Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 230058
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
858 PM EDT Tue Aug 22 2017

.SYNOPSIS...
A cold front will cross the region tonight into Wednesday
morning. Reinforcing upper level energy will help to push the
front offshore and allow for high pressure to build in from the
northwest Thursday into Friday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Much of the convective activity so far today has remained north
of the Mason Dixon line or west of the Allegheny Front. However,
now with lowering heights and increasing shortwave energy as the
upper trough moves into the region, in addition to an
approaching cold front, we`re starting to see an uptick in
activity. Expecting two "rounds" with the first being the
southern end of a developing squall line across Pennsylvania.
This has the highest chance to become strong to perhaps locally
severe as it traverses across northern Maryland over the next
1-2 hours through an environment with 1000+ J/KG of MLCAPE and
40-50 knots of effective shear. The second will be scattered
showers and isolated thunderstorms moving in from West Virginia
later this evening and overnight. Instability will be lessening
overnight, so not expecting any additional severe threat in
these cells.

By morning, the front will be draped across the region,
continuing to push southeastward. Temperatures will still be
quite mild out ahead of the push of cooler/drier air, with lows
from 68-75F.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Showers/isolated thunderstorms will be possible across the
southern 2/3 of the forecast area Wednesday. By Wednesday
precipitation should be well offshore. Tonight`s fropa will
bring an end to this recent heat wave. Highs Wednesday back
into the mid 80s/dewpoints back into 60s. Conditions will
continue to become more comfortable Wednesday night and
Thursday.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
The long term period looks fairly dry with surface high
pressure dominating the weather conditions over our area. Some
diurnally or terrain driven showers and thunderstorms could
develop at times with shortwaves moving through, but at this
moment looking at mostly dry weather conditions. Temperatures
will be slightly below normal, with highs around 80 degrees,
near 70 at higher elevations.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
Cold front will cross the region tonight into Wednesday morning.
This will bring scattered showers and isolated thunderstorms to
the region, with the highest chances of thunderstorms at
MRB/IAD/BWI/MTN. Brief reductions to ceilings/visibilities are
possible, and a stronger storm or two has the potential to
bring gusty winds and lightning.

Otherwise, VFR conditions expected at all terminals Wednesday
through Sunday with high pressure gradually building over our
area.

&&

.MARINE...
Small craft advisories remain in effect through 2 AM for all
waters and through 5 AM for much of the Chesapeake and lower
Tidal Potomac with gusty southwest winds out ahead of an
approaching cold front. In addition, thunderstorms are possible
through this evening, and Special Marine Warnings may be
necessary, especially across the northern Chesapeake Bay.

No marine hazards expected Wednesday through Sunday.

&&

.TIDES/COASTAL FLOODING...
Anomalies are around 0.5 to 0.7 ft this evening. No flooding is
currently forecast with Wednesday morning`s high tide cycle,
but may come close at Annapolis, Straits Point, and Washington
DC. Then northwest winds will arrive Wednesday, and no
additional flooding is forecast past this cycle.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 5 AM EDT Wednesday for ANZ531>534-
     537>543.
     Small Craft Advisory until 2 AM EDT Wednesday for ANZ530-535-
     536.

&&

$$
SYNOPSIS...MM/ABW
NEAR TERM...MM/ABW
SHORT TERM...ABW
LONG TERM...IMR
AVIATION...MM/IMR/ABW
MARINE...MM/IMR/ABW
TIDES/COASTAL FLOODING...MM/ABW


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