Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 240803

Area Forecast Discussion
National Weather Service Wakefield VA
403 AM EDT SAT SEP 24 2016

A backdoor cold front drops south across the region Today. High
pressure tracks across Southeast Canada early next week. A second,
stronger cold front will cross the region later Tuesday.


Latest analysis features strong 1026+mb high pressure over Ontario
into the Upper Great Lakes. Subjective wx analysis places weak
cool frontal boundary from Southern New Jersey back into the
Mason-Dixon line and the lower Ohio Valley early this morning.
Meanwhile, weak ~1018mb high pressure is in place across the
region. Aloft, prominent upper level ridging remains in place,
centered across the mid-south and Mississippi River Valley. this
is keeping PW values suppressed in the 1-1.25" range across the
region per early morning Blended TPW sat product.

Have noted some areas of ground fog, dense in spots along the
southern tier of the forecast area. Will likely have to handle
with a round of targeted statements this morning, but otherwise
expect fog and any lingering stratus to get mixed out quickly
after sunrise this morning. After fog scours out, expect a partly
to mostly sunny start, with clouds quickly increasing across the
northern tier of counties from Late Morning through the aftn as the
front drops across the area. Winds shift to the N-NE during this
timeframe. High-res models resolute in showing an area of rather
shallow lift along the front as it drops across the southern half
of the area from late aftn through about midnight. Have
accordingly kept the forecast dry through the day, introducing
some sct showers tonight, mainly across the piedmont and I-85
corridor. QPF will be minimal with still relatively dry air aloft.
and only weak isentropic lift. Thickness tools and Conshort/HRRR
basically identical wrt temps, producing highs in the mid to upr
70s eastern shore...low to mid 80s RIC metro...and mid to upper
80s far SW zones.

Front drops south of the area late tonight, with sct showers
along the boundary likely lingering into the morning hours. Clouds
will be on the increase post-frontal, especially inland with post
frontal nne flow as high pressure ridges down and cool air wedge
begins to set up. Accordingly beefed up sky cover tonight and into
Sunday. Lows Sat night in the mid 50s north to mid 60s south.



Front continues to push south into the Carolinas Sunday in
response to high pressure sliding across Southeast Canada. This
high extends south across the Mid Atlantic Region Sunday and
Sunday night. Latest data continues to focus on increasing low
level moisture and weak isentropic lift Sunday and Sunday night.
The depth of moisture remains rather shallow...favoring only low
end pcpn chances for pockets of light rain or drizzle mainly along
and west of the I-95 corridor. Kept slight chc pops (stratiform
rain rather than showers) across the Piedmont. The onshore flow
results in mostly cloudy/overcast skies for areas mainly west of
the Bay during this same time and partly cloudy for the Eastern
Shore. Highs Sun 70-75. Lows Sun night in the mid 50s to lwr 60s.
If it clears early enough...SBY could drop to near 50 by 12Z Mon.

High pressure moves north of New England Monday with the next
front approaching from the west during the afternoon. Slight chc
showers across the Piedmont ahead of the front. Onshore flow and
clouds keeps it cool with highs in the low to mid 70s.


Medium range period has become somewhat clearer with the latest
12Z model suite trending further into at least modest agreement.
There are still significant timing differences that exist
regarding a cold frontal passage Tue into early Wed followed by a
large area of High pressure building into the local area from the
west as an upper level trough becomes centered over eastern Canada
and the NE CONUS/New England Tue/Tue night, then shifts off the E
coast by Thu. Have raised POPS Tue/Tue night to 30-40% with the
front, along with a chc for tstms Tue aftn/evening. Beyond that,
will linger 20-30% POPS mainly along the coast Wed in case the
front trends slower, with mainly dry conditions expected Wed night
through Fri. Temperatures will avg close to seasonal averages,
with highs Tue ranging from the mid 70s NW to around 80 F S/SE
(where more sun may occur ahead of the front). Highs Wed-Fri
generally in the 70s with lows in the 50s, except in the 60s SE.


Mostly clear skies this morning as weak high pressure slides over
the area. Given light winds and still wet grounds, noting areas
of low Stratus/fog across the SE coastal plain, impacting KECG,
and eventually KSBY and KPHF after 08z. Expected low clouds/fog
will scour out quickly after sunrise this morning, improving
quickly from LIFR/IFR at ECG to MVFR/VFR after 14z.

Thereafter, primarily VFR conditions expected. A backdoor cold
front drops across the area through the day Saturday...primarily
spreading widespread high clouds across the area during the day.
Given the abundant/recent rainfall from the past several days and
persistent onshore/ne winds, expect SCT cumulus to develop during
the aftn...especially near coastal sites. KSBY will likely
experience MVFR cigs given frontal timing, and Hi-res models
continue to support VFR farther inland. Could see some Sct showers
west of KRIC after 21z this aftn, but minimal support for pcpn at
terminals with plenty of dry air in place aloft.

The front pushes south of Albemarle Sound after midnight Saturday
night with stronger central high pressure sliding across Southeast
Canada and building down into the Mid Atlantic Region through
Sunday night before sliding off the New England coast early next
week. Areas of fog and some low stratus expected once again across
the southern terminals late Tonight into early Sunday morning.

Cigs trend back toward VFR for most locales along the coast as
cool air wedge sets up across the piedmont. Lingering low
clouds/light rain possible at KRIC and west.


Latest obs continue to depict diminishing NE flow across the
waters, generally 5-10 KT. Seas avg 3-4 ft with 10-12 second
dominant periods and wave in the Bay are 1-2 ft. Trends are slower
with the approaching cold front from the N later tonight into Sat,
now the winds tonight will avg 5-10 Kt or less and gradually
shifting to the SSW after midnight.

On Sat, front progged to push through the waters from N to S,
pushing into NC by late afternoon. Did not raise SCA headlines as
winds should stay below thresholds, but there will probably be
about a 3 hr period with occasional gusts to 20 KT. Waves in the
Bay should build to 2-3 ft by late morning/early aftn and to 2 ft
in the rivers so still not ideal boating conditions even without
headlines (may need to issue an MWS). For the coastal waters,
distant tropical Cyclone Karl Invof Bermuda looks to aid in seas
building to 4-5 ft. Trends in wavewatch are slower and slightly
weaker however, so did not issue SCA headlines as this is marginal
and will be late 2nd period (will allow next shift to determine if
seas ever do reach a widespread 5 ft). Wavewatch and NWPS both
depict seas subsiding once again for Sunday through Sunday night.
Next cold front approaching from the NW will shift winds back to
the SE on Mon and increase from the S Mon night/Tue. Still some
models differences/uncertainties but could see marginal SCA
conditions in the Bay Mon night/Tue and probably will have SCA
conditions behind the front sometime midweek as significantly
cooler airmass and strong high pressure builds in from the NW.


The Cashie River at Windsor continues to fall but remains in the
moderate flood range. The river is forecast to slowly fall below
flood stage late Sunday night. See FLSAKQ for details.




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