Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 230850
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
350 AM EST Fri Feb 23 2018

.SYNOPSIS...
A frontal boundary along southern Virginia this morning will
begin to lift northward today as a warm front. This boundary
will remain stretched across our area through Saturday. A
stronger cold front will sweep through the region on Sunday,
bringing drier and clearer conditions. High pressure builds in
to the region from the west for the first half of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Light rain showers are being observed across the northern third
of our CWA this morning, moving off to the northeast and
delivering only light accumulations of less than a tenth of an
inch. Cloudy skies blanket the region with temperatures
generally holding in the upper 30s to around 40 degrees. Earlier
issued winter weather advisory over western Grant, Mineral, and
Allegany counties will be lifted as available observations
indicate above freezing temperatures and model guidance actually
favors a slight rise in temperatures through daybreak.

A stationary boundary residing along the VA/NC border this
morning will gain some momentum and lift northward as a warm
front today, moving into our area by this evening. As a result,
shower activity will be mostly relegated to our northern zones
this afternoon, near the Mason Dixon Line. Morning showers will
wane by midday for much of the area with the exception of the
previously mentioned areas. Expect temperatures today to remain
seasonable in the upper 40s to near 50 degrees for much of the
area, with northern and northeast MD holding on to the middle
40s. The Potomac Highlands looked poised to break in to the
warm sector as the aforementioned warm front lifts northward,
which would result in temperatures well in to the 50s to near 60
degrees.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
As the warm front lifts in to our area by this evening, rain
chances will be favored over our far northern and western zones
of western MD and portions of the WV highlands. Much of the area
should remain fairly dry tonight, with areas of fog developing after
midnight. Temperatures will remain mild for this time of year, in
the mid- upper 40s to near 50 degrees.

Low pressure will move northeastward along the stationary
boundary across our area on Saturday, bringing increased rain
chances once again. The first half of Saturday does look drier
as rain should hold off for much of the area until Saturday
afternoon/evening. Highs on Saturday will be in the 60s across
the southern half of our area, with low to mid 50s likely
towards the MD/PA border as the frontal boundary bisects the
CWA. Lows Saturday night will not fall far, holding in the 50s
area wide, with continued periods of rain showers.

A stronger cold front will sweep through the area on Sunday,
currently progged to move through Sunday afternoon. We will see
showers and perhaps a thunderstorm or two with its passage.
Highs on Sunday will be quite warm, approaching 70 degrees for
much of the area, with upper 60s across northern MD. We will see
dryer and clearer conditions Sunday night as the front moves
south of our area. Lows will still be well above average Sunday
night, ranging from the low 40s to near 50 degrees.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
High pressure will be the primary player in the extended forecast.
However, there is some disagreement as to when it will take over
(Mon vs Tue) and when it will relinquish control to the next wave of
warm-frontal precipitation (Wed vs Thu). Due to these uncertainties,
will need to take the more pessimistic route, which is closer to the
ECMWF Mon but GFS Wed-Thu.

Temperatures will be safely above freezing through the period when
precip is a possibility, so no p-type concerns anticipated. Highs
will generally range from the mid 50s to around 60. Aside from
Monday night, when cold advection should be at its greatest, lows
will range from the mid 30s-mid 40s.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
Ample clouds and moisture across the terminals this morning is
bringing MVFR/IFR conditions. Light easterly wind will veer out
of the south and southwest today, with showers/drizzle this
morning. Conditions may improve to MVFR this evening for a
period, but IFR VIS/CIGs look to return overnight with areas of fog
at the terminals.

Low pressure will approach from the west with a frontal boundary
over our area, thus continued rain chances and low CIGs/VIS will
continue through Saturday night, bringing periods of IFR
conditions. A cold front will move across the terminals Sunday
afternoon, with periods of sub-VFR conditions ahead of it. High
pressure will start to build in to the region Sunday night with
improving flying conditions.

Any lingering restrictions Monday will clear. VFR anticiapted for
the duration of the period.

&&

.MARINE...
Small craft advisory remains in effect early this morning for
the southern portion of the Bay and portions of the Tidal
Potomac. Wind gusts up to 18 knots or so have been observed, but
am expecting them to subside in the next few hours. A warm front
will lift in to the area today, with winds remaining light
through Saturday. Thus no headlines expected during this time.

A cold front will approach from the west on Sunday, increasing
winds out of the south southwest, likely bringing wind gusts to
near SCA thresholds. High pressure will build in behind the
frontal passage Sunday night, resulting in lighter winds across
the waters.

Winds should remain below Small Craft Advisory thresholds Mon-Tue as
high pressure builds over the waters.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Dense Fog Advisory until 7 AM EST this morning for MDZ501.
VA...None.
WV...Dense Fog Advisory until 7 AM EST this morning for WVZ501-503.
MARINE...Small Craft Advisory until 6 AM EST early this morning for
     ANZ534-537-543.

&&

$$
SYNOPSIS...BKF
NEAR TERM...BKF
SHORT TERM...BKF
LONG TERM...HTS
AVIATION...BKF/HTS
MARINE...BKF/HTS


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