Area Forecast Discussion
Issued by NWS Wakefield, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 221736
Area Forecast Discussion
National Weather Service Wakefield VA
136 PM 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 /THROUGH TONIGHT/...
Latest GOES water vapor imagery depicts a broad, anomalous ridge
centered over the Southern Plains with a trough of low pressure over
the western Atlantic. At the surface, high pressure remains centered
well offshore, extending westward into the local area.
Temperatures as of 10 am range from the low to mid 80s across the
region with dewpoints in the low/mid 70s, with some sct cu pushing
ewd off the coast and thin cirrus moving in from the nw.
The upper ridge builds ewd today as 850mb temperatures warm to
20-22C (+2 standard deviation over the region. Expect temperatures
to warm into the low to mid 90`s. A southwest wind around 10 mph
will help mix dewpoints into the mid to upper 60`s today, outside
of low 70s in the far se, resulting in heat indices of 95 to 100.
A small convective complex is dropping sewd across wrn PA this
morning, but is expected to dissipate before reaching the local
area. Otherwise, pressure falls on the lee side of the mountains
induce a lee/thermal trough today, but a lack of appreciable
forcing, limited moisture, and warm temps aloft will keep the
forecast dry. Expect some afternoon cumulus, especially across the
southeast half of the area. A weak trough slides across the area
tonight, but should only result in passing mid level clouds. Humid
with lows in the low to mid 70`s.
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
The upper ridge dampens as it builds eastward through the
weekend. 850mb temperatures remain in the 20-22C range (+2
standard deviations). Highs forecast solidly in the mid 90`s
Saturday and Sunday. While winds will generally be less than 10
mph, soundings indicate deep mixing Saturday, which will help
dewpoints drop into the mid to upper 60`s inland. Warmer dewpoints
expected in the southeast, which will push heat indices into the
100 to 104 range. A weak frontal boundary clips the nrn Mid-
Atlantic Saturday night. Have maintained chance POPs for the
Eastern Shore given some elevated instability and the presence of
a shortwave trough within a NW flow regime. Humid Saturday night
with lows in the mid 70`s. The frontal boundary stalls/dissipates
over central/se VA/ne NC Sunday. This will result in highs in the
low 90s Sunday over the Eastern 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 /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --Surface high pressure has become centered well offshore over the
western Atlantic. VFR/dry conditions to prevail through Saturday
with mainly S/SW winds around 10 KT. Except will be during the 21Z
through 06Z time frame, when an increase in S/SW winds is expected
at KORF/KPHF/KSBY, with gusts perhaps reaching 20kt at KORF.
Increased mixing should prevent any fog development again tonight.
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.
-- End Changed Discussion --
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.
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)
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT
Saturday for ANZ630>632-634.