Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1012 PM EST Tuesday Dec 1 2015
a front south of the area will lift north as a warm front late
tonight. A cold front will cross the Carolina coast late
Wednesday. Strong high pressure behind the front will bring cooler
temperatures late this week into the upcoming weekend.
Near term /until 6 am Wednesday morning/...
as of 1000 PM Tuesday...the long-awaited warm front is moving
northward very very slowly...only just recently reaching The
Frying Pan Shoals buoy about 30 miles southeast of Cape Fear. With NE
winds will observed all along the SC coast to Charleston and
Beaufort it may be another 3-6 hours before the boundary moves
onshore. Areas of fog have developed but with the exception of
Georgetown and Whiteville visibilities have been bouncing from 1/2
mile to unlimited with no discernible pattern. I have held off
issuing a dense fog advisory this evening although areas of
fog...some locally dense...will undoubtedly continue overnight.
Holes in the middle and high level cloudiness have allowed
substantial radiational cooling to occur since sunset with
temperatures diving several degrees lower than anticipated. The
single exception has been in the Wilmington/Southport area where
low clouds originating within a region of low-level isentropic
lift have blanketed the sky. Patchy light rain has even occurred
although so far only trace amounts have been recorded at kilm. As
the warm front advances northward overnight low stratus should
fill in across the area with temperatures slowly rising even
Short term /6 am Wednesday morning through Thursday night/...
as of 255 PM Tuesday...currently a large storm system is on the move
through the Midwest with an elongated and trailing front moving
to the east through the southeast. This front will slowly move
across the area Wednesday as the middle level system is in no hurry.
I have increased probability of precipitation just slightly from previous forecasts based
on numerical guidance. We still remain just below likely criteria
as does most of the guidance. Only a couple of lightning strikes
to be found currently and since I cant completely rule out a
strike or two Wednesday added slight chance of thunder. Quantitative precipitation forecast
amounts should be one quarter inch or less with an isolated area
maybe approaching 0.50. Some consensus on guidance now with the
met numbers in play for Friday morning and this was the only
change to the temperature forecast...slightly cooler. Expect a
partly to mostly sunny cooler day Thursday.
Long term /Friday through Tuesday/...
as of 255 PM Tuesday...low amplitude middle level troughiness in place on
Friday while surface high pressure keeps things too dry for the
feature aloft to bring any weather. Models are showing cold
advection aloft into this feature mainly to our north. This should
favor an increase in mainly diurnal cumulus fields as middle level
lapse rates steepen over the weekend. This feature moves off the
coast Sunday night into Monday allowing for a brief ridge-building.
The next system will be bearing down on the area from the west
though its timing is poorly agreed upon between various guidance.
Some of the faster solutions imply coastal cyclogenesis by late
Monday whereas the more believable solutions target Tuesday for the
same. In addition to the timing differences there are considerable
differences in the prognosticated strength of the system early next week
with results varying from a rather low quantitative precipitation forecast frontal passage to a high quantitative precipitation forecast
coastal storm. Temperatures will begin the long term a little bit
shy of climatology but show a gradual moderating trend both due to solar
insolation and the building ridge aloft.
Aviation /00z Wednesday through Sunday/...
as of 00z...IFR conditions expected again tonight with fog and stratus
expected to develop in advance warm front approaching from the S.
A few showers are also possible but the probability of one at individual
taf locations is too low to include in the forecast. The warm front
should move through all taf sites in the 09z to 15z window...yielding
VFR conditions at all taf sites by middle morning Wednesday on S to SW
flow in vicinity of 10 knots. Late in the taf period...rain showers are possible...mainly
at flow and lbt and could yield tempo MVFR conditions.
Extended outlook...MVFR conditions possible in rain showers Wednesday
night...otherwise expect VFR through the extended period.
near term /through tonight/...
as of 1000 PM Tuesday...a warm front is very slowly approaching
the coastal waters from the southeast. Winds at The Frying Pan
Shoals buoy have become light and variable over the past two hours
but NE winds continue at the edisto buoy east of Charleston.
This front should advance northward across the area between 3 and
6 am with south winds increasing to 5-10 knots...perhaps exceeding
12 knots across the warmer water temperatures out near 20 miles
The biggest story will be fog. Although we have no reports to go
on...the Charleston National Weather Service office reports significant impacts due to
dense fog over the coastal waters down their way. Fog has
developed in Georgetown and even briefly in Myrtle Beach over the
past hour. This gives US enough confidence to issue a dense fog
advisory until 6 am Wednesday. Fog potential may be less across
the NC waters where water temperatures are warmer and the
developing southerly wind will create a fairly short fetch across
the colder nearshore environment.
Short term /Wednesday through Thursday night/...
as of 255 PM Tuesday...a decent southwest flow will develop across the
waters Wednesday. Wind speeds will increase to 15-20 knots for a few
hours ahead of the front. This front moves across around 0600 UTC
Thursday with a westerly then northerly flow developing. This flow
of 10-15 knots will continue through the end of the period. As for
seas...heights should remain just below small craft thresholds
Wednesday with 3-5 feet. Seas in the wake of the front drop to 2-4
feet. I have also added some patchy sea fog for part of the day
based on what is taking place currently offshore Charleston.
Long term /Friday through Sunday/...
as of 255 PM Tuesday...wind will remain out of the northeast for the
duration of the long term period. High pressure will be well
established across much of the eastern U.S. On Friday with a broad
center over the Ohio Valley and middle-Atlantic region. There will
be a gradual eastward shift of this high through the period
possibly leading to a slight veer to east-northeast. Most zones will likely
experience a general 15 to 20 knots forecast for most if not all of
the period. The strength of the gradient paired with the relative
persistence of the fetch will keep most of the zones very close to
advisory thresholds through the period.
Marine...dense fog advisory until 6 am EST Wednesday for amz254-256.