Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS63 KLOT 191915

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
215 PM CDT Mon Mar 19 2018

127 PM CDT

Through Tuesday...

Breezy east-northeasterly winds are expected to continue through
the period as low pressure tracks eastward well south of the area
and high pressure remains dominate over Ontario tonight into 
Tuesday. This northeasterly flow will transport a colder airmass 
over the area for Tuesday resulting in cooler high temperatures 
area-wide. High temperatures Tuesday are expected to be in the 
low to mid 40s well inland, but likely only in the mid to upper 
30s closer to the lake under partly cloudy skies. Conditions will
feel even cooler than these values, however, as winds continue to
gust up to 25 to 30 mph during the day. 



214 PM CDT

Tuesday night through Monday...

Overview...Temperatures look to be slightly cooler to near normal 
through the extended.  I have uncertainty about how the Friday 
night/Saturday system will evolve, but most if not all of the 
forecast area should see precip.

Cooler than normal conditions continue Tuesday night with moderating 
temperatures Thursday as an upper level ridge begins to push east. 
Quiet and near normal temperatures continue Friday under a broad 
high pressure ridge.  

The next low forms over the Southern Plains Friday night, and the 
low weakens as it passes over the Mid Mississippi Valley Saturday 
night.  An upper level wave passes over the region while the low 
passes to our south, bringing precip to the region.  Guidance 
differs on how far northeast the precip shield will reach, and I'm 
expecting mainly rain Saturday.  There could be a period of heavier 
rain Saturday evening before the forcing and precip shift east.  The 
ECMWF suggests precip may linger into Sunday morning, while the GFS 
has the system falling about quicker. 



For the 18Z TAFs...

There are no major weather concerns at the terminals through the
period. Overall, expect VFR conditions with gusty east-
northeasterly winds through the period as low pressure tracks
eastward south of the region.



214 PM CDT

Northeast times more due north or due east...will prevail 
across Lake Michigan through the next seven days. 

Speeds to 30 kt are expected 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 waves will continue through 
Tuesday  night. The highest wind and wave time in the Illinois and 
Indiana nearshore looks to be tonight and Tuesday during the day. 

Another low pressure is expected to move eastward across the middle 
of the country, likely south of the lake, over the weekend weekend. 
This again will strengthen east or northeast flow.



LM...Small Craft Advisory...IN nearshore waters until 9 AM Wednesday.

     Small Craft Advisory...IL nearshore waters until 9 AM Wednesday.




National Weather Service Glossary of Abbreviations