Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 200957

Area Forecast Discussion
National Weather Service Wakefield VA
457 AM EST Mon Feb 20 2017

High pressure over eastern Canada builds south across the region
today, then slides offshore tonight and Tuesday. A frontal boundary
stalls north of the area Tuesday night with low pressure tracking
across the region Wednesday. High pressure returns Thursday.


Latest MSAS has a 1020 mb high centered over the Ohio valley, a 1027
mb high centered up near Hudson Bay with a weakening dry boundary
located across the nern states. Models basically wash this boundary
out today as it sags southward while the high pressure systems merge
across the region this afternoon. Just enough CAA noted on north
winds to drop H85 temps to between 7-8C. Little if any moisture
noted to support nothing more than sct-bkn CI. Upshot will be a
sunny and continued mild holiday. Onshore flow keeps eastern areas
coolest with highs ranging from the mid-upr 50s across the eastern
shore, between 60-70 from the Ches Bay to the Piedmont with lwr 70s
across swrn most zones (FVX-AVC).


The high slides offshore tonight. Tsctns show high level moisture
increasing across the region after midnight due to the light onshore
flow. Clear skies this evening become pt cloudy after midnight. Lows
in the 30s to near 40 sern coastal areas.

The offshore high still dominates Tuesday ahead of a weakening mid-
level cold front approaching from the west. Pt to mostly sunny skies
expected with the most sun across the se closer to the offshore ridge.
Mixing will be limited, only to about 950-925mb, with highs ranging
from the low-mid 50s near the water, upr 50s-lwr 60s west of the bay.

The mid level cold front approaches from the west Tues night but stalls
across the mts with a sfc trof extending east across the Piedmont.
Moisture is limited, but latest guidance is a bit more bullish in
allowing this moisture to spread east into the Piedmont after midnight.
Thus, have added a low chc shwrs after midnight across northern and
western areas of the fa, highest pops west of I95. Otw, mstly cloudy
to cloudy with lows in the low-mid 40s.

Models diverge with Wed forecast to a degree where it has become a
low confidence forecast. NAM is a much wetter solution as it tracks
low pressure and categorical pops across the region. GFS has a weaker
system ahead of the sagging sfc trof with chc pops, SREF a model blend
while the ECMWF keeps a low suppressed well to the south. Won`t get
to fancy with timing and go with chc pops under cloudy to mstly cloudy
skies. Lowered temps by several degrees due to more clouds and pcpn
but temps still remain well above normal. Highs from the low-mid 60s
near the water, upr 60s to nr 70 west of the Ches Bay.


The models are in good agreement in the extended range showing a
flat ridge over the eastern US for the second half of the work
week. That ridge will amplify into Saturday as a trough lifts
out of the central plains into the Great Lake states which will
knock the ridge down by Sunday and return the area to more
westerly zonal flow. Overall, this will lead to another period
of above normal temperatures along with a chance for showers and
psbl tstrms as the cold front crosses the area Saturday.

On Wed night into Thursday as the high slides off the coast, the
flow will turn sw and should see a good warm up ahead of a weak
front that tries to drop in from the north. The guidance suggest
the possibility of some light showers especially across the
northern part of the cwa Thursday into Thursday night. But with
the area having been dry for the last several weeks will not
mention any chance of rain with this weak front as the ridging
aloft may end up keeping the front just north of the area.
Expect above normal temperatures with highs in the uppers 60s to
the mid 70s. The next strong sfc low will lift from the central
plains into the Great Lakes on Friday into Saturday dragging a
cold front across the region on Saturday. The guidance is in
better agreement for a swath of moisture and marginal dynamics
with the fropa so went ahead and added thunder to the grids Sat.
Behind the front, temperatures will return closer to normal but
still above normal, but just not 20 to 25 above normal as Thursday
into Saturday will be.


VFR through the forecast period as high pressure dominates. Only
SCT-BKN CI expected with north winds below 10 kts.

OUTLOOK...Sct shwrs psble Tue night across the Piedmont.Sct
shwrs Wed as low pressure crosses the region. Shwrs/psbl tstrms
Sat as a strong cold front crosses the area.


Sub-SCA conditions continue today as sfc high pres slides in from
the west. Brief CAA surge expected this morng in association with
pres rises as the high builds in, but expect winds only up to ~15
kt. North winds then drop to ~10 kt later this aftn with 1-2 ft
waves over the Bay and 2-3 ft seas over cstl wtrs. The high builds
directly over the wtrs tngt into Tue with winds aob 10 kt. Sub-SCA
S/SW flow then persists until Fri ahead of the next cold front,
which crosses the wtrs over the weekend with SCA conditions psbl.


Record Highs for Thursday 2/23 and Friday 2/24:

       2/23           2/24

RIC   75 in 1985    82 in 1985
ORF   79 in 1975    82 in 2012
SBY   74 in 1943    77 in 2012
ECG   77 in 1975    79 in 1985




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