Area Forecast Discussion
Issued by NWS Wakefield, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 301936
Area Forecast Discussion
National Weather Service Wakefield VA
336 PM EDT Fri Sep 30 2016
An upper level low lingers over the Ohio Valley today. Meanwhile,
high pressure builds well north of the region and steers a
moisture rich airmass into the region through today. Slowly
improving conditions are expected into the weekend as the upper
low lifts back to the north.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
The Delmarva is presently getting a much need break from heavy
rain, which has totaled up to 6-12" across DE/Lwr MD Ern Shore
over the past 48 hours. This water will result in rising main
stem rivers through the afternoon and potentially into tonight.
Follow the latest flood warnings for more details.
Current GOES WV imagery continues to depict a stubborn anomalous
upper low over central KY. A plume of deep moisture extends from
off the SC/GA coast nwd into central NC/s-central VA, and nw
across the central Appalachians. Another plume to the east has
pushed offshore brining the need break in rain to the Delmarva.
Showers and embedded tstms are developing across central NC and
streaming nwd into the Piedmont. This activity is being triggered
by the combination of the aforementioned moist plume/mid-level
theta-e ridge, a push of mid-level dry air on the wrn flank of the
moisture stream, a spoke of shortwave energy rotating around the
upper low. The interaction of the push of dry air into the moist
airmass will create some convective instability aloft. Strong
mid-level flow (55-65kt at 500mb) will result in strong deep layer
shear. This combination could trigger some strong to marginally
severe tstms this afternoon and evening, which is reflected in the
marginal outlook from SPC. The main threats are hail and locally
strong wind gusts. The main limiting factor will be the lack of
SB/BL CAPE with an in situ wedge airmass in place. The best
coverage will be west of Richmond initially through early
afternoon, before shifting ewd later this afternoon and evening.
Locally heavy rainfall will produce an isolated flood threat for
the more sensitive areas.
Otherwise, mostly cloudy to overcast. Strong high pressure to the
n will maintain the in situ wedge airmass over the piedmont with
highs around 70/low 70s, gradually ranging/rising to the low 80s
se where some breaks in cloud cover are expected.
Area of showers lifts northeastward this evening toward the
northeast zones as the front begins to lift. Deepest moisture flux
and convergence pushes offshore, which will limit overall rainfall
amounts. However, additional localized flooding is possible in the
areas sensitive from the previous days rain. Drying inland this
evening through the overnight with some breaks in the clouds
possible over the southern Piedmont. Mild again with lows in the
mid to upper 60s.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Dry air continues to entrain into the system Saturday as the
upper low fills and lifts northward. The result will be gradually
improving conditions. Addition energy lifts over the region in
southwest flow aloft, so can`t rule out isolated to scattered
showers east of interstate 95. Sky conditions also improve with a
partly cloudy sky inland, but remaining moistly cloudy near the
coast. Highs Saturday range from the upper 70`s to low 80`s, but
less humid as dewpoints drop into the upper 50`s to low 60`s
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Anomalous upper low over the Ohio Valley during the short term will
make its way slowly north and northeast early next week...allowing
for high pressure to build into the Mid Atlantic States. A chance
for showers remains Sunday over the Chesapeake Bay and portions of
Hampton Roads and east and end all areas by Monday morning. A strong
surface high will remain over southeast Canada which will increase
its influence across the Eastern Seaboard early next week with its
associated easterly flow. A chance for showers returns to the
forecast Tuesday and Wednesday. Tropical Cyclone Matthew may have an
influence late in the week...especially in the marine area.
Uncertainty remains in terms of the timing and track. Refer to
guidance from the National Hurricane Center and extended forecasts
from the Weather Prediction Center for details.
High temperatures from 75 to 80 Sunday and Monday lower to around 70
in the northern Piedmont to the upper 70s northeast North Carolina
by Thursday. Lows will range through the 60s.
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
The combination of low pressure over the Ohio Valley and a
stationary front from North Carolina to off the Virginia coast was
producing a moist onshore flow over the Mid Atlantic States.
Satellite showed clearing over the coastal waters and portions of
the Bay and mostly cloudy sky over the TAF sites. Occasionally where
the sky clears over southeast portions...the clouds fill back in
with a broken MVFR layer. IFR cigs were over SBY and may continue
through nearly all of the TAF period.
