Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 210129

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

A cold front will continue to drift south across North Carolina
tonight before lifting north as a warm front late Sunday. A
cold front will move through the area from the west Monday.
High pressure will briefly return Monday night before low
pressure develops over the Carolinas Tuesday and moves northeast
off the Delmarva into Wednesday. Upper level low pressure will
then linger over the area into Friday.


As of 9pm, a cold front is drifting into southern NC with 1032mb
surface high pressure centered over northern Quebec and 1006mb
surface low over northeastern Iowa. The warm sector of this low
extends to the Gulf of Mexico with a plume of heavy
thunderstorms extending into the Midwest.

An onshore flow is across the area with clouds over the area
except for lower southern MD. Expect low to mid 50s inland and
upper 50s urban/nearshore.

Onshore flow persists Sunday with the wedge firmly in place. Max
temps upper 60s with rain approaching from the west late.


The central CONUS low will lift to Lake Superior through Sunday
where it will linger through Monday as it becomes a sprawling
occluded low. The cold/occluded front will struggle to push east
through the area Monday with prefrontal showers crossing the
area Sunday night into Monday.

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 likelihood 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 continues well into Sunday. Surge this evening
in southern MD waters, easing after midnight when the SCA ends.

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 9 PM EDT this evening for ANZ532-
     Small Craft Advisory until midnight EDT tonight for ANZ534-537-


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