483 
fxus63 kpah 221149 aaa 
afdpah 


Area forecast discussion...updated 
National Weather Service Paducah Kentucky 
549 am CST sun Nov 22 2009 


Update... 
for 12z Sunday routine taf issuance presentation /see aviation section/. 


No change to discussion section. 


&& 


Discussion... 
lower dewpoints advecting in on a light east to northeast flow 
along with some high cloudiness building across the area from the 
south...is precluding fog development outside of areas of Illinois 
near and north of the Shawnee Hills. This is in response to a 
developing area of low pressure along the Gulf Coast which will be 
lifting northeastward before redeveloping east of the Carolina 
Outer Banks. 


The closed 500mb shortwave associated with this system will be 
opening up as it lifts northeastward across the Tennessee 
Valley...in response to the next shortwave tracking east out of The 
Rockies. This will allow for moisture to spread northward across at 
least the eastern half of our County Warning Area...in the middle/upper levels of the 
atmosphere initially. The low level easterly flow will gradually 
give way to veering and saturation from aloft on Sunday 
night...resulting in increasing clouds and eventually lowering 
ceilings. Restricted slight/low chance probability of precipitation to the pennyrile and extreme 
east after midnight on Sunday night into Monday morning. 
Questionable amount of forcing for any light rain...so either way 
amounts will be on the order of a few hundredths of an inch at most. 
Kept clouds more prevalent into Monday night. Bumped up temperatures 
sun/Monday nights and cut mondays highs by a couple in response. 


The upper flow becomes southwesterly by Monday night ahead of our 
next system. A closed low will develop in the Central Plains...and 
move east/northeast with time. Models have been all over the place 
regarding the timing of this system...but now seemed to have 
settled on a solution...at least for the quantitative precipitation forecast. As far as the upper 
low position...models solutions still vary greatly. 
Nonetheless...precipitation will be likely on Tuesday...with the 
best chances across southeast Missouri...southern Illinois and far 
west Kentucky. Chances for rain will move east throughout the day 
and into the evening. Things should begin to dry out after 
midnight on Tuesday. 


The GFS and European model (ecmwf) show yet another closed low dropping down out of 
Canada on Wednesday and diving down into our area. If any precipitation 
results from this wave...it will be up near the Interstate 64 
corridor. This system pivots around and brings a much stronger 
shortwave toward the area on Thanksgiving day. This will be a 
fairly deep shortwave trough and some very cold air will be 
associated with it. 850 mb temperatures drop down into the -5 to -7 degree 
celsius range for Thanksgiving day...which coupled with cloudy 
skies and brisk northwest winds...will yield a chilly day. Could 
see a few showers but the probability is too low and model consistency 
has not been that great to warrant the introduction of any pop at 
this time. Would prefer to wait until models get a better handle 
on how this next system will evolve before adding probability of precipitation. 


&& 


Aviation... 
other than a brief MVFR visibility restriction through 14z Sunday 
at kevv...VFR ceilings and visibilities will persist through 08z 
Monday. A gradual increase in coverage of cirrus will spread 
northward across each of the taf sites through the forecast 
period...as the upper low over the lower MS valley move into 
central Tennessee this afternoon. Broken and overcast high end 
middle cloud decks will move in later this afternoon and this 
evening. As low levels saturate after midnight...MVFR visibilities 
between 4-5 statute miles will be possible between 08-12z Monday 
at each taf site. 


&& 


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


$$ 


Smith