Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191818
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
218 PM EDT Fri Aug 19 2016

.SYNOPSIS...
Weak high pressure builds in through Saturday with a
cold front crossing the area Sunday evening. High pressure
returns for the first half of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure over the region this afternoon heading into
the weekend. Main area of showers and thunderstorms currently on
going down near the VA/NC border where a surface trough has
aligned. North of this boundary, a passing shortwave combining
with marginal instability and terrain influences could produce
isolated to scattered showers and thunderstorms. Expecting sub-
severe. Any storms that do form will diminish in coverage with
loss of daytime heating this evening as well as with the shortwave
energy pushing to the east. Patchy fog possible in the valleys
with moisture lingering in the lower levels. Lows tonight right
near normal.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Similar synoptic setup on Saturday with the persisting surface
high and an approaching mid level trough. Another shortwave
passing through on Saturday could trigger showers and
thunderstorms, again expecting sub-severe with marginal
instability and weak shear. High temps similar to today, though
could be 1-3 degrees too warm if precipitation becomes more
scattered.

A cold front will swing through the region on Sunday, with the 12z
model suite in general agreement with the passage late
afternoon/evening time frame. Ahead of this front, strong moisture
advection will push PWATs up to at least 2 inches. The best
forcing along the trough looks to be centered over PA, but there
is some suggestions in the models that enhanced heavy rain could
extend down into northeast Maryland. Thinking overall central
Maryland into areas to the north of DC and then east into southern
Maryland have the highest confidence/best chance of seeing showers
and thunderstorms with activity more scattered in nature over the
remainder of the CWA. Will continue to highlight enhanced flood
threat in the HWO with around one inch possible along the 95
corridor between DC-Baltimore. Flooding will be the main threat,
though cannot rule out isolated stronger gusts with some of the
heavier rain showers. As the front sweeps through, drier air in
the wake will dry things out fairly quickly, with only lingering
showers possible over the eastern fringe of the CWA by Monday
morning.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
A cold front should push offshore by Monday morning thanks to a
1022+mb surface high building in from the west. The weather
across the Mid-Atlantic will then be dominated by high pressure
through much of next week. This will likely result in near to
below normal temperatures and a mainly clear sky for at least the
first half of the week. As the center of the high slides offshore
during the second half of the week, temperatures will begin to
warm. A pop up shower or thunderstorm cannot be ruled out over the
terrain during this time as well.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
VFR conditions expected through the TAF period. Isolated
showers/thunderstorms possible at KMRB/KCHO this afternoon but
too low of confidence to include in TAF. Showers and thunderstorms
possible at all TAF sites on Saturday, which could produce brief
sub-VFR conditions. Winds through the period less than 10 kts from
the NW today, becoming SE on Saturday.

A cold front will cross the area Sunday, bringing widespread
showers and possible thunderstorms. Sub-VFR conditions are likely,
with the stronger storms producing heavy rain and gusty winds.

Mainly VFR conditions are expected during the first half
of next week in the wake of the cold front.

&&

.MARINE...
Sub-SCA conditions on all the waters through Sunday. An isolated
shower or thunderstorm is possible this afternoon and Saturday
afternoon which could bring gustier winds. More widespread showers
and thunderstorms expected on Sunday.

Small craft advisory conditions are likely Sun night and possibly Monday
and Monday night due to northerly channeling. Winds will then
become light as high pressure builds over the waters Tuesday into
Wednesday.

&&

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

&&

$$
SYNOPSIS...Sears/DFH
NEAR TERM...Sears
SHORT TERM...Sears
LONG TERM...DFH
AVIATION...Sears/DFH
MARINE...Sears/DFH



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