Weather

957 
fxus63 kiwx 212340 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
740 PM EDT Thursday Aug 21 2008 


Aviation (00z tafs)... 


Upper level low over the plains will allow for continued light 
southerly flow and an increase of moisture over the area tonight 
and into the morning hours on Friday. VFR conditions through the 
taf period except in areas of scattered showers mainly after 14 or 15z 
Friday where MVFR conditions are possible along with an increase 
in winds to at or below 10kts. 


&& 


Previous discussion... /issued 341 PM EDT Thursday Aug 21 2008/ 


Short term...tonight through Saturday morning... 


Remnants of the closed low that was meandering over the Southern 
Plains is lifting rapidly through the Mississippi River valley. This 
feature will be the weather producer for the short term. Increasing 
cloudiness and isolated showers will be the rule and consequently 
will play havoc on temperature forecasts. Expect above normal 
temperatures for tonight and Friday night. Maybe a few degrees above 
normal high on Friday. 


Model soundings suggest that the boundary layer will remain dry for 
the next 24 hours...so any precipitation that does fall with be 
light and spotty in nature. 


Next round of convection will be associated with a cold front that 
models seem to be struggling with. While the timing is 
questionable...this should be enough to keep an abundance of 
moisture and increasing instability over the Great Lakes region. 
While the timing is questionable...feel it is good to introduce 
chance pop for the period from Friday afternoon through Saturday 
morning. 


Long term...Saturday through Thursday... 


Complicated pattern evolution reliant on ingestion of former cutoff 
upper low into westerlies and track of remnants of Fay favor a 
persistence based forecast until large and small scale details come into 
better focus. 


Saturday... 
County Warning Area looks to be well into warm sector Saturday with heat and 
humidity quite prevalent. Nearly pulled probability of precipitation from 12-18z Sat grid as 
forcing should be limited...instability weak...and diurnal timing 
unfavorable. However...will stay consistent and leave a low chance in. 
Slightly better chances for probability of precipitation in the afternoon Saturday with 
forcing moving a touch closer and diurnal heating slightly 
increasing cape values. Moved highs up a tiny bit but still will be 
a few degrees under mav numbers with highs in the upper 80s Saturday. 


Sunday... 
kept probability of precipitation in the forecast as favor a slightly slower cold frontal passage than 
the GFS advertises...one more in line west/the sref. Once front 
passes...cooler and drier air will settle in from the northwest late 
Sunday into Sunday night. 


Monday through Wednesday... 
surface high pressure under upper ridging should provide seasonable temperatures 
and dry weather. 


Thursday... 
models...especially European model (ecmwf) beginning to indicate remnants of Fay to move 
into area but large differences in medium-long range guidance preclude 
mention at this time. 


&& 


Iwx watches/warnings/advisories... 
in...none. 
Michigan...none. 
Ohio...none. 
Lm...none. 
&& 


$$ 


Short term...Lewis 
long term...Simpson 
aviation...weisser/schott