088 
fxus63 kpah 091158 
afdpah 


Area forecast discussion 
National Weather Service Paducah Kentucky 
557 am CST Friday Jan 9 2009 


Update... 
updated aviation section for 12z taf issuance. 


&& 


Discussion... /issued 350 am CST Friday Jan 9 2009/ 
primary forecast concern remains potential for precipitation tonight 
and Saturday...followed by much colder air next week. 


Ridge of surface high pressure was oriented parallel to and in the 
vicinity of the Appalachian Mountains early this morning. This high 
will shift east today...allowing for an increase in southerly winds 
as low pressure organizes over the Southern Plains. This will result 
in warmer temperatures for the immediate area...as highs reach the 
upper 40s to lower 50s. Sunshine will abound for the first half of 
the day...but low clouds will likely begin to overspread the western 
half of the region during the afternoon. Forcing for precipitation 
appears to be best concentrated after 00z...so we eliminated any 
mention thereof this afternoon. 


The low pressure system shifts northeast across the region tonight. 
As the wave approaches...showers will break out across most of the 
region this evening...then continue overnight. A moist southerly 
fetch at 850 mb along with decent elevated instability should 
support a round of scattered thunderstorms as well...especially over 
the southern 2/3 of the area. The best time frame for thunderstorm 
activity appears to be from 03-09z. 


Falling temperatures will be the story on Saturday behind the cold 
front. We maintained precipitation chances through the course of the 
day. While most of the lingering precipitation will be in liquid form early 
in the day...light snow is more probable as the thermodynamic 
profile cools during the course of the day. Any wintry precipitation 
should be light enough so as to not result in any accumulation. 


High pressure will build in for Sunday...resulting in dry and milder 
conditions. After that...into the cold Arctic ice box we go as a 
series of frontal systems usher colder air into the region as the 
week progresses. Still some uncertainty as to how low we will 
go...but it is certainly possible that portions of the area may 
struggle to reach the 20s for highs...with lows in the single digits 
later in the week. Our new forecast package resembles the previous 
forecast with very few changes necessary beyond Sunday. 


Temperatures today are reflective of a MOS blend. However...we threw 
out MOS tonight and Saturday in favor of a nam12/gfs40/sref blend. 
This better accounts for rising temperatures and dew points ahead of 
the low tonight...followed by falling temperatures behind the front 
on Saturday. 


&& 


Aviation... 
VFR conditions will be the rule at least into the early evening 
hours. South winds will pick up today...and may gust near 20kts at 
times...especially west...as next front approaches. Conditions will 
deteriorate from west to east after 03z...as significant moisture 
increase begins. Model soundings indicate that showers and possibly 
a few lightning strikes will be possible along and immediately ahead 
of a surface low that is expected to develop along the front and 
lift northeast roughly from kpah/kcgi at 06z to kevv/kowb at 12z. 


Despite relatively good agreement in handling of front/low...model 
guidance is not in real good agreement with sensible weather ahead 
of it...indicating either low VFR or high MVFR conditions in 
scattered to numerous showers. Due to low coverage of thunder 
expected...decided to only mention a cumulonimbus overnight to indicate the 
potential. 


Worst conditions are expected behind the front/low...where IFR 
ceilings and IFR/MVFR visibilities can be expected in light 
rain/drizzle. The front will be near kowb at 12z...so did not 
indicate any wind shift or lower conditions there at this time. 


&& 


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


$$ 


Rjp/drs