fxus63 klot 191104 

Area forecast discussion 
National Weather Service Chicago/Romeoville, Illinois 
604 am CDT Mon Mar 19 2018 

Short term... 
348 am CDT 

Through tonight... 

Another day of generally quiet weather expected today, though 
becoming rather breezy by late morning. 

As low pressure tracks through southern Missouri later this morning 
and then continues into the Ohio Valley, while strong high pressure 
remains parked over central Canada, northeast winds will be in the 
increase through the day. By late morning or early afternoon, winds 
should increase to 15 to 25 mph with occasional gusts as high as 30 
to 35 mph. While temperatures inland should remain relatively 
moderate, with highs in the upper 40s to lower 50s under layered 
clouds and filtered sunshine, the Lakefront will remain cooler as 
the northeast winds draw lake-cooled air onshore. Lakefront 
locations should see temps top out in the low 40s. Strong, gusty 
northeast winds could cause some issues with spray impinging on the 
immediate Lakefront areas. Blustery conditions should remain into 
the evening and overnight as the low continues through the Ohio 
Valley. Temperatures overnight tonight are expected to drop into the 
upper 20s. When combined with 10 to 15 mph winds overnight, 
apparent temperature will be in the middle teens. 


Long term... 
348 am CDT 

Tuesday through Sunday... 

Blustery conditions should continue through Tuesday as northeast 
winds continue with highs ranging from the middle 30s across nern Illinois 
to the lower 40s well inland. Some moderation for much of the area 
is expected for midweek as a ridge of high pressure extends from 
Hudson Bay to along the Mississippi River. However, persistent flow 
off of Lake Michigan should keep Lakefront locations a bit cooler 
than inland areas. The next significant chance for precipitation is 
still not expected until Friday and through the weekend. The longer 
range guidance remains consistent in amplifying the upper level 
pattern by the end of the week, with an area of low pressure quickly 
tracking across the Central Plains late Friday. However, there are 
still significant differences among the models as to the exact track 
and intensity of the system into next weekend. The general model 
consensus at this point does indicate the decent potential for 
precipitation as a mid-level shortwave tracks across the region, the 
models diverge significantly on the track of the associated surface 
low moving through central Illinois. In general, thermal profiles 
generally support rain or a rain/snow mix across the area, with the 
greatest potential for any snow occurring during the diurnally 
cooler nighttime periods. 


for the 12z tafs... 

The aviation forecast for today and tonight centers on wind speeds 
as the critical element. Northeast winds will increase steadily 
through mid-afternoon and then remain at their peak through the 
evening. Frequent gusts of 22-25 kt are expected this afternoon 
and evening, with sporadic gusts of 26-29 kt likely 22z-03z. Gusts 
may become less frequent overnight but will increase again 
Tuesday morning. 

Confidence in wind speeds is medium-high. Confidence in wind 
direction is high, though some variability between 020-060 degrees 
is likely during the peak gust time late this afternoon into 

Despite flow off the lake, low clouds are presently not expected 
for Chicago sites due to dry air upstream and not enough cool air 
for lake effect cloud generation. It is possible few/scattered 
3000 ft or so clouds could be seen tonight into Tuesday morning. 



115 am CDT 

Northeast winds...at times more due north or due east...will 
prevail across Lake Michigan through the entire week. 

Speeds will be on the increase early this morning as the lake 
finds itself between strong high pressure to the north and passing 
low pressure well to the south. Small craft criteria winds and 
shortly after waves are expected to develop along the Illinois 
shore this morning and Indiana shore by mid-afternoon. The 
highest wind and wave time in the Illinois and Indiana nearshore 
looks to be tonight and Tuesday during the day. This will be a 
fairly long lasting event, with gusty winds and high waves 
lasting through Wednesday morning, and probably some 3-5 ft waves 
lingering even longer into Wednesday. 

Another low pressure is expected to move eastward across the 
middle of the country, likely south of the lake, late in the 
week/early weekend. This again will strengthen east or northeast 



Lot watches/warnings/advisories... 
Lm...Small Craft Advisory...lmz740-lmz741-lmz742...9 am Monday to 9 
am Wednesday. 

Small Craft Advisory...lmz743-lmz744-lmz745...3 PM Monday to 9 
am Wednesday. 



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