Weather

505 
fxus63 kjkl 070703 
afdjkl 


Area forecast discussion 
National Weather Service Jackson Kentucky 
303 am EDT sun Sep 7 2008 


Short term.../today through Tuesday/...updated 


Dense fog was expanding across eastern Kentucky. Issued a dense fog 
advisory in effect until 10 am. Visibilities will be down to near 
zero at times in the thickest fog. After the fog Burns off this 
morning...expecting partly cloudy skies through the day. A batch of 
middle level clouds will cross the region this morning and into the 
afternoon...and there will also be some diurnal cumulus development. Fog 
should not be as dense or widespread tonight...but still think some 
patchy valley fog will form. Expecting dry weather tonight through 
Monday as high pressure slides east across the Ohio Valley. Should 
begin to see an increase in moistrue Monday night as a cold front 
approaches from the west. Will maintain chance probability of precipitation for late Monday 
night...and increased probability of precipitation some for Tuesday to high chance with at 
least scattered convection expected. The WRF shows some decent 
moisture pooling along and to the east of the front. Generally 
follwed closer to the sref for timing of frontal passage Tuesday and Tuesday 
night. With a slower movement...increased probability of precipitation a little in the 
southeastern areas Tuesday evening as the front works its way out of 
the area. Generally used h10 to 800 mb thickness schemes and 800 mb temperatures 
with adjustments for cloud cover to determine high temperatures. Used a 
blend of model data with adjustments for local terrain effects for 
overnight lows. 


Long term.../Tuesday night through Saturday/ 


Could be a rather active time period...with a number of systems 
affecting the region. But...it also comes with a fair degree of 
uncertainty...especially late in the period. 


Behind the exiting cold front Tuesday night...drier air tries to move 
in. There is some conflict between the European model (ecmwf) and GFS as to how 
effectively our air dries out. The GFS is consistent run to run in 
bringing clearing skies and dry weather late Tuesday night through 
Wednesday...and is also backed by its 00z ensemble. The European model (ecmwf) is more 
moist...showing the dry air having a hard time penetrating any 
further south than Kentucky. However...it did trend drier from the 12z Friday 
run to the 00z Sat run. Have opted for a drier forecast at this time 
without any precipitation on Wednesday. 


With surface high pressure quickly skirting by to our north...warm 
air advection should return already Wednesday night. It is not clear 
how soon we will have enough moisture present in the warm air 
advection/isentropic lift to support precipitation. Have used a long period 
of 20 percent pop at this point from Wednesday night through Thursday 
night...but that number could easily go up or down in any of the 
three periods. 


Models all bring another upper trough and associated cold front to 
the area late in the week...although the exact timing is still 
questionable. At this time...the front is expected to make it southeast of 
US late Friday or Friday night allowing for drier air to arrive. 
However...just how far it GOES and how long drier air stays in place 
are the next big questions. The answers to these appear to lie with 
Hurricane Ike and its eventual track and timing. It is too early to 
have any kind of confidence in the tropical system. Have left low 
probability of precipitation in through Saturday because of the potential influence of Ike. 


For temperatures...saw no reason to stray far from mex guidance. It was 
near seasonal averages...except maybe a bit above normal for lows. 


&& 


Aviation.../06z to 06z/ 


VFR and MVFR conditions are expected to deteriorate during the next 
few hours at all locations. A period of dense fog is anticipated at 
the valley taf sites during the predawn hours which will result in 
vlifr conditions for both ceiling and visible. The fog should burn off 
quickly following sunrise returning aviation conditions to VFR. This 
is true even in places...mainly north of the taf sites...that see a 
ceiling at around 6k feet for a time on Sunday. Winds through the period 
will be relatively light with daytime speeds on Sunday averaging 
between five and ten knots from the west at all sites. 


&& 


Jkl watches/warnings/advisories... 
dense fog advisory until 10 am EDT this morning for kyz044- 
050>052-058>060-068-069-079-080-083>088-104-106>120. 


&& 


$$ 
Short term...wjm 
long term...hal 
aviation...greif