Weather

373 
fxus63 kpah 041522 aaa 
afdpah 


Area forecast discussion...updated 
National Weather Service Paducah Kentucky 
1022 am CDT Sat Jul 4 2009 


Update... 
updated morning forecast. 


&& 


Discussion... 
large batch of showers and embedded thunderstorms continues to 
impact a large portion of southern Illinois...all of southwest 
Indiana and small portions of southeast Missouri and northern Kentucky 
at this time...generally north of a Marble Hill MO...to Vienna Illinois 
to Calhoun Kentucky line. Over the last hour...additional scattered showers 
have been trying to develop further south...but the entire area of 
activity is steadily moving eastward. Adjusted probability of precipitation to account for 
all of this. Some embedded heavier storms are likely producing 
some good rainfall amounts. The rainfall is definitely holding 
temperatures down across the northern areas...so adjusted temperatures 
accordingly. 


Still waiting to see how much clearing can be realized early this 
afternoon after this mornings rainfall. It appears that more 
convection is going to be possible especially across southeast 
Missouri...far southern Illinois and parts of west Kentucky during 
the afternoon. Again...the severity will depend largely on how 
much of this cloudiness we can dissipate. Stay tuned. 


&& 


Previous discussion... /issued 626 am CDT Sat Jul 4 2009/ 
main concern with the forecast is the evolution of a line of 
potentially severe thunderstorms crossing the region today and how it will 
affect outdoor festivities. 


Warm advection precipitation was underway to our northwest as a middle level shortwave 
embedded in the wnwrly flow continued to move toward our region. 
There might be a sprinkle or two in parts of southern Illinois before 
sunrise. After that...the models show a 850 mb jet kicking in from 
west to east...helping to set up ample vertical wind shear during 
the day. This combined with cape as high as 2500 j/kg will provide 
a favorable environment for severe thunderstorms...with large hail and 
damaging winds being the primary hazards...in addition to 
frequent cloud to ground lighting. With a surface low moving through 
the region...low level winds near the low may remain backed for a 
while...creating a possibility for a brief tornado. The best 
guess at this time of the low track is perhaps from around Perryville MO 
at 00z...moving east-southeast into western Kentucky by 06z. 


Just ahead of the surface low...a line of shwrs/tstms...some possibly 
severe...is expected to develop in the afternoon heat and enter the northwestern 
corner of the pah forecast area by around 21z. This line of storms 
should be crossing the Ohio River by 00z-01z...then be through the 
Kentucky pennyrile region by 03z. The forecast timing of the storms reveals 
that residents of the Kentucky pennyrile region outdoors for the 
fireworks displays will be the most affected by the presence of 
thunderstorm activity. 


Overnight...there will be decreasing chances of precipitation behind the 
surface low/front...but not zero chances. There may be enough of a 
subtle impulse in the middle level flow to provide enough lift for 
some showers or even thunderstorms before the deeper moisture is swept away. By 
15z Sunday...the forecast area should be precipitation free and clouds will 
decrease from north to south during the day. 


Northwest middle level flow/high surface pressure will rule for most of the 
week...then we will be on the eastern edge of a southwestern Continental U.S. Middle/upper 
ridge. Gentle return flow will tend to raise dewpoints/humidity/temps 
toward the end of the week. No changes were made after day 5. 


&& 


Aviation... 
large area of showers and thunderstorms over ecntrl Missouri into 
southern Illinois moving east-southeast early this morning. The chances should 
spread west and south this afternoon and evening. Carried best 
thunderstorms and rain probs in roughly the 22z-02z time frame. Winds will be a 
little tricky with a surface low forecast to move across the 
region. In the wake of the passage of the low and associated 
convection...low clouds are forecast to advect in from the north. 


&& 


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


$$ 


Update...CW 
previous discussion...db 
aviation...cn