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Area forecast discussion 
National Weather Service Wilmington NC 
315 PM EST Wednesday Jan 7 2009 


Synopsis... 
blustery conditions will persist through Thursday as a potent storm 
system exits the area to the northeast and a strong middle level 
system moves across the region Thursday afternoon. High pressure 
will build in early Friday and persist through Saturday. Another 
cold front will move across the region later Saturday with chances for 
mainly light precipitation. High pressure will once again build in 
from the west through the first part of next week. 




&& 


Near term /until 6 am Thursday morning/... 
as of 3 PM Wednesday...cold front has cleared the coast and drier 
and colder air is filtering into the area at this time. The driest 
and coldest advection will follow the passage of a middle-level 
shortwave trough this evening. Ahead of this shortwave...just enough 
moisture is available to squeeze out another band of showers which 
will be traversing the area late this afternoon and then off the 
coast around 00z. Winds will continue to be strong and gusty 
through this evening. Westerly jet of 70-80+ knots up to 10 kft early this 
evening will gradually lower to 50-60 knots overnight. As an inversion 
develops...the mixed layer will shrink this evening and especially 
overnight and this will allow winds to slowly diminish. Given these 
conditions...will continue with the Wind Advisory. Expect winds will 
ramp up through the remainder of the afternoon before diminishing 
during the late evening and overnight. Sustained west-southwest winds of 20 to 30 
miles per hour will gust to 40 miles per hour and isolated wind gusts to 50 miles per hour are 
possible through this evening. Winds will back to SW overnight ahead of 
another trough. 


Expect temperatures and dewpoints to fall more sharply through midnight 
than from midnight through Thursday morning. Minimums tonight will be a 
function of advection until very near daybreak when there may be a 
modest contribution from radiational cooling as winds drop off. Will 
indicate coolest temperatures in these isolated areas where radiational 
cooling effects are maximized due to soil type. 






&& 


Short term /6 am Thursday morning through Friday night/... 
as of 3 PM Wednesday...a strong shortwave will move through the mean flow 
Thursday with modest cold air advection in its wake from late 
Thursday into early Friday morning as high pressure settles in at 
the surface. The GFS is trending wetter...relatively speaking of 
course with the system...generating a few hundredths of quantitative precipitation forecast just 
north of our area Thursday afternoon. Increased probability of precipitation slightly for 
Thursday with the highest values northern areas although this is 
primarily for the forecast graphs as the text products should remain 
void of any mention of probability of precipitation. Any lingering moisture in the way of 
clouds quickly dissipates early Friday with the departing short wave 
and loss of daytime heating. Precipitable waters drop into the teens 
early Friday and increase slowly through Saturday am which should 
keep skies clear. 


Temperature guidance has trended up slightly for highs Thursday and 
added a couple of degrees across the board to reflect 
this...otherwise the thermal forecast remains consistent for the 
remaining periods. 


&& 


Long term /Saturday through Wednesday/... 
as of 3 PM Wednesday...ll thermal ridge develops along coastline 
ahead of a cold front on Saturday. This should boost afternoon 
highs up into the lower 60s as 850 mb T averages 8-9c. Very small chance 
for some light rain showers associated with the warm air advection but most of the wet weather 
should stay west. There are some timing uncertainties with respect to boundary 
which should affect Sat probability of precipitation. Prefer slower timing as guidance 
usually too fast with fronts and their negotiation of the 
mountains. Slightly better rain chance...to the tune of lowest chance 
range...come with frontal passage Sat night. Temperatures knocked back down very 
close to climatology behind the front for the sun through Tuesday timeframe 
while low amplitude troughiness in the east brings dry middle level 
flow and generally minimal cloud cover through Monday. Forecast shows an 
increase in clouds on Tuesday as eastern trough may sharpen and flow backs 
at most levels. Timing of next front a little hazy but looks to be 
around Tuesday. GFS solution of phased branches and Arctic push into 
the east a fairly new idea...at least so early as Tuesday. Will 
continue to show a more modest drop in highs Wednesday into the 
40s...but agree that Arctic air may be in the cards some time middle 
Jan based upon teleconnection ensemble forecast indices. 


&& 


Aviation /20z Wednesday through Monday/... 
a cold front cleared all of the terminals earlier this morning. A 
strong pressure gradient will produce strong wind gusts to 35 knots 
this afternoon from the southwest to west southwest. Patchy light 
rain will continue to decrease in coverage through the afternoon. 
Ceilings and visibilities will remain VFR through Thursday 18z. 


Extended...a strong pressure gradient will continue to produce windy 
conditions before high pressure builds in from the west late Friday. 
VFR expected through Sunday. 


&& 


Marine... 
near term /through tonight/... 
as of 3 PM Wednesday...dry and cold advection will be enhanced with 
the passage of a middle-level shortwave this evening. Westerly jet of 
70-80+ knots up to 10 kft early this evening will gradually lower to 50-60 
knots during the overnight hours. The strongest winds are expected to 
coincide with the driest and coldest advection and tightest pressure 
gradient from late this afternoon through shortly after midnight. 
The pressure gradient will begin to relax with the approach of Thursday 
morning. Will maintain Gale Warning from Little River Inlet 
northward and extend through 11z to allow a buffer as winds drop 
below gale force late tonight. A strong Small Craft Advisory will 
continue from Little River Inlet to South Santee River. SW winds 
will veer to west this evening and then back slightly toward Thursday morning 
ahead of another trough. Seas will peak in 7 to 10 feet range through 
this evening...highest from Frying Pan Shoals north and then begin to slowly 
subside. Will initialize near shore seas lower with offshore 
trajectories laying seas down quickly tonight. 


Short term /Thursday through Friday night/... 
as of 3 PM Wednesday...small craft conditions will continue through 
most of the day Thursday across all waters as another trough axis 
moves across associated with a strong middle level system moving 
through the region. Low level wind fields through 850mb remain in 
the 30-40 knot range although warm air advection will be 
associated with these winds most of the day keeping the momentum 
Transfer to a minimum. This will warrant a range of 20-25 knots 
throughout the day. A brief period of cold air advection begins 
Thursday evening mainly across the northern waters which should 
increase winds to a range of 25-30 knots through about 0600 UTC 
Friday. Winds gradually subside into the day Friday as high 
pressure settles basically overhead. 


Seas will be compromised by the offshore wind direction at least 
across the near shore waters with a range of 5-7 feet Thursday 
backing off to 2-4 feet by Friday morning which should prevail 
through Saturday am. 


Long term /Saturday through Monday/... 
as of 3 PM Wednesday...looking for a fairly robust increase in winds and 
seas in warm air advection regime ahead of cold front Sat...possibly 
necessitating Small Craft Advisory. Timing of the veer to offshore 
winds behind front is a little iffy...could be as early as late 
day Sat but current thinking is Sat night. Winds likely stay up 
Sat night but the offshore direction will open up more of a range 
in seas as near shore wind waves diminish slightly. Light north winds 
will veer to NE as very flat surface ridge builds over the Gomex. 
Variable winds under 10 knots Monday with ill defined gradient. Seas 2-3 
feet most of sun and Monday. 


&& 


Ilm watches/warnings/advisories... 
SC...Wind Advisory until midnight EST tonight for scz017-023-024- 
032>034-039-046. 


NC...Wind Advisory until midnight EST tonight for ncz087-096-097- 
099>101. 


Marine...Small Craft Advisory until 6 PM EST Thursday for amz254-256. 


Gale Warning until 6 am EST Thursday for amz250-252. 


&& 


$$ 
Synopsis...shk 
near term...rjd 
short term...shk 
long term...mbb 
aviation...mrr 

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