552 
fxus62 kgsp 072005 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
305 PM EST Wednesday Jan 7 2009 


Synopsis... 
a fast moving cold front will cross the forecast area on Thursday 
and high pressure will quickly build in behind it Thursday night. 
This high will then move off the East Coast Friday night in advance 
of the next low pressure system which is expected to affect our 
region from the west on Saturday. 


&& 


Near term /through Thursday/... 
very gusty southwest winds will continue across the forecast area 
into the early evening. Between 23-1z...the mixed layer will become 
increasingly shallow with wind gusts falling into the 25-30 kts 
range. Gusts should dissipate by midnight...however...sustained 
speeds will likely remain around 10 kts. Uprooted trees may continue 
to occur into the early evening...as a result of saturated soil and 
gusty winds. The Wind Advisory will continue until midnight tonight. 


The main weather tonight will be increasing shsn across the NC mountains 
short range models indicate that moist west to northwest winds will 
develop after 0z. Models generate light quantitative precipitation forecast between 0-9z 
tonight...especially across the northern mountains short wave arrives over the 
southern Appalachians between 9-15z...with negative epv values. 
Cloud temperatures will likely fall -15c...aiding the development of 
healthy shsn. Snowfall rates should gradually decrease after 
15z...as the short wave pushes east of the region. Storm total snowfall is 
forecast to range from 3-5 inches above 3500 feet...to 1-2 inches in 
the valleys. We will issue a Winter Storm Warning for the High Mountain 
elevations with an advisory below 3500 feet...from 0z Thursday to 0z Friday. 
West-southwest will cover the mountains with the exception of Henderson County. In 
addition...moisture on mountain roads and bridges may freeze this 
evening...creating patchy black ice. 


Thursday...conditions should gradually clear east of the mountains after 
15z. Wind gusts should redevelop by middle morning and continue through 
the rest of the daytime. At this time...gusts should remain less 
that advisory criteria. 


&& 


Short term /Thursday night through Saturday night/... 
as of 150 PM Wednesday...fair weather Thursday night through Friday night. A 
positively tilted short wave will approach the region on Saturday. 
SW 800 mb flow increases to around 50 kts...though the upper support is 
lacking. This should be good for scattered convective coverage ahead 
of the surface front during the day on Sat and I have 30 to 40 probability of precipitation 
across the region in the zones. Frontal passage late afternoon Sat will be followed 
by fairly good cold advection in the mountains moisture looks 
shallow...so I just have a few snow showers along the Tennessee border Friday 
evening. 


&& 


Long term /Sunday through Wednesday/... 
as of 300 PM Wednesday...models in decent agreement with large scale 
features...but some disagreement remains in details...especially by 
the end of the period. Dry and seasonal high pressure builds into 
the area Sunday and remains over the area Monday as a clipper type 
system approaches from the northwest. Have dry forecast and near normal 
temperatures through Monday morning. Some did bring a slight chance of 
precipitation into the NC mountains Monday afternoon as the clipper approaches. 
Clipper moves through the area Monday night with best pop chance over the 
mountains rain will change to snow over the mountains...with sprinkles or 
flurries elsewhere. Short wave moves over the area Tuesday with best 
pop over the mountains again...precipitation would be snow over the mountains with 
sprinkles or flurries elsewhere. Right now...we have advisory level 
snow over the NC mountains...but a lot can change between now and then. 
Temperatures fall below normal. Models agree that another clipper 
type system approaches the area Wednesday. The European model (ecmwf) is faster and 
farther south than the GFS. Have trended toward the GFS ensemble for 
pop. This gives US a dry Tuesday night and slight chance pop Wednesday and Wednesday 
night for the NC mountains and dry elsewhere. Again...p-type favors snow 
with rain mixing in during the afternoon. 850 mb temperatures are very cold on 
the operational models...but not quite as cold on ensembles. However 
the ensembles do show significant Standard deviations. Therefore 
will forecast well below normal temperatures Tuesday night and Wednesday. 


&& 


Aviation /20z Wednesday through Monday/... 
at kclt...temperature profile over the terminal indicates that the 
mixed layer will remain 5-6 kft this afternoon and early evening. 
Mixing should become shallow by 1z...resulting in marginal gusts. It 
appears that the wind direction will 240-250 with gusts around 30 
kts through early evening. The rest of the night into Thursday 
morning...winds will remain southwest with speeds remaining around 10 
kts. Gustiness may return to the terminal late Thursday 
afternoon...however...gusts should remain around 20 kts. 
Otherwise...conditions should remain VFR with ceiling and 
visibility. 


Elsewhere...deep mixing will continue across the western Carolinas 
until sunset. Momentum Transfer within the deep mixed layer will 
continue to yield gusts of 25-35 kts through 23z. Gusts will remain 
possible into the evening...however...speeds will decrease by 10 
kts. The wind direction will generally range from 240-260 through 
the taf period. By middle Thursday morning...marginal wind gusts may 
redevelop across the region. However...gusts should remain capped 
around 20 kts. Otherwise...conditions should remain VFR with ceiling 
and visibility. 


Outlook...conditions should remain VFR Thursday afternoon into Friday 
with building high pressure. Saturday...a cold front will bring 
showers into the area...with the potential of restrictions. Drying 
high pressure builds in Sunday. 


&& 


Gsp watches/warnings/advisories... 
Georgia...Wind Advisory until midnight EST tonight for gaz010-017-018- 
026-028-029. 
NC...Wind Advisory until midnight EST tonight for ncz033-035>037- 
048>053-056>059-062>065-068>072-082-501>510. 
Winter Storm Warning from 7 PM this evening to 7 PM EST 
Thursday for ncz033-048>052-058-059-062-063. 
Winter Weather Advisory from 7 PM this evening to 7 PM EST 
Thursday for ncz053-064. 
SC...Wind Advisory until midnight EST tonight for scz001>014-019. 


&& 


$$ 
Synopsis...bsh 
near term...Ned 
short term...McAvoy 
long term...rwh 
aviation...Ned 

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