Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
305 am EST Wednesday Nov 25 2015
Synopsis...a ridge of high pressure will extend over the region
through the end of the week. A cold front will approach the area
from the north over the weekend.
Near term /today through tonight/...
as of 225 am Wednesday...
Today: continued quiet... but with a few more clouds and slightly
warmer temperatures. The surface ridge centered over New England this
morning will drift east-northeast to over Nova Scotia today will maintaining a
wedging ridge southeast through central NC. Further aloft... the 850 mb
anticyclone over Virginia/NC and the 925 mb anticyclone over the
midatlantic coast both shift offshore... introducing uniform low
level flow from the east-southeast... gradually drawing in both warmer and more
moist air. But the vast majority of the day will be mostly sunny
with just some high thin clouds resulting from the approach of the
weak and dampening middle level wave from the west. The mixed layer
should still be quite shallow despite the slow low level warming...
so expect a minor rise in temperatures from yesterday. Highs 56-61... just
slightly under normal for this time of year.
Tonight: stacked ridging remains in place across central NC from the
surface up through the middle levels. The increase in low level
moisture resulting from the uptick in 925 mb moisture transport and
nocturnal stabilization will manifest itself in the development of
patchy stratus and a little fog late tonight... likely most
pronounced in the eastern and southern County Warning Area where surface dewpoints should be
highest and where models depict weak low level moist upglide
commencing around 290-295k. Will trend skies to fair/partly cloudy
overnight. As the resident surface air mass continues its slow
modification... expect lows of 35-44. -Gih
Short term /Thanksgiving day and Thursday night/...
as of 240 am Wednesday...
Expect a quiet and dry Thanksgiving day and night. The surface high
center moves further out over the open northwest Atlantic Thursday while still
extending southeast through central NC. The middle and upper levels remain
dry... due in large part to persistent subsidence and weak height
rises as the axes of the 700-500 mb ridges hold in place across our
area. Modest moist upglide persists particularly across the southern and
western County Warning Area... so we should see greater coverage of flat stratocumulus
during the afternoon... although skies should be no worse than
partly cloudy for the majority of the day. Thicknesses will continue
to climb... reaching values above normal... so expect highs of 60-
69. Mild lows Thursday night of 41-49. -Gih
Long term /Friday through Wednesday/...
as of 305 am Wednesday...
Surface high pressure over the area will keep central NC dry with
above normal temperatures on Friday and Saturday with a cold front
holding off to the northwest. Cloud cover will increase in the
western Piedmont steadily through this period. Expect highs in the
low to middle 60s with nighttime lows in the 40s. Confidence in this
part of the forecast is high as models are in fairly good agreement
at this time. This holds true into Sunday but solutions do start to
diverge a bit with the handling of the surface high over the middle-
Atlantic. Slight chance probability of precipitation early on will progress to chance probability of precipitation
across the extreme western and northern counties of the County Warning Area. All
other areas may not see any rain through the end of the weekend.
Highs will drop back into the middle 50s with lows Sunday night in the
low to middle 40s.
On Monday...confidence in the solutions continues to go down but the
general upper level pattern is coming into shape with a weak upper
ridge moving over the area on Monday as part of an Omega block with
strong low pressure systems over the North Atlantic and the Rocky
Mountains. At the surface...a migratory high out of Canada will move
southeast over northern New England with a cad wedge front settling
in over the Carolinas by Monday night. This will sock in the area
with clouds and perhaps some very light precipitation with
Model solutions are generally in agreement that a low pressure
system will wrap up over the Great Lakes on Tuesday but the
strength of the low and its accompanying front are still in
question...with the European model (ecmwf) touting a much stronger system that the
GFS. This is mainly due to the dynamics associated with a singular
in phase upper level jet in the European model (ecmwf) solution as opposed to two
distinct...and weaker northern and southern stream jets in the GFS.
Regardless...rain chances will increase Tuesday into Wednesday.
Slightly warmer as winds go southerly...near 60 degrees with
overnight lows in the middle to upper 40s.
Aviation /06z Wednesday through Sunday/...
as of 1235 am Wednesday...
VFR conditions very likely today and through much of this evening...
however we will see a trend toward sub-VFR conditions later tonight.
Deep high pressure stacked over the region and generally dry sinking
air through the column has kept skies clear with unrestricted visibilities
over central NC. The surface high centered over New England will
continue to drift east-northeast over the coastal Canadian Maritimes through
tonight while extending SW across the forecast area. Expect little
more than high thin clouds today as a weakening middle level wave now
over Missouri moves eastward into the region. The increasing low
level flow from the NE/east-northeast later today into tonight will draw
increasing Atlantic moisture into central NC... leading to
development of IFR stratus and fog toward the end of the taf valid
Looking beyond 06z Thursday... sub-VFR conditions should persist through
sunrise... followed by improvement back to VFR through Thanksgiving
day and evening. Another round of sub-VFR stratus/fog is expected
late Thursday night into Friday morning... then VFR conditions should return
from middle morning Friday through Sat... as another surface high closes
off over the forecast area... bringing an end to the Atlantic
onshore flow. A backdoor front is expected to push southward through
NC late Sat into Sat night... leading to a chance of sub-VFR
ceilings behind the front late Sat night through sun. -Gih