Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 130008
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
808 PM EDT Wed Aug 12 2020

.SYNOPSIS...
A trough of low pressure east of the mountains, will keep
numerous showers and and thunderstorms in the forecast through
Friday. A cold front pushes into our area Friday night into
Saturday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 400 PM EDT Wednesday...
Thunderstorms have fired along the surface trough, generally
extending from Farmville through RIC and NE into the eastern shore.
Very little movement to these storms that have prompted flash flood
warnings and advisories for parts of the area already. Expect the
convection to fill in further west late this afternoon into this
evening as outflow from the initial storms help to develop new
storms in the NW Piedmont. As such, will maintain the flash flood
watch as is. Expect the convection to diminish after sunset, however
will need to maintain chance pops for the entire area tonight due
the trough remaining across the area. The 12z HREF continues to show
the possibility of heavy rain across the northern neck and even into
the eastern shore late tonight into tomorrow morning. As such, have
placed the highest pops in this area.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
As of 400 PM EDT Wednesday...
Latest guidance is in excellent agreement in showing the inverted
surface trough axis over the area on Thursday. In addition, the NWP
suggest the weak low over the Carolinas/Georgia will slowly move
northward along the boundary on Thursday. This will allow for
increase low level moisture convergence and low level theta-e
advection which should renew another round of showers and
thunderstorms with locally heavy rain. Much of the area is under a
slight risk of excessive rainfall on Thursday per WPC. The CAMS
suggest that the heaviest rainfall main be closer to the low
generally along/south of I-64 but in reality any location could see
heavy rainfall given the high precipitable water values of 2 inches,
slow storm motion and deep warm cloud depth near 15000 ft. Will
likely need another flash flood watch for Thursday, but will let the
current flash flood watch for today end and allow the mid shift to
try to fine tune any watch needed for Thursday.

Guidance starts to diverge on Friday, with the ECMWF and Canadian
showing the trough pushing just south of the area while the NAM and
GFS generally keep the front stationary over the area again. Without
a significant upper trough, it is very hard for troughs/fronts to
push south of the area this time of year. As such, have opted to
trend more toward the GFS/NAM solutions for Friday and keep likely
pops across the area generally across the southern half of the area.
Continued unsettled into Saturday with the front remaining across
the area with additional heavy rainfall possible especially
along/west of I-95.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 400 PM EDT Wednesday...

Unsettled weather continues into Sunday and even into Monday with
the surface trough remaining in place. A upper trough finally digs
into the Great Lakes and northeast early next week.
Unfortunately, it is unclear if this trough will allow the
front/trough to actually clear the area. Model guidance suggests
that it will continue to hang up nearby through midweek. As
such, will need to maintain chance Pops each afternoon/evening
through the extended. Am not expecting as much heavy rainfall as
the precipitable water values will not be as high. Otherwise,
temperatures should be seasonable with highs in the mid-upper
80s and lows in the mid 60s/lower 70s.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 805 PM EDT Wednesday...

Primarily VFR/MVFR conditions this evening. Expect thunderstorm
coverage to gradually diminish this evening with ECG/ORF/PHF
likely done with showers/storms. SBY could see some light
showers over the next couple of hours, then a lull in precip for
several hours before rain chances increase again late overnight
into the morning hours. RIC will likely see the best chance for
showers/storms tonight for at least the next two hours but
cannot rule out an isolated shower/storm at any point overnight.
There will be a potential for patchy fog/low stratus to develop
between 06-12z with decreased visibility as well as ceilings.
IFR conditions will be possible for the lowest ceilings and/or
areas of thickest fog (RIC/SBY are the most likely terminals
which may briefly drop to IFR). Otherwise, expect light and
variable winds tonight into tomorrow with more showers/storms
possible tomorrow afternoon into the evening. Generally VFR/MVFR
tomorrow except in thunderstorms where a brief drop in
visibility to IFR will be possible.

Outlook:
Shwrs/tstms become more widespread Thurs thru Sat as moisture
increases along the sfc trof/cold front.

&&

.MARINE...
As of 400 PM EDT Wednesday...

Fairly benign marine condition through the end of the week. An
inverted trough is located inland across the Mid-Atlantic. This has
lead to SE winds 5-15 kt across area waters. There will be a threat
of locally gusty winds near thunderstorms Thursday and Friday
afternoon (possibly as early as late morning). An area of surface
low pressure will move off the VA coast Friday night and into Sunday
morning. In combination with a high pressure system across New
England, winds will become NE 10-20 kt this weekend (highest winds
for coastal waters off Delmarva). Chance of thunderstorm will
decrease for the weekend.

Waves in the Chesapeake Bay will be 1-2 ft through the forecast
period. Seas will build from 1-2 ft Thursday and Friday to 3-5 ft
this weekend.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Flash Flood Watch until midnight EDT tonight for MDZ021-022.
NC...None.
VA...Flash Flood Watch until midnight EDT tonight for VAZ048-
     060>062-064-067>069-075-076-509>517-519-521-522.
MARINE...None.

&&

$$
SYNOPSIS...MPR/MRD
NEAR TERM...MRD
SHORT TERM...MRD
LONG TERM...MRD
AVIATION...RMM
MARINE...CP


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