741 
fxus63 kjkl 052350 
afdjkl 


Area forecast discussion 
National Weather Service Jackson Kentucky 
750 PM EDT Sat Jul 5 2008 


Short term.../tonight through Tuesday/ 


18z surface analysis shows a weak pressure field through east Kentucky 
with a washed out frontal boundary laying across the area. A more 
prominent mesoscale feature shows up in the pattern of cumulus on the 
satellite loop as a low spinning over central Kentucky. From a 
minimum at this point...the clouds pinwheel out bit thicker and 
more numerous to the east and north. Associated with the clouds are a 
few small clusters of showers and thunderstorms current concentrated 
mainly north of the mountain parkway and also over the Cumberland 
Valley. Temperatures through the region are responding to a return of 
some sunshine to climb into the upper 70s and lower 80s...aiding the 
instability fueling the scattered convection this afternoon. 
Meanwhile...dewpoints remain quite moist...generally in the upper 60s 
to around 70 degrees. 


The models are again in good agreement aloft for the bulk of the 
short term period. They all take a packet of shortwave energy into 
the southern Ohio Valley tonight and develop a weak...initially 
closed...upper low over east Kentucky for Sunday. This feature then 
lingers overhead into Monday before drifting off to the east... 
quicker in the GFS than the European model (ecmwf) and NAM. Given the building ridge 
off the southeast coast during this time period prefer the slower 
solution as depicted by the higher resolution NAM. However...this 
leads to significant questions for the forecast Monday night and 
Tuesday in regards a shortwave that the NAM pushes across Kentucky 
during this time frame. Prefer to dampen this feature out for now 
until there is more model support...but will not completely discount 
it as the other models do flatten their 500 mb pattern over the area 
at the same time. 


Sensible weather will feature the diurnal...mainly instability 
driven...convection dampening this evening. However...do expect a few 
showers or thunderstorms to pop up through the night. Less in the way 
of clouds and plenty of low level moisture will likely yield patchy 
fog late tonight. Sunday will be similar to today with scattered 
and diurnally peaking shower/thunderstorm activity...beneath the 
upper low. Expect a similar night to tonight with patchy fog 
developing once again...along with still some isolated convection. 
Monday was pegged as a dry day and likely will be so for most...but 
do not see enough of drying taking place to prevent isolated activity 
during peak heating. That night and into Tuesday will maintain a 
small chance of showers and thunderstorms...a bit higher in the 
northwest than south...in response to the upper wave slipping through 
the area. 


In general...leaned toward the warmer numbers from MOS through the 
short term...especially on Sunday when the met is inexplicably cooler 
than the mav by several degrees. As for probability of precipitation ended up near a blend or 
slightly higher through the period...but much closer the wetter met 
numbers on Tuesday than the mav. 


Long term.../Tuesday night through Saturday/ 


The long term portion of the forecast also features fairly good 
agreement regarding the longwave pattern of a low amplitude trough in 
the east and ridging to the west. The GFS is a bit stronger with a 
trough swinging through the Great Lakes Wednesday than the more 
climatologically favored European model (ecmwf) from 00z on the 5th. As a result have 
leaned heavily on the operational European model (ecmwf) for the extended forecast. 
Which does bring a more gentle wave through the area midweek before 
gradually building a ridge north from the deep south for the first 
part of the weekend. While the GFS is similar with the ridge late in 
the period...its northern jet stream is almost 180 degrees out of 
phase from the European model (ecmwf). However...for east Kentucky/S weather next 
weekend this will be immaterial. 


Sensible weather in the extended will feature continued unsettled 
conditions as a front sags into the area for Wednesday with high 
chance to likely probability of precipitation in order. This front will also be slow to 
clear...per the European model (ecmwf) and climatology so have run with moderate probability of precipitation 
through Thursday...keeping them highest in the south. This is a good 
deal different then the GFS and its idea of sweeping the front 
through and drying US out Thursday through Saturday. The European model (ecmwf) with 
its weaker front also pushes return moisture back into the area 
quicker than the GFS resulting in continuing pop chances Friday and 
Saturday despite the building upper ridge. Temperatures through the period 
will be near normal for this time of year...warming to above normal 
for next weekend. 


&& 


Aviation.../00z to 24z/...updated 


Isolated to scattered IFR/MVFR showers and thunderstorms will 
continue to die out as sunset approaches. Looks like current 
activity will not affect any of our tafs sites. Therefore removed 
thunderstorms in the vicinity. IFR to vlifr fog will likely form later tonight...with some 
stratification likely past 08z. With stratification expect terminals 
along the ridgetops to be more adversely affected by fog...and 
guidance suggest this will be the case. Beefed up fog at jkl as a 
result...especially since it has received some recent rainfall from 
late afternoon and evening thunderstorms. IFR deck will lift and burn 
off by the middle morning tomorrow...with VFR conditions returning 
thereafter. 


&& 


Jkl watches/warnings/advisories...none. 


&& 


$$ 


Short term...greif 
long term....greif 
aviation...geogerian/ray