Thunderstorm activity was beginning to develop over far southern
Virginia and south into eastern North Carolina and was spreading
northward. With the unstable airmass in place...put VCTS for
portions of the afternoon at all the TAF sites except SBY.
IFR (and possibly LIFR) redevelops late this evening and overnight
at RIC and SBY. It may need to be added to PHF but is unlikely at
ORF and ECG. Conditions improve during the mid to late morning
-- Changed Discussion --Seeing a gradual downward trend in seas and waves in the mouth of
Ches Bay. Will allow SCA for the Bay to expire at 400 PM as
planned and keep remaining SCA flags unchanged with regard to
previously determined end times. Main change has been increasing
wind speeds over the waters from Fenwick Island to Chincoteague
where sustained winds range from 10-20kt with gusts to around 25kt
possible. These speeds are anticipated to diminish through this
Strong/anomalous sfc high pressure remains over sern Canada
through tonight before weakening Sat aftn. Meanwhile, stacked low
pressure over the Midwest will continue to drift north and
slightly east during this same timeframe. This will translate into
winds becoming more se through tonight and then more sly on Sat.
Speeds will generally be aob 15kt during this time. Waves on Ches
Bay will average 1-3ft tonight into Sat...while seas generally
average 4-5ft until SCA expiration times when seas will then
average 3-4ft during the same timeframe. Onshore 9-10 sec period
swell should also be anticipated tonight through Sat aftn.
Calmer marine conditions expected Sat night through Mon. Wind
directions will be variable sw-w through Sun evening and then
shift to a more nly direction Mon into early Tue. Winds are then
expected to increase in response to a tightening pressure gradient
caused by Hurricane Matthew (located off the Atlantic coast of FL)
and another Canadian high pressure centered over se Canada/nrn New
England Tue aftn into Wed night. Still a lot of uncertainty
regarding Matthew`s storm track at this time, but the general
trend will be for increasing onshore winds and continually
building seas for the second half of next week.
-- End Changed Discussion --
-- Changed Discussion --Strong/anomalous sfc high pressure remains over sern Canada
through tonight before weakening Sat aftn as stacked low pressure
over the Midwest drifts north and slightly east during this same
timeframe. This will translate into onshore/se winds through
tonight and then more southerly (and decreasing) on Sat. As the
winds shift and decrease, tidal anomalies will decrease
incrementally by a few tenths of a foot with each passing high
Several areas of concern are as follows:
1. Coastal flood warnings are in effect for the Nrn Neck through
500 PM this evening and also for the MD Lower Eastern Shore on
Ches Bay through 900 PM tonight. These areas will be re-evaluated
shortly. At this time, it does appear that the Nrn Neck will be
transitioned to a coastal advisory for the next high tide
overnight...while the MD Lower Eastern Shore (primarily near
Bishops Head and vicinity) will continue in a warning for at least
the next high tide cycle overnight as well.
2. Wrn Ches Bay areas from Hampton Roads to the Middle Peninsula
will remain in a coastal flood advisory through tonight. With
winds becoming more southerly by Sat morning, advisories in the
far srn Bay may be allowed to expire with a continuation of
advisories for the lower to middle Bay areas into Sat aftn.
3. Coastal flood advisory for Maryland Beaches and Ches Bay side
of VA Eastern Shore will continue through Sat morning`s high tide
4. Coastal flood statement will be in effect for Virginia Beach
and Eastern Currituck this evening as tide levels end up within
0.3ft of minor flooding thresholds. Nuisance flooding may be
possible in the persistent onshore flow.
* Surf zone forecast has ended for the season.
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-- Changed Discussion --MD...Coastal Flood Advisory until 11 AM EDT Saturday for MDZ024-025.
Coastal Flood Warning until 9 PM EDT this evening for
VA...Coastal Flood Advisory until 4 AM EDT Saturday for VAZ089-090-
Coastal Flood Advisory until 2 AM EDT Saturday for VAZ084>086-
Coastal Flood Advisory until 11 AM EDT Saturday for VAZ099-100.
Flash Flood Watch until midnight EDT tonight for VAZ064-075-
Coastal Flood Warning until 5 PM EDT this afternoon for
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ656-658.
Small Craft Advisory until 10 PM EDT Saturday for ANZ650-652-
Small Craft Advisory until 4 PM EDT this afternoon for ANZ634.
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