Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
329 am EST Sat Dec 21 2013
High pressure will remain off the South Carolina coast this weekend.
Low pressure developing over Texas will track northeast Sunday
..reaching New England Monday. The associated cold front will move
into the middle-Atlantic region Sunday night...lingering across the
region Monday. High pressure will build into the area Tuesday through
Near term /today/...
As of 06z...a Bermuda high is in place and an upper trough axis is
over The Big Bend region of Texas. A surface trough extends from Texas to the
eastern Great Lakes. Precipitation has broken out across the front and will
continue to spread across the Ohio Valley and eastern Great Lakes. The
middle-Atlantic is firmly in the warm sector with S-southeasterly flow
(originating from the gulf) of 10 to 15 miles per hour and temperatures in the
middle to upper 50s. A few places...notably Frederick Maryland...have
decoupled and temperatures are in the middle 30s. Also...locations
down wind from the cool Bay waters could be as low as the low 40s
(such as kmtn). Temperatures should remain steady or be a degree
or two less by sunrise. Therefore...high min temperature records
are a pretty sure bet (see climate section below).
Today...warm air advection and thickening middle-level clouds. The
SW-NE oriented surface trough currently over Lake Erie drifts to central
PA today bringing isolated/scattered showers east from the Allegheny Highlands
to as far east as north-central Maryland. There may be some sprinkles across the
balt-wash metropolitan...but the cloud heights look to be around 12 kft...
so any precipitation may be just virga. The warming trend continues with
925 mb temperatures 1c to 2c higher today than yesterday. With strong
S-southwesterly mixing (winds 15-20 mph) it is hard to give much of a north
to south temperature gradient...but went just above guidance maximum
temperatures with upper 60s south of District of Columbia and low 60s for northern Maryland (mid 60s for
balt-wash metro). This should set some new maximum temperature records (see
climate section below).
Short term /tonight through Sunday/...
Tonight...trough/front over central PA lifts north to the New York border as
strong surface low pressure develops over the Midwest states. S-southwesterly
winds stay 15 to 20 miles per hour with more high min records expected. Mins
upper 50s to 60f would be close to the highest December min temperature
records (see climate section below). Light rain/sprinkles are
possible across the County Warning Area...with isolated/scattered shower wording added. The low
level jet increases through the night and ridgelines may require a
Wind Advisory for either 46 miles per hour gusts (40 kt) or sustained winds
over 30 miles per hour for three hours.
Sunday...the surface low slowly fills as it moves NE to New York state through
the day...with the trailing cold front reaching WV by sunset.
Showers ahead of the front likely west of the shen valley. These will
be disrupted by westerly downsloping flow so probability of precipitation were dropped to the
scattered range for most of the County Warning Area. A secondary round of precipitation
spreads in from the SW late in the day...with southeasterly zones in likely
probability of precipitation. The 00z GFS continues to give some negative lifted index
values. The low levels look quite stable in forecast soundings...so
the possibility of surface rooted convective storms and the associated
damaging wind threat looks limited for now. The threat would be best
where any thunder develops. Isolated thunder wording was entered for
mainly east of the Blue Ridge which is in keeping with previous schc
Maximum temperatures for Sunday were adjusted based on the current
thinking that precipitation would come last to areas east of 1-95. Here
temperatures reach the middle 70s...with low 70s west.
Long term /Monday through Friday/...
Fnt looks to be slow to exit the region Monday...caught up in a SW-NE jet.
Because of this have incrsd probability of precipitation to likely/Cat for Monday...but there is
no qustn as to p-type - it'll be much too warm for any wintry
pcpn: not as warm as Sunday but still xpctg u50s/l60s for the
majority of the area. Qpf's are expeceted to stay below flsh fld values.
The fnt is expeceted to push offshore Monday night...W/ colder air
beginning to filter into the region west/ lows dropping back below freezing.
Tuesday the upper trough will rotate through the region..bringing a chance for snsh
to the upslope regions. Tuesday should also be brzy as high pressure works
into the middle Atlantic. From the l70s Sunday temperatures Tuesday are expeceted to top
out in the u30s in the mountains...lm40s east of I-81.
Christmas evening...Christmas day. Both are looking very good as the
high settles over the east CST. And again...aftr lows in the 50s Sun night
the lows Tuesday night are forecast to be a20...middle 20s in the cities. Highs
Christmas day are expeceted to be in the u30s...about 5 degrees below normal.
Another chilly night on Christmas night..then temperatures begin to rebound
as the high moves offshore. An upper level short WV is prognosticated to
track north of the region...but we have slt chance probability of precipitation in forecast because of it.
No sig accumulations are expeceted.
Aviation /08z Saturday through Wednesday/...
VFR prevails today as middle level clouds thicken. S-southwesterly flow 10 to 15
knots becomes 15 to 20 knots this afternoon. Ceilings lower to MVFR through
the evening. The GFS lamp model has IFR ceilings tonight...though plenty
of mixing will occur and ceilings are expected to be closer to 1.5 kft.
Isolated thunder Sunday afternoon ahead of an approaching cold front.
Lowered ceilings expeceted Sun night and Monday as the fnt stalls along the eastern
Seaboard. Brzy conds expeceted Tuesday as high pressure builds in...clear skies/
light winds Christmas evening and day.
S-southwesterly flow from a Bermuda high and low pressure developing over the
Midwest continues through Sunday. Winds increase today with the Small Craft Advisory
expanding to all waters at noon. The Small Craft Advisory continues through Sunday
with winds generally 15-20 knots with gusts up to 25 knots. Isolated
thunderstorms are possible Sunday afternoon with special marine
warnings possible in the associated gusts.
Small Craft Advisory winds possible Monday night and Tuesday.
Below are the daily record high minimum and maximum temperatures for
District of Columbia/Baltimore/Dulles for Dec 21-23. Several new daily records are
expected...and the forecast is near the highest December min temperature of
all-time for Sunday (12/22).
Daily hi min temperature record (yr)...daily maximum temperature record (yr)
BWI...52 (1895)......62 (2011)
dca...51 (1895)......68 (1923)
iad...46 (1998)......61 (2011)
BWI...48 (1931)......70 (1889)
dca...49 (1923)......72 (1889)
iad...49 (1990)......67 (1984)
12/23...(hi min temperature only)
* = highest min temperature in December. The highest December min temperature
for the dca period of record was 59 on Dec 5 1973.
District of Columbia...none.
Marine...Small Craft Advisory from noon today to 6 PM EST Sunday for
Small Craft Advisory until 6 PM EST Sunday for anz532>534-537-