Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 211720
Area Forecast Discussion
National Weather Service Wakefield VA
120 PM EDT TUE JUN 21 2016
A cold front drops into the area late this afternoon and evening.
The front then stalls across the Carolinas Wednesday. The front
lifts back northward as a warm front Wednesday night as low
pressure tracks into the Great Lakes. Low pressure tracks into New
England Thursday with the front dropping back over the region
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --Severe thunderstorm watch 278 is now in effect along and north of
a line from Fluvanna to Mathews Counties VA (not including the
city of Richmond) to the Eastern Shore. The watch is in effect
until 9 PM. Latest regional radar mosaic depicts an area of
showers and thunderstorms developing along the cold front in
northern MD and moving east-southeast. South of this line,
isolated to widely scattered showers and thunderstorms have
developed over the Central Appalachians. Thanks to a warm and very
moist air mass, MLCAPE values have increased to around 1500 to
2000 J/kg across the northern local area. Effective shear also
analyzed around 30 to 35 knots. Confidence is increasing for the
area of showers/thunderstorms along the front to become better
organized and drop toward the Northern Neck to the Eastern Shore
through mid afternoon, reaching the area by mid to late afternoon.
Damaging winds and hail remain the greatest threats. Heavy
rainfall also expected due to an anomalously moist air mass. Back
toward the Piedmont, activity expected to remain isolated to
widely scattered. Cannot rule out gusty winds and hail under the
Latest radar trends depict a line of dissipating light showers
over central Virginia this morning. Observed and radar rainfall
amounts have been a few hundredths of an inch at best. Main impact
from the early morning showers is the cloud cover observed across
the region. The cloud cover has briefly suppressed temps this
morning, with many locales running slightly below model guidance.
Even so, expect temperatures to warm into the upper 80`s to low
90`s this afternoon as the sky becomes partly cloudy and southwest
winds increase to 10- 15 mph. Attention then turns to the
convective potential this afternoon and evening as a cold front
currently located over southern Pennsylvania slowly sags southward
toward the forecast area. Precipitable waters have increased to
around 1.5 to 1.75 inches per blended total precipitable water. A
moist boundary layer and warm afternoon temperatures will result
in a moderately unstable air mass, with MLCAPE values of 1000-1500
J/kg. Increasing winds aloft between the deepening trough over the
northeast CONUS and anomalous upper level ridging over the Desert
Southwest will result in effective bulk shear of 30 to 35 knots.
However, forcing remains rather weak with deep layer westerly flow
observed in the soundings. The overall lack of forcing is expected
to limit coverage from the Piedmont into central Virginia, with
better forcing along the frontal boundary providing better
coverage from the Northern Neck to the Maryland Eastern Shore.
Have maintained likely POPs northeast, tapering back to low end
chance (widely scattered) southwest. SPC maintains a slight risk
for the area with damaging winds and hail the main threats. WPC
has also issued a SEE TEXT for heavy rainfall across the Delmarva
thanks to better coverage.
Precipitation chances decrease this evening as storms push ahead of
the front and instability wanes. Sky averages mostly clear inland to
mostly cloudy along the coast. Mild, with lows in the upper 60s to
-- End Changed Discussion --
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
Mid-level trough axis pushes offshore Wednesday with
northwesterly flow aloft prevailing. Tuesdays front stalls over
northern North Carolina. Low pressure tracks across the Midwest
Wednesday, which will lift the western extent of the cold front
northward as a warm front into the central Appalachians.
Precipitable waters drop to at or below 1 inch Wednesday afternoon
with dewpoints near 60 northwest to mid 60`s southeast.
Disturbance progged to drop along the lifting warm front Wednesday
will result in a slight chance for showers/thunderstorms across
the southwest local area. Dry elsewhere. Still warm with highs
generally in the upr 80`s. Attention turns upstream Wednesday
evening as models continue to indicate upstream
showers/thunderstorms dropping along the frontal boundary into the
local area. Moisture returns quickly Wednesday evening as low
level flow returns to the southwest behind the lifting warm front.
Will keep mention of chance POPs as the front lifts through the
area Wednesday night. Mostly cloudy with lows generally in the upper
60`s to around 70.
Low pressure tracks into New England Thursday with an east to west
frontal boundary setting up over the northern Mid-Atlantic region. A
warm, moist, and unstable air mass will be in place across the local
area. Pressure falls on the lee side of the Appalachians will induce
low level convergence resulting in chance POPs across much of the
local area. Guidance indicating a hot day, but have undercut
guidance several degrees due to cloud cover and precipitation
potential. Highs in the upper 80`s to low 90`s. The front will
slowly slide southward Thursday night.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Cold front will drop acrs the area Thu ngt resulting in chc pops
(40%) for showers and/or tstms. Will linger sml chc (30%) or slgt
chc (30%) pops mainly ovr srn portions of the region on Fri. High
pres then blds in fm the NNE Fri aftn into Sat morng, then sits
off the Nrn Mid Atlc cst Sat aftn into Mon morng. A cold front
will slowly approach fm the W during Mon. Expect mainly dry wx Fri
ngt into Mon morng, then will have a slgt or sml chc for showers
or tstms mainly in the wrn half of the area Mon aftn/eveng. Lows
in the mid 60s to lwr 70s Thu ngt, in the 60s Fri ngt and Sat ngt,
and in the mid 60s to near 70 Sun ngt. Highs in the upr 70s to mid
80s Fri and Sat, in the 80s Sun, and in the mid 80s to near 90
.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
Vfr thru the 12z taf period. A cold front approaches the area from
the nw tda...with skies mainly sct-bkn ~8-10k ft. Chances for rain
are greatest at ksby (where shra was included) and kric (where
vcsh was included). Elsewhere...confidence is lower for late
aftn/eveng shras/tstms so kept any mention of rain out of the tafs
attm. Reduced cigs/vsbys likely in any tstms however coverage is
not expected to be widespread. Otherwise...expect gusty sw winds
tda ahead of the frnt...decreasing ovrngt as the frnt drops into
OUTLOOK...Drier weather returns Wednesday with a chance for
showers/thunderstorms Wednesday night through Thursday night.
Precipitation chances diminish Friday with dry weather returning
Extended SCA until 10am EDT over the lower Chesapeake Bay south
of New Pt Comfort/Currituck Sound and Lower James R. for low-end
SCA SW winds in association w/tightening pressure gradient ahead
of approaching front as high pressure builds off the SE coast.
This front will drop into the area tonight into Wed morning,
bringing a chance for Sct showers and gusty T-storms late today
and tonight. Have gone ahead and hoisted SCA through late tonight
over the coastal zones, mainly for seas 5-6 ft offshore. Front
will slip south of the region early Wed, partially washing out
over coastal NC. Lighter winds aob 10kt expected post-frontal on
Wednesday. predominate wind direction will be WNW. However, light
flow will allow seabreeze effects to take over by aftn over nearshore
S coastal zones. Boundary lifts back N as a warm front from late Wed
night into Thu morn. Good model agreement taking sfc Low pressure
east from the Eastern Great Lakes through the day Thursday, before
sliding off the Northern Mid-Atlc/Srn New England coast Thu aftn
and night. The trailing cold front drops across the region early
friday morning, with another period of marginal SCA possible.
1020+mb sfc High pressure will the build in fm the NNW through the
day Fri before pushing offshore Friday night/Sat.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT
Wednesday for ANZ650-652-654-656-658.