Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 232003
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
303 PM EST Thu Feb 23 2017

.SYNOPSIS...
High pressure will remain centered off the Mid-Atlantic coast
through Friday. A powerful cold front will cross the area
Saturday. High pressure then builds over the area through Sunday.
Another cold front will move through the area Monday night or
Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 2pm, 1012mb surface high is over southern West Virginia
with low pressure east of Florida and high pressure over
Bermuda. South winds around 10 mph have mix down the warmest air
of the year yet with upper 70s max temps. Water temps are still
in the mid 40s, so nearshore locations are cooler (60s in
Annapolis).

A Cu field has developed in a weak pressure trough west of the
Shenandoah Valley with scattered Cu elsewhere. 500 to 1000 j/kg
SBCAPE according to RAP. Isolated showers expected to develop
invof the Blue Ridge and west in the rest of the afternoon with
evening activity (possible thunderstorms) invof Frederick Co,
MD.

The pressure gradient increases overnight, so south winds should
continue. However, with clearing skies any areas that decouple
could fog up, particularly locations that see rain showers. Min
temps generally low to mid 50s (near afternoon dewpoints).

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Quiet, sunny, and very warm again Friday. See climate section
below for daily, monthly, and seasonal records. South winds 10
to 15 mph with max temps upper 70s to 80F again.

Strong cold frontal passage from west to east Saturday. Please
take particular note that strong, gusty showers and scattered
thunderstorms are expected. Max temps just before the front with
most areas reaching the 70s again, mid 70s possible in southern
Maryland. Generally a quarter inch rainfall expected, higher
amounts in the heaviest showers/thunderstorms.

Four to six hour strong gust window behind the cold front
Saturday evening. Wind advisories do not look necessary, but
widespread 35 to 40 mph gusts are likely.

Upslope snow begins at the highest elevations late Saturday
afternoon with up to an inch above 3500 ft and a dusting as low
as 2000ft west of the Allegheny Front.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
A dome of high pressure will build into the region Sunday and Sunday
night. Temperatures will be 15 to 20 degrees cooler through the
period.

As the high moves offshore Monday, a storm system will move parallel
to the Ohio Valley and push into the mid-Atlantic later in the day.
A chance of rain and snow showers are possible with the storm
system. If the storm tracks farther south, then precipitation could
become more of a light snow event.

The storm will move offshore Monday night as high pressure builds in
behind the storm system through Tuesday evening. Dry and seasonably
cool temperatures expected through the period.

The high will move northeast and offshore the New Jersey Coast
overnight Tuesday into early Wednesday. Some light rain could move
in from the southwest ahead of a warm front late at night and early
Wednesday.

A warm front should move north of the region Wednesday, as showers
and perhaps a rumble of thunder develop ahead of an approaching cold
front later Wednesday afternoon. Springlike-temperatures could
evolve in this warm sector of the storm system.

As the main trough of low pressure pivots across the region
Wednesday night and Thursday, cooler and drier air will follow with
high pressure building in from the west. Some upslope snow showers
could evolve as well through the day Thursday.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR through midnight with high pressure offshore. Patchy dense
fog possible again with a south wind keeping coverage low.

Cold front crosses the DC metros Saturday afternoon with
prefrontal showers and thunderstorms and possible brief IFR
conds. NWly flow behind the cold front gusts 30 to 35 knots
Saturday evening with 25 knots by Sunday morning.

Vfr conditions Sunday and Sunday night. Winds northwest 10 to 15
knots gusts to 25 knots Sunday, becoming light and variable Sunday
night. Mvfr to possibly ifr conditions Monday and Monday night.
Winds southwest 5 to 10 knots Monday, becoming light and southeast
around 5 knots Monday night.

&&

.MARINE...
South flow around 10 knots rest of today and through Friday
ahead of a cold front with high pressure offshore. Great boating
weather!

However, particular note should be taken for Saturday. Another
warm morning will give way to a sudden gale with a powerful cold
front crossing the waters late Saturday afternoon. Gales
possible through the evening before easing to 25 knots by midday
Sunday.

Small craft advisories likely Sunday. Winds northwest 10 to 20
knots gusts 25 to 30 knots Sunday. No marine hazards Sunday
night through Monday night. Winds becoming southwest 10 knots
Monday then light and southeast 5 to 10 knots Monday night.

&&

.CLIMATE...
Here are the high temperature records for today, February 23.
This has been broken at IAD (76F at the 2pm ob) and BWI should
also hit (76F at the 2pm ob). DCA (73F at the 2pm ob), next to
water temperatures in the mid 40s, will struggle to reach 78F.

BWI 78F (1874)
DCA 78F (1874)
IAD 73F (1985)


Temperatures Friday are expected to be at least the second
warmest day 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 high temperatures for February 24:
BWI 79F (1985)
DCA 78F (1985)
IAD 79F (1985)

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 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 22nd)
DCA: 45.5   BWI: 42.1   IAD: 42.7

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 22)
DCA: 43.1    BWI: 39.8    IAD: 40.1

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...BAJ
NEAR TERM...BAJ
SHORT TERM...BAJ
LONG TERM...KLW
AVIATION...BAJ/KLW
MARINE...BAJ/KLW
CLIMATE...BAJ/DFH



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