Scientific Forecaster Discussion
fxus61 kakq 211519
Area forecast discussion
National Weather Service Wakefield Virginia
1019 am EST Thu Nov 21 2019
high pressure will become centered along the Carolina coast this afternoon.
A cold front enters the region late Friday and lingers through
Saturday before a strong low pressure system pulls the front off
the coast by Sunday. High pressure returns late Sunday into
Near term /through tonight/...
as of 1015 am EST Thursday...
Latest analysis indicates ~1028mb sfc high pressure centered
from Georgia to the Virginia coastal plain, with a west-northwest flow aloft out ahead
of an upper ridge axis that extends north from the Gulf Coast to just west
of our County Warning Area to the eastern Great Lakes. Still mainly clear over
the local area late this morning with high clouds approaching
the area from the west. Temperatures have warmed into the 45-50f
range in most areas. The high is progged to shift east and become
centered along the coastal Carolinas this aftn, allowing winds
to turn to the south-southwest by late in the day inland (more of a light
west/SW near the coast and potentially local onshore flow along
the southeast Virginia/NE NC coast). While 850 mb temperatures are progged to
rise significantly to 8-11c by 21z this aftn, the increasing
and thickening mid/high level clouds and the lower November sun
angle will limit the amount of warming. Therefore, expect highs
to only range from the mid 50s north and along the coast to the
upper 50s across interior central/southern Virginia and NE NC. Milder
tonight as the sfc high begins to slide off the Carolina coast
and return south-southwesterly low level flow increases. Partly
cloudy with lows mainly in the 40s (generally coldest over
interior southeast Virginia/NE NC closest to the sfc high where some local
upper 30s/around 40f lows will be possible).
Short term /Friday through Saturday night/...
as of 330 am EST Thursday...
By Fri, a potent northern stream upper shortwave/sfc low will
be tracking ewd from Ontario to Quebec. This feature appears a
little stronger on latest 00z/21 model runs and will drag a
cold front toward the region. It will be weakening as it moves
into the area, but does look to reach into the northern portion
of the County Warning Area by late aftn. Deeper moisture (along with a series
of weak disturbances) moves in from the west-west-southwest during the day on
Fri. 00z/21 NAM/GFS/ECMWF are generally focusing deepest
moisture and lift for the northern 1/2 to 2/3 of the County Warning Area from west
to east from 15-21z Fri. Have raised pops to likely for a 3-6 hr
period over the north/traversing the north side of Metro ric and
off to the Eastern Shore/Northern Neck/middle peninsula by late
aftn. Will only have pops of 30-50% S of this and only to 20-30%
mainly late for NE NC. Quantitative precipitation forecast amounts on Fri look light (mainly
~0.10" with locally up to 0.20" possible). Given the rain (and
mostly cloudy skies), will go W/ highs in the upper 50s to low
60s in most areas (w/ some mid 60s across sern zones).
The front crosses most of the region Fri night, before
stalling/washing out near the Virginia-NC border as it becomes nearly
parallel to the mid level flow and developing sfc low pressure
hanging back over the lower MS valley as the upper low over the
plains slowly moves eastward. Expect some drying (with very
little chc for pcpn) behind the front Fri night, but will keep
slight chc pops for light rain across far SW overnight. Mostly
cloudy although there will likely be some clearing over the far
north/NE late. Lows in the lower to mid 30s far north and over the NE,
with mid 40s S.
The aforementioned surface low is progged to move eastward
towards the Ohio Valley on Sat. A warm front will try to cross
our region during the day on Saturday, but model consensus shows
the front not making it much past srn Virginia (becoming centered from
the srn Virginia Piedmont to the Virginia ern shore by Sat evening). Only a
few minor changes to the model trends and the overall forecast,
mainly to slow the arrival of rain over the eastern sections Sat
am as sfc high pressure noses down into the area. Most areas
will be dry Sat morning, but still mostly cloudy except over the
Eastern Shore and NE zones where some sunshine is expected until
midday. Still anticipate a quick overspreading of rain due to
deep lift/overrunning by late morning west of I-95 and to most of
the coast by late Sat aftn/early evening. Given low dew pts
initially, will continue with rather cold highs over the north and
especially the far northwest where low- 40s are forecast. Highs mainly
in the mid to upper 40s along and northwest of a fvx-ptb- cge line.
Temperatures should warm into the 50s across southeast Virginia/NE NC by late
Sat aftn. Have pops ramping up during the 18z Sat-00z sun
timeframe. Latest 00z/21 eps/gefs depict continue to depict
highest chance for widespread moderate rainfall to be Sat night
so have ~80 to 90% pops in all zones during this period as the
trailing cold front pushes through as the sfc low tracks to our
north. Quantitative precipitation forecast amounts from 12z Sat-12z sun are generally 0.50" to 1.00"
range (most of it Sat night). Temperatures will show a non-
diurnal trend Sat evening, tending to warm several degrees
during the first part of Sat night as the warm front continues
to slowly move northward while the main sfc low tracks to our north.
