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Area Forecast Discussion (AFD)

Issued by Chicago, IL (LOT)

FXUS63 KLOT 231720

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1220 PM CDT Fri Aug 23 2019

1220 PM CDT

Through Sunday...

Dry and cooler conditions will continue through Saturday, and 
generally for the weekend, though with plentiful sunshine.  

Inland clouds, with enhanced convergence in southern Wisconsin and 
northern Illinois and low coverage elsewhere, will shift inland 
and dissipate later this afternoon and evening. 

Otherwise, large surface high pressure over the upper Great lakes 
will slowly slide east this weekend, to be centered over New England 
by Sunday morning.  Conditions across the local area will be 
unseasonably cool and dry, with highs on Saturday in the middle to 
upper 70s and upper 70s to lower 80s for Sunday. Given the 
continental-polar origin of the associated air mass, dewpoints will 
also be relatively low, mainly in the middle 50s. Overall, this is 
expected to result in pleasant weather with ample sunshine across 
the area. As the high shifts and winds turn more solidly
southeast, the focus of higher waves will shift to the northeast 
Illinois shoreline. 



321 AM CDT

Sunday night through Thursday...

For Sunday night and into early next week, the longer range model 
guidance remains in good agreement with a well defined southern 
stream shortwave lifting through the Missouri Valley and into 
central Illinois late Sunday night and Monday morning and lift 
across southern lake Michigan and into Lower Michigan Monday night. 
Also, a northern stream short wave is expected to track across 
Northern Plains/Canadian border area while dragging a cold front 
across the Upper Mississippi Valley.  During this period from Sunday 
night through Tuesday, the large sfc high will move off the New 
England coast.  This will set up a period of unsettled weather 
across the region, with periods of showers and thunderstorms 
expected as a return flow of deep layer moisture sets up as the sfc 
high moves east and the double-barreled system approaches from the 
west and crosses the region.  Conditions should settle down as the 
system moves off to the east and high pressure builds out of the 
Central Plains and across the Middle Mississippi Valley. Another 
northern stream shortwave rotating around the base of a deep upper 
low expected to develop over Central Canada by mid week could bring 
the next chance for some scattered showers or thunderstorms for 
Wednesday afternoon into Wednesday night.


For the 18Z TAFs...

Northeast winds in excess of 10+ kt will continue through 01-02Z. 
Area VWPs support occasional gusts up to 20 kt. Expect VFR clouds to 
stream off the lake, with possible broken conditions north of the 
Chicago terminals and toward KRFD. High pressure gradually building 
into the Upper Great Lakes will continue to result in some form of 
east winds through the period. There will be fluctuation in wind 
direction between mainly 030 and 060 degrees at Chicago airports 
today. Winds will gradually ease in the 00Z- 03Z time similar to 
last evening. 

Winds will veer to be more southeasterly to start the day Saturday, 
but then shift back to an east-northeast with some aid off the 
lake in the afternoon. Speeds again will be back above 10 kt.



IL...Beach Hazards Statement...ILZ006-ILZ014 until 4 AM Saturday.

IN...Beach Hazards Statement...INZ001-INZ002 until 4 AM Saturday.

LM...Small Craft Advisory...nearshore waters 
     until 4 AM Saturday.