Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 201849

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
249 PM EDT Sat May 20 2017


A cold front is positioned across southern Virginia. The front
will return north into the area as a warm front late Sunday
ahead of a cold front which will move through from the west
Monday. High pressure will briefly return Tuesday before
another cold front impacts the area Wednesday. High pressure
will return for the end of the week.



Via a now-stationary boundary across southern VA and a 1032 mb
high over Quebec Mid Atlantic has moved into somewhat of a CAD
situation with a band of stratus setting up across PA into
northern VA. If history is an indicator this will be hard to
dislodge after sunset. Expect a mostly cloudy night with lows in
the 50s.

In the southwest portion of the forecast area...where there has
been a decent amount of insolation and temperatures have risen
to near 80...scattered convection is developing. RNK VWP is more
representative of the wind field there than our radar. All the
way to 30K ft the wind field is light. Brief heavy downpours
will be possible. Thunderstorms will be possible through around
9 pm.



Likewise the band of low level moisture will persist over the
region Sunday keeping it cloudy and relatively cool. Highs
around 70.

Things will change Sunday night as a cold front reaches the
Appalachians forcing the CAD-style cloud wedge to weaken but a
line of showers/isolated thunderstorms to move through the area.
Severe threat will be very low with this front as it will be
coming through at night after a day with very little heating.
Have upped PoPs to likely everywhere Sunday night.

Precipitation chances will continue Monday as the cold front
slowly works it way off the east coast. For the entire event
QPF of 1/2" west to 1" east is possible. Precipitation should be
ending in the west during the afternoon and east by evening.

Improvement in sky condition is expected Monday night. Lows in
the 50s except warmer in the cities and Lower Southern MD.



High pressure should keep the region dry Tuesday. The chance
for rain showers return Tuesday night with a liklihood of rain
showers Wednesday and Wednesday night as a broad storm system
over the Ohio and Tennessee Valleys send pieces of energy our
way from the southwest.

The chance for rain showers or perhaps a rumble of thunder or two
will linger Thursday and Thursday night as the main low pressure
system decides to trek eastward toward the East Coast. Timing is
uncertain as to how long it will take for the main low to move out
of the area.

There could be some leftover upper level energy overhead Friday.
This could spawn a shower or two, mainly across the north and
eastern areas.

By Saturday, broad high pressure works its way into the region. Dry
conditions and seasonable temperatures expected Saturday.



Cloud wedge hanging over the Mid Atlantic tonight. Ceilings
high MVFR to low VFR. Some improvement in cloud heights is
expected Sunday ahead of a frontal boundary. Sunday night should
be wet with multiple showers..continuing into Monday morning. A
return to VFR is expected late Monday and Monday night.

Vfr conditions Tuesday. Winds light and variable. Mvfr conditions
Tuesday night. Winds light and variable. Ifr to lifr conditions
possible Wednesday and Wednesday night. Winds south 5 to 10 knots
Wednesday becoming light and variable Wednesday night.



Easterly flow over the waters this afternoon with scattered wind
gusts into the SCA range across the central Bay and lower
Potomac. SCA will remain in affect through 6 pm.

Next possible SCA situation will be Sunday night ahead of a cold
front and Monday behind the front.

No marine hazards Tuesday through Wednesday night.



Easterly onshore flow has developed due to high pressure over
eastern Canada. Flow turns southerly Sunday night as warm front
lifts into the area. Water levels will gradually increase
through Monday, with anomalies supporting elevated/minor coastal
flooding at Annapolis, Straits Point, and DC by Sunday night.


MARINE...Small Craft Advisory until 6 PM EDT this evening for


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