Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
318 PM EDT Wednesday Apr 16 2014

high pressure will build overhead during midweek...before moving offshore
late in the week. An area of low pressure and cold front may
affect the area Saturday.


Near term /through Thursday/...
despite plenty of sunshine...cold air mass/northerly winds have held
temperatures down across the middle-Atlantic today. This will pave the
way for another cold night as the center of high pressure shifts
into New England. Clear skies in the evening will promote decent
radiational cooling. Some high clouds may increase overnight...but
likely not enough to prevent temperatures from dropping near or
below freezing overnight. Freeze warning has been issued east of the
Blue Ridge where the growing season is officially underway.
Temperatures may be a little more marginal near the Bay in southern
Maryland but interior portions should be at or below freezing even
if there/S still a light wind.

After the cold start Thursday...modified air mass and mostly sunny
skies should support temperatures rebounding into the 50s. But
with a cold wedge and easterly low level flow this will keep
temperatures below normal.


Short term /Thursday night through Saturday/...
a wedge of high pressure from New England to the Carolinas will
interact with an inverted trough of low pressure between the East
Coast and Bermuda to produce a moderate northeast to east flow.
Winds will be gusty Thursday evening but then diminish overnight.
Low temperatures will be about 5 to 10 degrees below normal.

As the high pressure pulls away to the northeast...the pressure
gradient will relax. An upper level system will pivot across
east-central Canada Friday and Friday night. A surface cold front
will push across the region late Friday night but should be a dry
front as there will be very little low level moisture. High and low
temperatures will be about 5 to 10 degrees below normal once again.

As the surface front moves south and east Saturday morning...high
pressure will build across the eastern Great Lakes into the middle
Atlantic region. Winds will become gusty out of the northwest
Saturday but should diminish Saturday night when high pressure
ridges southward along the eastern slopes of the mountains.


Long term /Saturday night through Wednesday/...
high pressure will bring dry weather with near normal temperatures
to the area for the second half of the weekend into early next week.
Ridging erodes by Monday night with low pressure approaching from
the Mississippi Valley by Tuesday. This low will bring a chance of
showers to the area late Monday night through Tuesday. Ridging then
re-establishes itself across the area during the middle of next week
leading to a return to dry weather.


Aviation /19z Wednesday through Monday/...
high pressure builds down through the middle-Atlantic through Thursday.
VFR conditions expected during the valid taf period...with winds
veering from north to east over the next 24 hours.

VFR conditions Thursday night through Saturday. Northeast winds may
gust 15 to 20 knots Thursday night near mountain...BWI and dca with a
pressure gradient along the coastal areas. Light and variable winds
Friday and Friday night. With the passage of a cold front
Saturday...winds will become northwest and gust 20 to 30 knots. VFR
conditions are expected Sunday with easterly winds 5 to 10 knots.


Small Craft Advisory remains in effect through the rest of the afternoon through much
of the Bay and lower tidal Potomac River. Wind gusts should diminish
late...but may increase again later tonight as winds veer to the
east. Small Craft Advisory is expected to expand across the waters on Thursday.

No marine hazards expected Thursday night through Saturday morning.
Small Craft Advisory conditions may be possible Saturday afternoon
with northwest winds expected to gust 20 to 30 knots. Sub-Small
Craft Advisory conditions are forecast Sunday into early
next week.


Tides/coastal flooding...
water levels remain 1 to 2 feet above normal but as winds diminish
and then veer to the east negative departures will continue to
ease tonight.


..near record cold temperatures this morning...

Two of the three major metropolitan area airports...BWI and close
to their daily record low temperatures this morning.

At Reagan National Airport...dca...a morning low of 34f was well
above the record of 29f set on this date in 1928.

At Baltimore-Washington international...BWI...a morning low today of
31f was just one degree off the record low for the date set in 1962.

At Dulles...iad...the min of 30f this morning was two degrees shy of
the daily record low of 28f set on this date in 1981.

Regarding record low daily maximum temperatures for April of 3pm
today...Dulles is still tied with its daily record low-maximum of 46f
but with several hours left of sun will likely rise above 46f. Both
BWI and dca have risen above their respective daily record low-maximum
temperatures for April 16.

Record lows for April 17...

BWI...26f in 1962
dca...26f in 1875
iad...27f in 1983


Lwx watches/warnings/advisories...
District of Columbia...freeze warning from 2 am to 9 am EDT Thursday for dcz001.
Maryland...freeze warning from 2 am to 9 am EDT Thursday for mdz004>007-
Virginia...freeze warning from 2 am to 9 am EDT Thursday for vaz036>040-
Marine...Small Craft Advisory until 6 PM EDT this evening for
Small Craft Advisory from 3 am to 6 PM EDT Thursday for
Small Craft Advisory from 6 am to 6 PM EDT Thursday for anz536-
Small Craft Advisory from midnight tonight to 6 PM EDT
Thursday for anz534-537-543.


near term...bpp
short term...klw
long term...dfh
tides/coastal flooding...bpp