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fxus63 kpah 041957 aaa 
afdpah 


Area forecast discussion 
National Weather Service Paducah Kentucky 
157 PM CST Thursday Dec 4 2008 


Short term.../tonight through Saturday night/ 
cold air will be the main theme for the rest of the work week...as a 
large high pressure system from Canada drops south into the center 
part of the country. Will likely see temperatures tonight fall down to 
near 20 in most locations...and may even get into the teens some 
areas if high clouds do not interfere too much. Also...will likely 
see day time temperatures struggle to get above freezing Friday along the I 64 
corridor. 


On Saturday...a quick clipper system will move through the Great 
Lakes region...and drag yet another cold front down through the 
area. For now...will go with a small chance for a little light rain 
or snow across southwest Indiana and a small part of southeast 
Illinois during the day on Saturday. Given the very low quantitative precipitation forecast 
suggested by the short range ensembles...as well as the latest 
deterministic runs of the GFS/ECMWF...this still looks more like a 
trace event. Warm up will be modest and brief ahead of the front. 
Will likely see temperatures back down in the 20 to 25 degree range Sat 
later Sat night. 


&& 


Long term.../Sunday through next Friday night/ 


For Sunday through Monday...the deterministic GFS is in phase with 
the slower European model (ecmwf) solution...therefore...I have continued a drier 
solution. With this in mind...leaned more heavily to lower dewpoints 
than advertised by the GFS...as Ely component still focuses dry air 
at low levels into the weather forecast office pah forecast area. For maximum/min 
temperatures...kept some continuity with earlier runs...but lowered 
Sunday maximum temperatures by 1-2 degrees and raised maxes on Monday 1-2 
degrees as southerly winds and warm air advection moves into the 
area. 


For Monday night through Tuesday night...this period will see the 
greatest precipitation type transition...mainly during the day on 
Tuesday and Tuesday night. Low level temperatures and dewpoints 
differences should keep wet bulb temperatures high enough to support 
rain through most of the night on Monday. On Tuesday 
afternoon...utilized deterministic influence from GFS in for top 
down precipitation algorithm application...since it was not much 
different than straight temperature conversion of precipitation type 
for that period. It is at this time...that an initial rain/snow mix 
will work across southeastern MO/southern Illinois/southwestern in...as cold air is advected in 
and works down along the northern limb of the surface low pressure 
system in the lower MS valley. Both the GFS/European model (ecmwf) are amazingly 
similar on the position of this low on Tuesday. Cold air advection 
infiltrates the low levels sufficiently late Tuesday evening to 
support a complete change to snow over the southeastern MO foothills and 
southwest Illinois...but moisture will also be lacking to support more 
than just a small chance or slight chance of snow in these areas. 
There is a little more robust chance for snow over southwestern in and 
western Kentucky in the pre-dawn hours of Wednesday...but for now...snow 
amounts in this area may only amount to a trace to locally one tenth 
of an inch at most. 


For Wednesday and Wednesday night...the greatest 
deterministic/ensemble model uncertainty shows up during this time 
period. There is some potential that measurable snow may be possible 
on Wednesday...especially over western Kentucky. Both the 00z Thursday European model (ecmwf) 
and 06/12z Thursday GFS deterministic runs suggest moisture/thermal 
profiles favorable for snow. However...timing...even with HPC 
guidance suggests high variability during this forecast period. So 
for now...will keep ongoing dry forecast in place for Wednesday. 
Given the persistence forecast for Wednesday...the Wednesday night 
period must be conditional dry as well. 


Finally...for Thursday through Friday night...dry forecast remains 
in place. There still may still be a low probability...trace snow 
event with the progressive northwesterly flow...but uncertainty remains too 
high to warrant a mention of any precipitation at all. Leaned closer 
to European model (ecmwf) maximum/min temperatures...but compromised with GFS on 
wind/dewpoints during this time period. 


&& 


Aviation... 
generally clear skies may give way to some VFR ceilings above 10 kft 
later today. No visibility restrictions expected. North winds may 
gust near 20 miles per hour at times this afternoon...but should settle down 
late in the day. 


&& 


Pah watches/warnings/advisories... 
Kentucky...none. 
MO...none. 
Illinois...none. 
In...none. 
&& 


$$ 


Short term...meffert 
long term...kes 
aviation...meffert