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Area forecast discussion...updated 
National Weather Service Baltimore Maryland/Washington District of Columbia
1036 am EDT Wednesday Jul 1 2015

a cold front will approach the region from the northwest today.
The front will stall out in central Virginia tonight. The front
will linger over the region through the weekend...with several
waves of low pressure moving east along it.


Near term /through tonight/...
weak cold front will cross the region later today. Instability out
ahead of the front will be marginal at best with isolated to
scattered coverage later this afternoon into the early evening
mainly to the south and east of the District of Columbia/Baltimore metropolitan areas.
Severe threat is minimal at this time. Afternoon high temperatures will
likely reach the middle to upper 80s east of the Blue Ridge...lower
80s to the west.

Shower and thunderstorm threat will diminish after sunset.
Overnight lows will dip back into the 60s in most
locations...except lower 70s in the metros.


Short term /Thursday through Friday night/...
low pressure will be tracking along the frontal zone...reaching
the lower Ohio Valley on Thursday. This will draw some moisture
into the front over our region. Still some timing/placement
differences amongst models...but expect a S to north progression of
showers and embedded thunder (at least some instability may be
present...especially southern tier). Questionable how much if any
precipitation reaches the M-d line during the day on Thursday. Heaviest
activity likely stays over Ohio Valley during the day.
Temperatures will be limited down a few degrees by the clouds and
precipitation...upper 70s to middle 80s.

Thursday night through Friday night...a great deal of uncertainty
remains...with differing solutions about the path and timing of
low pressure systems riding east along the front. Some guidance
like the GFS brings a significant wave of low pressure slowly
across the region during this period...which would result in
showers and perhaps a few isolated thunderstorms. The European in
contrast is notably slower...with the main wave of low pressure
waiting until Friday night to begin affecting the area. The
Canadian ggem is even slower...holding the most significant low
back even longer. With considerable uncertainty in the significant changes were kept chance to
low- end likely probability of precipitation and temperatures somewhat cooler than normal
in the forecast.


Long term /Saturday through Tuesday/...
uncertainty remains about the weekend into early next week with
the aforementioned significant timing discrepancies regarding
passing disturbances between various models. This makes any
attempt to Iron out details very difficult. The one constant is
the apparently never leaving quasi-stationary front. Inherited
generally chance probability of precipitation through the period and did not make major
changes. Temperatures start out below normal and *may* rise to near
normal if the front can finally nudge its way north of US early
next week. Confidence is low.


Aviation /15z Wednesday through Sunday/...
mostly VFR expected today into tonight. A few isolated/scattered
showers/storms possible later this afternoon and evening mainly
from kbwi and kmtn to kdca and kcho. VFR tonight...perhaps some
patchy fog in spots.

Next chance of precipitation will arrive Thursday...with greatest
potential for impacts at cho.

From Thursday night Onward...main concern is possible IFR ceilings and
visible from occasional heavier showers or thunderstorms as a front
remains stalled in the general area. With the front nearby...winds
will be hard to predict with significant certainty until the
period draws closer.


winds below Small Craft Advisory expected much of today. A few isolated/scattered
showers and thunderstorms could develop over a portion of the
waters later this afternoon and evening.

Main concern in the extended for marine is occasional heavier
showers and thunderstorms...with appears possible just about every
day from Friday into early next week. Winds should generally be
sub Small Craft Advisory but as disturbances pass through the area...a period of Small Craft Advisory
winds is not impossible.


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


near term...krw
long term...rcm

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