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Area forecast discussion 
National Weather Service Raleigh NC 
1017 am EDT Monday Mar 15 2010 


Synopsis... 
a strong upper low will meander off the middle-Atlantic coast today 
before finally moving out into the Atlantic waters on Tuesday. As 
this weather system moves away... high pressure will gradually build 
in from the west... bringing dry weather through middle week. 


&& 


Near term /through tonight/... 
as of 1015 am Monday... 


Morning upper-air analysis showed a vertically-stacked upper low 
near the New Jersey coast...with considerable moisture west of the 
upper low through 500mb over Maryland and northern Virginia. 
Regional radar images show a narrow area of showers moving south 
across eastern Virginia...with clouds spreading south ahead of the 
showers. The 06z NAM...06z GFS...and the local 00z WRF all show 
increasing mean moisture spreading south especially into northeast 
zones late this afternoon...with at least moderate lift developing 
by 21z associated...in part...with a modestly-strong middle-level 
shortwave and surface trough. All of the aforementioned guidance 
also provides for minimal quantitative precipitation forecast especially over the northeast between 
21z and 00z...with very minimal quantitative precipitation forecast noted on the GFS as far south as 
kgsb and kctz ending by 06z. The most likely result is for scattered 
showers to occur starting around 21z in the northeast coastal plain 
and the far northeast Piedmont...with showers turning to more 
sprinkles as they move farther south very late this afternoon and 
early this evening before diminishing as lift wanes and the 
shortwave weakens. Farther west...moisture does not appear as deep 
and the lift not as substantial for measurable rain...and left it 
out of the forecast. 


Low-level moisture appears ample enough to support at least mostly 
cloudy conditions for a large part of the night for the eastern 
two-thirds of central North Carolina. Will review the latest 
guidance during the afternoon...but currently it would seem the 
western edge of the better moisture lies mainly east of The Triad 
and the southwest Piedmont overnight. With mixing...winds could 
become modestly gusty this afternoon...probably a little higher 
toward The Triad than elsewhere where bufr soundings show middle 20s 
knots near the top of the mixed layer. High temperatures will mostly 
be in the 60s...from around 60 in the northwest Piedmont and the 
northern coastal plain to the middle 60s southeast. Lows from near 40 
to the lower 40s...though the fall could be slow overnight due to 
clouds. 


&& 


Short term /Tuesday through Thursday night/... 
as of 240 am Monday... 


Tuesday and Tuesday night... 
southwest extension of the upper low that has persisted across the east 
Continental U.S. For the past 4 days or so pivots east on Tuesday. This results 
in a backing and relaxing of the upper flow and a modest increase in 
500 mb heights on Tuesday and Tuesday night. Low level flow remains 
northeasterly though... and this which will transport a cooler and 
slightly more moist air mass into the region. Expect varied amounts 
of cloud cover given the NE flow with moisture persisting in the 
lowest 8kft below an intensifying inversion. Moisture is not very 
deep and forcing for ascent is lacking so precipitation is note 
expected. High temperatures in the middle 50s on Tuesday will be several degrees 
cooler then normal given the NE flow cloud cover. Low temperatures on Tuesday 
night will range in the upper 30s to lower 40s. 


Wednesday through Thursday night... 
brief rise in upper heights stops on Wednesday as closed low over the 
Desert Southwest at the beginning of the week moves east...weakens 
and opens up. As this disturbance moves into the northwest Gulf of Mexico 
on Wednesday...a disturbance in the northern stream drops south into the 
Missouri Valley. As these system try to phase...a positively tilted 
upper trough axis develops across the central or eastern Carolinas by 
around 12z Thursday. Low level flow remains primarily northerly 
across the southeast and the Gulf of Mexico which will obviously 
limit the amount of moisture available to the system. Nwp guidance 
is coming into better agreement with the overall pattern and 
confidence in the development of the upper trough and perhaps a close 
low is increasing. But given the lack of moisture transport...the 
likely placement of the trough axis across the eastern Carolinas and 
a surprisingly stable profile on Thursday suggests limited precipitation 
chances. Will increase the degree of cloud cover and knock temperatures 
back a degree or too but keep forecast dry for now. -Blaes 


&& 


Long term /Friday through Sunday/... 
as of 300 am Sunday... 


Friday through Saturday night...short wavelength upper trough off the 
Carolina coast on Friday pushes east allowing short wave ridging to 
develop on Friday night. Broad southwesterly flow develops on 
Saturday and persists into early Sunday as next trough in the northern 
stream approaches from the west. Mainly clear skies expected on 
Friday night with some increase in high clouds arriving by Saturday 
and Saturday night. This pattern suggest a notable warming trend 
with temperatures reaching the upper 60s and lower 70s by Sat. 


Sunday and Sunday night...guidance fairly consistent in bringing a 
northern stream trough across the region on Sunday. Details and timing 
of this feature are varied as is expected this far out. 14/12z European model (ecmwf) 
and 15/00z Canadian forecast the upper trough and attendant cold front to 
arrive early in the day on Sunday while the 15/00z GFS holds precipitation 
off until late in the day. The European model (ecmwf) closes off a low over the 
southern Appalachians with better forcing while the GFS pushes the 
best forcing further north. Current forecast includes a 30 pop on 
sun and have no reason to adjust this now. But timing and other 
details will likely evolve over the coming week. With increased 
cloudiness and a chance of precipitation...maximum temperatures on sun should be a few 
degrees cooler then Sat. -Blaes 
&& 


Aviation /12z Monday through Saturday/... 
as of 720 am Monday... 


VFR conditions through most of the 24 hour taf period. 


Upper low will meander off the Delaware-Maryland-Virginia coast today. Shortwave 
energy will slip south and east of the area between 12 to 15z. 
Subsidence behind this shortwave energy should translate into 
partial clearing late this morning. By the afternoon...March 
sunshine should support a fairly expansive cumulus field as middle-level 
moisture lingers in vicinity of of the upper low. Breezy northwest winds will 
develop by the afternoon as well...with gusts near 25kts expected. 


The gustiness will diminish during the evening...but pressure 
gradient remains tight enough to support a steady 5 to 10kt wind 
from the north overnight. Model soundings show MVFR ceilings 
developing late tonight by daybreak Tuesday as the northerly winds 
draw some Atlantic maritime moisture south into the area as the 
offshore low takes a turn to the south. 


VFR ceilings return for Tuesday as drier air moves into the region. 
A series of upper level disturbances/lows will approach the area by 
middle week. However at this time impacts will be marginal with only 
some clouds expected as this time. Northerly flow will gradually 
shift to easterly as the week progresses and winds should remain 
fairly light (5-10 kts) with minimal gusting. 


&& 




Rah watches/warnings/advisories... 
none. 


&& 


$$ 


Synopsis...cbl/Hartfield 
near term...djf 
short term...blaes 
long term...blaes 
aviation...cbl 

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