Another beautiful, warm, summer-like day is underway across the Chicago area with temperatures headed into the low to mid 80s. A cold front situated in western Iowa will move steadily east toward metro region arriving tonight, accompanied by showers and thunderstorms. The rain is not expected to begin in northeast Illinois until after sunset, with the first drops falling sometime between 8PM and Midnight.
There will be some subtle changes in today’s weather compared to yesterday. Cirrus clouds will decorate the sky for a change, but won’t be thick enough to block out much sun until late this afternoon. Winds will be stronger too, especially this afternoon, gusting at times to 28mph.
Rainfall totals tonight should range from 0.25″ to 0.60″. A few locations could see up to one inch of precipitation. Due to the progressive nature of the tonight’s rain event, significant flooding issues are not expected.
BELOW: Forecast maps for 4:30PM Saturday and 1:00AM Sunday.
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The nation’s largest fog machine? That would be Lake Michigan, at least for tonight. An expansive area of dense fog that’s been sitting over the southern end of the lake all day is starting to work its way onshore.
The fog is a by-product of moist air (dew point temperatures in the lower 60s) interacting with lake cooled air. As moist air drifts over the lake, it is cooled to the saturation point, which results in low level cloud or fog formation that hugs the surface. Another key ingredient for lake fog in this instance is light winds. Lake water temperatures are still on the chilly side, ranging from 48 degrees thirty miles offshore, to 61 degrees at Oak Street Beach.
Due to calm winds overnight, the fog is expected to persist until Tuesday morning. Inland locations may also experience some fog overnight.
BELOW: A Dense Fog Advisory continues for lakeshore communities in Cook, Lake(IL), Lake(IN), Porter and La Porte counties until 9AM Tuesday. Visibility will vary from 3 miles to 1/8th of a mile, and could drop to 100 feet or less at times near the Lake Michigan shoreline.
BELOW: A 40 mile wide blanket of dense fog that’s been sitting over the southern end of Lake Michigan all day continues to move onshore this evening.
This was the scence this morning in Momence, Illinois after strong thunderstorm winds toppled several trees on Thursday May 30, 2013.
The Storm Prediction Center is in the process of issuing Tornado Watch for much of Illinois just to the west of Chicago.
The Tornado Watch area may include some of Chicago’s west and southwest suburbs.
The threat of severe thunderstorms will be on the increase this afternoon as an upper air disturbance over Missouri lifts north into western Illinois by evening.
BELOW: The sections of Illinois most likely to see severe weather this afternoon and evening are outlined in red.
Clusters of showers and thunderstorms have been steadily building over northern Illinois since 10PM on this Memorial Day 2013. While these storms are expected to remain below severe limits, lightning, heavy downpours, and small pea sized hail are likely in some of the stronger storms overnight.
As of 11:45PM, there are no severe weather watches or warnings in the Chicago area.
Other than frequent cloud to ground lightning, locally heavy rainfall appears to be the only concern tonight. Rainfall totals through 7AM Tuesday are expected to range from 0.25″ to 2.00″ for most of the metro region. Rainfall totals of 1″ to 2″ may lead to some minor flooding. If rainfall exceeds 2″, flooding concerns will grow substantially.
A Flash Flood Watch is in effect for Kankakee, LaSalle and Grundy Counties through Tuesday morning.
BELOW: Radar image from 11:55AM 5/27
A few gusty thunderstorms may yet develop across the Chicago area this afternoon, but the threat of organized severe weather remains very low.
The Storm Prediction Center has removed Chicago from the “Slight Risk” categorization. For the Midwest, the main severe weather risk this afternoon is centered over Michigan, Ohio and eastern Indiana.
A strong warm front continues to slowly inch north through Chicago’s southern suburbs this afternoon.
At 1PM, temperatures north of the warm front are as cool as 39 degrees in Kenilworth and 40 degrees at the Waukegan Harbor. South of the front, temperatures are approaching summer-like levels in the 70s at Morris, Frankfort, Valparaiso and Michigan City.
This front may make it as far north as the Eisenhower Expressway and I-88 corridor in the next few hours before it starts to sag south once again. The warmup over the south suburbs will be short lived as temperatures will crash into the 40s once again by late this evening.
BELOW: 1PM Chicago area temperatures
A warm front approaching Chicago this morning will be accompanied by a complex of showers and thunderstorms that will produce locally heavy downpours. Monday morning commuters will be slowed by wet pavement, ponding water and reduced visibility.
Details on this morning’s rain include:
-The heaviest rain is expected to occur between 5AM and 10AM.
-Rainfall totals between .50″ and 1.00″ are likely.
-Although some thunder and lightning is expected, thunderstorms will be well below severe limits.
-Rain should exit the Chicago area by 1PM, with only a slight chance of a shower or thunderstorm redeveloping this afternoon.
BELOW: Despite a wet, gloomy and cool start to the day, conditions should improve dramatically this afternoon in time for the Cubs opener. Temperatures in the 40s this morning will rebound into the 60s later today with the passage of a warm front.
Moderate to heavy snow continues to fall across portions of central and southern Illinois late this afternoon. This area of snow has been very slow to move north into the Chicago area due to a very strong and dry northeast wind. This dry wind of Canadian origin is suppressing the snow to areas along and south of Interstate 80 as of 5PM. Eventually some light snow will reach into portions of northern Illinois. However, any accumulation over the metro area is expected to be very light.
Snowfall reports from across the Midwest as of 5PM include:
13.4″ O’Fallon, MO
8.7″ St. Louis, MO
7.0″ Lincoln, IL
6.5″ Champaign, IL
3.9″ Springfield, IL
1.2″ Moline, IL
A late season winter storm continues to churn it’s way across the county this morning. The storm will hit central Illinois as well as central Indiana the hardest with up to a foot of new snow by Monday morning.
At 11:20AM, heavy snow was being reported in Galesburg, St. Louis and Springfield, Illinois.
Travel conditions on Interstates 55, 57 and 65 south of Chicago are expected to rapidly deteriorate this afternoon. A Winter Storm Warning is in effect for much of central and southern Illinois including Champaign, Bloomington, Decatur and Springfield.
Locally, a period or two of light snow is expected across the Chicago area this afternoon and evening with relatively minor accumulation ranging from a dusting north, to perhaps as much as three to four inches near Kankakee.