Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
105 PM EST Thursday Dec 18 2014
high pressure builds into the area from the northwest through
Friday. One low pressure area will track from the Gulf Coast
states east northeast to off the southeast coast Saturday morning
into Sunday morning. Another low will move northeast off the
southeast and middle Atlantic coast late Sunday night through Monday
Near term /through tonight/...
late this morng...strong low pressure was over the Canadian
Maritimes...while broad hi pressure extended from the northern plains southeast toward
the Middle Atlantic States. The hi will spread east-southeast into the region this
afternoon...allowing for dry conditions under a partly to mostly sunny
sky. Hi temperatures will only range through the 40s due to weak cold air advection over
Dry weather continues tonight...with a middle-level short wave trough passing north of
the area. The middle Atlantic remains influenced by surface hi pressure centered
over the Midwest/Ohio Valley. Expect light northwest winds...a partly cloudy
sky...and low temperatures mainly in the upper 20s to lower 30s.
Short term /Friday through Saturday/...
hi pressure slides east through the Ohio Valley and NE states Friday into Friday
night with dry conds over the middle Atlantic. Hi temperatures in the middle to
upper 40s Friday with low temperatures Friday night in the upper 20 to lower
30s...and increasing clouds late. Attention then turns to surface low
pressure developing over the gom. All 00z and 06z guidance has shifted
the northern advancement of precipitation Sat farther S and delayed the
timing...so adjusted probability of precipitation accordingly. Model thicknesses show the
potential for sleet to mix in over the Piedmont at the
onset...before transitioning to plain rain. Probability of precipitation Sat afternoon range from
10-20% far north...to 30-40% around ric...to 60-70% far S. Precipitation
(mainly rain but snow possibly mixed in) will end quickly Sat night
with the upper-level flow being fairly progressive and the surface low
Long term /Saturday night through Thursday/...
drier air filters in from the northwest Saturday night behind the departing
low. Low temperatures should eventually fall to around 30 northwest to the
upper 30s southeast. However...any light rain/snow should end prior to
any surface temperatures falling to at or below 32f. Weak high pressure
should prevail Sunday...before another low forms off the southeast
coast and tracks NE Sunday night into Monday. At this time
temperatures appear warm enough for only rain. However...there
could be a brief mix of rain and sleet across the northwest Piedmont
Sunday night. Middle-level ridging builds in behind this system with
milder conditions expected by Tuesday. Low pressure tracks west of
the mountains Tuesday night into Wednesday bringing the potential
Aviation /18z Thursday through Tuesday/...
VFR conditions persist through the taf period...although expect to
see some middle level ceilings from 10-15 k feet this evening into early
Friday morning per latest satellite trends and BUFKIT soundings.
Winds generally will be less than 10 knots...except for some 10-15 knots northwest
winds through 22z this afternoon at ksby.
Outlook...high pressure dominates Friday with northerly winds averaging
10 knots or less and clearing skies. A low pressure system tracking well
to our south Sat/Sat night may bring a period of broken/overcast conditions
but ceilings are expected to remain 4-5 k feet or higher. High pressure builds
to the north of the area Sunday...with a wave of low pressure Monday bringing
the next chance for rain and lower cigs/vsbys.
have allowed remaining Small Craft Advisory to expire for the Bay as winds have now
dropped off to 10-15 knots. In coastal waters seas are highest in NC
waters due to winds from a direction more due north as opposed to
northwest. Seas briefly touched 5 feet at buoy 44100 although have dropped
off over the past hour so will not raise any headlines and just go
with "4 feet seas" through the afternoon.
Another weaker nearly surge seen tonight as a secondary trough crosses the
region...but will cap winds at 15 kts for now. Otw...N-NE flow
continues below Small Craft Advisory levels into the weekend.
Low pressure prognosticated to track east-northeast to immediately off the Carolina
coast Saturday morning through Sunday morning. Another low tracks
NE off the southeast and middle Atlantic coasts late Sunday night into
Monday. There continues to be too much uncertainty at this point to
speculate on the potential of Small Craft Advisory conditions.