931 
fxus62 krah 231131 
afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
630 am EST Monday Nov 23 2009 


Synopsis... 
a low pressure system over the Florida Panhandle will redevelop off 
the Carolina coast this morning. Rain will taper off to mainly 
drizzle by this afternoon...with high pressure and a cool airmass 
remaining over our area through middle week. 


&& 


Near term /through tonight/... 
as of 300 am Monday... 


06z observation analysis shows a 1036mb surface high over eastern 
Maine...with a ridge of high pressure extending far to the SW 
through the Carolinas. An upper low is lifting NE through the Tennessee 
Valley region...with weak low pressure along the eastern Gulf 
Coast. Widespread rain from earlier last evening has decreased in 
coverage...especially across southern NC...as drier air aloft is 
surging northward across the southeast US. 


As the upper low continues to lift northward...a couple weak 
perturbations will rotate around the southern periphery of the low 
and across the western County Warning Area...and may help to sustain light to 
moderate rain...even as moisture becomes increasingly shallow. The 
surface low along the Gulf Coast is expected to transition to off 
the Savannah coast...though currently the low is difficult to find 
in the convection that has developed offshore. The developing 
surface low will increase low level easterly flow over the County Warning Area 
somewhat through the morning hours...and isentropic fields from the 
RUC/12km NAM show isentropic lift persisting for several more hours. 
However...given the amount of dry aloft expected this morning 
(especially south)...precipitation will slowly transition to areas of 
drizzle...more spotty in nature south of the Triangle. Probability of precipitation will 
vary from categorical in the north to chance in the south...to 
likely in the north...and eventually chance probability of precipitation everywhere by this 
evening. Highs today wont budge too far from this mornings readings 
with a cad wedge air mass in place...49 to 56. 


Lingering patchy drizzle should for the most part come to an end 
after midnight tonight as weak lift associated with a 925mb front 
shifts north into Virginia. A saturated boundary layer will lead to fog 
development on the cool side of The Wedge boundary...which should 
encompass most of the County Warning Area. A light breeze in the pressure gradient 
on the back side of the passing coastal low...which is expected to 
be off the Delaware-Maryland-Virginia by midnight...should keep widespread dense fog 
from developing...but if winds settle to near calm...fog could 
become more dense. Lows 46 to 50. 


&& 


Short term /Tuesday through Wednesday/... 
as of 300 am Monday 


Even with the parent high influence well removed from our area...The 
Wedge airmass is likely to persist through Tuesday...and possibly 
into Wednesday with no significant air mass change and weak thermal 
advection. Model soundings agree more on the persist left over cad 
stable layer for Tuesday...but other than a nagging pocket or two of 
drizzle in the morning...Tuesday should be dry but overcast and cool 
with highs low to middle 50s. 


For Wednesday....an upper level low lifting into the Midwest will 
send a relatively dry front toward the western slopes of the 
Appalachians. The front stays west of the mountains on 
Wednesday...but increasing DPVA with the upper trough spins up a 
surface low along the coastal baroclinic zone...which then lifts 
northeast parallel to coast. Even though models (most notably the 
gfs) produce some light quantitative precipitation forecast over eastern NC...it looks like the 
effects of the low will be too far east for mention of pop at the 
moment. Also...highs are tricky on Wednesday due to the possibility 
of the lingering wedge air mass. With the surface front remaining 
west of the area...low clouds may hold for at least part of the day 
on Wednesday...at least until the boundary layer becomes a little 
more stirred between the two systems mentioned above...which would 
finally allow for more mixing. Have trimmed back highs a couple 
degrees given more indication of lingering low level moisture by 
most recent forecast soundings. Highs 60 to 64. 


&& 


Long term /Wednesday night through Sunday/... 
as of 300 am Monday 


A strong upper level wave will be dropping out of the Midwest into 
the upper Mississippi Valley Wednesday night as a weak inverted 
surface trough lingers off the Carolina coast. As the upper low 
moves through the Ohio Valley a deepening low develops over the Middle 
Atlantic States... which lifts toward New England Friday evening. 
This will leave west to northwest flow over North Carolina into 
Sunday as weak Midwest upper ridging drifts toward the Atlantic 
Seaboard. 


Will keep this period dry. A risk for trace rainfall Friday 
afternoon in instability showers. But the air mass looks too dry to 
expect measurable rainfall. 


Friday looks breezy... with west winds 15 miles per hour and gusts over thirty 
as mixing heights approach 6000 feet during the afternoon to tap 
winds of thirty to forty knots at the top of this layer. 


Afternoon highs in the middle 60s Thursday... then middle 50s into Sunday. 
Overnight lows in the middle 40s Wednesday night... falling into the 
low to middle 30s for Friday and Saturday nights. 


&& 


Aviation /08z Monday through Friday/... 
as of 630 am... 


LIFR to IFR ceilings through the taf period. Northeast flow near 10 
miles per hour. Rain giving way to light drizzle or unrestricted visibility by 
afternoon. 


A few breaks in the clouds Tuesday afternoon then MVFR fog Tuesday 
night. VFR conditions Wednesday afternoon then fog Wednesday night 
with some low stratus in the east. Breezy Friday with west winds 15 
miles per hour and gusts in excess of thirty. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...Smith 
near term...Smith 
short term...Smith