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fxus62 kilm 081936 
afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
236 PM EST Thursday Jan 8 2009 


Synopsis... 
high pressure will build in tonight and persist through Saturday. 
Another cold front will move across the region late Saturday. High 
pressure will once again build in from the west through the first 
part of next week. 


&& 


Near term /through tonight/... 
as of 2 PM Thursday...reinforcing cold front will move across the 
area northwest-southeast 21-01z. High pressure will build across the area from the 
west overnight. Still an isolated sprinkle is possible across 
northern tier counties until the front moves through. Otherwise dry 
and cold airmass will be reinforced this evening and overnight. 800 mb temperatures 
will drop as low as -6 degree c tonight. Winds will shift from SW to northwest 
with passage of the cold front and stay up through the evening hours. 
However...as Friday morning approaches...north-northwest to north winds will drop to 5 
miles per hour or less in most areas. There will be some contribution from 
radiational effects and will maximize these effects in those 
isolated rural areas where soil type is conducive for rapid cooling 
under clear skies and light to calm winds. 


&& 


Short term /Friday through Saturday night/... 
as of 2 PM Thursday...a west to northwest flow aloft will flatten briefly 
before another short wave dives in from the northwest through the 
Midwest late Saturday into early Sunday. At the surface...a cold 
front will sweep across our area late Saturday and early Sunday. 
Until then high pressure will be the dominant feature with basically 
a temperature forecast. 


The forecast models continue to trend wetter with the front with 
precipitable waters increasing on the strength of a 40 knot 
southwesterly jet with a range of near 0.75 inches late Saturday 
afternoon to 1.25 inches early Sunday. Forcing for precipitation 
looks to be concentrated to the lower levels via impressive 
frontogenesis on the cross sections...although there is a small 
contribution from the right entrance region of the 300 jet. 
Numerical guidance is now firmly in the likely Camp for all 
stations. It is Worth noting the NAM has a slower solution when 
compared to the GFS...although the mass fields are almost 
identical...just a few hours later. Have increased probability of precipitation for all 
areas while remaining below likely values to represent the trend in 
both condense and the fact the models are trending wetter. 


Overall temperature guidance remains consistent with seasonal values 
or just under through Saturday morning. Did add radiational affects 
to Saturday morning lows as ideal radiational conditions should be 
present. Saturday should see readings warm into the 60s ahead of the 
front. 




&& 


Long term /Sunday through Thursday/... 
as of 2 PM Thursday...strong cold air advection underway on Sunday behind departing 
cold front...possibly causing a non-diurnal temperature curve. Middle level 
flow west-southwest as eastern U.S. Trough grows very broad as it enters a 
phase of retrogression. Cloud cover should thus be minimal through 
Sunday night with only a slight increase Monday. Temperatures back up to climatology 
on Monday ahead of next cold front...which is expected on Tuesday 
and should generally be deprived of moisture. Strong shortwave 
bottoming the main trough will make a dry forecast tough though so 
probability of precipitation generally 20-30 percent...highest north. After a chilly day with 
highs in the upper 40s Wednesday Thursday may be similar to Sunday. Eastern 
trough grows very broad...bringing nearly zonal flow locally. 
Arctic cold front still expected some time just beyond the long 
term but could be as early as Thursday according to some guidance. 


&& 


Aviation /20z Thursday through Tuesday/... 
current forecast on track. Cloud ceilings upstream lower to 8k...but that 
should be about as low as we go. Satellite loop shows ceilings will 
scatter by late afternoon...as the weak disturbance rotates east and 
out of the region. Light winds overnight with scattered skies. High 
pressure in control Friday...with light winds. 


Extended...a cold front will bring US our next shot at showers late 
Saturday afternoon...ending early Sunday morning. High pressure will 
build in behind this front bringing a welcome stretch of quiet 
aviation weather late Sunday through early next week. 


&& 


Marine... 
near term /through tonight/... 
as of 2 PM Thursday...cold front will move across the waters an hour 
either side of 01z. Winds will veer from SW to northwest with its passage 
and to north-northwest overnight. A fairly tight pressure gradient will exist 
across the waters first ahead of front as gradient gets pinched and 
then behind the boundary as a brief modest northerly surge of dry 
and cold air develops. As high pressure to the west moves closer with 
the approach of daybreak Friday...winds will diminish substantially. 
Given this scenario...decided to extend the Small Craft Advisory for 
all waters until midnight. Offshore trajectories will aid in 
flattening seas especially near shore overnight. 




Short term /Friday through Saturday night/... 
as of 2 PM Thursday...mariners will enjoy a welcome break from the 
relentless winds and seas the past few days...although the respite 
will be brief. High pressure will settle basically overhead Friday 
and move slowly to the east through Saturday. Winds will be 10 knots 
or less from midday Friday through Saturday morning with a variable 
direction. A more pronounced southwest flow will develop Saturday 
ahead of the next front...in fact low level wind fields are 
impressive with a 40 to 50 knots moving across the waters late 
Saturday and early Sunday. All waters should see small craft 
conditions late Saturday through early Sunday courtesy of the winds. 
Momentum Transfer or the lack thereof should keep conditions under 
gale criteria. Regarding seas...wavewatch guidance is showing one 
footers across the waters late Friday into early 
Saturday...indicative of the very weak winds for this time. Seas 
will show the typical increase ahead of the front late Saturday 
through early Sunday. 


Long term /Sunday through Monday/... 
as of 2 PM Thursday...most active weather of the long term should be right at 
the beginning. Moderately strong Post-frontal cold surge should 
bring marginal Small Craft Advisory conditions. However...the 
offshore wind direction should quickly open up a nearshore vs 
offshore range in sea heights as the former decrease quickly. 
Moreover the wind speeds themselves may decrease rather 
significantly as the day wears on...depending on the exact timing 
of the boundary which is still a little uncertain at this time. 
High builds in on Monday and winds should be light...getting the 
direction changes associated with the progression of the high offshore 
is tough. Not only will the ridge be moving offshore but a rather 
potent cold front will approach from the west...slated for 
Tuesday. A short duration of Small Craft Advisory conditions 
cannot be ruled out either ahead or behind the Tuesday front. 


&& 


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


&& 


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

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