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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
358 am EDT Tuesday Jul 28 2015

Synopsis...

A weak stationary front will dissipate over the area today.
Meanwhile...hot and humid weather is expected during the middle
portion of the week as high pressure strengthens offshore resulting
in southerly flow. A cold front will cross the region late
Thursday bringing scattered showers and thunderstorms. High
pressure builds back in Friday and remains through the weekend.

&&

Near term /through Wednesday/...

Seasonably warm/hot and humid for late July with high temperatures
within a few degrees of 90 for most today and tomorrow. Dewpoints
around 70 will feel uncomfortable with the heat in the afternoon
and evening. Not a lot going on synoptically with a weak
stationary front decaying today...followed by weak high pressure
reasserting itself tomorrow. Scattered showers and thunderstorms will be
more pronounced in the SW than the NE today and Wednesday. Not
expecting any organized convection.

&&

Short term /Wednesday night through Thursday/...

Wednesday night...storm chances in southwest diminish fairly rapidly
Wednesday night as instability wanes and inhibition strengthens. It
will remain rather warm and moist...so a stray shower along residual
boundary not entirely out of the question...though kept out of grids
for now.

Thursday...500 mb height rises continue through early Thursday...as
ridging over the central United States continues to expand toward
our area. Expect heights to begin to lower slightly by midday as
wave approaches from the northwest. Main piece of energy will stay
to our north...but sagging cold front will impact the entire area
through the day. Before frontal passage...expect temperatures to
warm up into the 90s...and when combined with surface dewpoints in the
l/70s...expect another day of heat indices around 100f.

Near/along the front...confidence continues to increase in line or
broken line of showers and thunderstorms impacting the area from
northwest to southeast Thursday afternoon and evening. It appears
that most areas will receive some precipitation...though timing is still
uncertain. NAM/European model (ecmwf) move front through metros before 8 PM...while
slower GFS moves front through metros after 8 PM. Anemic deep layer
shear continues to be the limiting factor to more robust severe
threat...as belt of stronger westerlies aloft remains well to the
north...and its hard to get sustained organized severe with 500 mb winds
at or below 20 kts. However...instability will be moderate over parts of the
area...so isolated pulse severe with gusty winds a possibility. At this time
think progressive nature of boundary should preclude any widespread
flash flooding threat...despite precipitable waters at or above 1.75 inches and weak
steering layer flow. Shower/storm activity could linger overnight
Thursday south and east of District of Columbia...but most activity should move
through the County Warning Area by 8 am Friday.

&&

Long term /Thursday night through Monday/...

Sensible weather impacts during the long term rather benign...as primary
front remains to our south and broad surface high pressure over the
Midwest builds into the region. Frontal passage late Thursday will
knock the dewpoints back into the u50s to l/m60s...which will be
much more comfortable. Expect temperatures near normal (m/u
80s)...with a slow warming trend through Monday. Precipitation chances at
any one location during the long term are very low...due to the lack
of discernible lifting mechanisms and poor quality moisture.

&&

Aviation /08z Tuesday through Saturday/...

With the weak stationary front slowly dissolving over the
region... the winds will be light and more erratic in direction.
Wednesday the southerly flow will become more established. Scattered and
mainly afternoon/evening showers/thunderstorms will persist over
the region today and tomorrow. Fog and ceilings will also be erratic
overnight and the following night as well...with some VFR and some
IFR.

VFR conditions expected overnight Wednesday under high pressure. Sub-
VFR conditions possible at all terminals Thursday afternoon and
evening near showers and thunderstorms along cold front. VFR
conditions return to most terminals by late Thursday night and
remain through the period as high pressure builds back in.

&&

Marine...

With the weak stationary front slowly dissolving over the
waters...the winds will be light and more erratic in
direction...especially the North Bay. Wednesday the southerly flow will become
more established.

Southerly channeling could lead to Small Craft Advisory gusts Wednesday night on the
Bay. Small Craft Advisory conditions could redevelop Thursday afternoon as cold front
approaches the waters. High pressure regains control Friday through
the remainder of period with sub-Small Craft Advisory winds.

&&

Tides/coastal flooding...

Coastal Flood Advisory will be lowered for Anne Arundel and
Annapolis as the current high tide is remaining just below the
threshold. The afternoon high tide will be lower...and the
following early Wednesday morning should be similar to the current tide.

&&

Climate...

For Washington...June and July have been consistently stormy. There
have been more days with rain in June and July this year /30/...than
any June/July combo since 2000 /31/. If we exceed 2000...the only
year on record /since 1871/ with more is 1906...which had 33.

Baltimore has had significantly fewer days with rain showers...25
days this June/July. The record is more distant...35 days in 1889.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...none.

&&

$$
Synopsis...cas
near term...cas
short term...mse
long term...mse
aviation...cas/mse
marine...cas/mse
tides/coastal flooding...cas
climate...cas

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