493 
fxus62 krah 061921 
afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
321 PM EDT Sat Sep 6 2008 


Synopsis...skies will continue to clear and winds to diminish in 
the wake of ts Hanna...which is currently over northern Virginia 
and moving rapidly north. 


&& 


Near term /through tonight/... 
as of 310 PM EDT Saturday... 


Excess water is everywhere...and with skies clearing and winds 
becoming light...think we could see some fairly dense fog late 
tonight. Forecast lows in the middle and upper 60s look good. 


&& 


Short term /Sunday through Tuesday/... 
as of 310 PM Saturday... 


A lingering surface trough in the far S-southeast and residual moisture 
will support isolated late day convection Sunday. Low level thicknesses 
continue to support maximum temperatures around 90. 


On Monday...high pressure migrating east and offshore begins to 
produce increased return flow...with 850 mb winds becoming southeast 
late in the day. Instability will be increasing...with convective available potential energy 
exceeding 1k joules and middle level lapse rates steeper than 6 degree 
c/km. Low level forcing appears weak...though...thus will continue 
only a slight chance pop through Monday night. Thicknesses Monday 
will be similar to Sunday...supporting upper 80s to lower 90s. 


On Tuesday...better forcing and dynamics will be in place 
as an approaching cold front struggles east and eventually sags 
southeast through the area Tuesday night. Concurrent with the 
front will be the associated upper trough rotating across the Great 
Lakes with an 80 knot upper jet aligned up the Ohio Valley 
providing modest upper divergence. Should be a decent day for 
scattered convection if we get insolation to any degree...will have 
chance probability of precipitation everywhere pending a better handle on the details. 


&& 


Long term /Tuesday night through Sunday/... 
as of 300 PM Saturday... 


The 12z/06 GFS and the 00z/06 European model (ecmwf) both continue to depict a cold 
front moving into the region late on Tuesday day into Wednesday 
morning. Models then begin to stall out the front across central 
North Carolina... as high pressure at the surface attempts to ridge 
into the state from the north. If this holds true... a potential cad 
event could be in the fold. This would present a cool and damp 
overcast day... with scattered showers for Wednesday. For now will 
advertise highs in the upper 70s to lower 80s. However... if the cad 
event does set up then forecast highs may be as much as 5 to 10 
degrees to high. Regarding precipitation for Wednesday morning into 
Wednesday afternoon... have bumped probability of precipitation up to high chance. Future 
shifts will likely need to up probability of precipitation if models continue to show good 
run to run continuity. 


For Thursday... the washed out front remains across the region... as 
high pressure continues to nose into the region from the northeast. 
This will likely lead to another damp cool day... with scattered 
showers possible. High temperatures again are expected to be in the upper 
70s to lower 80s... which could likely be too high still. Lows in 
the lower to middle 60s. 


Unsettled weather appears to continue to be in the cards for next 
Friday into Saturday... as another cold front approaches the region. 
Meanwhile... TPC continues to show Hurricane Ike moving into the 
Gulf of Mexico during middle to late week. At this time it still is 
unknown where Hurricane Ike will make landfall and if any of his 
moisture will combine with the front to bring the threat of heavy 
rainfall to the region again. For now will continue to forecast 
mostly cloudy skies... with forecast highs near climatology and lows a 
category above. 


&& 


Aviation /00z Saturday through Wednesday/... 
as of 140 PM Saturday... 


The center of ts Hanna has moved northeast of the State of North 
Carolina this afternoon. However... lingering affects from the ts 
are still being felt at the taf forecast sites across central NC. 
Due to the tight pressure gradient still in place across the area 
from ts Hanna... gusty winds of up to 25 miles per hour will be possible for 
the remainder of the day. In addition... low level clouds continue 
to hinder northeast portions of the state. However... all terminal 
ceilings have lifted across central NC. 


As skies clear over night and winds begin to weaken a bit... fog 
and low clouds will be possible across central NC. The best residual 
low level moisture appears to be in the east... as heavier precipitation has 
fallen there. Thus... have introduce LIFR visibilities and IFR ceilings 
at the eastern terminals.... and only IFR to MVFR visbys at the 
western terminals. After sunrise the fog and low clouds should mix 
out within a couple of hours... and yield clear skies with light 
winds. 


Otherwise...mostly VFR conditions forecast from Monday Onward... 
with the exception of morning fog. A cold front is expected to move 
into the area from the west late Tuesday into Wednesday... which 
will bring the threat for scattered showers and thunderstorms back to 
the forecast. 




&& 


Hydrology... 
as of 300 PM... 


Runoff through base flow will continue due to the widespread 
nature of a 3 to 5 inche swath of rainfall across the central 
County warning forecast area. Thus...flooding will linger well into the evening on the 
smaller streams and in poorly drained areas. This lingering 
flooding covers much of the eastern County warning forecast area and has been handled 
with an areal Flood Warning which will be updated around 20z. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...mlm 
near term...mlm 
short term...mlm 
long term...bsd 
aviation...bsd 
hydrology...