314 
fxus62 krah 200234 
afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
1015 PM EDT Friday Mar 19 2010 


Synopsis... 


High pressure will linger over our region through Sunday bringing 
dry warm days and cool nights. A storm system will approach from the 
west Sunday night and move into NC Monday and Monday night. 
&& 


Near term /until 6 am Saturday morning/... 
as of 1015 PM Friday... 


The latest satellite data indicated clear skies across the entire 
southeast and middle-Atlantic regions. The surface high was centered 
over the Appalachians. The middle/upper level ridge axis extended from 
Florida northward into Ohio. The 1000 PM surface observations indicated 
light winds and large T/dew point spreads (20 to 35 degrees). This dry air 
with light wind will lead to excellent radiational cooling overnight 
with a large range in urban versus rural areas... and hill tops 
versus valleys. Readings at 1000 PM ranged from the middle 40s to lower 
60s (even within the same County - see the Yadkin River valley 
observations) which is an unusually large range for central NC. The 
only change tonight will be to forecast more of a range in lows. 
Expect lows of 32-45 or about 12-15 degrees cooler than the 1000 PM 
readings. -Badgett 
&& 


Short term /6 am Saturday morning through Sunday/... 
as of 300 PM Friday... 


Saturday and Saturday night: heights aloft will continue to build 
over the region... ahead of a closed upper low expected to evolve 
from the central rockies to the Southern Plains this period. 
Accordingly expect continued dry and mild/warm conditions... with 
temperatures generally 74 to 78 for highs... given projected low 
level thicknesses 7 to 10 meters higher than those that supported 
generally lower 70s temperatures on Friday. A pair of upper level 
short wave troughs... which extended from West Texas to southern 
Arizona this afternoon... may provide for some passing cirrus 
through an otherwise clear sky. Suspect cirrus will not be 
thick/widespread enough to keep lows from dipping into the 45 to 
50 degree or so range. 


Sunday: another mild/warm day expected... as southwesterly flow 
increases ahead of the aforementioned upper low and attendant surface 
frontal system. Despite a comparable air mass to that of Saturday... 
expect increasing cloud cover in southwest flow aloft to nudge up to 
a category off saturdays highs... mainly in the west... with 
generally lower to middle 70s expected. 


Forcing for ascent remains weak throughout the daylight hours... as 
height falls attendant the upper low should hold to our west. 
Nonetheless... increasing low level Theta-E advection/isentropic 
lift on the anticyclonic shear side of an approaching low level 
jet concurrent with weak instability owing to rising surface 
dewpoints rising into the upper 40s to around 50 and steepening 
lapse rates aloft (though still less than 5.5 c/km) could support a 
few showers over the southern and western Piedmont late in the 
afternoon. 


&& 


Long term /Sunday night through Friday/... 
as of 300 PM... 


Increasing low level flow from the southeast Sunday night with winds 
becoming increasingly convergent and cyclonic. Current forecast of 
potential thunder retained. However minimal cape and only mildly 
negative lifted indices so thunder quite isolated to absent. 
Surface air mass will stabilize with the rainfall and thunder 
threat likely confined to near precipitation onset. 


Near surface winds shift to southwest Monday with the upper low 
pressure system forecast into western South Carolina Monday 
afternoon. Low level drying should end any chance for rain in the 
early morning in the west with rain chances ending elsewhere by 
early afternoon. 


Although 850 millibar winds increase to 45 to 50 knots Sunday night 
convergence nor isentropic lift never become particularly strong for 
an extended period of time and upper level dynamics are minimal 
Sunday night. Precipitation totals at around one half inch with 
locally higher amounts. 


As the upper low moves through the Carolinas Monday night cold 
advection throughout the air column commences. Models in agreement 
in low level moisture returning around the back side of the 850 
millibar low. Forecast soundings are strongly capped below 15000 
feet and suspect only a few brief showers possible until around noon 
Tuesday when the 850 millibar low completely exits central North 
Carolina. 


Middle and upper level ridging moves over the area for Wednesday... but 
it is quickly flattened ahead of the next low pressure system. If 
current timing of systems hold... a rain chance will be justified 
for Friday afternoon. 


High temperatures not far from climatology Monday and Tuesday with 
60s forecast. Wednesday and Thursday will be the warmest days of 
this period with afternoon low level thicknesses rising above 1365 
meters. High temperatures in the low to middle 70s. Friday high 
temperatures near 70. Overnight lows in the 40s most locations. 


&& 


Aviation /00z Saturday through Wednesday/... 
as of 730 PM Friday... 


Clear skies and light and variable winds are expected through 
Saturday afternoon...as subsident deep layer ridging continues to 
move across the region. Some high clouds will start to move into 
central North Carolina late Saturday ahead of the next storm system. 


VFR conditions are expected to prevail until Sunday night... when a 
cold front will likely bring widespread showers (with possible 
isolated thunderstorms) and MVFR/IFR ceilings and visbys to the region. 
Scattered instability showers are then expected as the upper low 
moves slowly across the region Monday afternoon through early 
Tuesday. 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...Badgett 
near term...Badgett/mws 
short term...mws 
long term... 
aviation...krr/mws