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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
339 PM EDT Thursday Jul 2 2015

a stationary front will remain over central Virginia and southern
Maryland through the weekend. Several waves of low pressure will
move east along the front as an active pattern continues. High
pressure will return for the first half of next week.


Near term /through Friday/...
quasi-stationary boundary appears to be located at the far
southern extent of the County Warning Area...if not farther...with a weak surface low
over the Chesapeake Bay. The front will serve as the conduit of
unsettled weather through the upcoming weekend. In the near
term...widespread showers are located ahead of a vorticity maximum in the
Ohio Valley. These will skirt southern areas through the remainder
of the afternoon. Very little instability has built with extensive
cloud cover and therefore expect thunder to be rather limited in
our County Warning Area. Orange-St. Marys seeing a few sun breaks and on northern
edge of instability perhaps a little higher chance there.
Farther north...shower activity will be isolated/scattered.

Expect some downturn to shower activity after the vorticity maximum passes
this evening. However...scattered showers will remain possible with
the front in the vicinity through the night. Did not want to go
completely dry as any impulse could spark a shower in the moist
environment...however it/S plausible the northern half to two-thirds
of the area could be dry. Some patchy fog may develop but at this
time does not appear to be dense. Overnight lows will remain
mild...with lower 60s northwest to around 70 southeast.

A wave of low pressure will track east along the stalled front on addition to potential middle-level disturbances rotating
out of a deepening trough over the Ohio Valley. Expect showers to
increase in coverage from SW to NE from morning into the
afternoon. A little questionable how far north the activity gets
and whether it will be in one slug or the off/on variety.
Therefore have a gradient of probability of precipitation from 40 to 80 NE to SW...but
these may need to be raised. We will likely be on the stable side
of the thunder should be rather limited...especially
with northward extent. Think that the rain will fall at a slow
enough rate to limit a flood threat...but with a moist atmosphere
and wet soils...this will need to be monitored. Went on cool side
of guidance for highs with clouds/precip...with most locations in
the 70s.


Short term /Friday night through Saturday night/...
frontal boundary will remain just south of the region with waves
of low pressure riding northward along the boundary. Showers will
remain in the forecast Friday night and into the 4th of July
Holiday. Winds will likely remain out of the east or northeast
which will keep the atmosphere cooler and more stable. Have
removed mention of thunderstorms from the forecast at this time. High
temperatures will likely only reach the middle to upper 70s
during Saturday with lows in the 60s.


Long term /Sunday through Thursday/...
frontal boundary south of the area drifts farther south Sunday
and Monday as upper ridge builds east over the Midwest. Any isolated
to possibly scattered thunderstorms both day look to be diurnally
driven. By Tuesday front returns to area and a coastal low develops
off Delaware-Maryland-Virginia in response to upper level trough. Increasing chance
of convective development especially over eastern Maryland and Virginia
Tidewater. Next cold front approaches region from the Midwest
Wednesday and slows with more active weather into late next week.


Aviation /20z Thursday through Tuesday/...
an unsettled forecast is expected through Friday due to a stalled
front across southern Virginia. Cho has the highest chance of seeing
multiple rounds of showers through the period...with more uncertain
coverage for the metropolitan terminals. Any period of steadier rain could
bring MVFR or possibly IFR conditions. Tough to time these out now.
The most numerous coverage is expected Friday afternoon. There is a
limited chance of thunder during the afternoon hours. In
addition...fog and/or low ceilings may develop tonight into Friday
morning. Generally have MVFR conditions indicated...but IFR is
possible. Light winds expected from the North/East quadrant.

Overcast conditions along with a chance for showers will persist
Saturday and perhaps into Sunday. Conditions will liely improve
later Sunday and into early next week.


front stalled south of the area through Friday. Sub-Small Craft Advisory conditions
likely. However by late Friday afternoon...low pressure will track
along the front and may increase easterly winds over the southern
parts of the waters. Periods of showers will cross the waters. Their
main impact will be to reduce visibility...but embedded thunderstorms
could also bring gustier winds. Expect these to be
isolated...relegated to afternoon/evening hours...and most likely
over southern parts of the waters.

Winds are expected to remain below Small Craft Advisory levels Saturday into
Monday. Occasional showers could impact the waters during this
time but the threat for thunderstorms is low.


Lwx watches/warnings/advisories...
District of Columbia...none.


short term...krw
long term...cem

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