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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
928 PM EDT Friday Jul 25 2014

Synopsis...
high pressure will continue to push offshore tonight. A weak
trough will set up over the area Saturday. An unseasonably strong
cold front will approach the area Sunday before moving through
Monday. Canadian high pressure will return for Tuesday and
Wednesday.

&&

Near term /through Saturday/...
as of 01z...1018 mb surface high centered over southeastern Virginia/northestern NC border.
Southeasterly flow from this is across the lwx County Warning Area...allowing dewpoints to
return to the middle to upper 50s...low to middle 60s for central Virginia. Min
temperatures generally low 60s northwest...middle 60s south...and upper 60s to 70f
for urban near shore locales.

High pressure will be well off the East Coast Saturday morning and
southerly flow will continue to draw in higher dewpoints as well as warmer
temperatures. Forecast maximum temperatures will reach the middle to upper 80s Saturday
afternoon. Westerly flow aloft will lead to upstream disturbances
reaching the middle-Atlantic and a Lee trough to form. A shortwave
trough currently responsible for showers and thunderstorms across
Iowa-Illinois will reach the area Saturday afternoon. It is expected to
weaken but with the southerly flow advecting warm and moist conditions
into the region a few showers will be possible in The Highlands
and ahead of the Lee trough. Scattered showers with isolated
thunderstorms are possible across the I-95 corridor Sat late
morning through the afternoon. Activity will wane towards sunset.

A strong shortwave trough will drop into the northern plains Saturday
while convection will be ongoing ahead of a cold front across the
Midwest Saturday afternoon and evening. Some showers and
thunderstorms are expected to become severe and this activity will propagate
eastward and potentially impact the Potomac Highlands late
Saturday night/early Sunday morning. There are uncertainties
pertaining to the track of a potential mesoscale convective system Sunday morning which
will then impact the amount of cloud cover and therefore instability
the middle- Atlantic gains on Sunday.

&&

Short term /Saturday night through Sunday/...
a warm front will move across the region Saturday night/Sun
morning and moisture will continue to advect into the middle-Atlantic
Sunday. Low pressure will be across the Great Lakes and a cold
front will be stretched from PA to Ohio to MO. As the strong
shortwave trough nears shear will increase and showers and
thunderstorms are likely. Depending on the amount of instability the
region gets with the departing mesoscale convective system from the Ohio Valley... severe
storms may be possible with the threats of damage winds large hail
isolated tornadoes and heavy rain. Sref ensemble members show a
range of cape solutions for Sunday with 500 to 3000 j/kg possible.
One thing that is certain is that shear profiles increase Sunday
and hodographs become linear with 40-50 kts at 10-15k feet. A
strong line of thunderstorms will be possible Sun afternoon and
evening.

Outflow boundaries and the close proximity to the surface low across
Ohio/PA/NY will lead to the threat of severe thunderstorms capable of
producing tornadoes.

&&

Long term /Sunday night through Friday/...
shear profiles increase markedly Sunday evening...including in the
lowest few kilometers. This will enhance/organize convection on the
nose of a 50+ knot 500 mb jet. High precipitable waters and moderate cape suggest
a myriad of hazards from severe weather to heavy rain persisting
well into Sunday evening as a strong shortwave trough dives towards
the region from the Great Lakes.

Models differ in how quickly the upper trough and surface cold front
cross the area...but if the front does not clear the coast by Monday
afternoon then a severe weather threat could arise again. Best
chance for this would be east of the Blue Ridge mountains.

Following an active start to the week...a large area of high
pressure will build toward the region from Canada resulting in dry
weather and below normal temperatures and humidity for most of the
week.

&&

Aviation /01z Saturday through Wednesday/...
VFR conditions prevail outside of valley fog locations tonight as
moisture increases with the high now off the coast. Southerly winds
around 10-15 kts will occur through the afternoon. A few isolated
showers will be possible near dca-BWI-mtn Saturday afternoon.
Showers and thunderstorms will be possible Sunday and MVFR/IFR
conditions will be possible. A few thunderstorms may produce gusty
winds...large hail and isolated tornadoes.

MVFR or lower ceilings/visibilities in showers/thunderstorms Sun night-Mon...improving to
VFR Monday night. SW wind around 10 kts becoming northwest 15-20 kts and gusty
Monday evening west/ cold frontal passage.

&&

Marine...
southerly flow 10 to 15 knots...with some possible Small Craft Advisory gusts late
tonight...midnight shift will have to monitor this. Southerly flow will
increase Saturday afternoon as channeling occurs. A Small Craft Advisory is in
effect from the Maryland Chesapeake Bay south of Pooles Island and lower
tidal Potomac River Sun afternoon through the evening. Isolated
showers are possible Sat afternoon.

A cold front approaches Sunday and showers and thunderstorms are
likely. Some storms may produce gusty winds large hail and
waterspouts creating low visibilities.

Showers/strong storms likely Sun night-Mon...subsiding Monday evening.
Small Craft Advisory winds/seas probable Monday evening into Tuesday with gusty northwest flow
behind cold front.

&&

Climate...
a record event report (rer) was sent for the 57f that BWI reached
this morning. That is a new min temperature record for Baltimore. It
broke the old record of 59f.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 1 PM Saturday to 2 am EDT Sunday for
anz531>534-537-539>543.

&&

$$
Synopsis...baj/has
near term...baj/has
short term...has/dfh
long term...dfh
aviation...baj/has/dfh
marine...baj/has/dfh
climate...baj

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