Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 140130
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
930 PM EDT Thu Jul 13 2017

.SYNOPSIS...
A stalled front will remain to the north of the region through
tonight while a Bermuda High persists. The front will push
south through the area as a cold front Friday night. Weak high
pressure will influence the weather over the weekend, before
another cold front lingers over the area Monday through
Tuesday.

&&

.NEAR TERM /TONIGHT/...

Instability persists overnight, so nocturnal convection/
propagation of MCS activity into our area overnight is possible.

Min temps mid to upper 70s inland to around 80F in urban heat
islands.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...

The upper level trough shifts east across the eastern Great
Lakes Friday. The associated cold front will shift south across
the area Friday evening. Hot/humid conditions persist until then
with active weather ahead of the front. One or two rounds of
severe activity expected Friday with a Slight Risk across the
area. Should be limitations of morning cloud cover again. This
will limit the need for heat headlines and should reduce the
potential instability. Shear improves to 25 knots or so, but
note that westerly flow often leads to reduced severe potential.

High pressure builds Friday night through Saturday night with
drier conditions and temperatures near normal (upper 80s).

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
High pressure will shift offshore Sunday and a return southerly flow
will develop. The southerly flow will bring more seasonably hot
conditions. An increase in moisture may trigger an isolated shower
or thunderstorm late Sunday and Sunday night. However...the deep
moisture should remain to our south so most areas should turn out
dry.

An upper-level trough will build overhead for Monday and Tuesday
while high pressure remains over the Atlantic. A surface trough will
also develop overhead during this time. A southerly flow around the
high will allow for deeper moisture to move into the area. At the
same time...with falling heights associated with the trough this
will destabilize the atmosphere. More widespread showers and
thunderstorms are possible during this time. Some storms may be
strong with locally heavy rainfall. Still difficult to pinpoint
exactly when the best chance for storms is...but as of now it
appears most likely to follow climo with the bulk of the convection
during the afternoon and evening hours each day.

The upper-level trough is expected to slide off to the east for
Wednesday and Thursday. Exact timing of this remains uncertain.
However...rising heights and a southerly flow around high pressure
over the Atlantic will usher in more hot and humid conditions. A few
showers and thunderstorms are possible due to the heat and
humidity...especially during the afternoon and evening hours each
day.

&&

.AVIATION /TONIGHT THROUGH TUESDAY/...

VFR conditions expected tonight. Thunderstorms Friday ahead of
a cold front.

West flow persists through Friday with NW flow behind the cold
front Saturday.

VFR conditions are most likely Sunday. Showers and thunderstorms are
possible Monday and Tuesday...especially during the afternoon and
evening hours each day.

&&

.MARINE...
Increased chances for thunderstorms Friday.

Cold front crosses Friday night with SCA possible in NW flow
Saturday.

High pressure will move offshore Sunday and a return southerly flow
will develop. The southerly flow should remain in place through
early next week...but wind speeds are expected to remain below SCA
criteria most of the time. Showers and thunderstorms are possible
Monday and Tuesday...especially during the afternoon and evening
hours each day. Some storms may produce locally gusty winds.

&&

.CLIMATE...
Hot and humid weather continues through Friday. KDCA recorded a
low of 79F this morning. Records are listed below. Highs today
in parentheses

RECORD DAILY HIGH TEMPERATURES
Washington DC area (Ronald Reagan Washington National Airport, DCA)
July 13th: 100 degrees F (set in 1954) (today 97)

Baltimore MD area (Baltimore-Washington International Thurgood Marshall
Airport, BWI)
July 13th: 99 degrees F (set in 1966, 1954 and 1880) (today 95)

Dulles VA area (Washington Dulles International Airport, IAD)
July 13th: 97 degrees F (set in 1986 and 1966)  (today 94)


RECORD DAILY WARM LOW TEMPERATURES
Washington DC area (Ronald Reagan Washington National Airport, DCA)
July 13th: 78 degrees F (set in 1993, 1992 and 1981)

Baltimore MD area (Baltimore-Washington International Thurgood Marshall
Airport, BWI)
July 13th: 77 degrees F (set in 1880)

Dulles VA area (Washington Dulles International Airport, IAD)
July 13th: 74 degrees F (set in 2016)

Note: Temperature records for the Washington DC and Baltimore MD areas
date back to 1872. Records at IAD go back to 1960.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

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



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