Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Wakefield Virginia
125 PM EST Mon Dec 5 2016

Synopsis...
low pressure passes south of the region this morning. A complex
area of low pressure crosses the region Tuesday. A strong cold
front crosses the area Thursday.

&&

Near term /through tonight/...
Sat loop/sfc obs showing St quickly dissipating this afternoon
allowing the sun to finally go to work. Temps should rerapond to
the sun over the next few hrs with highs in the low-mid 50s.

Pvs dscn:
rain chances ramp back up late tonight, as wind fields back to the
south-southwest as sfc low pressure deepens over the Gulf Coast. Isentropic
lift similarly ramps back up late this evening through the
overnight hours, and rain chances increase from SW to NE during
this period. Meanwhile, sfc high pressure builds across the
interior northeast, with weak cad setting up as sfc high noses
down into the Piedmont. Cams indicating increase in pops after 06z
but have increased pop after midnight, as deterministic models
generally underestimate just how fast pcpn breaks out in and
overrunning scenario. Clouds thicken/lower once again in the
evening with rain overspreading the fa SW-NE after midnight. Lows
upr 30s north to upr 40s southeast.

&&

Short term /Tuesday through Wednesday/...
Tuesday remains a challenge as low pressure rides NE along the
southern Appalachians with a secondary low pressure tracking NE
along the Carolina coast. Given the current temp/dp temp scheme,
it is not out of the question to see a few sleet pellets mix in
with the rain at the beginning across northern most zones early
Tuesday morning before the column wet bulbs out above freezing.
While this won't result in any significant impacts, have allowed
mention for potential brief period of sleet across far northwest tier of
counties late tonight and early Tuesday morning.

Deterministic models and majority of ncar ensembles indicating
period of moderate rainfall Tuesday morning through afternoon as
Gulf/Atlantic moisture become entrained and track across the
region. 00z/05 models consistent in tracking the triple point low
across the northern Outer Banks keeping the center ivof eastern
Albemarle Sound. This track will likely keep pcpn type mainly
stratiform across the fa but may become convective across the
extreme sern zones for a few hours during the afternoon. Temp
forecast tricky due to a strong in-situ- wedge holding readings
arnd 40 most of the day across the nwrn most zones (lku) ranging
to the low-mid 60s ivof the northern Outer Banks (onx). Forcing
strong enough for a several hour period of MDT to psbly heavy
rainfall with widespread rainfall amounts between 1/2 to 1 inch.
Pcpn slowly ends SW-NE Tuesday night as the best lift moves NE.
Lows 35-40 west, 40s east.

The low slowly pulls away from the region Wednesday with deep
layered SW flow behind it. Decreasing clouds in the morning bcmg
mostly sunny in the aftn. Highs in the mid-upr 50s.

&&

Long term /Wednesday night through Sunday/...
upper trough tracks into the northeast states Thursday, with an
associated cold front quickly pushing across the local area
Thursday. Medium range guidance now in better agreement with the
frontal timing and evolution of the upper wave. Moisture will be
limited along the front as the best dynamics lag behind. As a
result, have maintained only a slight chance to low end chance pop
Thursday morning for the Piedmont into central Virginia, and then
pushing toward the coast Thursday afternoon. Highs Thursday in the
mid/upper 40s northwest to the mid 50's southeast. Better chances
expected in the north/northeast forecast area nearest the deepest
moisture. Front and moisture quickly push offshore late Thursday as
a cold and dry Arctic air mass surges into the region. Lows drop
into the 20's Thursday night. Cool, breezy, and dry Friday as
surface high pressure builds in from the west. Latest gefs still
indicates 850mb temperatures of -10 to -12c (-2 Standard
deviations). Highs are expected to warm only into the upper 30's to
low 40's. Add in a breezy northwest wind and wind chills will
struggle to reach the mid 30's. High pressure centers over the area
Friday night as temperatures drop into upper teens to low 20's
inland to mid/upper 20's near the coast. 850mb temperatures progged
to moderate slightly Saturday (-6 to -8c) as cold high pressure
centers over the region. Less mixing will result in another cool
day, with highs back around 40 under a mostly sunny Sky. High
pressure slides offshore Sunday as return flow and quasi zonal flow
aloft results in moderating temperatures. Highs Sunday forecast in
the mid to upper 40's to low 50's southeast.

&&

Aviation /19z Monday through Saturday/...
stubborn IFR stratus hanging on a bit longer than expected today,
however the Sat trends are noting this quickly burning off allowing
the IFR St to dissipate with VFR conditions over the next 1-2 hours.

High level moisture will begin to increase after 00z as the moisture
from the approaching storm from the south moves NE. Rain will quickly
overspread the region around 12z Monday with lowering cigs and vsbys.
IFR conditions along with areas of fog and MDT pcpn expected just
before the end of the forecast period.

Outlook: IFR conditions continue into Tuesday night as the storm
slowly pulls away to the NE. Improving conditions to VFR behind
the system on Wednesday. A strong cold front crosses the area
Thursday with sct shwrs.

&&

Marine...
high pressure located just offshore this morning, with an area of
weak low pressure along the southeast coast. Observations indicate a
light south to southeast wind over the waters, generally at or below
10 knots. Waves 1-2 feet and seas 2-3 feet. The low lifts off the
Outer Banks early to mid morning as high pressure builds in from the
northwest. Winds in the southern waters become north to northwest 10-
15 knots early morning, then northwest 10-18 knots all waters by
late morning. With a brief period of increasing onshore flow in the
southern waters, seas will build to 3-4 feet, possibly reaching 5
feet briefly out 20nm. High pressure builds into the region this
afternoon as the low slowly pushes offshore. A northwest wind around
15 knots in the coastal waters expected to keep seas in the 2-4 ft
range. High pressure centers over the northeast tonight through
Tuesday as another area of low pressure lifts along the southeast
coast. Flow becomes onshore late tonight and Tuesday. Pressure
gradient strengthens as height falls spread northward over the
coastal waters. Seas expected to build to 4-5 feet in the southern
waters, then 4-6 ft all waters Tuesday afternoon as east winds
increase to 15 to 25 knots. Waves 2-3 feet in the north and 3-4 feet
in the Lower Bay. Small Craft Advisory headlines have been issued for the Bay,
Atlantic waters, and sound. The low lifts northeast away from the
coast Tuesday evening with flow becoming northerly. Speeds remain 10
to 20 knots and seas 4-6 feet. Small Craft Advisory headlines for the Atlantic waters
run through 4th period. The low pushes farther offshore Wednesday
with northwest winds decreasing to 10-15 knots in the afternoon.
Seas subside to 3-4 feet late. A strong cold front pushes across the
waters Thursday, with strong Small Craft Advisory conditions (or low end gale
conditions) possible Thursday night. Small Craft Advisory conditions expected to
linger into the weekend.

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...Small Craft Advisory from 10 am to 6 PM EST Tuesday for
anz630>634.
Small Craft Advisory from 1 PM Tuesday to 6 am EST Wednesday
for anz650-652-654.
Small Craft Advisory from 10 am Tuesday to 6 am EST Wednesday
for anz656-658.

&&

$$
Synopsis...mam
near term...mpr/mam
short term...mpr/mam
long term...Sam
aviation...ajb/mpr
marine...Sam

National Weather Service Glossary of Abbreviations