884 
fxus62 kilm 080152 
afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
952 PM EDT sun Sep 7 2008 


Synopsis... 
a weak trough of low pressure will remain over the Carolinas 
through Tuesday. A cold front will move into the region on 
Wednesday and move just to the south and east to the area and 
then dissipate late in the week. High pressure will build into 
the region on Saturday and Sunday. 


&& 


Near term /until 6 am Monday morning/... 
as of 9 PM Sunday...a weak front or trough across the east-central 
Carolinas separates a tropical airmass over the coastal region from 
a slightly drier airmass inland. The boundary between the two has 
just enough wind convergence along it to help support a few showers 
& T-storms. No convective cap exists overnight and there is plenty 
of potential energy embodied in the middle-70 dewpoints in the boundary 
layer tonight. It cannot be completely ruled out that another shower 
or storm will develop overnight...but areal coverage is likely be 
less than 10%. 


Once debris cloudiness from afternoon convection dissipates we 
should have good radiational conditions overnight. Both the mhx and 
chs 00z soundings show the very high surface dewpoints extend at 
least 1000 feet vertically before appreciable drying begins: this 
should be sufficient for areas of fog to develop overnight. 


&& 


Short term /6 am Monday morning through Wednesday/... 
as of 3 PM Sunday...a weak surface trough will persist over the 
area on Monday and GFS indicates weak upward motion over the inland 
areas on Monday afternoon but the latest NAM show lift 
concentrated below 850 mb. This is associated with sea breeze and 
is in contrast with the deep weak lift of the lower resolution 
GFS. Moisture is limited in both models and only anticipated 
isolated convection on Monday afternoon. 


Changes are coming as frontal boundary drops down from the 
northwest and this combined with the easterly flow on the northern 
side of Ike will bring in copious deep moisture, this is seen in 
the precipitable water field with over 2 inches by late Tuesday. 
Lift will be only okay with the best lift anticipated to be to the 
north closer to the low pressure center. So expect an increase 
in the probability of convection late Tuesday afternoon into 
Wednesday morning but only a chance at this time. 


&& 


Long term /Wednesday night through Sunday/... 
as of 3 PM Sunday...best chance for wet weather comes at the start 
of the period. Front will be stalled just to the south Wednesday but most 
of the ll flow will remain southerly. This should lead to good 
overrunning of the surface boundary and possibly some appreciable quantitative precipitation forecast. 
Probability of precipitation have been some and are approaching likely realm. Highs 
generally in the low to middle 80s but should an all-day rain pan out 
some spots could stay cooler. Surface high ridges down the east slopes 
of the Appalachians Thursday while coastal tries but largely fails 
to move back towards shore. Overrunning surface still present but ll 
flow may back to more easterly and so slightly lower probability of precipitation/quantitative precipitation forecast 
shown. NE surface flow paired with clouds still to bring below climatology 
highs. The front will remain largely unmoved by Friday but should 
be in a weakening state. Look for lower probability of precipitation and increased 
sunshine to bring high temperatures back near climatology. Bermuda high regime 
returns for the weekend. This should lead to climatology temperatures and isolated 
to scattered afternoon convection. 


&& 


Aviation /0z Monday through Saturday/...previous tafs are in great 
shape with just some fine tuning of the IFR periods tonight. The 
main concern for the aviation community will be the development of 
fog Monday morning. A weak pressure pattern with plenty of low level 
moisture and dry air aloft is a recipe for a significant event. Will 
use prevailing MVFR from about 0600 UTC with tempo IFR groups in 
ilm...lbt...and flow. Previous forecast had some concern with 
boundary layer winds being strong enough in The Myrtles to prevent 
IFR fog. Surface observation at The Myrtles show the winds have already 
decoupled and therefore IFR visibilities due to fog are likely. 


Outlook through Thursday...chance IFR visibilities Monday and 
Tuesday mornings. Isolated thunderstorms Monday and Tuesday. 
Scattered thunderstorms Wednesday and Thursday. 


&& 


Marine... 
near term /through tonight/... 
as of 9 PM Sunday...light southerly winds will continue overnight 
across the waters. The bigger story is a long period southeast swell 
courtesy of Hurricane Ike which will also continue overnight. The 
spectral wave plot from The Frying Pan Shoals buoy shows virtually 
all the wave energy out there tonight is from this swell. Periods 
are 13-14 seconds. Although total wave heights within 20 miles of 
shore will remain less than 5 feet...it is Worth noting that 
conditions near inlets...jetties...and especially in the shallow 
water near Frying Pan Shoals will be rough tonight through at 
least Monday. 


Short term /Sunday through Tuesday night/... 
as of 3 PM Sunday...flow should back from south to southeast as 
combination of flow ahead of cold front to the northwest and 
Hurricane Ike passing well to the south will increase the 
southeasterly flow and with local winds around 10 knots swell from 
Ike will continue for this period with a peak in seas for the waters 
of Long Bay at 3 to 5 feet and 2 to 4 feet north in Onslow Bay. 
Front is forecasted to near coastal waters by the end of the 
forecast period. 


Long term /Wednesday through Thursday/... 
as of 3 PM Sunday...best chance for wet weather comes at the start 
of the period. Front will be stalled just to the south Wednesday but most of 
the ll flow will remain southerly. This should lead to good 
overrunning of the surface boundary and possibly some appreciable quantitative precipitation forecast. 
Probability of precipitation have been some and are approaching likely realm. Highs 
generally in the low to middle 80s but should an all-day rain pan out 
some spots could stay cooler. Surface high ridges down the east slopes 
of the Appalachians Thursday while coastal tries but largely fails 
to move back towards shore. Overrunning surface still present but ll 
flow may back to more easterly and so slightly lower probability of precipitation/quantitative precipitation forecast 
shown. NE surface flow paired with clouds still to bring below climatology 
highs. The front will remain largely unmoved by Friday but should 
be in a weakening state. Look for lower probability of precipitation and increased 
sunshine to bring high temperatures back near climatology. Bermuda high regime 
returns for the weekend. This should lead to climatology temperatures and isolated 
to scattered afternoon convection. 


&& 


Climate /changes to Florence rainfall/... 
as of 9 PM Sunday...after reviewing this year's daily rainfall for 
Florence SC (flo) several minor discrepancies have been noted and 
corrected in the official record. The net effect is that yearly 
total rainfall for Florence (as of Sep 8th) has been reduced by 
0.01" to 35.76" from 35.77" 


Here is a summary of the changes that have been made to the daily 
rainfall statistics for Florence SC. 


Date original rain new rain reason for change 


2/5/2008 0.01" 0.00" dense fog erroneously tipped the rain 
gauge between 05/0600z and 05/0700z 


2/24/2008 0.00" trace light rain fell for a short while between 
24/2200z and 24/2300z 


5/4/2008 0.00" trace light rain fell periodically from 
04/0500z to 04/0700z 
&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...none. 


&& 


$$ 


Near term...tra 
short term...Hawkins 
long term...mbb 
aviation...shk/heden 
climate...tra 

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