Area Forecast Discussion
Issued by NWS Wakefield, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 250100
Area Forecast Discussion
National Weather Service Wakefield VA
900 PM EDT SUN JUL 24 2016
An upper level ridge prevails over the Mid-Atlantic region through
Tuesday. A weak cold front approaches from the north Tuesday and
drops into the region Tuesday night into Wednesday.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --Early evening satellite imagery shows a strong upper ridge
centered over the Southeast US. At the surface, high pressure
remains centered from the Southeast to the wrn Atlantic, with a
lee-side trough embedded to the east of the Blue Ridge.
Localized convergence triggered a few isolated showers/tstms over
the Middle Peninsula late this aftn. As with activity yesterday,
loss of heating and minimal forcing has allowed this activity to
quickly dissipate. Watching some sct showers back into the Blue
Ridge associated with a weak shortwave slipping across the
Mason-Dixon line. Possible that a brief shower could occur across
far NW tier of counties over the next hour or two, but HRRR/CAMs
do not favor any significant convective development surviving into
the area, instead remaining just to our NNW. As such, will stick
with a silent pop overnight.
Very warm and humid overnight, as temperatures slowly fall into
the low to mid 80s by midnight. Overnight/early morning lows
falling only into the mid/upper 70s.
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.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
The broad upper ridge dampens over the Ohio Valley
Monday but remains firmly entrenched over the wrn Atlantic. 1000-
500mb thickness values rise to around 5820m over the Piedmont and
850mb temperatures average around 22-23C across the region. This
should easily support highs in the upper 90s to near 100 across the
area with even low 90s at the immediate coast. Dewpoints again
should remain in the low/mid 70s through peak heating across
central/se VA and ne NC. The boundary that brought some reprieve in
dewpoints today from the Nrn Neck to the Lower MD Ern Shore will
retreat to the ne allowing for dewpoints in the low/mid 70s by
Monday. This result in widespread heat indices of 105 to 109. The
only exception is the MD beaches with heat indices of 100 to 104.
Given this a heat advisory has been issued for the entire area
Monday with the exception of the MD beaches. Urban locations of
Hampton Roads could push warning criteria Monday afternoon (110+).
Confidence is not high enough to go with a warning at this time and
subsequent shifts can re-evaluate. Forecast soundings continue to
depict a strong cap around 800mb Monday, so no convection is expected
during the day Monday. There is a minimal chc (~20%) of a stray tstm
drifting off the higher terrain and reaching the far nrn tier
counties Monday evening.
The upper ridge begins to slowly break down Monday night into
Tuesday. Remaining warm and humid Monday night with lows in the
mid/upper 70s. Continued hot Tuesday as 1000-500mb thickness values
only drop to around 5780-5800m and 850mb temperatures drop only to
20-21C. This will support highs in the mid 90s. Dewpoints remain in
the low/mid 70s with heat indices again aoa 105 with heat advisory
criteria likely reached again for much of the area. The ridge breaks
down enough late Tuesday afternoon into Tuesday evening to allow a
weak front to drop into the area and shortwave energy to cross the
mountains. This will result in a 30-40% chc of showers/tstms mainly
after 19z west, and after 22z farther east. Still warm and humid
Tuesday night with lows in the mid/upper 70s. Westerly flow aloft
will allow for the boundary to stall over the region Wednesday.
24/12z data suggests the highest chc (30-40%) will be from central/s-
central VA to se VA and ne NC. Highs reach the low 90s under a
partly sunny sky. Dewpoints will be highest across se VA/ne NC with
heat indices of 100 to 104 possible.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Stacked high pressure over the Southeast Coast allows
zonal/westerly flow aloft to settle across the region through
the rest of the week. A series of weather disturbances will pass
across the region as a thermal boundary/lee trough sets up over
the area. This will provide a focus for thunderstorm development
and keep a chance for storms in the forecast each aftn/evening.
Areal coverage fluctuates with each passing model run and will
therefore maintain more broadbrushed POP grids. Pwats around
2.00-2.25 inches and dewpoints in the low-mid 70s will result in
muggy conditions with ample moisture present across the area.
Factor in weak steering flow aloft and the anticipated impacts
from any thunderstorms will be locally heavy rainfall and strong
gusty winds. Combine the humidity with temperatures remaining in
the lower 90s, and heat indices will continue to run around
100-104 degrees with a few pockets in far SE VA/NE NC reaching
105-106 degrees for an hour or two each aftn. Lows generally in
the low-mid 70s inland and mid-upper 70s beaches.
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
High pressure over the Northeast States helped to shift winds to an
easterly direction late Sunday at ORF and SBY. This high will
quickly weaken as low pressure moves across the Great Lakes. High
pressure off the SE U.S. coast will once again become the dominant
weather feature by Monday morning. No visibility restrictions are
expected overnight. A dry day is indicated for Monday with SW winds
of around 10 knots. A few higher gusts are possible.
OUTLOOK...A cold front drops into the area late Tuesday and then
stalls over northern portions of the Mid Atlantic States. A daily
chance for afternoon and evening thunderstorms can be expected
Tuesday through Friday.
Generally quiet/benign conditions expected the rest of this week.
Winds generally s-sw aob 15kt during this time as high pressure
remains steadfast over the Southeast Coast. Meanwhile, westerly
flow aloft will allow a series of weather disturbances to cross
the region and keep a chance for thunderstorms in the forecast
each aftn/evening. Seas average 2-3ft...waves average 1-2ft.
There may be a surge in sw winds to 15kt srn Ches Bay/Sound and
15-20kt coastal waters Monday night ahead of the approaching
weather, however SCA flags are not anticipated at the moment.
Seas may briefly build to 3-4ft nrn coastal waters...waves to
2-3ft srn Bay Monday night.
-- Changed Discussion --While its certainly going to be hot thru Tue, climatologically
this is the hottest time of the year with several heat waves having
occurred in the past that have been more intense than what we
will experience. No records were set Sunday. Record highs are
not expected to be set Mon/Tue.
* RECORD HIGHS:
For Sunday (7/24)
* RIC:105 (2010) (Actual high 96)
* ORF: 105 (2010) (Actual high 100)
* SBY: 101 (2010) (Actual high 94)
* ECG: 97 (2012) (Actual high 95)
Records Mon (7/25) Tue (7/26)
* RIC: 105 (2010) 100 (1940)
* ORF: 105 (2010) 100 (1940)
* SBY: 100 (2010) 102 (1940)
* ECG: 97 (1949) 97 (1949)
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MD...Heat Advisory from noon to 8 PM EDT Monday for MDZ021>024.
NC...Heat Advisory from noon to 8 PM EDT Monday for NCZ012>017-
VA...Heat Advisory from noon to 8 PM EDT Monday for VAZ048-060>062-