Weather

582 
fxus63 kmkx 211926 
afdmkx 


Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI 
226 PM CDT Thursday Aug 21 2008 


Forecast focus on two main chances of precipitation...one tonight with 
northward moving short wave in moist srly flow...and the second on 
Saturday with frontal passage. 


Tonight...showers have been making steady progress north into the 
County Warning Area today...but struggling to produce much rain with dry easterly 
flow working against it. Rain is associated with well defined 500 mb short wave 
circulation that slowly gets absorbed into larger longwave trough 
tracking quickly out of the Pacific northwest. Not encouraged by the 
scattered looking nature of the regional radar returns of the rain 
area. Have a hard time accepting the likely probability of precipitation from the MOS 
guidance and will therefore keep it in the scattered/chance category 
overnight. 


Friday...not much in the way of deep forcing on Friday as main 500 mb 
short wave circulation now north of the area. But there is some lingering 
subtle 500 mb trofiness and surface dewpoints should climb into the upper 
60s...maybe low 70s. These dewpoints are already in southern Illinois and Don/T 
have far to travel. Soundings show some instability and can/T rule 
out some diurnal development. Continued moist srly flow will 
linger the small chance through Friday night. 


Saturday...frontal passage is expected during the morning and early 
afternoon. This is not a diurnally favorable time. 
Additionally...the main upper support is lifting well to the NE...deep 
into Canada...far away from southern WI. At the surface...the front begins 
to get pinched by high pressure and this is never a good situation 
for needed rainfall. Guidance has pulled back to chance values and 
this is clearly the way to go. Unfortunately...for those looking 
for rain over the next couple of days...it is not looking like 
anything beneficial is on the way. 


After frontal passage...high pressure begins to build in for another period 
dry weather that should last from Sunday through about next 
Thursday. 


&& 


Aviation...precipitation shield will lift through forecast area with short wave in 
north nctrl Illinois at 18z with mainly VFR ceilings/visibilities though some MVFR 
conditions with scattered heavier showers. Instability minimal so expect 
little if any thunder and have left out of tafs. Increasing 
southerly winds in the low levels will bring deeper low level moisture 
and return of MVFR ceilings later tonight with more light fog...with 
boundary layer mixing limiting potential for IFR conditions. 


&& 


Marine...south-southeast winds will approach Small Craft Advisory levels Friday 
afternoon and early evening. Will hold off on headline for now as 
forecast soundings indicate frequent gusts will be around 20 kts...with 
fetch building 2 to 4 foot waves. 




Mkx watches/warnings/advisories... 
WI...none. 
Lm...none. 
&& 


$$ 


Short/long term...05 
aviation/marine...09