Weather

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fxus63 kiwx 272338 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
738 PM EDT Wednesday Aug 27 2008 


Aviation... 


Forecast area remains between Fay remnants to the east and 
approaching system from the west. Increasing low level moisture 
overnight coupled with light winds should allow fog to form with 
MVFR visible restrictions. Continued tempo group for this. Increasing 
high clouds from west on Thursday but taf sites should remain dry 
through 00z. Weak front will push through Thursday night and could 
see some scattered thunderstorms and rain with this front...especially closer to ksbn 
between 00z and 06z. 


&& 


Short term... 
primary dilemma lies west/surface frontal zone associated/west energetic SW troughs 
embedded in polar westerlies across southern Canada. Lead system already well 
wrapped up west of Hudson Bay west/secondary quick on its heels across northern 
Montana. Fairly robust mesoscale convective system earlier across western Iowa/eastern NE within favorable ll 
Theta-E wedge and modest frontal scale lift...however frontal scale 
circulation weakens considerably as secondary SW trough dampens eastward 
and overnight timing of frontal passage again largely unfvrbl in light of 
stabilizing surface layer. Best chance...albeit conditional...remains across northwest 
Thursday evening in closer proximity to likely mesoscale convective system shifting out of Illinois. 
Taken as a whole...12z guidance looks just as dismal as previous 
solutions west/precipitation chances and will temper probability of precipitation Thursday night even further 
especially west/eastward extent. Otherwise will generally fvr large diurnal temperature 
ranges as seen in mav guidance. 


&& 


Long term...Friday through Wednesday 


Main forecast issues this package revolve around precipitation chances 
Friday morning...temperatures this weekend into early next 
week...and precipitation chances by the middle of next week. 


Friday and Saturday...cold front associated with shortwave pivoting through 
the Great Lakes should clear southeast portions of the forecast area 
by middle-morning on Friday at the latest. As a result...decided to 
continue with slight chance probability of precipitation Friday morning in the south and east 
as the 12z NAM and several GFS ensemble members are a little slower 
with frontal passage timing when compared to the 12z operational GFS. Still 
think only slight chance probability of precipitation warranted as better forcing and DPVA 
stays well north along with unfavorable early morning frontal passage. 
Otherwise...expect mainly clear skies...dry conditions...and 
seasonable temperatures late Friday into Saturday with a surface high 
building eastward into the southern Great Lakes. 


Sunday through Wednesday...main feature through early next week will 
be a large upper ridge that will build northward into the Great 
Lakes/Ohio Valley in response to a highly amplified trough that will 
dive into the western Continental U.S.. this will result in dry 
conditions...little in the way of cloud cover...and above normal 
high temperatures. Extremely dry soil and 850 mb temperatures in the 17-20c 
range should result in highs in the middle/upper 80s through the 
period...possibly low 90s on Tuesday. 


Medium range models differ with timing of next piece of energy that 
will eject from The Rockies northeastward to the upper Midwest and 
northern Great Lakes by the middle of next week...and its potential 
interaction with the remnants of Gustav. Prefer the slower European model (ecmwf) 
solution...due to there being such a strong upper ridge in place 
and that it seems to have a better handle on the evolution of 
Gustav. As a result...will leave Wednesday dry with wet weather 
possibly returning by Wednesday night or Thursday. 


&& 


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


$$ 


Short term...holsten 
long term...steinwedel 
aviation...Lashley