Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 250909

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
409 AM EST Sat Feb 25 2017

A cold front will cross the area today. High pressure will
return to the area Sunday through early next week. A warm front
will then lift north into the area Tuesday into Wednesday
followed by another cold front Wednesday night.


Weather story for today: Severe storms possible, especially
east of the Blue Ridge, while cold front brings sharp weather

A cold front is crossing the Ohio Valley this morning, trailing
low pressure over Lake Huron. With southerly winds established
locally, temperatures are very warm for this time of year, in
the 50s and even 60s. Low clouds and fog have failed to form as
aggressively as models suggested, although there has been a
recent trend downward from Baltimore to Westminster. Wouldn`t
think this would have an impact on sensible weather, but if
thicker cloud cover can develop, it could affect temperatures
and destabilization later today.

At this time, most lightning strikes are south of the Ohio
River, so would expect the weakening band of showers to continue
to progress toward the mountains by daybreak. The cold front
will march eastward across the area through the day. Ahead of
it, temperatures have a good shot of topping out in the upper
60s to lower 70s on breezy south winds. While the showers may
break apart somewhat, am expecting a reinvigorated line to form
east of I-81 around the midday hours, as the strong low level
forcing encounters increasing instability (possibly around 1000
J/kg MLCAPE near the I-95 corridor). Parameters such as updraft
velocity/helicity and max lightning suggest the strongest storms
will be east of US-15 after 2 PM. Strong unidirectional deep
layer shear will support some bowing segments, and instability
should be sufficient to bring down higher winds aloft. SPC has
thus highlighted the eastern portion of the area in a Slight
Risk. While strong to damaging winds will be the main threat,
mid-level lapse rates are fairly steep, so the strongest
updrafts could also contain some hail. Brief locally heavy rain
will also be possible, but no problems are expected due to fast
movement and dry conditions. The line of storms will push east
of the Bay between 5-8 PM.

Temperatures will fall quickly as the front passes, and
westerly winds will increase with gusts of 30-40 mph possible.
The best surge of winds may come during the early evening. Lows
will ultimately bottom out in the 30s, with some 20s west of the
Blue Ridge. A period of upslope snow showers could produce
localized amounts up to an inch west of the Allegheny Front.


High pressure moves in from the west Sunday, allowing winds to
gradually relax. Highs will be much cooler but closer to normal
in the mid 40s to lower 50s. Lows will fall back to the upper
20s and 30s Sunday night as the high begins to move east.

While no well defined system is expected for Monday into Monday
night, there will be increased isentropic lift, and an inverted
trough may develop along the Carolina coast to SE VA. Will have
gradually increasing chances of showers through the period,
highest S/E of DC Monday night. Temperatures will gradually warm
back up as well.


Another system will slowly lift northeast across the Plains and
Great Lakes Tuesday through Wednesday night. This system will
push a warm front back northward across the region Tuesday
and Tuesday night, with solid warm sector weather expected by
Wednesday afternoon. Showers will be possible through this
entire period. Then the cold front will cross the region
Wednesday night with more showers and perhaps a stray
thunderstorm. This system looks a little weaker than the current
one but not a whole lot so we may have some of the same
concerns. After the system passes, we turn notably cooler
Thursday and Friday as Canadian high pressure tries to build in.
A weak clipper could even try to sneak across the area at the
end of the week but this is highly uncertain. There is a small
potential that this system could even try to bring a little
snow, but odds again are quite small at this point. In any case,
after all this mild weather, the slightly cooler than normal
weather expected for the end of this week will feel pretty cold.


Given current trends low cloud fog potential is iffy at best
this morning, with the best chances of MVFR or briefly lower at

The main story today will be a sharp cold front crossing the
area this afternoon. Expect a line of showers/storms to
accompany the front, which could pose brief IFR conditions and
strong wind gusts above 40 kt. Winds will sharply shift to the
west behind the front, with 30-35 kt gusts possible through mid-
evening or so. Winds gradually diminish through Sunday as high
pressure builds.

No major impacts are forecast Monday and Monday night, although
there will be increasing chances for some light rain showers.

Potential for sub-VFR conditions Tuesday through Wednesday night
as a warm front moves north followed by a cold front, with
showers reducing visibility along with low clouds possible.


Southerly flow 10-15 kt should increase through mid morning. In
first period forecast, have Gale Warning starting at 10 AM,
although strongest gusts will be later. Sharp cold front will
move eastward this afternoon, accompanied by strong showers and
storms with 40+ kt wind potential. Winds also shift to west,
with continuing gusts near gale force possible through the
evening. The main story is the sudden onset, which may catch
boaters off guard after the mild morning.

SCA conditions then continue through Sunday afternoon. Brief
lull Sunday night with high pressure, but southerly winds could
again reach SCA criteria on Monday into Monday night.

System moving through Tuesday/Wednesday may result in continued
SCA conditions as southerly flow continues.


Record high maximum and minimum temperatures for February 25:
BWI 83F (1930), 52F (1930)
DCA 84F (1930), 54F (1891)
IAD 79F (2000), 47F (2000)

Warmest Februaries (average temperature)
   DCA           BWI           IAD
1. 46.9 (1976)   44.0 (1976)   42.1 (1990)
2. 45.2 (1990)   43.9 (1949)   41.1 (1976)
3. 44.7 (1997)   43.3 (1890)   41.0 (1998)
4. 44.3 (2012)   42.7 (1932)   40.9 (2012)
5. 43.9 (1949)   42.6 (1909)   40.5 (1997)

Feb 2017 (through the 24th)
DCA: 47.1    BWI: 43.7    IAD: 44.5

Warmest Winters (Dec 1-Feb 28/29)
   DCA              BWI              IAD
1. 44.7 (1931-32)   45.3 (1931-32)   40.0 (2011-12)
2. 44.3 (1889-90)   44.4 (1889-90)   39.7 (2001-02)
3. 43.3 (2011-12)   42.4 (1948-49)   39.4 (1997-98)
4. 43.2 (2001-02)   41.9 (1949-50)   39.0 (2015-16)
5. 42.8 (1949-50)   41.3 (1879-80)   38.3 (1990-91)

Winter 2016-17 (through Feb 24)
DCA: 43.7    BWI: 40.3    IAD: 40.7

Driest Februaries (total precipitation)
   DCA           BWI           IAD
1. 0.35 (2009)   0.26 (2009)   0.25 (1978)
2. 0.42 (1978)   0.36 (2002)   0.35 (2009)
3. 0.47 (2002)   0.56 (1978)   0.46 (2002)
4. 0.62 (1901)   0.63 (1977)   0.49 (1977)
5. 0.66 (1977)   0.65 (1901)   0.68 (1968)

Feb 2017 (through the 24th)
DCA: 0.16    BWI: 0.46    IAD: 0.25


MARINE...Small Craft Advisory from 1 AM to 4 PM EST Sunday for
     Gale Warning from 10 AM this morning to 1 AM EST Sunday for


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