Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 241803
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
203 PM EDT Wed May 24 2017

.SYNOPSIS...
Unsettled conditions return this evening through Thursday as an
upper level trough approaches from the west. Conditions improve
on Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
FA remains stuck under in-situ wedge attm this afternoon...w/
w/ widespread lo clouds/cigs...onshore winds and temps mainly in
the l-m60s. Near term models continue to show that the wedge
hangs on over most of the FA through through 23Z/24-04Z/25...then
there is a surge northward of instability...mainly on the
coastal plain up into the eastern shore thereafter. Increasing
vertical ascent as upper level trough approaches from the WSW
combined w/ the surge of lower level moisture/instabilty (as
low level jet strengthens) will result in the development of
widespread SHRAS and at least ISOLD-SCT tstms over the FA. Will
be mentioning locally heavy rainfall...as QPF averages
0.50-1.00" (higher amounts possible). The low level wedge likely
hangs on over the (far) interior locations...w/ temperatures
not rising much above the m60s before tailing off late. To the
E...expecting temps and dewpoints to rise through the 60s even
l-m70s (far SE VA-NE NC) as sfc warm front pulls N. SPC
continues to highlight areas near-S of the VA-NC border SLGT
risk severe...will maintain heightened mention in the HWO for
now.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
Upper low begins to lift NE across the mountains Thursday. A
strong shortwave trough will lift across the mid-Atlantic
during the afternoon/early evening. Once again PoPs increase...to
~60-70% from the Piedmont to central VA to the MD Ern Shore,
with 40-50% far SE. 500mb flow of 45-55 kt is expected along
with modest instability. Therefore...a few stronger to
marginally severe storms are possible. The main threat would be
wind and hail as low-level shear is minimal but a decent cold
pool aloft will exist. Additional QPF Thu aftn/evening should
average up to ~0.25" with locally higher amounts possible. Highs
Thu in the m70s W of I 95 to the l80s across eastern portions
of the FA.

The upper low continues to lift NE across PA/NY/New England
late Thu night into Fri. Drier conditions finally arrive as
deep layered WNW flow develops over the region. Some lingering
mid-level energy could result in SCT-BKN CU mid/afternoon Fri.
Otherwise...drier and breezy with highs in the u70s to l80s,
after morning lows in the m50s W to l60s at the coast.

Weak ridge aloft nudges into the region from the WSW Fri night
into Sat. Differing potential/timing in arrival of weak S/W
tracking into the FA by Sat afternoon. Combination of daytime
heating and that S/W in WNW flow aloft may result in at least
SCT convective development. Otherwise...partly cloudy Fri
night-Sat morning...then becoming mostly cloudy Sat afternoon.
Lows from the u50s NW to the l60s SE. Highs Sat from the m70s-
around 80F on the eastern shore to the m80s inland.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Shortwave ridging builds over the Northeast Saturday as an
upper level low tracks into the Great Lakes region. Weak area of
surface high pressure slides off the Mid-Atlantic coast
Saturday as a warm front lifts through the region. Weak
perturbations in fast westerly flow aloft will result in low end
chance POPs Saturday afternoon for showers and thunderstorms.
Otherwise, warming trend continues with highs in the low to mid
80`s. The warm front locates/stalls over the northern Mid-
Atlantic region Saturday night, resulting in continued chances
for showers/thunderstorms over the northern local area as
perturbations in the westerly flow track across the region. The
upper low slowly pushes across the Great Lakes region Sunday
with an associated cold front progged to reach the central
Appalachians late Sunday. Pressure falls ahead of the
approaching front will induce a lee side/thermal trough over the
region and better chances for diurnally driven showers and
thunderstorms. Highs Sunday generally in the mid 80`s. The cold
front reaches the local area Monday, but is expected to stall
over the region as subtropical high pressure strengthens off the
Southeast coast. The weak front remains over the eastern local
area through Tuesday, with chances for diurnally driven showers
and thunderstorms. Highs Monday and Tuesday in the low to mid
80`s.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Mainly lo end MVFR cigs into early this evening as winds remain
generally E aob 15 kt. Increasing coverage of SHRAS w/ ISOLD-
SCT tstms after 22Z/24-02Z/25 until Thu morning...w/ periods of
IFR CIGS/VSBYs possible...esp in heavy RA. Additional SCT
SHRAS/tstms possible again Thu afternoon/evening. Drier/VFR wx
returns by Fri as weak high pressure builds over the region.
Unsettled conditions return for the weekend when another frontal
boundary affects the Mid Atlantic States.

&&

.MARINE...
Latest MSAS showing frontal boundary nearly stnry just south of the
VA/NC line. Weak low pressure that moved along this boundary last
evening now offshore. Still a challenging marine forecast given
model projections versus the actual obs. Thus, will be making some
adjustments to SCA headlines which will be based off of current obs.
NE winds still gusting in places to around 20 kts so plan is cont
the SCA headlines through 7 / 10 AM across the Ches Bay and adjacent
coastal waters through the day for 4-5 foot seas. Seas expected to
drop below 5 ft all areas by evening. Interesting to note the 180
degree change in wind direction due to the frontal position over
ANZ656 (NE at Cape Henry / SW at Ches Light).

The next in a series of low pressure systems lifts into the Ohio
Valley tonight with a meso-low lifting along the Appalachians. Data
suggests marginal SCA conditions possible tonight for a several hour
period with this feature. Given medium confidence in a widespread
SCA event and not wanting double headlines for separate events, will
hold off on any second/third period headlines for now.

SW flow increases Thursday as the low lifts north of the region,
with speeds of 10-20 knots expected. Yet another marginal SCA event
is possible Thursday night as the low tracks off the NE coast.

&&

.TIDES/COASTAL FLOODING...
A period of onshore flow and higher astro tides (moving toward a
new moon) will result in elevated water levels through Friday.
Several tidal sites reached action stage during last nights high
tide cycle. Todays high tide cycle is forecasted to be the lower
of the upcoming 2 cycles with some sites reaching action stage.
However, tonights high tide cycle is a different story. Many sites
are forecasted to approach if not reach minor flooding levels.
Forecasted levels at both Ocean City, MD and Jamestown, VA are
high enough to warrent an advisory attm. However, confidence at
other sites along the Bay and coastal waters is not high enough
for an advisory at this time so elected to hold off and let day
shift evaluate the need for either a statement or advisory.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for
     MDZ024-025.
NC...None.
VA...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Thursday for VAZ089-090-093.
MARINE...Small Craft Advisory from 6 PM this evening to 7 AM EDT
     Thursday for ANZ630>632-634.
     Small Craft Advisory until 4 PM EDT this afternoon for ANZ652-
     654.
     Small Craft Advisory until 7 PM EDT this evening for ANZ650.

&&

$$
SYNOPSIS...ALB/JDM
NEAR TERM...ALB
SHORT TERM...AJZ/JDM
LONG TERM...SAM
AVIATION...ALB/JDM
MARINE...MPR
TIDES/COASTAL FLOODING...



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