Scientific Forecaster Discussion
fxus61 kakq 200200
Area forecast discussion
National Weather Service Wakefield Virginia
900 PM EST Tue Nov 19 2019
weak low pressure will cross the region tonight, then exit off
the coast Wednesday. High pressure builds in from the west
Wednesday through Friday. A cold front enters the region late
Friday into lingers through Saturday before a strong low
pressure system pulls the front off the coast on Sunday..
Near term /until 6 am Wednesday morning/...
as of 900 PM EST Tuesday...
First S/W is exiting NE and away from the area while a second S/W
apprchs from the west. Clouds assctd with this feature are alrdy
overspreading the fa. High res data keeps most if not all pcpn
with the second S/W south and west of the local area through the
night. Thus, a cloudy to mstly cldy night ahead. Some patchy
fog is possible, but not widespread enough to include in fcst.
Lows mid 30s west to lwr 40s se.
Short term /6 am Wednesday morning through Friday/...
as of 345 PM EST Tuesday...
The exiting long wave trough and building ridge will allow for
clearing conditions on Wednesday as a strong surface high builds
into the area. This surface high will slowly slide across the
eastern US and dominate the conditions across the area. This
will result in dry weather and mainly clear sky from Wednesday
PM in Friday morning. For temperatures for this period expect
slightly milder conditions for highs in the mid 50s on Wed and
mid to upper 50s on Thursday. For lows on Wed night expect good
radiational cooling conditions with lows in the 30s expect right
near the coast. Conditions on Thursday night may be a little
warmer if the southwest flow increases ahead of the front.
For Friday uncertainty exist as the models differ on the timing
of a cold front moving into the area with the GFS 12z the
fastest model, the nam12 12z the slowest and the European model (ecmwf) 12z
splitting the difference on the movement of the front. With a
strong shortwave trough moving into the Southern Plains on
Friday amplifying a wave on the front, the slower movement seems
more likely so have gone slower to introduce pops on Friday,
mainly in the afternoon and pushed temperatures a little warmer
into the mid to upper 60s.
Long term /Friday night through Tuesday/...
as of 350 PM EST Tuesday...
The weekend begins with a mid level cutoff low over the central US.
Out ahead of this, a surface low is expected to develop in the
vicinity of the Southern Plains and move eastward towards the Ohio
Valley. A warm front will try to cross our region early on the day
on Saturday, models differ on the extent the front moves through,
with the GFS carrying the front all the way through the area and the
European model (ecmwf) stalling the front out about halfway across our forecast area.
This will have implications for temps and precip on Saturday. For
now kept the northern half of the area cooler on Saturday with temps
struggling to reach 50 while the southern half will be in the mid to
upper 50s. For precip kept chance pops in early in the day and
bringing likely pops into the southern half of the area for later on
Low pressure drags a cold front through the area by Sunday morning,
bringing an end to the rain chances, and high pressure centered over
Texas will build in for Sunday. The high will shift east on Monday
to the Mississippi Valley and then up the mid-Atlantic coast on
Tuesday. This will keep things dry both days and a west/SW flow will
moderate daytime high temps to near seasonal averages.
Aviation /02z Wednesday through Sunday/...
as of 615 PM EST Tuesday...
Low level moisture assctd with the first departing S/W continues
to lift NE this eve. Thus, ceilings have improved to VFR (bkn ac deck
above 10k ft). Second S/W progged to track across the region later
tonight with another round of broken-overcast ac deck (btwn 6-9k ft). This
continues through midday Wed with clouds scattering out in the aftrn
as the S/W pulls away from the area. Light winds become northwest behind
the S/W Wed (15-20 kts along the coast).
VFR conditions prevail late into the week.
as of 400 PM EST Tuesday...
Afternoon weather analysis shows an upper shortwave crossing the
area, with developing sfc low pressure a few hundred miles off the
Virginia/NC coast. Not much of a pressure gradient over the area this
aftn. As a result, winds are west at ~5 kt over the waters. All scas
that were in effect for seas have been cancelled (seas are now below
5 ft in almost all locations). As the upper shortwave moves offshore
this evening, the aforementioned area of sfc low pressure deepens as
it tracks north-northeast away from the area from tonight through the day on
Wednesday. At the same time, high pressure slowly tries to build in
from the west. Winds turn to the northwest tonight and increase to 15-20 kt on
the Bay/20-25 kt on the ocean (sustained) by the late morning hours
on Wednesday due to an increasing pressure gradient between the back
side of the deepening coastal low and the high to the west. Wind
gusts are expected to be in the 20-25 kt range on the ches Bay,
lower James River, and Currituck Sound from late Wed am through
early Thu am. Over the ocean, gusts are expected to range from 25-30
kt. As a result, scas have been issued for the ches Bay, ocean,
lower James River, and Currituck Sound from late morning/midday Wed
through Thu am. The current forecast has wind gusts remaining just
below Small Craft Advisory criteria on the upper rivers, but will have to monitor
trends to see if scas need to be issued. Seas are expected to remain
in the 3-4 ft range through tonight before building to 4-6 ft by
late Wed (highest 20 nm offshore). Seas fall to 2-4 ft by Thu aftn.
Winds are progged to diminish to 5-10 kt by late Thursday afternoon
as the center of the high moves over eastern VA/NC. An increasing SW
wind of 15-20 kt will develop Friday morning as a weak cold front
approaches the area from the northwest. The cold front will cross
the area late Fri-Fri night before another (deepening) area of low
pressure tracks across the region on Sat before moving offshore Sat
night. Scas appear likely Sat night as northwest winds increase after the
low moves offshore.
as of 845 PM EST Tuesday...
Coastal Flood Warning in Dorchester was replaced with a coastal
flood advisory as levels at Bishops Head have fallen below
moderate. All advisories will end after this evenings high tide
Increasing northwest winds tonight-Wed should allow tidal anomalies to fall
significantly across the upper ches Bay, largely ending the threat
for coastal flooding after this evening's high tide cycle.
Maryland...coastal flood advisory until midnight EST tonight for
Virginia...coastal flood advisory until 11 PM EST this evening for vaz075-
Marine...Small Craft Advisory from 7 am Wednesday to 7 am EST Thursday
Small Craft Advisory from 10 am Wednesday to 10 am EST
Thursday for anz633-656-658.
Small Craft Advisory from 10 am Wednesday to 4 am EST Thursday
Small Craft Advisory from 10 am Wednesday to 7 am EST Thursday