Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 201852
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
252 PM EDT Sun May 20 2018

.SYNOPSIS...A weak cold front will cross the area tonight and
settle over the Carolinas on Monday. High pressure will build
over the area on Monday. The front will return north as a warm
front on Tuesday with a cold front expected to pass through the
area on Wednesday. Weak high pressure will build over the area
for the second half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...

An isolated shower or t-storm will remain possible into early
this evening as a weak cold front crosses the area. Otherwise,
just sct-bkn cumulus clouds. Models now indicate the front will
make it much farther south into southern VA and North Carolina
on Monday leading to a dry day on Monday. Areas of fog are
possible late tonight given strengthening mid-level subsidence
and very wet/moist ground despite lowering sfc dewpoints/dry air
advection.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...

Sct-bkn mid-high level clouds Mon under sfc high pressure.
Strengthening warm air advection pattern Mon night and Tue
associated with front lifting north will bring another round of
showers late Mon night into Tue evening with between a quarter
to half inch of rain expected. Chance of elevated t-storms Mon
night mainly west of the Blue Ridge. Things begin to dry out
late Tue night as main shield of rain lifts to the east and cold
front begins to push south.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...

A upper level trough over eastern Canada will slowly shift southward
into Maine and New England on Wednesday. A surface low associated
with the trough will settle over New England. A frontal boundary
associated with the low will become stalled to the southeast of our
county warning area. Both GFS 12Z and the 00Z Euro show a chance for
showers moving through our region on Wednesday. Precipitation will
be most likely on the western side of the Shenandoah mountains and
our western parts of our CWA due to upsloping flow out of the west.
The area should remain on the cold side but the front doesn`t look
to shift out of the region until early Thursday as a upper level
ridge shifts into the region from the west. Temperatures will hover
in the upper 70s to mid 80s throughout the region.

Thursday into Saturday, a upper level ridge shifts eastward over
our region. A high pressure system will slowly shift eastward into
our area from the Great Lakes. Skies will slowly clear and a
southerly flow forms as the high pressure shifts eastward off the
Atlantic coast on Friday. Temperatures will slowly build into the
low 80s thursday and then rise up into the mid to upper 80s toward
the end of next week. On Saturday, a cold front will approach from
the west leading to stronger warm air advection into the region.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...

Patchy dense fog possible at KMRB late tonight, otherwise 3-5sm
br at KCHO and KIAD. Showers return to the area late Mon night
and Tue with possible flight restrictions.

On Wednesday, a frontal boundary will be stalled to the southeast of
the county warning area. A westerly to northerly flow is expected
to the north of the boundary. Precipitation is possible which could
lead to the dropping of both visibilities and ceilings on
Wednesday. Thursday, skies begin to clear and winds look to remain
mostly light.

&&

.MARINE...

Winds should diminish below SCA by 22Z today then remain below
SCA through Tue morning. Possible SCA Tue afternoon into Wed as
winds turn southerly as warm front lifts through.

A frontal boundary to the southeast of the CWA will lead to winds
out of the west and the north. A northerly flow could lead to longer
fetches and the need for small craft advisories. Thursday, skies
are expected to clear as high pressure settles over the region.
Winds should remain below Small craft advisor thresholds.

&&

.TIDES/COASTAL FLOODING...

Moderate coastal flooding at Georgetown through 6PM this
evening. Otherwise, minor coastal flooding expected at DC
Waterfront and Georgetown into Monday afternoon.

&&

.CLIMATE...

It has been an unusually wet pattern over the last week. For DCA
(Reagan National), there has been at least 1/4" of rain each of
the last 7 days. This is the longest streak on record. The previous
longest was 5 days in 2011, 2009, 1975, 1950, 1942, and 1937.
Precipitation records date back to 1871.


&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Warning until 6 PM EDT this evening for DCZ001.
     Coastal Flood Advisory from 6 PM this evening to 6 PM EDT
     Monday for DCZ001.
MD...None.
VA...Coastal Flood Advisory until 6 PM EDT this evening for VAZ054.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for
     ANZ530>543.

&&

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



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