172 
fxus61 krlx 231037 
afdrlx 


Area forecast discussion 
National Weather Service Charleston WV 
537 am EST sun Nov 23 2008 


Synopsis... 
high pressure today. A cold front brings mostly rain on Monday. A 
return of snow showers and cold temperatures for late Monday night 
through Wednesday. 


&& 


Near term /through tonight/... 
h500 short wave axis moving east of Ohio River at this time...with 
middle clouds quickly dissipating or moving east. Expecting clear 
skies by 12z...with nothing to prevent abundant sunshine during the 
daylight hours. Surface high moves east of mountains this 
afternoon...starting up weak south/southwest flow by late in the 
day. H850 warm advection is fairly weak. As a result...have leaned 
a bit cooler than MOS temperatures today. Still...readings will be 
some 10 to 15 degrees warmer than yesterday. Streak of sub-40 
degree days at crw will end at 7...longest recorded run of such 
temperatures for the month of November. 


Moisture increases from the top down tonight as warm advection 
pattern continues ahead of warm frontal boundary. Pace quickens 
as h850 winds increase to 20-25 knots. Prefer the faster GFS 
here...as quicker is usually better in such patterns. Can see some 
isentropic lift on the 290k/295k surfaces after 06z. Still...with 
some quite dry air to overcome at the surface...was not as bullish 
with quantitative precipitation forecast as GFS would indicate. Could easily see precipitation end up as 
virga while moistening up the boundary layer. Have kept probability of precipitation in the 
slight chance range and confined them to the far SW areas through 
12z. Low temperatures will be reached around 06z...with a slow rise 
thereafter as clouds and winds increase. Ended up with minimums 
close to the warmer met numbers. 


&& 


Short term /Monday through Wednesday night/... 
still concerned about evaporative cooling with onset of 
precipitation Monday. 850 temperatures in the mountains will not be 
far from zero. Did include some rain or wet snow at the onset around 
Pocahontas County for example. If precipitation arrives a bit 
early...could not completely rule some pockets of freezing rain 
elsewhere. 


Trimmed back the high temperature Monday a bit...from our previous 
forecast. Tried to stay under most of our MOS guidance. I could get 
burnt late in the afternoon...say around The Heights tri state...as we 
have the main rain shield racing NE and exiting that area. 


Was slower in dropping temperatures Monday evening. Have the surface 
front not crossing until 00z to 04z Tuesday. 


Moisture may thin for a time over eastern Kentucky and southern West 
Virginia Monday night before increasing again on Tuesday. 


With moisture deeper over eastern Ohio and northern West 
Virginia...around the 500 mb cutoff...increased probability of precipitation for the snow 
showers Tuesday and Tuesday night across the lowland 
counties...especially pkb-ckb. 


Best combination of moisture depth and flow veering more toward northwest 
appears to be late Tuesday and Tuesday night. With 850 temperatures 
not as cold as the 2 cold outbreaks last week...the Crystal growth 
becomes limited on Wednesday and Wednesday night. 


All in all...event still likely to lead to some advisories...and 
maybe a few watches/warnings. Not an organized storm...but another 
snow shower event enhanced by upslope. 


&& 


Long term /Thursday through Saturday/... 
early in the period the models continue to show the closed low over 
the northestern US with the northwest flow holding on to the snow showers through 
Wednesday. But by Thursday...the 12z GFS and European model (ecmwf) both show the 
upper low pulling NE and the northwest flow weakening. The moisture depth 
also decreases so expect mainly dry weather on Thanksgiving. 


For Friday and Saturday...the models are in much disagreement from 
run to run and with the ensembles. HPC has gone toward the ensemble 
means with its guidance and keeps the wave that ejects out of the 
southwestern US suppressed over the southeast Gulf Coast and holds the upper closed 
low over the northestern US with northern flow continuing. But the 12z 
operational model runs of both the GFS and European model (ecmwf) are still 
suggesting...like they did Friday...that this wave will slide across 
the Tennessee River valley and through moisture into the southern Ohio 
Valley. So with the uncertainty...have held onto the low chance 
probability of precipitation across the south on Friday night and Saturday and have played a 
little more cloud cover as a result. 


For temperatures...maintained the cooler than normal temperatures 
Wednesday and Thursday with the northwest flow. On Friday and Saturday...begin to 
allow a little moderation in temperatures assuming that the northern flow ends 
and the wave adds a little southerly component to the flow. 


&& 


Aviation /12z Sunday through Thursday/... 
12z Sunday through 12z Monday... 
VFR through the period. High pressure will keep sky clear conditions 
through the day...with light winds. Some high clouds will begin to 
invade once again after 00z ahead of next system. Clouds will 
thicken and lower through 12z...but still remain generally above 
5000 feet. A sprinkle or light rain shower may reach heights by 12z but 
chances too low to include at this time. 


Aviation outlook /beyond 06z Monday/... 
cold front Monday...followed by northwest flow and upslope 
precipitation Monday night into Tuesday...could lead to IFR 
conditions especially for the mountain terminals. 


&& 


Rlx watches/warnings/advisories... 
WV...none. 
Ohio...none. 
Kentucky...none. 
Virginia...none. 


&& 


$$ 
Synopsis...ktb/cl 
near term...cl 
short term...ktb 
long term...ess 
aviation...cl