Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 212047
Area Forecast Discussion
National Weather Service Wakefield VA
447 PM EDT THU JUL 21 2016
High pressure prevails through the weekend, with heat returning
Friday into early next week. Heat indices will climb to 100 to 108
degrees Saturday through Monday. The next cold front approaches the
region late Monday.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Current wv imagery depicts a broad ridge from the
central and srn Plains through the Southeast states, with a trough
pushing through the Great Lakes region and a lingering trough off
the East Coast. At the surface, weak high pressure is situated over
the Southeast and Mid-Atlantic. Temperatures this afternoon average
in the mid/upper 80s across the area with dewpoints in the mid/upper
60s. Visible satellite imagery shows sct afternoon cu. A brief
shower is possible over the Piedmont and along the sea-breeze.
However, coverage will be very limited so forecast PoPs will be <
15% through the late afternoon. High pressure gradually slides
offshore tonight with a light SE wind becoming SW. Lows drop into
the upper 60s to around 70 under a mostly clear sky.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
An anomalous upper ridge over the n-central US dampens
and build ewd Friday through the weekend. 850mb temperatures warm to
20-22C (+2 st dev) by Friday afternoon. These values will support
highs solidly in the low/mid 90s Friday. A deep well-mixed boundary
layer combined with a SW wind around 10 mph will help dewpoints mix
down into the mid/upper 60s resulting in heat indices no higher than
the upper 90s. High pressure remains over the wrn Atlantic as
pressure falls on the lee-side of the mountains induce a lee-
side/thermal trough over the Piedmont. Limited forcing, a lack of
moisture, and warm temperatures aloft should result in dry
conditions. A weak trough slides across the area Friday night, but
should only result in passing mid-clouds as forcing remains limited.
Warm and humid with lows in the low/mid 70s. The airmass continues
to warm Saturday resulting in highs solidly in the mid 90s inland.
Dewpoints again mix down into the upper 60s over the Piedmont.
However, dewpoints may remain in the low 70s over SE VA/NE NC and
this will result in heat indices of 100-104.
A weak frontal boundary clips the nrn Mid-Atlantic Saturday night. A
20-30% PoP has been introduced to the lower MD Ern Shore given some
elevated instability and the presence of a shortwave trough within a
NW flow regime. Warm and muggy with lows in the mid to potentially
upper 70s. The frontal boundary stalls/dissipates over central/se
VA/ne NC Sunday. This will result in highs in the low 90s Sunday
over the Ern Shore. However, higher dewpoints should pool along the
old boundary and highs remain in the mid 90s from inland VA to NE
NC. This results in forecast heat indices in the 100-104 range from
the Piedmont to the I-95 corridor to 105-108 over se VA/ne NC. An
isolated tstm is possible in vicinity of the boundary, or along a
sea/bay breeze. However, coverage will be very limited.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --Not as hot acrs the region thru the extended period, with Mon and
Tue being the hottest days in advance of a cold front approaching
fm the NW. Unstable airmass combined with a lee trough ovr the
area on Mon and a cold front pushing into and acrs the region on
Tue will result in isolated to sctd showers and tstms. That
frontal boundary will then become nearly stationary along the
VA/NC border or just S of there ovr NC Wed thru Thu. So, the best
chc for showers and tstms will be acrs the srn half of the area
during this period. Highs in the lower to mid 90s Mon and Tue, in
the upr 80s to lower 90s Wed, and in the mid 80s to lower 90s Thu.
Lows will range thru the 70s Sun ngt and Mon ngt, and mainly in
the lower to mid 70s Tue ngt and Wed ngt.
-- End Changed Discussion --
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Surface high pressure settles over the western Atlantic and
Southeast Coast through the weekend...resulting in primarily
Weatherwise, isolated seabreeze thunderstorms are possible near
the coast this aftn/early evening. A brief period of shallow fog
development is possible at KRIC and KSBY between 22/1000-1200Z.
KECG may also experience shallow fog within this timeframe,
however confidence is much lower and can be added as a tempo group
if needed. Otherwise, conditions are dry on Saturday with another
round of isolated to scattered storms possible across the area on
Sunday. A cold front approaches the region on Monday and then
crosses the area on Tuesday. There is enough incoming moisture to
interact with a thermal trough on Monday and with the cold front
on Tuesday to trigger a higher chance for scattered thunderstorms
both days...primarily during the afternoon/evening hours. Locally
heavy downpours, strong gusty winds, and brief reductions in
flight conditions to MVFR/IFR ceilings and visibilities will be
the primary impacts with thunderstorms early next week.
-- Changed Discussion --No headlines in the short term tngt thru Sat, though conditions
may come close to reaching SCA thresholds Fri night. High pressure
will slide offshore tngt and become centered off the mid-Atlc coast
Fri, then a weak front approaches from the NW Fri night into Sat.
This front looks to remain N of the CWA, with a pre-frontal
trough in place over the region on Sat. Winds will be light from
the E-SE (<10kt) this evening and transition to the S to average
around 10 KT overnight into Fri morning. Bay waves will average
1-2 ft with coastal seas 2-3 ft. The pressure gradient will
increase a bit by late Fri, especially by Fri night, so S/SW winds
will ramp up and average around 15 KT during this period. A few
gusts could reach SCA thresholds across the Bay (20 KT) and
northern coastal waters (25 KT) Fri night, as warm water temps
will be conducive to mixing the low level nocturnal Jet. Still
would be marginal at best, with waves over the Bay building to 2-3
ft, and coastal seas to around 4 ft N and 3 ft S. The sfc
trough/boundary drops into the area on Sat with lighter W/SW flow
turning back to the S later Sat into Sat evening. The front then
washes out/dissipates on Sun.
-- End Changed Discussion --