Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
633 am 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/...
latest surface analysis depicts ~995 mb low pressure over Nova Scotia with
broad ~1029 hi pressure over the northern plains and Midwest states. A weak
surface trough dropped through the middle Atlantic this morng...with drier northwest
flow behind the front preventing any fog formation unlike the past
couple nights. The hi will spread east into the middle Atlantic today
allowing for the dry conds to continue. Otws...expect a
prtly/mostly sunny sky with temperatures only climbing into the middle to upper
40s with weak cold air advection over the area.
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 prtly coudy
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 Wednesday/...
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 /12z Thursday through Monday/...
VFR condition through the forecast prd with only broken cirrus clouds
expeceted. Nrth winds at or below 10 kts as trough moves east across the region.
Outlook...high pressure dominates Friday. The next low pressure
system tracks across the southern states this weekend. High pressure
builds to the north of the area Sunday.
will keep Small Craft Advisory going through the late morning hours as first cold air advection surge
works it way through the waters. Anthr 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
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.
Marine...Small Craft Advisory until 10 am EST this morning for