Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
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FXUS61 KAKQ 220704
Area Forecast Discussion
National Weather Service Wakefield VA
304 AM EDT FRI JUL 22 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 THIS 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
.SHORT TERM /6 AM THIS 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 /07Z FRIDAY THROUGH TUESDAY/...
Surface high pressure has become centered well offshore over the
western Atlantic, with more mixing of SSW winds than past several
nights. This should preclude any fog development at TAF sites and
have removed this from SBY. VFR/dry conditions to prevail today
and Saturday with mainly S/SW winds around 10 KT.
Isolated/scattered tstms possible Sat night at SBY, and then
across southern VA and northeast NC Sun afternoon and evening. A
cold front approaches on Monday and crosses the area on Tuesday
bringing scattered showers and tstms both days...primarily during
the afternoon/evening hours. Brief reductions in VSBYS and CIGS to
MVFR/IFR levels with the storms.
S Winds currently avg around 10 KT across most of the area, with a
few locations as high as 15 KT. Bay waves will average 1-2 ft
with coastal seas 2-3 ft through early this afternoon. The
pressure gradient will increase a bit more later today, and
especially tonight, so S/SW winds will ramp up and average 15-20
KT during this period over much of the Bay and the coastal waters.
With water temps in the 80s and a decent SSW low level Jet
strengthening by tonight, should be a favorable enough setup for a
southerly overnight SCA event in the Bay. Will be raising SCA
headlines there with the 4 am issuance. Expect a few gusts in the
rivers to approach 20 KT as well, but should be shorter lived and
will allow next shift to evaluate need for a SCA there (as well as
in the coastal waters off the VA/MD eastern shore for gusts to 25
KT and seas approaching 5 ft out near the 20 NM offshore areas).
Waves over the Bay building to 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, with
winds to avg < 10 KT and becoming onshore by afternoon with the
seabreeze. Another front approaches from the NW early next week.
-- Changed Discussion --While its certainly going to be hot Sat-Mon, climatologically this
is the hottest time of the year with several heat waves having
occurred in the past that have been far more intense than what we
will experience. Record highs are unlikely to be set and in most
cases, doubt they will even challenged within 5 degrees.
* RECORD HIGHS:
* Sat (7/23) Sun (7/24) Mon (7/25)
* RIC: 103 (1952) 105 (2010) 105 (2010)
* ORF: 103 (2011) 105 (2010) 105 (2010)
* SBY: 103 (2011) 101 (2010) 100 (2010)
* ECG: 104 (1952) 97 (2012) 99 (1949)
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-- Changed Discussion --MD...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT
Saturday for ANZ630>632-634.
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