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Area forecast discussion 
National Weather Service Raleigh NC 
219 am EDT Thursday Jul 24 2008 


Synopsis... a cold front will move offshore this morning... as high 
pressure builds into central NC from the northwest. Drier and slightly 
cooler air will overspread our region today and tonight. The high 
will begin to shift offshore Friday... allowing for hotter and more 
humid conditions to return for the weekend. 
&& 


Near term /through tonight/... 
as of 130 am Thursday... 


Today: unseasonably strong deep layer baroclinic trough (tilted 
westward with height) and attendant surface cold front will continue 
to pivot slowly eastward across central NC through middle morning... 
then to the coast by late this afternoon. Despite convective 
overturning and stabilization... DCVA and right entrance jet induced 
lift attendant the upper trough... in conjunction with the lower 
level frontal circulation... should sustain a few showers in the 
coastal plain through daybreak. Much drier air -- characterized by 
precipitable water values below three quarters of an inch per latest 
GOES sounder dpi estimates -- has already spread into western NC 
this morning... and will continue to spread eastward in the wake of 
the trough today. Thus... expect that any afternoon shower and 
thunderstorm re-development should remain confined to coastal 
locations... in vicinity of the slowly eastward moving cold front and pinned 
sea breeze front. Diurnal cumulus should be most prevalent in the east... 
where surface dewpoints are apt to hold in the middle 60s. With full 
sun west to at least partial sunshine east... forecast low level 
thicknesses in the 1410 to 1420 meter range and middle teen 850 mb 
temperatures suggest highs this afternoon from about 87 northwest to 91 
S/se. 


Tonight: a 1019 surface high centered just south of Chicago this 
morning will settle over the virginias tonight. Light northerly flow 
and dry advection (dewpoints well into the 50s across the north) 
should allow temperatures under mostly clear skies to dip to around 
60 degrees north to upper 60s south. -Mws 


&& 


Short term /Friday through Saturday night/ 
..as of 145 am Thursday... 


Friday: the dry... stable subsidence inversion aloft should continue 
to reign supreme... while the surface ridge will continue to extend 
southwestward into our area. Despite some cirrus increase in 
northwesterly flow aloft... projected low level thicknesses increase 
by 5 to 10 meters relative to Thursday... and this suggests highs 89 
to 92. 


Friday night through Saturday night: our low level flow will 
gradually veer to southerly on the western periphery of the 
departing surface high... while 850 mb-700 mb warm advection and resultant 
weak ascent and moistening should result in increasing cloudiness 
spreading eastward across the mountains from the Tennessee Valley. A return 
to typical diurnal convection along the mountains (differential 
heating) and foothills (lee trough) is expected to resume Saturday 
afternoon. The mean steering flow could allow some of this 
convection to make inroads into the western Piedmont... in closer 
proximity to the 850 mb Theta-E ridge nosing in from the west. Deep 
convection should remain isolated elsewhere... however... as no 
discernible triggers at the surface or aloft are evident to provide 
for lift. Lows in the upper 60s Friday night... then around 70 
Saturday night. Highs Saturday in the lower 90s. -Mws 


&& 


Long term /Sunday through Wednesday/... 
as of 315 PM Wednesday... 


Respectable l/west trough (for this time of year) will maintain a 
position over the eastern Seaboard through the Carolinas through middle 
week. Meanwhile a stalled...wavy frontal system will stretch across 
the area. The combination of moisture pooling along the surface 
boundary and perturbation rounding base of upper trough will provide 
an environment for the development of scattered convection. 
Convection should be more prominent during the afternoon/evening 
hours when air mass most unstable. Will need to monitor upstream for 
possible mesoscale convective system development. Any remnants or mesoscale convective system-induced vortices would 
enhance convection coverage. Maximum temperatures dependent upon degree of 
cloudiness. For now...will stick close to near normal temperatures. 


&& 


Aviation /06z Thursday through Monday/... 


The convection has moved east of all taf sites as of 0535z today. 
There were still some high clouds from krdu eastward... but these 
will thin out over the next few hours. 


WV and infrared satellite data indicate very dry air aloft spreading east 
of the mountains and over the Piedmont. As this drying aloft spreads 
east through daybreak... the clearing skies over top the wet ground 
will combine with nearly calm conditions... spelling fog and low 
stratus. LIFR conditions will be forecast to develop prior to 
daybreak at krdu/krwi/kfay... and IFR visibilities expected at kgso/kint. 


These conditions will improve rapidly after sunset as mixing from 
aloft over the very dry air will rapidly evaporate the fog and 
stratus. 


VFR conditions are forecast for all taf sites after around 14z 
today... as dry high pressure builds overhead (today through 
friday). MVFR to IFR ground fog will be possible at many locations 
Friday morning (09z-13z)... and again Saturday morning. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 


Synopsis...Badgett 
near term...mws 
short term...mws 
long term...wss 
aviation...Badgett