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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
258 PM EDT Tuesday Jul 22 2014

Synopsis...
high pressure will near the eastern Seaboard today and tonight. A
cold front will approach from the west Wednesday...and move
through the region Wednesday night into early Thursday. High
pressure is expected to return to the region to end the work week.

&&

Near term /through Wednesday/...
high pressure persists along the middle-Atlantic coast late this
afternoon. S-southeast winds have set up over the forecast area...with
moist air advecting into the region. Isolated to scattered showers
have popped up...and will continue to affect portions of the area
this afternoon. 12z soundings indicated a warm nose around
600mb...and this appears to be holding in place as showers have
had little vertical extent with tops reaching not far above the
freezing level. This will minimize the potential for thunderstorm
activity...although isolated thunderstorms will remain possible over some
of the mountains today. Otherwise expect some isolated to
scattered shower activity to continue...mainly along and west of
the Blue Ridge/catoctins...with a few spots receiving brief heavy
rainfall. High temperatures generally in the m80s across the forecast
area.

Shower activity decreases this evening...with dry conditions
expected in the overnight hours. With moist air in place...some
fog is possible...most likely in the sheltered valleys. Met/mav
guidance are in good agreement tonight. Lows in the 60s for
most...with low 70s in urban areas and near marine zones.

Wednesday starts with high pressure extending from the offshore
waters and into the Carolinas...with a cold front extending across
the lower Great Lakes and Ohio Valley. The cold front will
approach during the day...while a 500mb trough strengthens over
the the same region. Combination of instability...lift and
moisture is expected to support showers and thunderstorms...with
activity more likely over northern and western portions of the
forecast area that will be closer to the approaching front.
Isolated severe storms will also be possible across western Maryland and
the eastern WV Panhandle...which should be in the right entrance
region of the jet stream by late in the day. Damaging winds is
likely to be the main threat.

Wednesday will be the warmest day of the week...with highs in the
low 90s at most locations.

&&

Short term /Wednesday night through Thursday night/...
the cold front is expected to move through most of the forecast
area Wednesday night...and should be east of the I-95 corridor by
Thursday morning. Shower/thunderstorm activity should shift eastward
accordingly. Severe threat is uncertain...as better dynamics will
be offset by lower nighttime instability. Lows range from the middle
60s over eastern WV...behind the front...to the middle 70s along and
east of I-95.

Cold front moves east of the region on Thursday...while an upper
trough approaches from the west. Shower/thunderstorm chances continue with
cooler air aloft...but with a north-northwest flow chance of severe weather is
unlikely at this time. Temperatures will be cooler with highs ranging
from the upper 70s over higher elevations to the middle 80s elsewhere.

Upper trough moves through Thursday night...with dry conditions
expected except possibly over southern Maryland and portions of the Piedmont.
Lows drop into the 50s and 60s.

&&

Long term /Friday through Monday/...
a ridge of high pressure will build in from the northwest Friday and
Friday night to allow cooler and drier air to push into the region
through Saturday.

With the high moving to the coast and offshore during the day
Saturday...southeast to southerly winds will evolve...thus perhaps
spawning a shower in the Potomac Highlands with the upslope
component.

Disturbances in the upper levels will rotate in from the Ohio Valley
and lower Great Lakes Saturday night and Sunday...thus...bringing
the chance for showers and thunderstorms.

As for Sunday night through Tuesday...a potent upper level storm
system will linger across the Great Lakes region. Several waves of
energy will rotate around it and across the middle Atlantic region. The
chance of showers and thunderstorms...once again...will become a
nuisance to the region.



&&

Aviation /19z Tuesday through Sunday/...
isolated shower or maybe a brief thunderstorm possible this afternoon. Winds
from the S-se...less than 10kt.

VFR most of the night...but MVFR visibilities with fog is possible late
tonight into the early morning hours with moist air over the region.

Scattered showers and thunderstorms possible Wednesday afternoon into early Thursday. An
offshore high will push up the heat/humidity before thunderstorms
arrive/develop...while a cold front approaches from the northwest. The
front will likely move across the area late Wednesday into early
Thursday...sweeping this activity off the coast by late Thursday afternoon.

VFR conditions with light and variable winds expected Friday
through Saturday at all terminals.

&&

Marine...
winds below Small Craft Advisory values today/tgnt with southerly winds around 10kt.

Light S-SW flow will continue Wednesday and maximize just before the
passage of a cold front early Thursday. Showers and thunderstorms possible Wednesday
evening into the overnight.

No marine hazards expected Friday through Saturday.

&&

Tides/coastal flooding...
the daytime high tide cycle is the lower of the two
astronomically...hence there will be no need for an advisory during the
day. Will continue to monitor for potential minor flooding at high
tide early Wednesday morning.

&&

Climate...
yesterday was one month since the Summer solstice. We're a little over
halfway through what is considered met Summer. How does this Summer
shape up so far temperature-wise? Looking at the past 30 yrs...

6/1-7/21...1984-2014...

Station average maximum rank average min rank average daily rank

Dca 87 12th 70 6th 78.5 9th
BWI 84.3 23rd 64.3 15th 74.5 19th
iad 83.6 23rd 63.6 12th 73.6 20th

An interesting stat - dca...average low temperatures for the past 30 yrs...
five of the top six warmest have been 2010 through 2014. Rankings:

1 2010 72.1
2 2013 71.6
3 2011 71.0
4 1994 70.9
5 2012 70.2
6 2014 70.0
7 2008 68.9

Even if you extend to the entire District of Columbia record - since 1871...2014 ranks
#7 for warmest average low temperatures for the period 6/1-7/21.

&&

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

&&

$$
Synopsis...kcs
near term...kcs
short term...kcs
long term...klw
aviation...kcs/klw
marine...kcs/klw
tides/coastal flooding...Woody!/Kcs
climate...Woody!

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