691 
fxus63 kdtx 282333 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
733 PM EDT Thursday Aug 28 2008 


Aviation... 


Latest observations and regional satellite indicate the persistent 
MVFR cloud deck now beginning to scatter out...as higher cloud 
cover filters in. Will hang on to a tempo at kdet...where MVFR 
ceilings may linger for an hour or two beyond 00z. Otherwise... 
attention turns toward a weak cold front currently dropping 
southeast across the Upper Peninsula. Sufficient convergence along 
this boundary will help focus a few showers as it lifts across 
Southeast Michigan late tonight/early Friday. This may lead to brief 
periods of MVFR conditions. Moistening boundary layer conditions 
may also create some lower visibility restrictions outside of any 
precipitation. Skies will gradually clear through midday Friday 
behind the front...with winds shifting toward the north. 


&& 


Previous discussion...issued 318 PM EDT Thursday Aug 28 2008 


Short term...through tonight 


Cloud cover continues to slowly shift east and out of Michigan 
this afternoon as the remnant low pressure center from Fay continues 
to move away from the state. Will then see a brief decrease in cloud 
cover late this afternoon and evening before middle-level deck (already 
into western michigan) blankets the area ahead of the approaching 
surface trough. 


Cold front associated with this feature will push down across 
Southeast Michigan late tonight and early tomorrow. Available 
moisture will increase overnight as southerly flow strengthens 
slightly and advects higher upstream dewpoints up into lower 
Michigan. Low-level convergence along the front looks decent...but 
without any upper level forcing...lift will become increasingly 
shallow as you move southward towards the Ohio border. Will continue 
to carry likely probability of precipitation from I-69 northward...and scattered probability of precipitation that 
taper southward for the remainder of the forecast area. With 
instability very limited most of the precipitation will simply be 
showers...however a rumble of thunder is also be possible. 


Long term...Friday through next Thursday 


Timing of frontal passage for early tomorrow still on track and will 
maintain minimal probability of precipitation for the morning hours far southeast counties. 
With zonal flow still in place for Friday and into Saturday... 
another weak front will try to make headway through Northern Lake 
Huron and into The Thumb late by Saturday and Saturday night. 
However... upper ridging will quickly build into the Great Lakes and 
likely prevent the boundary from dropping all the way down the 
lake. By Sunday afternoon the NAM and GFS each bring unseasonably 
high heights into the region... and we should see a nice jump in 
maximum/min temperatures through the end of the weekend and early part of 
next week. Latest mex guidance pushes highs to around 90. Have 
also introduced probability of precipitation for later next week... although there is a 
great deal of uncertainty regarding tropical systems. Latest GFS 
does bring a front into the vicinity Wednesday night and stalls it 
or moves it slowly southeast Thursday.... enough to justify adding 
small introductory probability of precipitation for the end of the week. 


Marine... 


Southeast winds will increase late this afternoon and evening ahead 
of an approaching cold front. Wind gusts will not get too 
strong...topping out at around 20 knots over the northern half of 
Lake Huron. The cold front will then push down across Lake Huron 
late tonight...and across Lake St Clair and Western Lake Erie 
tomorrow morning. Showers are likely late tonight as the cold front 
pushes across Lake Huron...with scattered showers expected south of 
there through tomorrow morning. A few thunderstorms will also be 
possible. 


High pressure will then build in for the Holiday weekend late on 
Friday and hold over the region into Tuesday. This will provide calm 
and dry conditions. 


&& 


DTX watches/warnings/advisories... 
Michigan...none. 
Lake Huron...none. 
Lake St Clair...none. 
Michigan waters of Lake Erie...none. 


&& 


$$ 


Aviation.....Mr 
short term...hlo 
long term....05 
marine.......hlo 




You can obtain your latest National Weather Service forecasts online 
at www.Weather.Gov/Detroit (all lower case).