Temperatures then fall during the latter half of Sat night as
the cold front crosses the region from northwest to southeast. Lows sun am
range from the upper 30s northwest to the upper 40s/lower 50s across southeast
Long term /Sunday through Wednesday/...
as of 330 PM EST Wednesday...
Rain chances end in all areas (except for the lower Maryland ern
shore) by 12z sun as the low quickly moves offshore. Skies
eventually become partly-mostly sunny by sun aftn as weak high
pressure builds toward the region. Highs mainly in the 50s on
The beginning of the week starts off dry as high pressure will be in
control. On Monday the high will be centered over the Florida Panhandle
resulting in a cool west/northwest flow, thus temps will run several degrees
below normal. On Tuesday the high shifts either right over the area
or just to our east. A resulting S/SW flow will bring temps up
towards seasonal norms, with highs in the upper 50s to lower 60s.
A low pressure system strengthens by mid week as it moves from the
mid west up towards the Great Lakes by Wednesday. As this system
continues moving northeast it will drag a cold front across the
eastern US. Some minor timing differences between the GFS and European model (ecmwf)
on the frontal passage across our area, but it should be through the
area by late Wednesday into early Thursday. Both models are in
agreement as of right now that precip will be drying up as it
crosses the mountains, so rainfall amounts over our area will likely
be minimal. Assuming that the cold front doesn't cross the area
until later in the day on Wednesday, we'll still be in a warm S/SW
flow ahead of the front, so high temps on Wednesday will be slightly
above normal in the low to mid 60s.
Aviation /15z Thursday through Monday/...
as of 700 am EST Thursday...
VFR conditions prevail through the 12z taf period. Skies are
clear early this morning and will only see some mid/high clouds
overspreading the region later today with cigs at or above
15,000 ft. Winds early this morning will be light from the north to
northwest expect winds to shift to west/SW later this aftn and then to
the south-southwest tonight, generally below 10 kt. Partly cloudy tonight.
Outlook...there will be a chance for brief flight restrictions
in showers Fri mainly during the aftn (continuing into the
evening over southeast Virginia/NE nc). Winds shift to the NE Fri night into
Sat morning. Low pressure approaches from the SW on Sat before
tracking across the region Sat night. Rain is likely, as well as
flight restrictions during the Sat aftn-Sat night timeframe
(due to both cigs/vsbys). VFR/drying out for sun with a breezy
as of 500 am EST Thursday...
Small Craft Advisory remain in effect for the Chesapeake Bay and Atlantic Ocean
for a couple more hours this morning. Winds in the Bay
(especially eastern side of the bay) are still gusting to 20-25
kt. Winds over the Atlantic are sustained near 20 kts with gusts
up to 30 kt (wind drop off closer to the coast). Winds will
quickly diminish after sunrise this morning as a sfc high
pressure moves over the area. Small Craft Advisory will likely be allow to expire
at 12z/7am Thursday for the Chesapeake Bay and Atlantic Ocean
along Delmarva, and 15z/10am for Atlantic waters from the mouth
of the Chesapeake Bay to Currituck County, NC for seas greater
than 5 ft.
Winds will continue to decrease to 5-10 kt by the afternoon on
Thursday with an area of high pressure overhead. Seas in the
Atlantic will come down to 2-3 ft this afternoon and waves will
be near 1 ft in the Bay and tidal rivers.
Winds will increase again late Thursday night as a low pressure
system tracks well north of the area, across southern Canada,
suppressing the sfc high pressure to the south of the area. The
pressure gradient will increase which will lead to a southwest
wind of 15-20 kt in the Chesapeake Bay and near 20 kt with gusts
of 25 kt for the ocean Thursday night-Friday. Winds will
decrease slightly as a weak cold front pushes across area waters
Friday afternoon, with a weaker pressure gradient. Winds will
increase for a brief period behind the front on Friday night as
high pressure builds in before decreasing further for Saturday.
Scas are possible Thursday night- Friday night. Seas in the
ocean waters will be 3-5 ft and waves 1-2 ft in the Bay and
Sfc high pressure will be over the central Virginia Piedmont to d.C.
Saturday, leading to light and variable winds for the Chesapeake
Bay and ocean off of Delmarva and a slight onshore flow south
of the mouth of the Chesapeake Bay for most of the day on
A low pressure system will track just east of the Appalachian
Mountains across the Carolinas Saturday afternoon, then across
our area Saturday night. Southerly winds will increase to 10-15
kt (possibly up to 20 kt for the ocean) Saturday night as the
low tracks across Virginia and Maryland. The low pressure will continue to
track northeast towards NYC and Boston Sunday. Winds will turn
west-northwest 15-25 kt (highest winds likely north of the Virginia/Maryland border)
once the low passes to the north. Seas in the Atlantic will be
4-6 ft, waves in the Bay around 3 ft and 2 ft in the rivers
Saturday night and Sunday.
Marine...Small Craft Advisory from 1 am to 10 am EST Friday for
Small Craft Advisory from 1 am to 1 PM EST Friday for anz650-
Small Craft Advisory until 1 PM EST this afternoon for anz658.