Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 281903

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
303 PM EDT SAT MAY 28 2016

High pressure will remain over the area through the first part of
the coming week with low pressure impacting the area from the
south. A cold front may push through the region at the end of the


Surface high combined with ridging aloft over the eastern
portions of the US keeping warm conditions in place. Temps this
afternoon reaching the 80s across the board except for isolated
spots right along the shoreline. Isolated thunderstorms popping up
on radar this afternoon, mainly impacting right along the Mason-
Dixon and northward. The warm temps leading to marginal
instability but with lack of any real forcing mechanism both at
the surface and aloft along with minimal shear, not anticipating
anything severe, only brief heavy rainfall.

Any activity drops off after sunset with the loss of diurnal
heating. Thinking dry conditions for most of the area most of the
night. Increasing moisture in the low levels could result in
patchy valley fog as we saw last night. The 12Z guidance has
slowed the precip down a bit for tomorrow, but cannot rule out
showers reaching the southern fringes of the CWA by daybreak Sun


Increasing coverage in rain and thunderstorms Sunday. As
previously mentioned, latest guidance showing that the rain will
reach the area slightly slower than previous runs indicated. TD 2
nearing the SC coast this afternoon is expected to be right along
the coast by Sun morning, then slowly progressing nearly parallel
to the coast into the first part of the coming week. Please refer
to NHC products for the official forecast.

Also to monitor during this time is an approaching trough across
the northern US. As energy from the low to the south swings
around the western side of the ridge aloft, it becomes sandwiched
between the ridge to the east and this approaching trough from the
west. There remains some question exactly where this energy
becomes trapped, but the latest guidance shows to be right across
the Mid- Atlantic. This will aid in enhancing further shower and
thunderstorm development across the CWA.

Moisture advection will increase Sun from the low to the south and
combined with the aforementioned features, the potential exists
for moderate to periods of heavy rain. With the overall flow on
the lighter side and the potential of training activity, will
continue to highlight flooding potential in the HWO. At the moment
can not pinpoint exactly where, but the latest thinking is that
the heaviest band sets up between the Blue Ridge and Chesapeake

The rain will continue into Monday, especially over eastern areas.
Subsidence builds in later in the day with the next ridge nudging
in from the west so should see precip cutting off over western
areas with a possible dry period over the east before the remnants
of the low finally move north mid week.


Upper level ridging starts building up on Tuesday and a low
pressure system stalls over the North Carolina coast through
Thursday. Moisture advection from this system will depend on its
location... but guidance is showing that showers and thunderstorms
are possible over our CWA from Tuesday into Thursday.

A cold front approaches from the west on Friday and moves across
Friday night into Saturday, continuing with the chance of showers
and thunderstorms during this period. Upper trough approaches the
eastern CONUS during the weekend.

High temperatures will be in the upper 70s and low 80s before the
cold front... in the 70s for Saturday. Low temperatures will be in
the 50s and 60s.


VFR conditions through at least the first half of tonight.
Possible patchy fog dropping vis to 4-5SM late tonight, around
daybreak. Rain moves in generally late tomorrow morning into Sun
afternoon. With the heavier rain later in the day comes sub-VFR
conditions in both the cigs and vis, lasting into Sun night.
Improvement back to VFR returns on Monday. Winds less than 10
knots through the period, southerly becoming easterly.

VFR conditions expected for Tuesday through Thursday...with some
showers and thunderstorms possible bringing brief periods of sub-
VFR conditions due to a low pressure system to our southeast.


SCA gusts on the open waters of the Chesapeake Bay this afternoon
on southerly flow. Sub-SCA on the remaining waters. Any stronger
gusts will diminish after sunset, with sub-SCA conditions on the
waters through the first part of the coming week.

Sub-SCA conditions expected as winds will be below SCA criteria.
Showers and thunderstorms possible during the waters during this
period with low pressure system to our southeast.


MARINE...Small Craft Advisory until 7 PM EDT this evening for


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