Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 260752
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
352 AM EDT Fri May 26 2017

.SYNOPSIS...Weak high pressure will return to the area tonight
before moving off the coast Saturday afternoon. A warm front
will stall out overhead Saturday night through Sunday. A stronger
cold front will pass through the area late Sunday night.

&&

.NEAR TERM /THROUGH SATURDAY/...

Low pressure is located over Long Island NY this morning. A closed
upper low is across E PA/NJ and will continue to depart to the NE.
Light showers will continue to move across the northern half of the
outlook area this morning. Upslope showers along the Allegheny Front
will continue through the day today. Light W-NW winds will also
continue across the Mid-Atlantic region early this morning before
ramping up after sunrise. Breezy conditions expected today with NW
winds 15-20 mph with gusts up to 30 mph by afternoon. Partly sunny
conditions expected today with temperatures rising into the 70s.
Isolated showers can not be ruled out mainly across northern MD this
afternoon.

High pressure moves overhead tonight. Clearing is expected this
evening but clouds return after midnight as the next system
approaches from the Mid-West. Temps will drop into the mid to upper
50s tonight.

Low pressure will move into the southern Great Lakes tonight while a
warm front approaches the Ohio Valley/Appalachians Mtns. Showers are
expected to move across the mtns into Saturday morning. The ECMWF-Hi
Res is depicting a complex moving into the region Saturday morning
that may bring widespread showers across the area. At this time
conditions will likely be stable and due to the spread in QPF
guidance confidence is low in the coverage. The warm front will move
into the Mid-Atlantic region by Saturday afternoon. Showers and
thunderstorms are expected in the warm sector mainly south of a line
stretched from the Potomac Highlands to southern MD. 0-6 km bulk
shear will increase to 40-50 kts across the warm sector. Dewpts will
rise into the mid to upper 60s and 1-2 J/Kg of CAPE are expected.
This will allow some thunderstorms to become strong to severe. There
is a slight chance/15% of severe weather Saturday afternoon in the
locations mentioned above. All threats, large hail, dmg winds and
isolated tornadoes are possible. People planning to be outside
Saturday should remain aware of changing weather conditions.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...

Low pressure from the Great Lakes will move east and stretch down
into the Mid-Atlantic region Sat night. This will push the warm
sector to the south and east. A shortwave trough is expected to dive
south across New England Sat night and showers will be possible
through the night mainly across northern MD. An upper level ridge
will move overhead by Sun morning and a brief period of dry
conditions are expected. The active period continues later Sunday as
another low pressure system approaches from the Great Lakes. Showers
will move across the Appalachians Sunday afternoon. At this
time...areas east of the Blue Ridge should be mostly dry Sun
afternoon however this system may speed up resulting in showers
across the region Sunday. Temps will reach the 70s Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...Sunday evening
could be a very active period according to latest 00Z ECMWF as
it shows a sharp cdfnt moving through the area. Flash flooding
appears the biggest concern given very wet antecedent
conditions. A flash flood watch may be needed for the 18Z Sun-
06Z Mon time frame for parts of the area. By 06Z Mon, the cdfnt
should be east of the area with wx conditions improving. Next
week, conditions look relatively bening compared to this week as
dry westerly flow establishes. Memorial Day looks nice under
weak high pressure. A weak cdfnt will bring a chance of showers
around the Tue-Tue night time frame with weak high pressure
building again for the second half of next week.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...

BCFG reported around IAD this morning. There may be some patchy
fog around IAD/BWI this morning prior to winds increasing. VFR
conditions expected today through Saturday night. West to
northwest winds will gust around 20 to 25 knots Friday. A few
showers and thunderstorms are possible Saturday. Some storms may
become strong to severe during the afternoon and evening hours.


Sub-VFR conditions expected Sunday into Monday with rounds of
showers and thunderstorms moving through our region with a
boundaries stalled/moving through.

Conditions will begin to improve late Sun night through the
first half of next week as cdfnt pushes east and sw flow
develops allowing for much needed drying.

&&

.MARINE...

A Small Craft Advisory is in effect for most of the waters this
mroning as westerly flow increases behind departing system. Gusts up
to around 20 knots expected this morning.

A Small Craft Advisory is in effect for all of the waters today due
to gusty west to northwest winds expected behind departing low
pressure. Winds will quickly diminish toward sunset. Weak high
pressure will build overhead Friday night before moving offshore
Saturday. A warm front will stall out near the waters later Saturday
through Saturday night. Additional showers and thunderstorms are
possible during this time...especially Saturday afternoon and
evening. Winds remain below SCA through Sunday afternoon.

Gradient winds will remain below SCA all of next week, but winds
and waves can be locally higher near thunderstorms especially
Sunday night.

&&

.TIDES/COASTAL FLOODING...Moderate coastal flooding is occurring
at Straits Point. Minor coastal flooding is occurring
elsewhere. This morning`s high tide should be the last with
coastal flooding issues for most locations except at Straits
Point where water anomalies are higher and will take longer to
return to normal.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 11 AM EDT this morning for DCZ001.
MD...Coastal Flood Advisory until 10 AM EDT this morning for MDZ014-
     018.
     Coastal Flood Advisory until 10 AM EDT this morning for MDZ011.
     Coastal Flood Warning until 4 AM EDT early this morning for
     MDZ017.
     Coastal Flood Advisory until 7 AM EDT this morning for MDZ017.
VA...Coastal Flood Advisory until 11 AM EDT this morning for VAZ054.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for
     ANZ530>534-536>543.
     Small Craft Advisory until 6 PM EDT this evening for ANZ535.

&&

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


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