Weather

246 
fxus63 klot 112004 
afdlot 


Area forecast discussion 
National Weather Service Chicago/Romeoville Illinois 
304 PM CDT Sat Oct 11 2008 


Discussion... 


247 PM...highs this afternoon 15+ degrees above normal for middle 
October and these highs will continue Sunday and Monday. High 
pressure across the eastern lakes and New England will slowly build 
south across the Middle Atlantic States Sunday night and Monday which 
will maintain southerly flow across the region into Monday night. 
Highs expected in the lower 80s Sunday and near 80 Monday...with 
potential for a bit more cloud cover...especially by afternoon. Only 
exception will be along the lake. With a lake breeze today...ugn/cgx 
holding near 70. Similar temperatures near the lake the next few days... 
though southerly flow should prevent lake breezes from moving too 
far inland...until just before sunset. 


As the high builds southeast across the middle Atlantic...system over 
the plains is forced northeast across the upper Midwest/Ontario 
Monday and Monday night. Trailing cold front sags southeast across 
the area and stalls/weakens as it bumps into the high. Chance of 
precipitation Monday night into Tuesday morning with this front appears to 
be decreasing with each run. Best chance of precipitation may be late 
Tuesday into Wednesday as a wave lifts out of the plains along this 
stalled front/boundary. Interesting that the European model (ecmwf) has been fairly 
consistent with this solution over the past few days and the GFS and 
the NAM...through 84 hours...are trending that direction and the Canadian 
also adds confidence to the European model (ecmwf). So have maintained high chance 
probability of precipitation Monday night into Tuesday then introduced low chance probability of precipitation 
Tuesday night into Wednesday...showing some clearing/timing by Wednesday 
afternoon as all models show precipitation ending quickly by that time. 


As noted a few days ago...temperatures middle week will be challenging. Should 
the front slide far enough south by Tuesday morning...lows could 
easily slide into the 40s and with a new surface low lifting north through 
the County Warning Area Tuesday night...temperatures could well be on the rise through night 
with Wednesday highs in the morning. But at this distance...have 
kept temperatures middle of the Road with no non-diurnal trends yet. Cms 


&& 


Aviation... 
1240 PM CDT 


Little or no change to previous forecast. With building middle level ridge over eastern 
Continental U.S. Through period...large surface hi pressure over lower Great Lakes will 
continue to be dominating influence on weather across northern Illinois/northwestern ind 
through Sunday...supressing cloudiness and keeping deeper moisture 
field off to S and west of area. As a result...cigs/vis will remain 
unrestricted. Light and variable winds at start of period will become 
prevailing from S during this afternoon...except for some lake breeze influence 
in vicinity of Lake Michigan during 20z-00z time frame when winds are expected to back 
to more of an Ely component...but remain relatively light. 


Merzlock 


&& 


Marine... 
253 PM CDT 


With high pressure continuing to slowly move off to the east and 
an area of low pressure slow to develop into the Central 
Plains...winds across Lake Michigan will vary between south to 
southeasterly flow today and tonight. This area of low pressure 
will slowly track northeast into the northern plains on Sunday and 
eventually into southwest Ontario Sunday night. In response to 
this...winds will shift to the south and maintain that direction 
through the end of the weekend. This low will continue northeast 
and then drag a cold front across the Great Lakes region on Tuesday. 


Rodriguez 


&& 


Lot watches/warnings/advisories... 
Illinois...none. 
In...none. 
Lm...none. 
&& 


$$