Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
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FXUS61 KAKQ 140252
Area Forecast Discussion
National Weather Service Wakefield VA
952 PM EST Fri Jan 13 2017
A cold front will stall over the Carolinas overnight as high
pressure builds east from the Great Lakes. The high will weaken
over New England on Saturday, as low pressure lifts northeast
through the mid Atlantic region. Another high pressure system
will become centered from the Great Lakes to New England
Saturday night through Monday as the frontal boundary remains
nearly stationary across the southeast states.
.NEAR TERM /THROUGH SATURDAY/...
Sfc analysis late this evening indicates sfc cold front now
south of the CWA and pushing into South Carolina with
strong/1045mb sfc high pressure centered over the Great Lakes.
N/NE low level flow prevails locally, with temperatures dropping
through the 40s most locations. Clouds have begun to
increase/thicken late this evening and the sky will become
overcast all areas thru early Sat AM.
Overnight, as the strong high pressure system continues to
drift E from the Great Lakes to New England, a trough of low
pressure lifts ENE from the TN Valley to the central
Appalachians. 13/12Z guidance overall trended a bit warmer than
last night`s 00Z runs (which makes sense given today`s
temperatures). Expecting light overrunning precipitation, with
GFS/NAM 295K surfaces spreading the overrunning moisture across
the northwest half of the local area toward the Maryland Eastern
Shore mainly after 06Z. Enough low level cold air arrives late
(mainly below 900mb) to bring a chance of rain/freezing
rain/sleet across the far northern forecast area (but have
trended the forecast warmer and expect sfc temperatures to be
above freezing as the precip begins (in most cases well above
freezing). 850Mb temps expected to stay between +3 to +5C,
except will fall to +1 to +2C across the MD eastern shore. Best
chances for light rain to possibly transition to light freezing
rain for a few hrs would be over the far N of the CWA, from
Louisa to Caroline Co. and interior northern Neck counties from
about 10-12Z. The warm nose aloft might be too shallow over the
eastern shore for any freezing rain (thinking more sleet or a
rain/sleet mix with temperatures staying above freezing there).
From 12-15Z, as mid level warming aloft pushes a bit more to the
NE, could see a brief period of light freezing rain mixed with
sleet or plain rain over the MD eastern shore. Still appearing
very marginal as sfc temperatures will likely have to column
cool just to get down to 32 F (and if precip stays too light
temperatures may remain above 32 F for the entire event). Also,
ground and roads should be well above 32 F due to the warmth of
the past few days. Therefore, confidence is not high due to
borderline temperatures and onshore flow. Little, if any ice
accumulation is expected (would be mainly for elevated surfaces
if it were to occur).
High pressure slides off the New England coast Saturday aftn as
the frontal boundary stalls over the Southeast. The result will
be ongoing northeast flow and wedge conditions. Maintained
60-80% POPS across the north and northeast half of the local
area Saturday morning/early aftn tapering to low end chance
across the southwest. Increased POPs for the Maryland Eastern
Shore to categorical Saturday afternoon as a shortwave
approaches from the west. Temperatures and low level thicknesses
warm through the afternoon, with the p-type becoming all rain
across the entire forecast area. Overall, forcing and moisture
will be limited, resulting in only light QPF amounts (a tenth to
a quarter of an inch north to a few hundredths south). Continue
to undercut guidance due to cloud cover and northeast winds.
Highs in the mid-upper 30`s north to low 40`s south.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Low pressure develops offshore the Mid- Atlantic coast Saturday
night as shortwave energy digs over the Delmarva. Will linger
40-60% POPS along the coast Saturday evening as the moisture
plume begins to push offshore and southward. Lows in the low
30`s north to upper 30`s south.
Latest guidance has backed off on precip chances Sunday as the
plume of moisture pushes south of the region. BUFR soundings
indicate drying in the mid levels, but low level moisture will
keep cloudy conditions in place through the day. A few breaks in
the clouds expected across the northeast late Sunday. Will keep
mention of slight chance to low end chance POPs for the
Piedmont, but silent elsewhere. Highs in the low 40`s north to
the upper 40s S. Lows in the 30s to around 40 F Sun night and
mainly cloudy (except across the ern shore). By Mon, deep
cutoff upper low begins to eject NE from west Texas to the
southern central Plains as it become engulfed by the northern
stream energy. Sfc low pressure moving from the southern Plains
to the mid-MS valley will help lift a warm front through the
region by late in the day. Still expecting mostly cloudy and
cool conditions locally, with highs mainly in the 40s along with
a 20-30% POP for light rain.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Above normal temps expected acrs the fcst area thru the extended
period. At this time, will go with a blend of the ECMWF and GFS
with respect to the timing/placement of fronts and the chcs for
showers. Best chcs will be Wed/Wed night and again on Fri.
Highs will range fm the mid 50s to mid 60s thru the period, with
lows in the mid 30s to lower 40s Mon night, and ranging fm the
lower 40s to lower 50s Tue night, Wed night, and Thu night.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions with mostly mid and high cloud ceilings continue
to prevail across the region this evening. The cold front that
moved through the region is over northern NC and nearly
stationary. Arctic high pressure centered over the Great Lakes
will push colder air into the Mid Atlantic region overnight. Some
overrunning warm air from the west will move over this colder
air late tonight into Sat and bring a chance of a wintry mix
over portions of the Md Eastern Shore and Northern VA
northward. Light rain is expected to occur over much of the
remainder of the CWA. Cloud ceilings expected to lower to MVFR
by Sat morning daybreak and to MVFR/IFR condition by the
afternoon and evening. Vsby will likely stay 3 mi or better.
The lower ceilings will linger in place into early Sunday and
some light rain/drizzle will be possible into Sunday morning.
Conditions will gradually improve Mon as the cold air erodes and
southerly flow begins. Some clouds will linger but expect VFR
conditions into Tue.
-- Changed Discussion --Cancelled SCA for the James River Bridge and allowed SCA for
the northern Chesapeake Bay to expire.
Will maintain SCAs for Ocean/lower Ches Bay/Currituck sound for
this tonight thru Sat morning, due to NNE surge as colder high
pressure slides acrs the Great Lakes ewrd into New England.
Expect speeds to pick up to 15 to 20 kt with gusts up to 25 kt
this evening into the overnight. That sfc high will slide into
the Atlc during Sat, but another sfc high will build fm the
upper midwest ewrd into the northeast U.S. later Sat thru Sun
night. This will maintain persistent NW thru NE winds acrs the
waters into early Mon morning, altho speeds expected to be a
few/several KT lower. Winds then turn to the S or SW and
increase Tue thru Wed, as that high moves into the Atlc and a
cold front approaches fm the west.
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-- Changed Discussion --MD...None.
MARINE...Small Craft Advisory until 11 AM EST Saturday for ANZ634-654-
Small Craft Advisory until 4 AM EST Saturday for ANZ632.
Small Craft Advisory until 6 AM EST Saturday for ANZ633-650-
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