Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 280802
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
402 AM EDT Sun May 28 2017

.SYNOPSIS...A surface trof will move across the area tonight
followed by a weak cold front Monday afternoon. Upper level low
pressure will linger north of the Great Lakes Monday night
through the remainder of the week with persistent weak high
pressure over the Mid-Atlantic.

&&

.NEAR TERM /THROUGH TONIGHT/...Dense fog has formed across the
northern part of the fcst area with many sites reporting less
than a quarter mile visibility.

For today, weak sfc front/trof will get hung up across the area
today and this evening with models indicating decent sfc
convergence across the nrn part of the fcst area. A shortwave-
trough will move across the area this evening and help trigger
numerous to widespread showers and t-storms. Overall, trend in
the models and ensembles the past 24 hrs is for weaker sfc
convergence and less QPF than yesterday. Despite this, there is
still some concern for flash flooding mainly across the far
northwest part of the fcst area where sfc convergence/lift will
be strongest and a plume of 1.5+ inches of PW will advect in.
1-2 inch hourly rain rates can be expected with heaviest
showers. Isolated instances of flash flooding are possible
mainly across Allegany, Mineral, and Grant counties. Think
severe threat will be more limited due to plenty of cloud cover
and weak instability below 1000 J/kg.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...Things will calm
down somewhat as drier air filters in on westerly flow, but it
won`t be completely dry. Still risk of showers/t-storms Tue
afternoon as a weak cdfnt moves through.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...

The upper level pattern for the middle and end of the week will
feature a closed low drifting across eastern Canada. While
increasing model spread of this feature late in the week lends some
uncertainty, there is some signal in the noise.

On Wednesday, a weak cold front will be drifting south of the area.
There are some indications this front could waver, resulting in
lingering chances of showers, but eventually high pressure building
from the west should lead to higher probabilities of dry conditions.
Thursday has the highest probability of being dry this week. Return
flow will begin on Friday, although forcing/instability aren`t that
notable. A cold front will be sinking southward next weekend,
although progress will be slow since it will be parallel to the
upper flow. Thus an unsettled period appears probable, but timing is
uncertain.

Temperatures will settle close to normal behind the front on
Wednesday and Thursday, then warm back up (highs in the 80s) ahead
of the next front on Friday and Saturday.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...LIFR conditions
through 12Z today at KCHO and KMRB due to dense fog. Then,
showers and t-storms this afternoon and evening with brief
MVFR/IFR cigs in t-storms with heavy rain.

Overall Wednesday should be VFR, but there is a small chance of
showers as a front sags south of the area. Winds could also gust
around 20 kt. VFR conditions are expected Thursday as high pressure
builds in from the west.

&&

.MARINE...Winds should remain below SCA through the first half
of the week, but higher winds and waves can be expected near
thunderstorms.

Depending on the position of a cold front, winds could near SCA
levels on Wednesday but confidence is low. Lighter winds are
expected on Thursday as high pressure builds in from the west.

&&

.TIDES/COASTAL FLOODING...Water anomalies will continue to rise
through 12Z Mon with minor coastal flooding expected at many of
the coastal sites. Winds turn westerly on Mon, but they will be
generally light and may not be able to lower anomalies that
much.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory from 8 AM this morning to 2 PM EDT this
     afternoon for DCZ001.
MD...Dense Fog Advisory until 7 AM EDT this morning for MDZ003>005-
     501-502.
     Coastal Flood Advisory until 10 AM EDT this morning for MDZ014.
     Coastal Flood Advisory until 8 PM EDT this evening for MDZ017.
VA...Dense Fog Advisory until 8 AM EDT this morning for VAZ028-031.
     Coastal Flood Advisory from 8 AM this morning to 2 PM EDT this
     afternoon for VAZ054.
WV...Dense Fog Advisory until 8 AM EDT this morning for WVZ053.
     Dense Fog Advisory until 7 AM EDT this morning for WVZ050>052-
     504.
MARINE...None.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...ADS
AVIATION...ADS/LFR
MARINE...ADS/LFR
TIDES/COASTAL FLOODING...LFR



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