Area Forecast Discussion
Issued by NWS Wakefield, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 220122
Area Forecast Discussion
National Weather Service Wakefield VA
922 PM EDT Fri Apr 21 2017
A cold front crosses the area tonight then becomes nearly stationary
across the Carolinas through the weekend. Low pressure will track
eastward along the front Saturday through Sunday, then slowly drift
offshore Monday through Tuesday.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Latest MSAS has the cold front crossing the mts with a weak bndry
located across the lwr MD ern shore, denoted by the BKN-OVC ST
layer and onshore flow at OXB. Meanwhile, sct convection developing
in warm sector across the fa.
Cold front sags south across the region this evening to a position
near or just south of the VA/NC border by 12Z. Weak wave riding east
along this feature will likely serve to keep chc convection going
through the night, highest pops south. High pressure nudging in from
the north may cut off moisture supply along the eastern shore / nrn
neck after 06Z thus lowest pops there. However, guidance shows
areas of fog expanding west a a bit along the ern shore as winds
remain onshore. Lows from the mid 50s north to low-mid 60s south.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
A wet period ahead with rainfall amounts between 1-3 inches
through Monday, highest (2-3 inches) over the piedmont.
Potent upr level low tracks slowly se and takes on a neg tilt by
Sunday, spawning a sfc low along the sern coast which then is
progged to get cut off from the main flow and drift ivof the Gulf
Stream wall into the middle of next week. Models show both spacial
and timing differences with the moisture fields but the jist of the
forecast will be for waves of Atlantic moisture to rotate inland
resulting in periodic shwrs (embedded tstrms especially over the
sern zones). Lclly hvy downpours psbl starting late Sat. Meanwhile,
high pressure to the ne results in a cool in-situ wedge over the
piedmont along with areas of fog. Likely to categorical pops through
the period except Sat morning with chc pops.
One caveat will be the frontal position on Saturday. Thinking is
that any severe threat stays across NC, but SPC has the MRGL risk
for damaging winds/large hail as far north as VA Route 460. Will
limit thunder chcs to extreme srn VA / NE NC Sat.
Highs Sat from the upr 50s nwrn zones to the lwr 70s across interior
ne NC. Lows Sat / Sun nights in the upr 40s to lwr 50s. Highs Sun in
the upr 50s to mid 60s. Highs Mon upr 50s NW to near 70 SE.
Hydro wise, no flood headlines expected attm despite the expected
rainfall. Will probably have to wait until the first round or
two of QPF falls then assess the situation. Do expect some
healthy rises in local river by early next week, especially if
the heavy rainfall falls over the headwaters.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Long term period will feature a trend towards drier and warmer
conditions. For Mon night/Tue, mid-level cutoff low and associated
sfc low continue to spin south of the area, allowing for moisture to
stream in off the Atlantic. Bumped up PoPs to likely for most of the
area Mon night and chance far NW, with models tending to push
cutoffs lows offshore too quickly. Slightly lwr PoPs for Tue, with
the best chance near the cst. Temps Tue slightly below
normal...highs in the upr 60s most spots. Warming trend then
commences for Wed as deep SWly flow develops across the eastern
seaboard, lasting through the end of the week with temps reaching
the 80s most areas Thu and Fri.
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 01z...a frontal boundary extends from Maryland and northern
Virginia to the Tennessee Valley. Scattered thunderstorms were over
northern portions of the area affecting RIC and to affect other
locations overnight. IFR stratus was present along the coast of the
Lower Eastern Shore. AS the front moves to near the VA/NC border
Saturday...IFR ceilings are expected to expand across much of the
area (north of the front) by Saturday afternoon.
OUTLOOK...Low pressure will move out of the Mid South to the
Carolina coastal waters where it will linger into early next week.
Unsettled conditions...widespread precipitation and degraded aviation
conditions are expected through Monday. Conditions slowly improve
but some rain may continue especially toward the coast. Currently a
dry forecast is in place for Wednesday and Thursday.
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A cold front drops through the wtrs tonight. Expect a brief CAA
surge behind the front Sat midday/aftn. Marginal SCA conditions are
psbl over the Bay but held off on any headlines attm...confidence
not high enough to issue a headline due to winds mainly expected to
be around 15 kt, and a short duration of any SCA conditions. Several
days of NE flow then as low pres develops over the SE states then
slowly slides offshore. Still some uncertainty over when SCA
conditions will commence, but they are likely for at least Sun
through Tue, with 5-8 ft seas over the ocean and 3-4 ft waves over
the Bay. Gale gusts are also psbl but expect mainly 15-25 kt winds
with gusts up to 30 kt over the ocean. Improving marine conditions
thereafter into midweek as the sfc low weakens and pushes off to the