Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 220154
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
954 PM EDT THU JUL 21 2016

.SYNOPSIS...
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/...
Latest wv imagery depicts a broad ridge extending from the
central and srn Plains toward the Southeast/Deep South. To the
north, 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, and will
slide offshore overnight, with light onshore winds becoming S-SW
overnight. Any lingering CU and rogue shower activity from
earlier this evening have diminished with loss of heating. Have
maintained a dry forecast overnight. Only adjustment to the
forecast was to bump up clouds overnight in association with some
remnant mid to high clouds from upstream convection over the Ohio
Valley. These clouds will be thin enough that they`ll have
minimal operational impact overnight, so forecast will average
out at partly to mostly clear through Friday morning. Look for a
mild night with early morning lows into the upper 60s to around
70.

&&

.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/...
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.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Surface high pressure settles over the western Atlantic and
Southeast Coast through the weekend...resulting in primarily
VFR conditions. Some shallow fog possible tonight but not expected
to be significant. Winds will be generally SE-S less than 5-10 kt
tonight...and less than 15 kt on Friday. Conditions will be dry
on Saturday with another round of scattered storms possible
across the area on Sunday. A cold front approaches on Monday and
crosses the area on Tuesday. There is enough moisture on Monday to
trigger a chance for scattered showers and thunderstorms both
days...primarily during the afternoon/evening hours.

&&

.MARINE...
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.

&&

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

&&

$$
SYNOPSIS...AJZ/SAM
NEAR TERM...AJZ/MAM
SHORT TERM...AJZ/SAM
LONG TERM...TMG
AVIATION...BMD/JEF
MARINE...TMG


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