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fxus62 krah 080218 
afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
1018 PM EDT sun Sep 7 2008 


Synopsis...a weak surface trough over southeast North Carolina will 
give way as high pressure builds into the area from the west 
tonight. High pressure will strengthen and build into the area from 
the middle Atlantic coast on Monday... and remain in place until early 
Tuesday ... a cold front approaches the area from the west. 


&& 


Near term /through Monday/... 
as of 1015 PM EDT Sunday... 


A weak surface trough analyzed over the southeast coastal plain proved 
to be sufficient to generate isolated convection south of 
Fayetteville and Goldsboro earlier this evening. All convection has 
since ended with the loss of diurnal instability. Weak high pressure 
will try to nose in from the north by morning...but the pressure 
gradient will be very weak across the County Warning Area for the rest of the 
night...which is reflected by almost all surface observation already reporting 
calm conditions. Fog will once again be the main concern for the 
overnight period. For the most part...it failed to materialize 
yesterday evening...but that was likely due to just enough middle level 
moisture and clouds to limit the radiational cooling. No such 
moisture is present tonight with clear skies expected...perhaps with 
the exception of some passing thin cirrus which will have no effect 
on radiational cooling. Dewpoints are running higher than what 
guidance had suggested...ranging from the middle 60s in The Triad to 
the low and middle 70s across the southern Piedmont...sandhills and 
coastal plain. This is likely due to the guidance being unable to 
capture the excessive ground moisture produced by the widespread 
rainfall from Tropical Storm Hanna. Therefore...will forecast patchy 
dense fog across all of the area with the exception of the northwest 
Piedmont. Will monitor observations through the night for the 
possibility of a dense fog advisory. Also raised min temperatures a few 
degrees across the board given the higher dewpoints. Lows expected 
to be in the upper 60s to lower 70s. -Jfb 


Will begin to see an east to southeast low level flow later 
tomorrow as the high pressure moves offshore. Upper dynamics are 
not impressive...consisting mainly of a northward shift in the 
weak shear axis currently off the coast as the upper ridge is 
nudged eastward by the approach of Ike well to the south. There 
are no definitive low level forcing mechanisms outside of the weak 
lingering surface trough...so will keep probability of precipitation in the isolated 
range...and mainly southeast during the day. Expect more cumulus 
coverage but highs will be similar to today...generally upper 
80s...with no airmass change and plentiful insolation. -Mlm 


&& 


Short term /Monday night through Wednesday night/... 
as of 300 PM Sunday... 


Upper trough over the northern Continental U.S. Begins shifting east and low 
level moisture depth continues to increase through Tuesday in 
southerly flow...especially in the southeast. Low level forcing 
remains weak...however...and expect shower activity to be preferred 
in the west coincident with weak upper diffluence and upslope 
flow ahead of an approaching cold front...and in the southeast where 
there could be inland advecting shower activity as the tropical 
moisture plume becomes more prevalent. Highs will be a few degrees 
cooler with more cloud coverage and scattered showers/tsra. 


Good chance probability of precipitation will continue Tuesday night and Wednesday as the cold 
front sags southeast across the area. Highs will be much cooler as 
we high pressure builds down the eastern slopes in a cool damming 
scenario and producing overrunning rain. Highs in the middle and 
upper 70s. 


&& 


Long term /Thursday through Sunday/... 
as of 200 PM Sunday... 


NHC and the latest 12z models were in general agreement with the 
forecast of Hurricane Ike late this week. Ike is expected to 
track westward across the central Gulf of Mexico Thu-Fri... before 
possibly making landfall over the western Gulf Coast toward next 
weekend. 


A strong but seasonable surface high pressure (1027-1030mb) is 
expected to extend from the Great Lakes to New England Wed-Thu... 
before building down the eastern Seaboard of the U.S. Thu-Fri. This 
high essentially is forecast to protect the eastern Seaboard from 
Ike... as the flow around this large sprawling high is expected to 
continue pushing Ike westward later this week. 


Sensible weather over central NC for thus-sun will begin with much 
cooler/cloudy weather Thursday... courtesy of the NE flow around the 
strong surface high over New England. This high is expected to shift 
slowly offshore Sat-sun... but still extend SW into NC into a 
portion of the weekend. If this turns out to be correct... there 
will be little support for showers Thu-sun. We will continue low 
chance pop for Thursday with the lingering coastal trough... and until 
the ridging to our north takes hold. No pop mentioned Friday-sun with 
partly cloudy skies. 


Temperatures will begin cool Thursday... with the NE low level flow 
and lingering clouds... then moderate back to near normal levels by 
the weekend. Highs Thursday should remain in the 70s... but return to the 
lower to middle 80s Fri-sun. Lows 60-65 Thursday... moderate to between 
65-70 sun. 


&& 


Aviation /00z Monday through Friday/... 
as of 835 PM Sunday... 


A surface boundary will remain just east of the Fay taf area through 
the overnight hours... an isolated shower or two is possible in 
association with this feature. Otherwise VFR conditions can be 
expected. Clear skies... calm winds and linger moisture... dewpoints 
in the low to middle 70s over the eastern taf area... will enhance the 
development of fog over the area. LIFR to IFR conditions in fog over 
the eastern tafs...krdu... kfay and krwi between 09-12z... with MVFR 
conditions kint and kgso. Conditions will improve to VFR between 
12-14z and continue through the balance of the forecast. 


Surface high pressure will build over the area from the middle Atlantic 
Monday through early Tuesday. A moist easterly flow will continue 
the chance of early morning fog in the east... otherwise VFR 
conditions will prevail. 


A cold front will approach the area late Tuesday... move through the 
area overnight... and be southeast of the area by Wednesday evening. 
Showers and thunderstorms will be possible with the frontal passage. 


High pressure will build down the Atlantic Seaboard Wednesday night 
..and move into North Carolina Thursday. The combination of high 
pressure to the north and an inverted trough along the coast could 
lead to a period of unsettled weather Thursday into Friday due to 
the moist easterly flow. The increased moisture will also lead to at 
least MVFR ceilings. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...rhj 
near term...jfb/mlm 
short term...mlm 
long term...Badgett 
aviation...rhj 

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