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afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
1015 PM EDT Wednesday Mar 17 2010 


Synopsis... 


An upper level low will move slowly off the southeast coast tonight... then 
out to sea Thursday. High pressure will build in from the west into 
the weekend... bringing warm dry weather. 
&& 


Near term /through Thursday night/... 
as of 1015 PM Wednesday... 


The middle/upper low continued to move east-northeast across coastal Georgia/SC this 
evening. Upper diffluence over NC has led to a thick canopy of middle 
and high clouds all the way back into NE Tennessee... southern 
wva... and SW Virginia. It appears that they will remain in place over our 
region for much of the night. The bulk of the stratiform rain has 
been tracking just south of the NC/SC border. There have been a few 
light showers around Laurinburg and Lumberton where the 
temperature/dew point temperature spreads were 5-10 degrees. We will 
bump pop up into the slight chance category for our zones from 
Laurinburg to Fayetteville to Goldsboro and Clinton. Rainfall would 
be very light (a few hundredths) if it measures there. To the north 
the T/dew point spreads significantly drier (20-30 degrees). No pop appears 
necessary with such a dry subcloud layer north of Fay. 


The only other change to the forecast is for the clouds to continue 
thick enough to keep the temperatures much milder than previously 
thought. Late evening readings were rather uniform in the lower to 
middle 50s. Expect lows generally in the lower to middle 40s by daybreak. 
-Badgett 


For Thursday/Thursday night: deep moisture persists above 9 kft 
Thursday morning according to forecast soundings. The surface low 
remains well offshore but as it strengthens a bit the tightening 
mslp gradient will cause surface winds to increase from the 
northeast. The 850 mb circulation is near atop the surface low 
Thursday morning and as such the degree of onshore-directed flow at 
this level will be minimal with winds holding northeasterly keeping 
Theta-E advection into central NC neutral or negative. But even with 
such a dry subcloud layer... the upper level forcing along with deep 
moisture aloft may be sufficient over the far southern and eastern 
County Warning Area for virga yielding a few sprinkles at the ground. Otherwise 
skies should be mostly cloudy (albeit a thin veil over the northwest 
portions of the area) through midday Thursday with gradual clearing 
as we get on the subsiding side of the middle level low. Highs 66-71 
Thursday... warmest across the north... following patterns and 
trends of low level thicknesses but factoring in the reduced 
insolation across the southeast County Warning Area. Lows 37-41 Thursday night with 
skies mostly clear except for some evening clouds in the southeast. 
-Gih 


&& 


Short term /Friday through Saturday/... 
as of 250 PM Wednesday... 


Weak surface low will be moving away from the coast on Friday 
morning as surface high pressure builds east across the southeast states 
and an upper level shortwave ridge axis shifts to to near the 
appalachian spine. Precipitable waters  bottom out around 0.25" on Friday...and as 
the ridge axis builds east and low level winds begin to turn to 
southwesterly...low level thicknesses climb to around 1360m. Expect 
very little cloud cover and highs in the lower 70s. Overnight lows 
in the lower 40s. As the surface high slides offshore and a deep 
upper trough begins to dig through the central US on Saturday...a 
more entrenched S-SW return and deeper mixing should help tack on a 
couple more degrees of warmth to afternoon highs. Highs 
72-76...slightly under some of the warmer medium range guidance. 


&& 


Long term /Saturday night through Tuesday night/... 
as of 250 PM Wednesday... 


A fairly Stout shortwave is expected to dive through the inner 
mountain west Saturday...swing through the middle Mississippi River 
valley...then lift toward the Great Lakes on Sunday. This will push 
a cold front in vicinity of the Appalachians by Sunday afternoon. Guidance 
from HPC prefers the slower and deeper solution of the 
European model (ecmwf)/Canadian due to their flow separation...and thus this solution 
depicts the wave becoming negatively tilted as it lifts along the 
Appalachians to the middle Atlantic late Sunday into Sunday morning. 
Many uncertainties remain as to the impact of this system...mainly 
due to the timing of better forcing crossing the area. Convective 
potential will be driven by the possibility of a strong 850mb jet 
and a decent southerly flow out of ahead of this system...with the 
potential for a bit of an Atlantic fetch... aiding moisture return 
and instability. In addition...a southern track of the upper wave 
will promote stronger height falls. However... the slower timing of 
the system overnight Sunday night could be a strong limiting 
factor. These details will need monitoring. 


Due to the slower cold frontal passage...have steered away from all GFS based 
temperature guidance for Sunday through Tuesday...which would suggest a 
40-50m low level thickness drop on Sunday and Sunday night. Cloud 
cover ahead of the approaching trough will impact highs on Sunday 
especially in the west. Think upper 60s to middle 70s east-west could be 
reachable. In the wake of the cold front...high pressure quickly 
building east across the Gulf Coast looks to keep readings from 
dipping much below seasonal normals before rebounding once again 
next week. 


&& 


Aviation /00z Thursday through Monday/... 
as of 800 PM Wednesday... 


VFR conditions are expected through Thursday across all taf sites. 


A low pressure system currently moving off the North Florida coast 
will migrate to the east-northeast tonight and Thursday bringing an 
increase in cloud cover to the area. Middle and upper level ceilings 
are expected to be at or above 8kft tonight. All precipitation with this 
system should stay to the south. However...sprinkles are possible 
across kfay in association with the wrap around moisture as the low 
pressure system drifts eastward tonight. Winds will be light and variable 
tonight around 4-5kts. As the low pressure system moves further out 
to sea Thursday...clouds will clear from west to east. After 
daybreak...with broken ceilings and radiational heating...winds will 
increase to 8-10 kts from the northeast across all taf sites. Kfay 
may experience higher gusts (12-15kts) Thursday...especially if the 
cloud cover is less than expected. 


Beyond 00z Friday...VFR conditions are expected through Saturday 
ahead of another storm system moving in from the west. This system 
may bring MVFR conditions to the area late Sunday night. Strong 
southwesterly flow may also be an issue for runways oriented NW-se. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 


Synopsis...Badgett 
near term...Badgett/Hartfield 
short term...Smith 
long term...Smith 
aviation...pagano 

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