scattered
showers/thunderstorms arrives late Thursday into Friday as upper
level energy approaches.

&&

.MARINE...
Southerly winds from 5 to 15 knots will continue this evening
before a cold front moves through the waters tonight into Tuesday
morning and winds become W to NW behind it. There may be a brief
period when winds turn west/northwest where SCA conditions may be
approached or met. For now, will plan to handle with Marine
Weather Statements if needed. Showers and thunderstorms are
possible again Tuesday afternoon mainly across the southern
waters and again on Wednesday as the front stalls out.

While gradient winds remain below SCA criteria through the end of
the week, thunderstorms will be possible Thursday and Friday. The
best chance for showers/storms is late Thursday into Friday as upper
level energy approaches.

&&

.CLIMATE...
The last time we hit 100 degrees:
DCA: July 26th 2012 (100)
BWI: July 18th 2012 (104)
DMH: July 19th 2013 (100)
IAD: July 18th 2012 (101)
CHO: July 8th 2012 (106)
HGR: July 7th 2012 (101)
MRB: July 7th 2012 (100)

Record maximum temperatures for July 25th:
DCA (DC area): 100 (1930)
DCA only: 99 (2010, 1987)
BWI (Baltimore area): 100 (2010)
BWI only: 100 (2010)
DMH: 100 (2010)
IAD (Dulles area): 98 (2010)
IAD only: 98 (2010)
CHO: 101 (2010)
HGR: 98 (2010)
MRB: 101 (1933)

DCA (DC area): 79 (1965)
DCA only: 79 (1965)
BWI (Baltimore area): 77 (1887, 1885)
BWI only: 76 (2001, 1965)
DMH: 78 (2011)
IAD (Dulles area): 76 (1965)
IAD only: 76 (1965)
CHO: 74 (2010)
HGR: 75 (2001)
MRB: 73 (2010, 2001, 1989, 1979, 1965)

"Area" denotes ThreadEx sites which are the numbers used for RERs.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...Heat Advisory from noon to 8 PM EDT Tuesday for VAZ036-037-050-
     056.
WV...None.
MARINE...None.

&&

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



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