Scientific Forecaster Discussion
fxus62 krah 131124
Area forecast discussion
National Weather Service Raleigh NC
334 am EST Wed Dec 13 2017
a strong cold front continues to push off-shore early Wednesday
morning, leaving in its wake much colder temperatures and strong
wind gusts. High pressure will briefly build in Wednesday ahead
of a fast moving upper level disturbance expected to move just
north of the region Wednesday night.
Near term /through tonight/...
as of 330 am Wednesday...
..gusty winds expected to continue early this morning, with
wind chill readings falling to the single digits and teens just
Early morning surface analysis shows a cold front continuing to
push well off of the mid Atlantic Seaboard early Wednesday morning,
leaving cold temperatures and diminishing winds in its wake.
Temperatures continue to fall steadily overnight, with a steeper
drop off expected just before sunrise as dewpoints plummet and skies
remain clear. Wind gusts have begun to relax a bit as gradients
loosen, but sustained winds of 6 to 10mph are still common, and will
lead to wind chill concerns by mid morning. Expect apparent
temperature values to dip into the teens for most, with isolated
single digits possible in the northern and western Piedmont counties
Cold temperatures will be main weather story during the day
Wednesday, as 850mb temps continue to drop and drier air mixes
to the surface behind the frontal boundary. Temperatures will
start the day in the low 20s before rising steadily into the
upper thirties west to low forties east, remaining roughly 10
degrees below normal for this time of year. No precipitation
of any type is expected during this period.
Short term /Thursday through Thursday night/...
as of 330 am Wednesday...
Higher clouds will begin to mix in across the northern Piedmont
counties early Thursday as a short wave crosses the Appalachians,
east across portions of the Delaware-Maryland-Virginia peninsula, and eventually east
into the Atlantic prior to sunrise. Forecast soundings continue to
show the 500-700mb layer becoming a bit more saturated Wednesday
evening in advance of the short wave, mainly north and east of
Raleigh. However, the airmass below 700mb is forecast to remain dry.
That said, while the moisture and lift in that layer would suggest
some light precip between 7 PM and midnight, given the dry air below
the cloudy layer, it would be difficult to get any more than just a
few flurries with no impacts. For now, have taken out mention of snow
in these areas and just introduced scattered to broken cloud layers.
Skies will clear out again after midnight in the wake of the
departing short wave, with lows from the mid 20s to around 30.
Southwesterly flow returns during the day Thursday, allowing
temperatures to inch closer to normal, especially for those who
are a bit closer to the Atlantic coastline. Expect 40s in the
Piedmont counties, 50 near rdu, and low to mid 50s as you
progress east toward the coast.
Long term /Friday through Tuesday/...
as of 615 am Wednesday...
Much of Friday and the weekend will be characterized by a flattening
out of the upper trough to a more zonal pattern and a moderating
trend to near normal temperatures as surface high pressure moves
across the deep south and over the Carolinas.
For the beginning of next week, a low pressure system coming out of
the Gulf of Mexico will move northeastward bringing rain chances to
the area as early as Sunday night but more likely on Monday through
Monday night. No threat of any wintry precipitation with this system
as temperatures will be well into the 50s to near 60 degrees on
Monday. The system may clear out by Monday night but the GFS is
showing a secondary wave moving up the front and brining a second
round of rain to the area on Tuesday. This is completely
inconsistent with the European model (ecmwf) solution which does not show any wave
whatsoever and thus keeps the forecast dry during this time. Have
introduced very low slight chance pops at this time. Temperatures
Tuesday remain in the mid 50s to near 60 degrees for highs.&&
Aviation /06z Wednesday through Sunday/...
as of 1230 am Wednesday...
Next 24 hours: vfr+ conditions continue at all taf sites, with
little in the way of changes expected during the day Wednesday. A
short wave looks to rotate north of the area Wednesday evening after
dark, introducing 9,000+ ceilings at gso/int by Wednesday evening,
and potentially some low level wind shear issues rwi/Fay.
Extended discussion: VFR conditions are expected Wednesday through
Sunday. A passing disturbance Wednesday evening will bring a period
of mostly cloudy skies and spotty light precip though ceilings
should remain VFR. Later in the weekend, another system will bring a
slightly better chance for spotty rain showers, although ceilings
are still expected to remain VFR.