Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 190110
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
910 PM EDT Tue Jul 18 2017

.SYNOPSIS...
A trough of low pressure will keep isolated showers and
thunderstorms around the area Wednesday. High pressure
builds toward the Mid Atlantic for the rest of the week,
bringing a return to hot and humid conditions.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Mid evening MSAS has a sfc trof across the mts with high pres
over the area. Most convection from the afternoon has dissipated
with loss of heating except for nern NC just south of ECG attm.
High res data shows another weak impulse riding NE along the
Outer Banks/ VACAPES late tonight/early Wed morning. Thus,
dropped pops for the rest of the night except for low chc across
nern NC. Otw, some patchy fog possible after midnight given light
se winds. Lows 70-75.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Other than the building heat through Friday, there will really
not be much of any other weather concerns. As the upper trough
over the area today continues to slowly move east, expect
heights to gradually rise across the area through Friday with
broad westerly flow developing. This will allow for increasing
heat and humidity through the period. Wednesday will see temps
top out in the mid 90s across most areas, then rising to near
the triple digits by Friday. With the 850mb temps forecast by
the GFS and the ECMWF to be around +24c Friday afternoon and
700mb heights of around dam (as well as relatively dry ground),
a few locations with high temps in the triple digits does not
seem terribly unreasonable. In fact, will go with temps of 100F
in the RIC metro for Friday. A heat advisory seems likely on
Friday, and possible on Thursday. For now, will continue to
highlight the heat/humidity in the Hazardous weather outlook and
various social media outlets. Certainly not unprecedented heat
for this part of the country during this time of year, but it
will be very hot nonetheless and potentially dangerous for those
not prepared for it.

Otherwise, one cannot rule out a stray thunderstorm Wednesday
afternoon especially along any boundary as the upper trough. See
no reason why we would not need a head advisory on Friday, and
it is very close on Thursday.will still be close enough to
perhaps help trigger storms. Beyond Wednesday, it looks just dry
and hot.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Bermuda High retrogrades to a position well off the Southeast
Coast Fri night into early next week. This allows the overall
upper level flow to flatten...becoming more swly early next week
as another upper trough drops out of Canada and over the Upper
Midwest. Hot and muggy conditions will persist through the
weekend. Expect high temperatures in the upper 90s to around
100F inland and low-mid 90s beaches. Lows in the mid-upper 70s
Fri-Sun nights. Dewpoints in the low-mid 70s will result in
widespread heat indices of 105-109F (heat advisory criteria). If
forecast highs increase a degree or two (which has been the
trend in 12z model runs over the past several days), this would
be enough to push heat indices into excessive heat warning
values; will monitor closely. Although Monday highs are a few
degrees cooler than the weekend, they could end up being just as
hot as the upper trough starts to dig into the Upper Midwest and
reinforces sw flow over the region and thus the continued influx
of hot 850mb temps. Periods of isolated to scattered
thunderstorms should be anticipated each aftn/evening...
especially invof lee trough axis which remains steadfast in this
hot/humid airmass regime.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
Convection dissipating with loss of heating this evening with
only sct CU and bkn CI around the area. Thus, VFR conditions
to start off the forecast period. Given a light onshore flow,
expect some MVFR fog to develop after 06Z. Kept fog out of ORF
for now, but would not be surprised to see some there given the
seabreeze tstm that develop there this afternoon.

Another persistant forecast Wed as the main trigger for sct
convection will be across the piedmont. However, sct convection
possible on local seabreezes once again.

OUTLOOK...VFR conditions expected Thu into the weekend, as high
pressure builds toward the Mid Atlc region.

&&

.MARINE...
Isolated thunderstorms have developed along the leading edge of
an upper level trough as well as along seabreeze boundaries near
the coast this aftn. As the trough shifts ewd through this
evening, thunderstorms may migrate over srn waters from the
mouth of Ches Bay to Duck. Once again, storm movement is slow
and therefore heavy rainfall and frequent lightning will be the
main impacts from any storm that develops. Otherwise, the
Bermuda High settles over the cntrl Atlantic through Friday as
upper level troughing persists over the Eastern Seaboard. Expect
periods of unsettled weather and generally south winds aob 15kt
during this timeframe. The Bermuda High retrogrades to a
position well off the Southeast Coast Fri night into early next
week. This allows the overall upper level flow to flatten...
becoming more swly early next week as another upper trough drops
out of Canada and over the Upper Midwest. Winds generally SW
aob 15kt during the later forecast periods. Seas average 2-3ft;
waves 1-2ft.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.

&&

$$
SYNOPSIS...MPR
NEAR TERM...MPR
SHORT TERM...MRD
LONG TERM...BMD
AVIATION...MPR
MARINE...BMD



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