Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 241441
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
941 AM EST Fri Feb 24 2017

.SYNOPSIS...
High pressure will remain centered off the Mid-Atlantic coast
today. A cold front will cross the area Saturday. High pressure
then builds over the area Sunday through early next week.
A warm front will then lift north into the area Tuesday followed
by another cold front on Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Very warm day in store today with the area ensconced in the warm
sector of a low pressure system passing through the Great Lakes.
Warm southerly flow expected through the day with mostly sunny
skies and only scattered cumulus and some areas of high cirrus.
925/850mb temperatures are very similar to yesterday, so
expecting highs roughly the same as what was observed yesterday,
perhaps a degree or two warmer. This should put highs in the 70s
to near 80F, challenging the daily records, and possibly even
the all-time February record at Washington/Dulles (see climate
section below).

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
A very mild night is in store with low temperatures (50s)
likely warmer than normal highs in most locations. A southerly
wind likely remains established for most locations, which will
limit fog potential. However, there are some indications low
stratus could develop. If so, their rate of dissipation Saturday
could affect high temperatures and destabilization.

A strong cold front will cross from west to east on Saturday. A
weakened line of convection is likely to cross into the
mountains during the morning hours, reaching the Blue Ridge
around midday or early afternoon. What remains of the line may
be reinvigorated east of the mountains as it encounters a
potentially warmer and more unstable airmass, contingent on the
aforementioned clouds. Even so, dew points are expected to
remain under 60, with CAPE values likely less than 1000 J/kg.
Mid-level winds will be strong though, and SHERB parameter backs
up the potential for a high-shear/low-CAPE environment.
Marginal Risk remains justified, with strong to locally damaging
wind gusts being the main threat. The line should exit southern
MD between 5 and 8 PM. QPF less than a third of an inch for
most...and possibly much less if the line is thin/broken.

Temperatures likely spike into the 70s ahead of the front, with
falling temperatures behind it. Besides the gusty shower/storm
threat, a pressure surge may follow a few hours behind the
front, resulting in wind gusts of 30-40 mph during the early
evening. These winds will bring in colder air, with lows falling
into the 20s and 30s. Upslope snow showers will be possible,
especially during the evening, with amounts less than an inch.

High pressure will build from the west Sunday, allowing winds
to gradually relax. Temperatures will be much cooler, but closer
to normal in the 40s and 50s. The high will begin to move
offshore Sunday night, with lows dropping into the 30s. Sub-
freezing readings are possible if a location decouples and
thicker cloud cover holds off.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Models have backed off on precipitation returning to the region
on Monday. The front which had been expected to move in from the
northwest on Monday now looks to completely dissipate before
reaching the area, so POPS have been cut back and temperatures
should not drop at all. Instead, developing low pressure to the
west in the Plains will push a warm front northward across the
area on Tuesday and Wednesday, bringing temperatures back above
normal but bringing the return of showers. By Wednesday night,
the low will pass to our north in southern Canada, sending a
cold front across our region. There might be some thunder with
it but right now indications are minimal in this regard. Cooler
more seasonable weather will return Thursday as we dry out with
high pressure returning briefly.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
The region will remain in the warm sector of a low pressure
system passing to the northwest today and tonight. No aviation
weather concerns expected through the day today with only some
high cirrus and scattered cumulus. Otherwise, southerly winds
with some gusts to 20 kt possible.

Clouds will increase tonight. Guidance indicates IFR potential,
especially east of the Blue Ridge, but will not be biting on
that quite yet, preferring a trend to MVFR. Strong cold front
will cross the area on Saturday, likely reaching the metros
during the afternoon. Thin line of gusty showers/embedded
thunderstorms likely (brief IFR possible) , followed by a
several hour period of potential 30+ kt westerly gusts. Winds
will subside through Sunday morning as high pressure builds in
from the west.

No aviation concerns Monday. Sub-VFR possible Tuesday and
Wednesday with showers.

&&

.MARINE...
Southerly flow 10-15 kt today and tonight with high pressure
offshore and low pressure moving toward Great Lakes. Am thinking
warm air over cold water will minimize potential for higher
gusts. Fog will be possible mainly around the northern Bay this
morning.

Have raised a Small Craft Advisory starting at 10 AM Saturday,
although how quickly mixing commences is in question as low
clouds may be present. A cold front will bring dramatic change
in conditions during the late afternoon to early evening. Line
of gusty showers/possible storms will mark sharp wind shift to
west. Pressure surge will lag behind the front, so at this time,
thinking gradient gale conditions may occur more during the
evening hours. However, SMWs will be likely with the line of
showers. Winds slowly taper through Saturday night and Sunday
morning, although SCA likely continues a good portion of Sunday.
There should be a lull Sunday night with high pressure moving
across the area.

Warm front looks to lift north across the region Tuesday followed
by a cold front Wednesday. These features could result in at
least small craft conditions.

&&

.CLIMATE...
Temperatures today are expected to be at least the second
warmest Feb 24th on record (if not break or tie the record from
Feb 24, 1985). High minimum records are possible for Friday and
less likely for Saturday due to evening temperatures dropping
behind an afternoon cold front. Record highs are less likely
overall on Saturday as showers and clouds should limit how warm
it gets, while DC/Baltimore both set their all-time February
highs on that date back in 1930, making them hard to reach.

Record high maximum temperatures for February 24 and 25:
BWI 79F (1985), 83F (1930)
DCA 78F (1985), 84F (1930)
IAD 79F (1985), 79F (2000)

Record high minimum temperatures for February 24 and 25:
BWI 55F (1985), 52F (1930)
DCA 52F (1975), 54F (1891)
IAD 53F (1985), 47F (2000)

Warmest temperatures ever observed in February
BWI 83F (2/25/1930)
DCA 84F (2/25/1930)
IAD 79F (2/25/2000, 2/24/1985)

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 23rd)
DCA: 46.3    BWI: 43.0    IAD: 43.6

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 23)
DCA: 43.4    BWI: 40.1    IAD: 40.4

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 10 AM to 6 PM EST Saturday for
     ANZ530>543.

&&

$$
SYNOPSIS...RCM
NEAR TERM...ADS/MM
SHORT TERM...ADS
LONG TERM...RCM
AVIATION...ADS/MM/RCM
MARINE...ADS/MM/RCM
CLIMATE...BAJ/DFH/RCM



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