Area Forecast Discussion
Issued by NWS Wakefield, VA

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434
FXUS61 KAKQ 231118
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
718 AM EDT Sun Jul 23 2017

.SYNOPSIS...
Very hot and humid conditions will continue over the region
today. A weakening cold front will gradually push across the
area late tonight through Monday and stall across the Carolinas
through the middle of the upcoming week. Temperatures will cool
down to near normal levels Monday through midweek.

&&

.NEAR TERM /THROUGH TONIGHT/...
Latest analysis features a decaying MCS pushing offshore of the
Delmarva early this morning. Sct to numerous batches of
additional convection occurring back into Central VA and farther
into the Tn River Valley.

Once again, a couple of headlines to deal with for the weather
story today. First, another very warm to hot summer day
expected. Another Heat Advisory issued for the southern 2/3 of
the CWA (along/S of WAL to RIC to Lunenburg Co. line), with
heat indices of 105 to 109 F expected. Could potentially reach
to 110+ briefly from the Dismal Swamp area down into NE NC but
as we do anticipate highs a little cooler than Saturday, have
opted just to stick with the advisory.

The other story, once again, is the potential for strong to
severe storms this aftn into this evening. Northern half of the
area is once again in a convective slight risk from SPC...and
also highlighted in a marginal Excessive Rainfall Outlook from
WPC. As expected, a myriad of convective boundaries evident on
IR satellite and radar imagery, and expect these boundaries to
serve as a focusing mechanism for the first wave of afternoon
convection across the Northern third of the area later today.
CAMs indicating lingering clouds likely for the early to mid
morning hours over the piedmont to I-95. Will need to watch the
degree of lingering clouds into peak heating, as this will serve
to keep a lid on convection a bit longer than currently modeled.
At this time, expect subsidence behind the MCS to serve to
clear us out by midday...but again this will bear continued
watching.

Nam Conest and Time-lagged HRRR seem to be handling pop
timing/QPF reasonably well thus far, and have again leaned in
their direction for the aftn/evening.

Upper Trough over the Grt Lakes will continue to nudge E-SE
towards the interior northeast today, with resultant height
falls likely to provide the trigger for additional convection
and perhaps another convective complex approaching late this
aftn through the evening. Given the high precipitable water
values (00z sounding indicating 2"+ at WAL/1.88" at IAD),
another round of heavy rainfall is possible. have therefore
included some heavy rain wording over the Eastern Shore.

Cold front drops south into the area late tonight/Early Monday.
Convection again wanes toward morning. Continued warm and muggy
overnight, with lows ranging through the 70s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
Cold front slated to pass through while weakening on Mon. Deep
moisture shifts toward and south of the VA/NC border and
therefore will favor highest PoPs Mon similarly shifting south
across SE VA & NE NC with 20% PoPs for the N. Slightly less
humid Monday over the NW CWA. Not quite as hot, with highs Mon
90 to 95 F over most of the area. Front stalls in NC Tue, with
mainly diurnal tstms possible again over the S, 15-20% N.
Seasonable highs upper 80s to lower 90s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
High pressure moves off the coast Wed with any support for pcpn
across southern half of fa closer to a stalled frontal boundary.
Highs in the mid-upr 80s. Lows in the upr 60s-lwr 70s.

This boundary begins to drift north Thurs resulting in slight
chc pops across the region. Highs in the upr 80s-lwr 90s. Lows
70-75.

Next boundary approaches from the north, then stalls across the
region Fri and Sat. Chc pops each day though pcpn may tend to
concentrate across the southern half of fa Sat depending on how far
south the boundary actually gets. Highs Fri in the upr 80s- lwr 90s.
Lows in the upr 60s-mid 70s. Highs Sat in the mid-upr 80s.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
VFR conditions at PHF/ORF/ECG...with MVFR/IFR conds in SHRA/TSRA
at RIC/SBY early this morning. Expect a return to VFR conditions
all terminals within the next few hours as convection wanes, and
expect a relative lull thereafter through early afternoon.
However, expect convection to re-develop ahead of an approaching
upper shortwave by mid-afternoon. In general, expect most
organized activity will be over the northern half of the area,
and have accounted for rain chances after 20z at all but ECG.
However, confidence in areal coverage of storms remains quite
low attm and while confidence has increased enough to include
VCTS RIC/SBY, have elected to keep any vicinity thunder wording
out of ORF/PHF for now. Hoping CAMs will hone in a bit more on
convective chances for the 18z cycle, and will re-access at that
time.

Outlook: Convection slowly shifts south into south central VA
and NC for Monday. VFR should dominate through this period, with
periods of periods of sub-VFR possible in heavier showers/TSRA.
A weak cold front pushes into the area for the mid week period.

&&

.MARINE...
High pressure is well-rooted over Bermuda with a sfc thermal
trough in the lee of the mountains and flat/zonal flow aloft
across the region. This pattern will persist through today
with a cold front approaching the waters on Monday...slowly
crossing the waters late Monday night. Isolated to scattered
aftn/evening thunderstorms will be possible each day. Main
impacts will be locally strong wind gusts, heavy rainfall and
frequent lightning. Winds will generally be SW aob 15kt with
seas averaging 2-3ft and waves 1-2ft during this timeframe.
Models continue to hint at a brief uptick in wind speeds
tonight, which is likely associated with thunderstorms rather
than synoptically-driven conditions. As a result, any increase
in wind speeds will likely be covered by marine weather
statements or special marine warnings rather than SCA flags.

The cold front gradually stalls out just south of the area by
late Tuesday night/Wednesday morning with weak troughing along
the Mid Atlantic/Carolina coasts. The troughing is expected to
persist in this area through the rest of the week. Best chances
for aftn/evening thunderstorms should remain confined to srn
waters invof the weak trough as well as seabreeze boundaries.
Wind speeds aob 15kt the rest of the week. Wind direction veers
to the north behind the cold front late Monday night/Tuesday...
becoming onshore/E-SE Tuesday night through Thursday...then
becoming S-SW Thursday night/Friday. Seas average 2-4ft; waves
1-2ft.

&&

.CLIMATE...
Heat wave continues through today. The 2nd half of July is
climatologically the hottest few weeks of the year, so we still
may not set any daily records at our main climate sites. For
reference, record highs for today are listed below:

* Date: Sun(7/23)

* RIC:  103/1952
* ORF:  103/2011
* SBY:  103/2011
* ECG:  104/1952

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...Heat Advisory from 10 AM this morning to 8 PM EDT this evening
     for NCZ012>017-030>032-102.
VA...Heat Advisory from 10 AM this morning to 8 PM EDT this evening
     for VAZ065>068-078>090-092-093-095>100-512>516-518-520-
     523>525.
MARINE...None.

&&

$$
SYNOPSIS...MAM
NEAR TERM...AJZ/LKB/MAM
SHORT TERM...LKB/MAM
LONG TERM...MPR
AVIATION...MAM
MARINE...AJB/MPR
CLIMATE...



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