Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 150027
Area Forecast Discussion
National Weather Service Wakefield VA
727 PM EST Tue Feb 14 2017
Low pressure moves across the southeastern states tonight, then
moves offshore as a cold front crosses the area Wednesday. High
pressure builds into the region Thursday through Saturday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Latest MSAS has sfc high moving off the coast with the mid
level shortwave trof tracking south across the fa. Most if not
all the echo coverage this afternoon has been aloft (virga) as
low levels remain dry (dp temps in the 20s resulting in rh`s
btwn 30-40%). This feature progged to drift south into the
evening hours keeping skies cloudy across the south, mstly
cloudy across the north. Kept the forecast dry through late
evening given CIGS above 8K ft.
Models deamplify the moist srn stream shortwave as it tracks ENE
across the south tonight. Meanwhile, a potent/anomalous northern
stream upper low digs over the Great Lakes region. Northern stream
cold front reaches the WVA/VA border late tonight, while the
srn stream low lifts into the southern Mid-Atlantic region. This
will quickly spread moisture across the region as an elongated
area of isentropic lift increases and height falls spread into
the region after 06Z. Pops quickly ramp up (into likely category)
mainly south of a SBY-OFP-FVX line with categorical pops across
the swrn piedmont zones after 09Z. Tsctns show the potential for
a sharp moisture gradient north of this line resulting in less
QPF with only chc pops there. Lows in the upr 30s to lwr 40s.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Upper level jet couplet over the region will also aid in favorable
forcing for ascent Wed. With increasing pw`s, could see an few hour
period of mdt rainfall across sern zones through 18Z or so ahead of
the advancing cold front. Kept high end likely to categorical POPs
across the southeast half of the forecast area through mid afternoon
Wed. Sharp cut-off in pcpn expected across the northwest Piedmont as
the northern stream cold front drops into the region and dry air
surges in behind the front. The front pushes across the region late
Wednesday afternoon, with precip pushing offshore by 00Z Thu. Appears
enough dry air comes in for some partial sun across the Piedmont late.
This makes for an unusual temp forecast where the coolest readings
(upr 40s to near 50) will be across the south where the rain/clouds
hang on the longest with the warmest readings (lwr 50s) across the
piedmont given any sun. Total QPF ranges from just a few hundredths
across northern most zones, up to a quarter inch close to a WAL-RIC-
FVX line to around one third inch across the se.
Trough axis pushes offshore Wed evening with sfc high pressure building
south across the nations mid section. Drier air overspreads the region
resulting in mostly clear to partly cloudy skies. CAA on NW winds
allows temps to drop into the mid-upr 20`s, except lwr 30`s near the
coast. Dry/cool Thurs as high pressure builds in from the west. Highs
in the 40s. Lows Thurs night in the mid 20s to lwr 30s. Dry/warmer
Fri as low level thicknesses rise. Highs 50-55 west of the Ches Bay,
mid-upr 40s along the coast.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Long term period will feature mainly dry weather with slowly
increasing temps through the period. For Fri night, an upr-level
shortwave ridge builds into the area with sfc high pres remaining in
the vicinity. Expect low temps in the 30s under a mostly clear sky
with light southerly flow. Winds remain southerly into Sat as low-
level thicknesses rise, allowing for well above normal temps...highs
in the low/mid 60s most areas; upr 50s Lwr Ern Shore. Southern
stream trough approaches the region Sat night, pushing across the
region Sun. An associated weak area of low pres is progged to lift
along the SE coast. Clouds increase Sat night along with a slight
chance of rain over the srn half of the FA. The trough pushes
offshore Sun night with dry and clearing conditions. High temps Sun
and Mon in the mid 60s most areas; near 60 Lwr Ern Shore.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --Mid and high level clouds will continue to increase tonight for all
TAF sites as low pressure develops south of the region. Light rain
is expected to develop after 06Z at RIC/PHF/ORF with heavier rain
developing at all TAF sites after 12Z. Visbilities could be
occasionally reduced to IFR in heavier bursts of rain Wednesday
morning and into early afternoon. MVFR ceilings also develop at all
TAF sites after 12Z with some potential for IFR ceilings, especially
across southeastern portions of the area, into Wednesday afternoon.
A cold front pushes through the region Wednesday afternoon bringing
an end to the rain and a return to VFR conditions for the end of the
Outlook: VFR conditions are expected Wednesday night through
Saturday. Winds will be gusty behind the front on Thursday, winds
could occasionally gust in excess of 20 knots out of the NW. The
next potential for sub-VFR conditions will be Saturday night and
into Sunday as weak low pressure lifts along the southeast
-- End Changed Discussion --
Sub-sca conditions continue tonight as sfc high pres slides
offshore. Expect southerly winds up to 10-15 kt over the wtrs with 1-
2 ft waves over the Bay and 2-4 ft seas over cstl wtrs.
Winds/waves/seas then ramp up late in the day Wed as a cold front
slowly crosses the wtrs. Expect sca conditions to commence over the
Bay/Sound/cstl wtrs Wed eveng, but started headlines at 4pm as there
may be some gusts near 20 kt over the Bay/Sound or 5 ft seas out 20
nm starting shortly after then. Continued these headlines through
Thu aftn as CAA continues. May need to issue a SCA for the rivers as
well at some point but held off for now with it being 4th period
there and marginal. Marine conditions then slowly improve Thu night
through Sat as weak high pres builds into the area.
MARINE...Small Craft Advisory from 4 PM Wednesday to 7 PM EST Thursday