126 
fxus63 kpah 051905 
afdpah 


Area forecast discussion 
National Weather Service Paducah Kentucky 
205 PM CDT Sat Jul 5 2008 


Discussion... 


Quiet day today with decent cloud cover...but not enough to block 
the sun completely. Clouds mostly likely aided by the upper level 
wave rotating across the area today. Convection is to our south 
along the frontal boundary that caused our area some showers and 
storms yesterday. The front is actually very close by as dewpoints 
tell the tale...with 72 degree dewpoint at Walnut Ridge Arkansas and 
a 64 dewpoint in Poplar Bluff. It is this front that will be only 
real weather feature of concern over the next 24 to 36 hours. 12z 
GFS and NAM indicate that convection will continue firing along 
that front tonight...but most of it should stay to our south. 
However...the front will be lifting back northward on Sunday and 
then dissipating. The NAM and GFS hardly indicate any 
precipitation breaking out as this occurs. Dont feel right 
dropping the low pop for tonight with a front in the vicinity. 
Even tomorrow...models are really not real excited about painting 
any quantitative precipitation forecast. Guess its possible to see something isolated right along 
the front across southeast Missouri. We will mostly likely keep 
that pop going for Sunday just in case...and to give a little 
weight to the latest sref which indicates some precipitation across semo 
tomorrow. 


The 12z NAM run is showing much of the same scenario for Sunday 
night as it did with yesterdays 12z run. It indicates convection 
firing way to our north on Sunday and Sunday evening...and then 
tracking it southward into the area. Looking back on the 
00z NAM run last night...it tried to do this very same thing...but 
by 12z Monday...the convection was still not to our northern 
counties. But still...the NAM is really consistent on that type of 
solution. Mondays forecast will really be dependent on what 
happens upstream. The differences in the upper level flow pattern 
also differ somewhat between the GFS and NAM...which might be 
another cause for their quantitative precipitation forecast differences. The GFS keeps the area 
dry for Monday. Feel better keeping a slight chance in for Monday 
just given the two difference scenarios. 


By Monday night...the next frontal system to affect our area will 
be impinging on our area. The NAM continues painting convection in 
the warm sector during Monday night...which might be aided by 
increasing low level flow throughout the night. The GFS paints a 
drier picture as far as quantitative precipitation forecast...but looking at the frontal 
position...it is similar to the NAM. Believe the northwestern 
sections of the County Warning Area have the best chance of seeing any precipitation. We 
remain in the warm sector most of the day on Tuesday...with models 
hinting at a pretty dry day actually. Will trim probability of precipitation back a bit to 
indicate a slower arrival of the front. 


Will follow the European model (ecmwf)/HPC timing for the cold front which brings it 
to just northwest of the Ohio River at 7 am Wednesday. The GFS is slower and 
much messier with this system in part due to its pairing of the main 
precipitation chance with a 500mb short wave which is likely to alter 
between now and then. 


All guidance has trended toward eliminating rain chances across the 
north for Wednesday night and Thursday but the picture becomes less clear 
across the south part of the forecast area. Given July climatology with the 
southward progression of surface fronts I plan to leave in chance 
probability of precipitation across the southern part of the forecast area Wednesday night and Thursday and parts 
of semo Thursday night as return moisture creeps in from the southwest. 
Will continue a small chance on Friday but will again limit to the 
S/SW part of the forecast area given the influence of the Great Lakes surface 
high that ridges SW across our forecast area...especially the NE part of the 
forecast area. By next Sat...our airmass is likely to become increasingly 
capped as middle level temperatures warm with a 500mb high setting up over 
the lower miss valley. As a result...hotter and drier conditions 
still appear on target next weekend. 


Trimmed maximum temperatures a degree for 2 days following frontal passage...otherwise 
the main change was for min temperatures Wednesday night which were reduced about 
5 degrees to account for the Post frontal airmass. 


&& 


Aviation... 


Scattered-broken cumulus about today across the entire area. Should see 
this diurnal cumulus dissipate by sunset. There is some fog potential 
late tonight/tomorrow morning...so have tempo groups at all sites 
for either MVFR or IFR visibilities. Much of the same weather tomorrow 
with cumulus developing by late morning and winds shifting around to 
the south...as a frontal boundary to our south lifts back 
northward at US. Threat for convection appears limited at this 
time for late tonight and Sunday morning to include in the 18z 
tafs. 


&& 


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


$$ 


Short term...CW 
long term....Shanklin 
aviation...CW