Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 141452

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1052 AM EDT Wed Mar 14 2018

Low pressure will remain over the Canadian Maritimes through
Friday while high pressure builds south and east from the
central CONUS into our area. Weak low pressure will pass by to
the south Saturday and high pressure will return for Sunday into
Monday. Low pressure may impact the area during the middle
portion of next week.


Blustery and cold conditions expected for today with deep upper
trough overhead and 850-mb temperatures dropping to near -10C.
This will result in surface temperatures around 10F degrees
below daily normals for mid-March, with highs ranging from the
upper 30s to mid 40s. Instability clouds with the trough
overhead are filling in, likely leading to a mostly cloudy
afternoon. A few flurries are possible as well. In the northwest
flow, upslope snow showers are ongoing near and along the
Allegheny Front, and this will continue through the day. Most of
the accumulating snow however will taper off by mid-afternoon,
with a relative lull in the activity this evening, so extended
the advisory just until 2PM. With deep mixing expected, wind
gusts reaching 25-35 mph. Thus, wind chills are likely to hold
in the 20s/30s through the day.


Gusty northwest winds during the evening will lessen overnight,
and mostly cloudy skies will trend clearer through the night.
Cold air mass will remain in place, so lows expected to fall
into the 20s to low 30s again. The next frontal system will be
quickly approaching by Thursday morning as it rotates around the
deep upper trough that will still be in place. Therefore,
chances for upslope snow showers along and west of the Allegheny
Front will be increasing towards sunrise. May need to issue
another advisory for this.

This system will cross the region during the day Thursday. While
a mainly dry passage is expected, did increase chances for
some rain/snow showers/sprinkles/flurries, mainly north/east of
the DC metro during the day Thursday. In addition, upslope snow
showers are expected, and another round of accumulating snow is
likely. Temperatures will be a bit milder, with highs in the
40s/50s, but winds are expected to increase once again out of
the west/northwest behind frontal passage by later in the

Quiet weather is then expected for Thursday night through much
of Friday night as surface ridging builds overhead.
Temperatures will still run below normals, with highs from the
upper 30s to upper 40s, and lows in the 20s. Warm air advection
will then be on the increase late Friday night into early
Saturday morning, and some light precip will become possible
across the region mainly south and west of DC metro. Given cold
temps at the surface and marginal temps aloft, this could be a
mixed bag.


Low pressure will track east from the central CONUS and it will
pass by to the south Saturday. The low should weaken as it does
so since it is running into a confluence zone between closed upper-
level low pressure over the Canadian Maritimes and upper-level
ridging over the north-central CONUS. A period of light
precipitation is possible especially across southern areas.
Light wintry precipitation cannot be completely ruled out if the
precipitation can move in quick enough before temperatures rise
well above freezing. Confidence in any wintry precipitation
remains very low at this time.

High pressure will build in from the north Saturday night through
Sunday, bringing dry and seasonable conditions. Stronger low
pressure may impact the area later Monday and Tuesday, bringing
the next significant chance for precipitation. A blocking
pattern with plenty of cold air to the north suggests that
wintry precipitation is possible. Latest deterministic guidance
has trended a bit weaker with the blocking high to our
northeast, which would mean that the main p-type would be rain
with the low tracking a bit farther north. However, confidence
remains very low this far out especially with such a blocked
pattern. Will continue to monitor over the next several days and
for now, will continue with rain or snow possibilities in the


VFR is expected through Friday night. Broken-overcast ceilings
will develop each afternoon/evening in the 4000-7000 foot
range, but remain VFR. A few flurries are possible this
afternoon and some light rain showers/sprinkles are possible
Thursday, but no significant reductions in visibilities are
forecast. Gusty northwest winds are expected today with gusts to
around 30 knots. These winds will lessen overnight, turn more
southwesterly Thursday morning, before returning to the
northwest Thursday afternoon with gusts around 25 knots.
Northwest winds will persist into Friday as well.

Weak low pressure will pass by to the south late Friday night
and Saturday. Light precipitation is possible, especially
across KCHO, and it could be wintry. High pressure will return
for Sunday.


SCA conditions are ongoing in gusty northwest winds this
morning. Winds are forecast to increase this afternoon, and a
Gale Warning goes into effect at Noon today. Winds are expected
to peak during the late afternoon and evening hours, before
gradually abating overnight. A SCA continues overnight across
portions of the waters. Another round of gusty winds is expected
on Thursday, especially in the afternoon, and a SCA goes back
into effect for all waters at Noon Thursday. These conditions
likely persist through Friday.

Weak low pressure will pass by to the south Saturday and high
pressure will return for Sunday. Winds may approach SCA criteria
during this time but it does appear marginal.


Low pressure will remain over the Canadian Maritimes through
Friday. High pressure will approach from the north and west
during this time. A tight gradient between these systems will
bring gusty winds to the area, especially from the late morning
through the early evening hours each day. A downsloping west to
northwest flow will cause low relative humidity.

For today, frequent wind gusts around 25 to 35 mph along with
relative humidity ranging from 15-25 percent across central
Virginia and 25 to 35 percent across other locations may enhance
the threat the spread of wildfires. Chilly conditions (temps in
the 30s and 40s this afternoon) and higher fuel moistures will
limit the threat somewhat. Therefore, no headlines have been

For Thursday, lower fuel moistures are expected along with
gusty winds and low relative humidity. Temps will be in the 40s
and 50s, a bit warmer compared to today. There will be an
enhanced threat for the spread of wildfires, especially across
central Virginia where winds will be strongest and relative
humidity will be lowest (20-30 percent).

For Friday...more gusty winds are expected. Somewhat chillier
conditions may limit the RH drop a bit, but fuel moistures will
be quite low.


VA...Winter Weather Advisory until 2 PM EDT this afternoon for
WV...Winter Weather Advisory until 2 PM EDT this afternoon for
MARINE...Small Craft Advisory until noon EDT today for ANZ530>543.
     Small Craft Advisory from midnight tonight to 6 AM EDT Friday
     for ANZ530>534-537>541-543.
     Gale Warning until midnight EDT tonight for ANZ530>543.
     Small Craft Advisory from midnight tonight to midnight EDT
     Thursday night for ANZ542.
     Small Craft Advisory from midnight tonight to 3 AM EDT
     Thursday for ANZ535-536.
     Small Craft Advisory from noon Thursday to midnight EDT
     Thursday night for ANZ535-536.


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