Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
410 PM EST Wednesday Dec 17 2014
high pressure builds into the area from the northwest this
afternoon through Friday. One low pressure area will track from
the Gulf Coast states east northeast to just off the North
Carolina 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 /until 6 am Thursday morning/...
drier northwest flow will filter into the region tonight into Thursday morng...as
a piece of hi pressure builds in from the west-northwest. Mostly clear and cold with
low temperatures ranging from the upper 20s to middle 30s.
Short term /6 am Thursday morning through Saturday/...
dry conditions will prevail Thursday into early Friday night...as dry/zonal
flow dominates the region and surface hi pressure builds across the Great Lakes
into southeast Canada. Shortwave energy tracking from west-east in fast flow aloft
will produce a little more cloudiness Thursday night into Friday morng.
Otherwise...mostly clear or partly cloudy Thursday through Friday...with hi
temperatures ranging through the 40s both days. Lows Thursday night mainly in the
upper 20s to lower 30s.
Friday night through Sat...leaning closer to the slightly faster GFS...esply
regarding onset/overspreading of precipitation across the region. At this
time...went closer to the GFS thicknesses/model soundings...esply
during Sat morng with the onset of precipitation...where a chance of sleet
(maybe some snow) was added generally north of a South Hill to
Williamsburg line. By late morng or early afternoon...precipitation will become
just rain everywhere...as layers warm and surface temperatures climb into
the upper 30s to middle 40s. Highest quantitative precipitation forecast amts with this system could
end up across extreme southern/southeast Virginia and NE NC.
Long term /Saturday night through Wednesday/...
continue to favor a blended solution leaning toward the European model (ecmwf) and
its member ensembles over the weekend into early next week. Primary
forecast challenge is in regards to the amplitude of the upper
pattern and the eventual storm track of developing low pressure
developing across the western Gulf Coast later Friday. While
deterministic models have been literally all over the map with this
system, the European model (ecmwf) ensembles and to a lesser extent the operational
Canadian remain the most consistent with this system.
Models can agree that high pressure over the northeast will be
ridging south into the area to begin the forecast period Friday
night. Also widespread consensus in increasing clouds across the
area late Friday night and Saturday morning as developing upper
disturbance slides NE from the Red River valley towards the
middle-south by 12z Saturday, with surface cyclogenesis occurring Friday
night over the western Gulf Coast. Despite some continued temporal
differences, models are more or less coming into consensus with
depiction of a lower amplitude upper system. The resultant storm
track would track surface low across the deep south and off the Carolina
coast early Sunday. Model guidance and analogs continue to support
overrunning precipitation quickly increasing, with likely probability of precipitation appearing
reasonable by early Saturday morning across our southern tier of
counties. Given the track and the transient, relatively weak surface
high to the north, still appears to be just a cold rain for our
area (have added slight chance ice pellets for about northwest 1/2 half of forecast area lt Friday
night/Sat morning given model soundings showing ice pellets profile over inland
portions of forecast area as precipitation arrives). Have held on to some snow rain showers
mention Sat night over interior zones as few snowflakes will be
possible as precipitation comes to an end Saturday night/early Sun morning.
Otherwise, precipitation comes to an end quickly inland as system
pushes east-NE offshore Sunday aftn/eve. High pressure will build in
behind the system Monday and Monday night. Temperatures will
gradually warm through the period, reaching above climatology by Monday
and Tuesday ahead of next system, which approaches from the west
by the middle of next week.
Aviation /20z Wednesday through Monday/...
VFR conditions and light west to northwest winds are expected through the
18z taf period.
Outlook...high pressure dominates with dry weather through Friday.
The next low pressure system impacts the Middle Atlantic States
later Saturday with the possibility of widespread light rain.
a cold front will push farther offshore this morng with westerly flow
left in its wake. Surface hi pressure then slowly builds in from the west today through
Friday. Winds will generally be west/northwest through the period. Did hoist a Small Craft Advisory
for northern coastal waters tonight where 20-25 knots winds are expected due to a
trough of low pressure sliding through and subsequent cold air advection surge. May come
close to criteria over the Northern Bay as well so will continue to
monitor...may also be brief enough to handle with a mws if necessary.
Otws...seas over coastal waters mainly 3-4 feet with waves over the Bay 2-3
feet. Similar conds into Thursday and Friday with just a slight decrease in
winds each day. Attention then turns to a coastal low that will track up
near the Carolina CST this weekend. Chance for Small Craft Advisory conditions will be
dictated by the track and strength of this low...for which there's
still a lot of uncertainty.
Marine...Small Craft Advisory from 10 PM this evening to 10 am EST
Thursday for anz650-652.