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Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
1150 am EDT sun Mar 14 2010 


Synopsis... 
a broad upper level low will move slowly east across the Carolinas 
through today. The low will continue to drift eastward over the 
Atlantic Monday and Tuesday...allowing a Canadian air mass to build over 
region through middle week. Another upper level low is forecast to move 
across the southern Appalachians late Wednesday into Thursday. 


&& 


Near term /through tonight/... 
water vapor imagery shows the next strong vorticity center over eastern 
Kentucky poised to drop down across the southern Appalachians this afternoon. 
Infrared imagery has already shown the arrival of a large area of colder 
cloud tops over the NC mountains and kmrx radar trend is for 
increasing coverage of showery elements. Upslope should continue to 
force the development of showers for the rest of the day. All in 
all...the forecast looks like it is in good shape with only minor 
changes needed to keep it in line. 


Steep 850 to 500 mb lapse rates across the NC foothills and Piedmont 
could allow showers to spill out of the mountains this afternoon with the 
shortwave approach. Will keep the solid chance to likely probability of precipitation in 
the mountains...chance probability of precipitation for the rest of western NC...and then mainly 
slight chances across NE Georgia and the SC upstate. 


The bulk of the measurable precipitation is still expected tonight 
across the NC mountains as better moisture rotates in. The upslope flow 
into the western mountains is never very strong during the near term 
period...however...it does become more orthogonal to the mountain chain 
tonight along with deeper moisture. Snow ratios will be fairly low 
given the marginally cold profiles...but high elevations near the Tennessee 
border will likely see 1 to 3 inches of total snow 
accumulations...with 4 or 5 inches possible along peaks in the 
smokies. A Winter Weather Advisory will be posted starting this 
morning and running through tonight...mainly for higher elevations 
near the Tennessee border. 


&& 


Short term /Monday through Monday night/... 
as of 145 am Sunday...a closed middle level low will remain off the 
coast of the Middle Atlantic States on Monday. Both the GFS and European model (ecmwf) 
indicate that the last significant short wave associated with this system 
will push across the forecast area between 09z-18z Monday. The short wave will 
be accompanied by fairly deep layer of moisture and weak 850 mb cold air advection. In 
addition...850 mb flow across the NC mountains will remain northwest at 
15-30 kts through the daytime Monday. I will highlight the mountains with 
30-40 probability of precipitation with no mentionable probability of precipitation east of the mountains based on 
diurnal temperatures...snow should continue across the high terrain 
through the morning hours. High temperatures are forecast to range 
from the l50s in the valleys to l40s across the higher terrain. 
Precipitation should fall as -ra...with a mix on snow/rain above 4500 feet. An 
additional...half inch of snow may accumulate across the highest 
ridges Monday morning...otherwise...little to no accumulation is 
expected. Conditions will remain dry with marginal gusty winds east 
of the mountains temperatures across the foothills and Piedmont are 
forecast to range from the low to middle 60s. 


Monday night...850 mb winds will veer north across the mountains...especially 
after 6z. Moisture will continued to decrease through the 
night...with saturation only expected across the Tennessee border areas. 
Model quantitative precipitation forecast favors a mention of light quantitative precipitation forecast across the Tennessee border 
counties. Min temperatures are forecast to cool to the u20s to middle 
30s. These temperatures will keep the measurable snow limited to the 
highest elevations of the western NC mountains 


&& 


Long term /Tuesday through Saturday/... 
as of 330 am Sunday...the region will see middle level heights fall 
with the arrival of a l/west trough Tuesday into Thursday evening. A 
compact closed low is expected to track south across the Mississippi 
River valley Tuesday through Thursday morning. The greatest moisture 
and lift will remain confined to the track of the closed low. Weak 
upslope flow and an area of low level moisture should support a few 
showers across the mountains and upper Savannah River valley Tuesday 
night through Wednesday night. Near normal temperatures will allow 
most of the precipitation to fall as rain...with patches of snow 
across the highest terrain. 


Friday and Friday night...a middle level ridge will nose across the 
southeast...remaining into Friday morning. Deep return flow and 
increasing insolation should support temperatures 2-4 degrees above 
average...near 60 in the valleys to middle 60s east. 
Otherwise...conditions should remain dry and quiet. 


Saturday...ridging will ripple east as a potent closed low swings 
across the Heartland. A cold front associated with the low may push 
across the County Warning Area Saturday evening and overnight. Rain coverage should 
gradually expand across the County Warning Area during the day time. Temperatures 
are forecast to remain within normal values. 


&& 


Aviation /16z Sunday through Thursday/... 
at kclt...VFR level clouds will increase today ahead of a passing 
upper shortwave. West-southwest winds will persist through the daytime 
hours...with occasional gusts to 17 knots with mixing this afternoon. 
Scattered showers are likely late in the afternoon...with a vcsh mention 
included for now. Flow should turn northwest after the main wave passage 
this evening...with scattered to broken stratocumulus overnight as additional 
weaker waves pass. 


At kavl...moisture will slowly return to the French Broad valley 
today through tonight. Mainly lower VFR level ceilings should develop 
through the day...with a transition to MVFR ceilings circa 04z tonight 
as the deepest moisture and a more northwest flow component return. Some of 
the vcsh could be snow showers later tonight as snow levels 
fall. 


Elsewhere...VFR conditions will continue through the period. VFR 
ceilings will develop by 17z or 18z most areas as moisture arrives with 
the next upper shortwave. Scattered showers should also develop...so 
a vcsh is included at all taf sites for the afternoon and early evening 
hours. Mainly west-southwest flow is expected...except west-northwest at khky. 


Outlook...low pressure will move farther off the East Coast through 
the middle of the week. Mainly VFR conditions are expected...but 
brief MVFR ceilings may linger at kavl into Monday. Some low level 
moisture may persist over the mountains through much of the week...but 
with low confidence on any restrictions. 


&& 


Gsp watches/warnings/advisories... 
Georgia...none. 
NC...Winter Weather Advisory until 6 am EDT Monday for ncz033- 
048>052-058-059. 
SC...none. 


&& 


$$ 
Synopsis...Ned 
near term...hg/PM 
short term...Ned 
long term...Ned 
aviation...hg/PM 

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