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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
350 am EST Friday Mar 6 2015

Synopsis...
high pressure builds overhead today...then settles over the
southeastern states through this weekend. A weak cold front crosses
the middle-Atlantic Saturday night with high pressure then building
overhead through Sunday night. Low pressure moves along the Carolina
coast Tuesday with a cold front crossing the middle-Atlantic Tuesday
night.

&&

Near term /until 6 PM this evening/...
center of surface high pressure is over the lower MS valley this
morning. Still a pressure gradient over the region...although a few
sheltered observation are 3 knots or less. These two factors are combating each
other in the resulting wind chills...as temperatures are falling a little
more slowly than forecast. Will keep the advisory going until 10
am as criteria still remains possible.

The high will slide east today...resulting in quiet but very cold
conditions with low level thermal trough overhead. Highs will likely
fall short of the freezing mark except in central Virginia...some 20-25
degrees below normal. Moisture fields indicate possible
stratocu...mainly west of the Blue Ridge...and advancing middle/high
clouds late ahead of a short wave trough.

Temperatures will fall again tonight...and with a weaker gradient and snow
pack...expect another night of teens and single digits. Blended in
European model (ecmwf) data with current forecast which captures areal distribution
well. Slightly higher dewpoints and perhaps some cloud cover
associated with the upper trough may limit the fall.

With the center of the high to the southeast by Saturday...return flow will
help temperatures rebound nicely from the cold morning. However
highs will still be below normal. Clouds will increase late in the
day ahead of another weak northern stream trough.

&&

Short term /6 PM this evening through 6 PM Saturday/...
no longer a simple warming trend this weekend through midweek
as previously thought. The surface high does remain anchored over the
southeastern Continental U.S.. however...a weak cold front from a low over the St.
Lawrence Valley shifts east across the middle-Atlantic Saturday night.
Expect an inch of upslope snow west from the Allegheny Front...with
just clouds east across the County Warning Area. West flow Sunday will downslope and
warm for middle to upper 40s north and low to middle 50s S.

&&

Long term /Saturday night through Thursday/...
surface high settles over the area Sunday night. This is downstream of a
southern jet stream trough over the Southern Plains. This trough will produce
a low off the Carolina coast Monday night/Tuesday. Rain from the
precipitation shield could skirt the southern portions of the County Warning Area. Went a little
above wpc guidance with 40 probability of precipitation Tuesday for southern Maryland and chances for
southern half of County Warning Area and east from I-95. So far this looks to be rain.
Though should precipitation come in earlier and be farther north...some mix
of sleet or freezing rain would be possible.

Upper trough sets up over northestern Continental U.S. Wednesday...progressing east
Thursday. This will increase west winds over the area...but expect
dry and near normal temperatures.

&&

Aviation /09z Friday through Tuesday/...
VFR conditions are likely through the taf period under high
pressure. The only exception would be possible stratocu at mrb today
which may fall into the MVFR category if they become broken. Think this
is a small probability. Also a small subset of guidance showing possible
visibility reductions late tonight as slightly higher dewpoints work
in...but am not sold on these solutions yet with the dry Arctic
airmass in place. Northerly winds around 10 knots today become
light/vrb by evening...then southerly Saturday around 10 knots.

VFR conds Saturday night through Monday night. Light SW flow
Saturday night becomes westerly behind a weak cold front. Light west/northwest flow
then through Monday. Light rain possible Tuesday as low passes
the Carolina coast.

&&

Marine...
occasional Small Craft Advisory level gusts continue on the waters early this
morning. Will monitor the need for possible extension for the
segments which expire at 6 am. However...all gustiness should
subside by midday as high pressure builds in. By Saturday afternoon
southerly winds develop but appear to stay below Small Craft Advisory levels.

Light southwesterly flow Saturday night...then light westerly/northwesterly flow Sunday
through Monday. Light rain possible Tuesday as a low passes the
Carolina coast.

&&

Hydrology...
ice jam appears to not be broken yet on cacapon river near Great
Cacapon. Will continue to monitor rises there and any other rises.
Ice jams appear to have broken on Goose Creek in Leesburg.

&&

Climate...
snowfall during meteorological winter (december 1st
through February 28th...or 29th if it is a leap year) was near
normal at our three main climate sites. However...adding early
season snowfall from November and the recent snowfall so far in
March pushes the annual snowfall totals above normal.

Below is a table of normal annual snowfall (recorded from July 1st
of a given year to June 30th of the following year to encompass the
entire cool season)...compared to observed 2014-15 values through
March 5th.

... Annual snowfall (inches)....................
...
Washington District of Columbia...0.5...2.3...5.6...5.7...1.3...0.0...15.4............
Baltimore Maryland....0.4...3.0...6.8...8.0...1.9...0.0...20.1............
Dulles Airport...
*normal values for the entire month of March

... 2014-15 snowfall (inches, through March 5th)....
...
Washington District of Columbia....T.....T....3.6...9.8...4.9...18.3...(+2.9).........
Baltimore Maryland....0.3...0.2...5.9..14.6...6.5...27.5...(+7.4).........
Dulles Airport...
*values listed are totals through March 5th...and are already well
above normal for the month.

Meanwhile...as has been the case many times in recent months...
record cold temperatures are in jeopardy as another cold airmass
pivots across the region during the next 24 hours. Below is a list
of record daily low temperatures for March 6th and 7th...and
record daily low maximum temperatures for March 6th.

Site...record min 03/06...record low maximum 03/06...record min 03/07...
dca.....10 f (1988).........21 f (1901)...........13 f (1890).......
BWI.....13 f (1901/1873)....21 f (1901)...........10 f (1960).......
iad.....15 f (1978).........32 f (2007)...........14 f (1985).......

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...Wind Chill Advisory until 10 am EST this morning for
mdz003>006-011-501>508.
Virginia...Wind Chill Advisory until 10 am EST this morning for
vaz025>031-040-501-503>508.
WV...Wind Chill Advisory until 10 am EST this morning for
wvz050>053-055-501>506.
Marine...Small Craft Advisory until noon EST today for anz532>534-537-
540-541-543.
Small Craft Advisory until 6 am EST early this morning for
anz530-531-536-538-539-542.

&&

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

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