Winter Storm Watch has changed to a Winter Weather Advisory. A Winter Weather Advisory is usually issued when snowfall is expected to be greater than four inches and less than seven inches in a 24-hour period — and beginning within the next 12 hours. The timing of the changeover from rain to snow is a strong factor in forecasting whether Chicagoland will get less than seven inches of snow or get seven inches or more of snow.
URGENT – WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE CHICAGO IL
1110 AM CST THU FEB 23 2012
…RAIN TO CHANGE TO A WET SNOW AND BE HEAVY AT TIMES TONIGHT..
.RAIN WILL CHANGE TO A WET SNOW FROM WEST TO EAST ACROSS THE AREA
THROUGH THIS EVENING AS A COMPLEX LOW PRESSURE EVOLVES ACROSS
SOUTHERN ILLINOIS AND INDIANA. THE SNOW WILL BE HEAVY AT TIMES
THIS EVENING…ESPECIALLY IN THE HOURS JUST AFTER CHANGEOVER TO
SNOW. SOME ACCOMPANYING THUNDER IS POSSIBLE…AND WHERE THIS OCCUR
THERE WILL BE LOCALIZED HIGHER AMOUNTS. THE MOST FAVORED AREA TO
SEE LOCALIZED HIGHER AMOUNTS GREATER THAN SIX INCHES IS ACROSS
DEKALB…KANE…DUPAGE…AND NORTHERN COOK COUNTIES. THE SNOW WILL
GRADUALLY TAPER FROM WEST TO EAST ACROSS THE AREA LATE TONIGHT
THROUGH FRIDAY MORNING.
LAKE IL-DUPAGE-COOK-WILL-
INCLUDING THE CITIES OF…WAUKEGAN…WHEATON…CHICAGO…JOLIET
1110 AM CST THU FEB 23 2012
…WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO
9 AM CST FRIDAY…
THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW…WHICH IS IN EFFECT FROM 6 PM THIS
EVENING TO 9 AM CST FRIDAY. THE WINTER STORM WATCH IS NO LONGER IN
EFFECT.
* TIMING…RAIN WILL CHANGE TO A WET SNOW ACROSS FAR NORTHEAST
ILLINOIS…INCLUDING CHICAGO…EARLY THIS EVENING. SNOW MAY
BECOME HEAVY AT TIMES DURING THE EVENING AND EARLY OVERNIGHT
HOURS…BEFORE GRADUALLY TAPERING IN INTENSITY INTO EARLY FRIDAY
MORNING.
* ACCUMULATIONS…FOUR TO SEVEN INCHES…WITH THE HIGHEST AMOUNTS
ACROSS DUPAGE…NORTHERN COOK…AND SOUTHERN LAKE COUNTIES.
* MAIN IMPACT…HEAVY WET SNOW MAY FALL AT RATES GREATER THAN AN
INCH PER HOUR AFTER 8 PM. THIS WILL LIKELY RESULT IN QUICK
ACCUMULATION OF WET SNOW ON ROADS…RESULTING IN SLIPPERY AND
POTENTIALLY HAZARDOUS TRAVEL CONDITIONS.
* OTHER IMPACTS…IN ADDITION TO ACCUMULATION AND SLIPPERY
TRAVEL IMPACTS…STRONG WINDS WILL RESULT IN WIND WHIPPED
HEAVY WET SNOW CAUSING SEVERELY REDUCED VISIBILITIES THIS
EVENING THROUGH TONIGHT. DUE TO THE HIGH LIQUID CONTENT OF THE
SNOW…THOSE WITH HEALTH CONCERNS SHOULD USE CAUTION WHEN
SHOVELING.
PRECAUTIONARY/PREPAREDNESS ACTIONS…
A WINTER WEATHER ADVISORY FOR SNOW MEANS THAT PERIODS OF SNOW
WILL CAUSE PRIMARILY TRAVEL DIFFICULTIES. BE PREPARED FOR SNOW
COVERED ROADS AND LIMITED VISIBILITIES…AND USE CAUTION WHILE
DRIVING.
NWS FORECAST (as of 11:30 a.m. Thursday, February 23, 2012) …
This Afternoon: Rain before 3pm, then rain, possibly mixed with snow. Temperature falling to around 37 by 5pm. East wind between 10 and 15 mph, with gusts as high as 20 mph. Chance of precipitation is 90%. Little or no snow accumulation expected.
Tonight: Rain, possibly mixed with snow, becoming all snow after 9pm. The snow could be heavy at times. Some thunder is also possible. Low around 30. North northwest wind around 15 mph, with gusts as high as 30 mph. Chance of precipitation is 100%. New snow accumulation of 4 to 8 inches possible.
Friday: Snow, mainly before 9am. High near 36. Northwest wind around 15 mph, with gusts as high as 25 mph. Chance of precipitation is 100%. New snow accumulation of less than one inch possible.
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