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afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
610 PM EST Friday Nov 21 2008 


Synopsis... 
modified Arctic high pressure will crest across the area through 
the weekend bringing very dry and unseasonably cold temperatures to 
the area. The only chance for measurable precipitation will come 
Monday afternoon into Monday night...as a cold front crosses the 
area. Dry high pressure will follow Tuesday through Friday...with 
temperatures remaining below normal. 


&& 


Near term /until 6 am Saturday morning/... 
as of 3 PM Friday...vigorous upper trough over the Carolinas is 
cranking up a surface low east of Hatteras...while a cold 1037mb surface 
high builds in from the Mississippi Valley. Blustery north/northwest flow is 
funneling unseasonably cold air into the eastern Carolinas...as 
temperatures have struggled into the upper 40s today. Cloud cover is now 
limited to cold pool cumulus...which will dissipate after Sundown. 


With the clearing skies and a very dry airmass...a very chilly night 
is in store. Temperatures should quickly drop into the 30s after 
sunset...with wind chills in the Lower/Middle 20s early this evening 
before the winds diminish. Will maintain 4-6 knots winds through the 
night...which will keep temperatures from bottoming out...but record lows 
still in jeopardy. Expect readings in the lower 20s...the 
traditionally colder wind-sheltered locations even dipping into the 
teens. 


&& 


Short term /6 am Saturday morning through Sunday night/... 
as of 3 PM Friday...a modified Arctic airmass will settle across the 
area through the period. The coldest of air will be waning Sat 
morning as 800 mb temperatures recover from -8 to -12 at the start of the day 
to around zero during the afternoon. If we mix out to about 3 
kft...highs Sat afternoon despite bright sunshine will only manage 
lower to middle 40s. Another day of readings 10 to 12 degree below normal. 
Winds will be lighter on Sat than on Friday...and so for some it might 
feel a little more comfortable. Dewpoints will drop into the 10 to 
15 degree range Sat with perhaps briefly some single numbers owing to 
the very dry airmass. Minimum relative humidities near 25 percent 
are expected. A jet streak and accompanying short wave embedded in 
west-northwest flow will move across the area overnight Sat. Some middle and high 
clouds will invade the sky Sat evening. Column too dry to support 
anything other than perhaps virga. These clouds may serve to 
interrupt what will otherwise be an ideal night for radiational 
cooling. Will forecast coldest temperatures in areas where radiational 
cooling is known to maximize. 


Record lows for: November 23rd 


Ilm: 23 degree set in 1981 
cre: 24 degree set in 1949 
flo: 24 degree set in 1976 




Modified Arctic high pressure will crest overhead Sat night and sun 
and will not be so quick to move high pressure off the coast Sun 
night. Any morning cloudiness early sun will give way to sunny skies 
once again and will carry these clear skies through Sun night... 
delaying any increasing high clouds until after sunrise Monday. Airmass 
will continue to modify and so will continue to forecast 
temperatures approaching normal levels...but still falling 10 to 15 
degree shy of climatological normals...so still chilly for later Nov. 


&& 


Long term /Monday through Friday/... 
as of 3 PM Friday...the extended forecast will feature one chance 
for rain with the cold and dry pattern prevailing for the most part. 
A strong shortwave will ride the ridge late this weekend and tap 
into a bit of Gulf of Mexico moisture Monday and Tuesday. This will 
push a front into the area late Monday and early Tuesday. Models are 
in good agreement on the better lift/dynamics moving to the north as 
phasing of a couple of short waves occurs...establishing an East 
Coast trough for the remainder of the period. Will maintain the 
slight chance probability of precipitation for Monday and early Tuesday. 


The latest temperature guidance remains consistent with a brief 
warm-up Monday preceding the front with a return to cooler than 
average for Tuesday through the remainder of the forecast. 


&& 


Aviation /00z Saturday through Wednesday/... 
VFR. Winds diminish overnight with a moderate temperature inversion 
setting up. Continued northwest flow on Saturday. Winds will likely 
go variable toward the end of the forecast period as the center of 
high pressure moves overhead. 


Outlook through Wednesday...VFR. Possible showers Monday night as a 
weak cold front passes through. 


&& 


Marine... 
near term /through tonight/... 
as of 3 PM Friday...well-mixed boundary layer is the understatement 
of the day with air temperatures in the Lower/Middle 40s and water temperatures in 
the 60s. Winds out of the north-northwest around 25 knots but the offshore 
trajectory is limiting sea growth. Buoys 41013 and 41036 showing 
6-7 feet but would figure 5 feet is the maximum within 20 nm. 


Expect the cold air advection surge to continue into tonight with wind speeds 
touching 30 knots at times. Gradient will relax a bit after midnight 
as the upper trough axis shifts offshore and the surface high finally 
builds closer to the Carolinas. Winds and seas should be just below 
Small Craft Advisory criteria by daybreak Saturday...but will maintain status quo 
with the advisory set to expire at 12z. 


Short term /Saturday through Sunday night/... 
as of 3 PM Friday...winds and seas will continue to abate during Sat 
and this trend will persist through the period as modified Arctic 
high pressure crests overhead. North-northwest winds will slowly veer to north 
during sun and may become light and variable late in day sun and Sun 
night. Conditions may be near exercise caution levels Sat 
morning...before falling well below such levels by Sat afternoon. 


Long term /Monday through Wednesday/... 
as of 3 PM Friday...the period begins with a decent southwest flow 
ahead of the front Monday although remaining below flag 
criteria...basically around 20 knots. Winds will veer quickly to 
northwest in the wake of the front Tuesday and Wednesday. Cold air 
advection does not appear to be as strong as the past couple of 
events and winds may very well remain just under small craft 
criteria...too early to tell at this point. A mostly offshore wind 
component will keep the higher seas well outside of 20 nautical 
miles as well. 


&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...Small Craft Advisory until 7 am EST Saturday for amz250-252- 
254-256. 


&& 


$$ 
Near term...Ras 
short term...rjd 
long term...shk 
aviation...dl 

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