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Area Forecast Discussion (AFD)

Issued by Chicago, IL (LOT)

FXUS63 KLOT 230712

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

212 AM CDT

Through Tonight...

Pleasant and quiet apparent weather for the area today, although 
breezy northeast winds near Lake Michigan will continue dangerous 
swimming conditions due to high waves and rip currents.

Satellite water vapor imagery this morning reveals subsidence 
and drying in the mid and even lower levels moving in over the 
Lower Great Lakes from the north. Resulting surface high pressure 
of 1025 mb over central Ontario this morning will gradually expand
southward through the day. Much of the CWA and Lake Michigan will
remain in the gradient around this, with a tightened clockwise 
flow and thus northeast winds with occasional gusts to 20 mph. 
Near the lake front, the sustained winds at times will approach 20
mph, and these will help to sustain the ongoing high wave action.
While this is not to the level of lakeshore flooding, some higher
waves can cause dangers for those walking near the lakeshore. The
perpendicular flow to much of the shore will continue the rip 
current risk and wind direction and speed look enough for this
threat to go into this evening. There may be a brief lull late 
this morning in wave action due to slightly veered winds, but that
looks temporary.

Otherwise today should realize high temperatures at or a couple 
degrees below yesterday given the cold advection at the top of the
mixed layer that has occurred in the past 12 hours and will 
continue through midday. With a clear sky by tonight and weakening
flow, though maybe not completely calm until late, low 
temperatures look to drop into the lower 50s in outlying areas and
suspect a few of the typical cool spots touch upper 40s.



151 PM CDT

Saturday through Thursday...

Surface high pressure is expected to dominate across the Great
Lakes region through much of the upcoming weekend. Overall, this 
is expected to result in pleasant (early autumn-like) weather 
across the area. High temperatures are expected to be mainly in 
the 70s, with overnight lows in the 50s Saturday night. Winds 
will primarily be onshore, especially Saturday. 

Early next week forecast guidance continues to be in good 
agreement with a well defined mid/upper level trough digging over
the Upper Midwest. With an associated surface frontal trough 
likely to approach the area later Monday and Monday night, we will
have some decent chances for some showers and thunderstorms. 
However, these chances should abate quickly during the day Tuesday
as the surface front shifts east-southeast of the area. This 
looks to result in mainly dry and pleasant weather with seasonal
temperatures again for much of Tuesday and at least Wednesday. 



For the 06Z TAFs...

For the Chicago area TAFs today the main story are northeast
winds, with high confidence in these being 10+ kt from 14Z-01Z.

High pressure gradually building into the Upper Great Lakes will
continue northeast winds over the area. Early this morning there 
is 20-25 kt flow just 2,000 ft aloft per radar VWP. There will be
some fluctuation in wind direction between mainly 030 and 060 
degrees at Chicago airports today, but speeds should be fairly 
steady around 12 kt from mid-morning through afternoon. There will
likely be occasional gusts given the winds just off the deck, 
although those will ease some through the morning resulting in 
gusts largely if not entirely below 20 kt at ORD and MDW. Winds 
will gradually ease in the 00Z-03Z time similar to last evening. 



IL...Beach Hazards Statement...ILZ006-ILZ014 until 7 PM Friday.

IN...Beach Hazards Statement...INZ001-INZ002 until 7 PM Friday.

LM...Small Craft Advisory...nearshore waters 
     until 10 AM Friday.