Area Forecast Discussion
Issued by NWS Wakefield, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 301117
Area Forecast Discussion
National Weather Service WAKEFIELD VA
717 AM EDT Thu Mar 30 2017
High pressure becomes centered off the northeast coast tonight and
Thursday. Low pressure and associated frontal boundaries track
across the region Friday. High pressure builds over the area for the
.NEAR TERM /THROUGH TONIGHT/...
Latest upper air analysis reveals a potent low pushing across
the Central Plains toward the Middle Mississippi River Valley.
Closer to home, downstream shortwave ridging has pushed east
across the Mid-Atlantic into the southeast this morning. At the
surface, latest analysis shows ~1034mb high pressure centered
over James Bay, ridging south into the eastern Great Lakes and
the interior Northeast. Resultant light ENE has allowed some sct
low stratus to develop over the coastal plain this morning, with
some more widespread mid level cloudiness across the piedmont.
Temperatures this morning a bit chillier than the past few with
temps mainly in the lower and middle 40s at 07z, with some upper
40s to near 50 hanging on with lighter flow and increasing cloud
cover across the piedmont.
Overall, relatively quiet weather-wise today. Upper ridge slides
overhead today before pushing offshore tonight. Good model
agreement with respect to increasing/lowering clouds through the
day...first across the piedmont, then eventually spreading east
to the coast by afternoon. Kept pops out of the forecast, but
some patchy drizzle possible far west this afternoon. Otherwise,
mostly cloudy to overcast inland, increasing clouds after a
partly sunny start at the coast. Given weak/low mixing and the
cloud coverage, generally accepted the cooler MET numbers, and
accordingly took the forecasted maxima down a few degrees. Look
for a cooler day with highs in the middle to upper 50s north...55-60
SE VA and interior NE NC away from the immediate coast...50-55
at the beaches.
Overrunning moisture pushes across the area late this evening
and overnight ahead of approaching upr level low. Will keep the
evening dry for most with light rain showers overspreading the
area by midnight far west...and after midnight east of i-95
midnight. Pops range from chc along the coast to likely across
the Piedmont. Lows in the low- mid 40s.
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
Models remain in good agreement with handling of the upper level
low, which takes on a negative tilt as it lifts ENE across the
OH valley on Friday. While the main low remains north of the
local area, NAM and to a lesser extent the ECMWF key into weak
meso low formation along the attendant frontal zone Friday
afternoon, with the triple point feature lifting e-ne across the
area Friday afternoon. This would present two distinct periods
of rainfall; the first a strongly forced, quick moving line of
showers producing rain Friday morning into early afternoon, with
a second line of convection possible for the mid-late afternoon
as the upper low and attendant surface cold front push across.
PW`s in the 1.25 to 1.50 inches and strong lift argue for rain
to fall heavily at times friday morning. However, showers should
push through relatively quickly. Regarding the afternoon threat,
SPC has now put the entire AKQ CWA in a marginal risk. Best
thunder chcs remain confined mainly across the southern half of
the area, with a slight chc across the north, where appreciable
clearing and destabilization is least likely. Strong deep layer
shear values would argue for at least a loosely organized
convective line with any T-storms that do fire, and reasonably
steep mid level lapse rates, LIs <-4 Deg C and CAPE maximized
across South central VA and points south all argue for a narrow
window for strong to severe storms Friday afternoon across the
central/southern CWA, with the severe threat conditional upon
breaks in the overcast and resultant destabilization. In that
event, marginally severe hail, and damaging winds are the
primary hazards in any thunderstorms. Highs mainly in the 60s
to near 70 across the south, again dependant upon degree of
clearing after morning into Midday rainfall.
Likely to categorical POPS continue Friday evening with POPS
tapering off after midnight as the low pulls offshore. Thunder chcs
will be limited to the evening with forcing and instability
waning quickly after sunset Fri night. Lows in the upr 40s-mid
Trailing upr level energy tracks across the eastern shore with
any showers tapering off before sunrise. Look for decreasing
clouds w/highs in the low- mid 60s eastern shore, mid 60s-lwr
70s west of the bay.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Weak high pressure returns to the region Sat night/Sun with
NW flow aloft. Mostly clear skies and cool temperatures
anticipated with lows in the 40s Sat night and highs in the 60s
Sun (upper 50s Atlantic beaches). High pressure slides offshore
Sun night/Mon as the next low pressure system deepens over the
Arklatex Region/Lower Mississippi Valley. The low continues to
track NE into nrn OH/PA Mon night into Tue...dragging a cold
front through the Mid Atlantic Region Tue aftn/evening. Increasing
cloudiness late Sun night into Mon with similar temps to Sun. Lows
in the 40s Sun night, and highs in the 60s Mon (upper 50s Atlantic
beaches). Sfc pressure gradient tightens substantially late Mon
night into Tue ahead of the approaching cold front. S-W winds
gusting up to 25-30 mph will be possible. Widespread rainfall is
anticipated during this timeframe with very low thunderstorm
chances due to rain occurring primarily in the morning. Warmer
temperatures Mon night/Tue as a warm front lifts north through the
region. Lows Mon night in the mid-upper 40s far nrn counties (i.e.
north of the warm front) and in the lower 50s elsewhere. Highs
Tue in the 60s far nrn counties and in the lower 70s elsewhere.
.AVIATION /11Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --E-SE flow allowing for some sct low stratus and patchy fog along
and SSW of PHF/ORF this morning. Expect the Localized IFR/LIFR
to mix out this morning. However, expect trend of lowering
CU/Stratocu to continue today, albeit remaining in VFR range
through this evening. Strong low pressure over the southern
Great Plains will move northeast into the Ohio Valley later
Thursday, resulting in increasing mid to high clouds over the
Mid Atlantic region. Good model that ceilings will gradually
lower through the day from west to east with warm air advection
atop cool onshore flow at the surface. Mostly cloudy to overcast
conditions (ceiling in the 5 to 7 KFT range AGL) expected
through the day at RIC, reaching SE terminals at KORF/KECG by
mid to late morning.
OUTLOOK...Low pressure will move from the Ohio Valley across
northern portions of the Mid Atlantic States to south of New
England by Saturday morning. Widespread rain develops late
tonight into Friday morning with a chance for thunderstorms
Friday afternoon and evening. Periods of MVFR/IFR will be
likely with Visibility restrictions possible by Friday morning
and afternoon. Conditions improve quickly Saturday morning with
high pressure rebuilding back over the area for the weekend.
There will be a chance for showers western portions of the area
by late Monday as the next system develops over the Mississippi
-- End Changed Discussion --
Latest sfc analysis shows high pres stretching down through the
Mid Atlc with a stalled frontal bndry over the SE states. Will
maintain the SCA over coastal wtrs today for seas up to 5 ft out
20 nm. Mainly 10-15 kt NE/E flow today, with the high sliding
offshore tonight and winds subsequently increasing late tonight
and especially into Fri as the next low pres systm and
associated cold front approach from the west. Marginal SCA
conditions are psbl over the Bay and more likely over the cstl
wtrs Fri with seas up to 6-7 ft, but will hold off on any
headlines for now with this being third period and some
headlines already in effect for today. The front crosses the
waters late Fri night/Sat morning, with sub-SCA winds expected
behind the front. Hi pres then builds in over the weekend.
MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ650-