Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 240740
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
340 AM EDT Wed May 24 2017

.SYNOPSIS...
Weak high pressure prevails over the area today. Unsettled
conditions return this evening through Thursday as an upper
level trough approaches from the west. Conditions improve on
Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A shortwave trough will exit to the east of the area through
sunrise and will take with it the last widespread batch of light
rain currently seen on the radar. Some semblance of shortwave
ridging develops over the Mid-Atlantic today due to the
combination of the departing shortwave and a strong upper low
digging across the mid-MS valley. Therefore, after the current
light rain exits, will drop PoPs below 20% for most areas into
the afternoon. Low clouds will struggle to erode despite some
mid-level drying as the surface pressure gradient will be
rather nebulous resulting in weak low-level flow. The best chc
for any partial clearing will be across the MD Ern Shore. High
temperatures will remain below average today given the onshore
flow, ranging through the mid/upr 60s to low 70s, except mid/upr
70s across NE NC.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
The upper low digs into the Tennessee Valley with yet another
shortwave trough lifting NNE across the Carolinas and Mid-
Atlantic this evening through the early overnight hours. A
secondary wave lifts NNE across the Blue Ridge late this evening
through the overnight hours. PoPs quickly ramp up to categorical
across the SW piedmont/NE NC early Wednesday evening and
spreading NE into central/SE VA late evening through the early
overnight hours, before shifting to the Ern Shore after
midnight. Mid-level drying and subsidence will result in PoPs
quickly diminishing from SW-NE late Wednesday night into early
Thursday morning. There will be a chc of strong to severe
thunderstorms mainly along/south of the VA-460 corridor tonight
as 500mb flow strengthens to 40-50kt across far southern VA and
NE NC and the presence of a surface warm front will result in a
veering low-level wind field. SPC has upgraded our far southern
counties into a slight risk where locally damaging winds and an
isolated tornado may be possible if enough instability
develops. Additional QPF tonight averages 0.30-0.60".

The upper low finally 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 45-55kt 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 Thursday
aftn/evening should average ~0.25" with locally higher amounts.
High temperatures range from the mid 70s to around 80 after
morning lows ranging through the 60s.

The upper low continues to lift NE across PA/NY/New England
late Thursday night into Friday. Drier conditions finally arrive
as deep layered WNW flow develops over the region. Some
lingering mid-level energy could result in some sct-bkn cu
Friday aftn. Otherwise, drier and breezy with highs in the upper
70s to low 80s, after morning lows in the mid 50s to low 60s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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 /07Z WEDNESDAY THROUGH SUNDAY/...
Light rain will exit to the east thru 10z with relatively dry
conditions on tap for much of the rest of today. Unfortunately,
CIGS will improve very little if any through the day. Winds
will be from the northeast and east this morning then veer
to the southeast this afternoon at 10 knots or less.

OUTLOOK...Additional rounds of showers and thunderstorms are
expected Wednesday night into early Thursday morning and again
late Thursday. Aviation conditions will likely be impacted
through Thursday night. Dry weather returns Friday 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 Wednesday
night. Many tidal sites will reach action stage during this
evenings/overnights high tide cycle. Coastal flood statements
have been issued for the upper James and areas around Bishops
Head, Maryland. Low pressure lifts over the region tonight, with
onshore flow ramping up. However, the low is expected during
periods of low tide. Lower astro tides are expected Wednesday
morning. Higher levels are forecast Wednesday evening/night,
with minor flooding possible along the the Bay, James River,
and Atlantic waters.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 7 AM EDT this morning for
     ANZ630>632-634.
     Small Craft Advisory until 1 PM EDT this afternoon for ANZ654-
     656.
     Small Craft Advisory until 4 PM EDT this afternoon for ANZ650-
     652.

&&

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


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