Winter Storm in Illinois, March 2 to 3, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
240 AM CST SAT MAR 2 2002

BAND OF PRECIPITATION DRIVEN SOLEY BY WARM ADVECTION CONTINUES TO
EDGE EAST ACROSS MIDDLE/EASTER PORTIONS OF CWFA THIS MORNING.  THIS
HAS BEEN DROPPING 3-5 INCH AMOUNTS IN A FEW HOURS.  MEANWHILE
DYNAMICALLY DRIVEN SNOWS HAVE BEEN SHOWING AN INCREASE FOM EASTERN
KANSAS TO IOWA.  IT PROMISES TO BE AN INTERESTING DAY FOR OUR AREA.

IN THE SHORT TERM MODEL FORECASTS SUGGEST THE LOW LEVEL JET DRIVEN
PRECIP TO CONTINUE EAST AND DIMINISH BEFORE MID MORNING LEAVING MUCH
OF CWFA IN RELATIVE DRY SLOT WITH WEAK LIFT OR EVEN SUBSIDENCE.
THEN THERE ARE SUBTLE SUGGESTIONS OF A RENEWED PUSH OF WARM
ADEVCTION DRIVEN SNOWS TO FAR WESTERN PORTION OF CWFA AS 850 MB LOW
JUST HANGS AROUND THROUGH MIDDAY.  MUCH OF REST OF AREA SHOULD
EXPERIENCE A PERIOD OF RELATIVE CALM WITH LIGHT PRECIPITATION OF
LIQUID OR MIXED FORM FROM AROUND DAYBREAK UNTIL MIDDAY.  STRONG LIFT
DRIVEN MORE BY DYNAMICS KICKS IN FROM WEST TO EAST DURING THE
AFTERNOON
AND SHOULD BE ENOUGH TO QUICKLY TURN PRECIPITATION BACK TO SNOW AS
ATMOSPHERE BEGINS TO RAPIDLY COOL.  SNOW TO PERSIST INTO THE NIGHT
PERIOD OF AREA WITH THE AVN MORE SUBSTANTIAL THAN THE FASTER ETA ON
ACCUMULATIONS AFTER 6 PM EASTERN IL AND NORTHWEST IN. WILL SPLIT THE
DIFFERENCE REGARDING ADDED SNOW. IN ANY CASE...WIND WILL BECOME A
FACTOR OVERNIGHT.  ETA 1000-950 GEOSTROPHIC WIND REACHES 60 KNOTS
AND THETA/WIND SPEED PROFILES SUGGEST MIXING DOWN 40 KNOTS GUSTS
ANYWAY.  EVEN THOUGH (EXCEPT IN FAR NORTHWEST COUNTIES) MUCH OF THE
CURRENTLY FALLING SNOW MIGHT GET WET ENOUGH TODAY TO CRUST & PREVENT
DRIFTING WHEN IT COOLS,  FRESH SNOW AFTERNOON AND EVENING PLUS WIND
WILL MAKE FOR NEAR BLIZZARD CONDITIONS DEVELOPING OVERNIGHT. PERHAPS
A BLIZZARD WARNING WILL EVENTUALLY BE NEEDED FOR SOME AREAS.
HOWEVER AT THIS TIME WILL UPGRADE THE ENTIRE HEAVY SNOW WARNING TO A
WINTER STORM WARNING AND EXTEND IT INTO TONIGHT AND EMPHASIZE 1)
THAT THE CALM CONDITIONS SOME MAY BE EXPERIENCING NOW ARE JUST A
LULL AND 2) THE BLOWING/DRIFTING SNOW OVERNIGHT. ALSO WINDS CHILLS
BY MORNING NEAR 20 BELOW. COOORD WITH LINCOLN AND BASED ON ALREADY
4-5 INCHES IN NORTHWEST LIVINGSTON COUNTY, WILL ADD THEM TO THE
WARNING.  BASED ON TRACK OF SURFACE LOW, ADDITIONAL ACCUMULATIONS
THIS AFTERNOON AND EVENING IN THE 3-5 INCH RANGE ARE POSSIBLE
ESPECIALLY EASTERN IL PORTIONS OF THE CWFA. HOWEVER EXPECT
THE FIRST ROUND OF SNOW TO BE ABOUT OVER AT RELEASE TIME AND SINCE
CURRENT ADVISORY IS IN EFFECT FOR JUST OVERNIGHT, WILL HAVE NO
HEADLINES FOR SOUTHEAST COUNTIES.  SNOW AND BLOWING SNOW ADVISORY
LIKELY TO BE NEEDED BY LATE AFTERNOON BUT DO NOT EXPECT A WARNING
EVENT TO MATERIALIZE SO NO WATCH WILL BE ISSUED.

LAKE EFFECT COULD BE AN ISSUE BRIEFLY FOR NORTHWEST INDIANA COUNTIES
TOWARD MORNING, BUT WHEN THE AIR REALLY GETS COLD ENOUGH FOR BEST
LAKE EFFECT, TRAJCTORY WILL BE EAST OF OUR CWFA.

MODELS STILL ON TRACK TO BRING NEAR -25 850 MB AIR OVER US BY MONDAY
MORNING AND HIGH BUILDING TO SOUTH WITH RIDGE LINE OVER CWFA.  SOME
GRADIENT FORECAST AND WINDS MAY NOT COMPLETELY DECOUPLE BUT ANY WEST
WINDS
COMING OFF SNOW COVER SHOULD JUST BRING COLDER AIR IN ANYWAY.
SUBZERO READINGS EXPECTED MOST AREAS AND RFD SHOULD EASILY THREATEN
THEIR -6 RECORD. ORDS IS -12.

HAVENT HAD A CHANCE TO LOOK AT EXTENDED, SO NO CHANGES LIKELY.

.CHI...WINTER STORM WARNING TODAY AND TONIGHT GARY-PONTIAC
       NORTHWARD
       GALE WARNING LAKE MICHIGAN

KAPLAN

ILZ003>006-008-010>014-019>023-032>033-039-INZ001>002-010>011-019-
021800-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
600 AM CST/700 AM EST SAT MAR 2 2002

FOR NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA...

...SNOW...BLOWING SNOW AND BITTER COLD...

FOR TODAY INTO TONIGHT THERE WILL BE SNOW OF VARYING INTENSITY WITH
ADDITIONAL ACCUMULATIONS IN THE 3 TO 5 INCH RANGE GENERALLY NORTHWEST
OF A GARY TO PONTIAC LINE. OVER EASTERN PORTIONS OF THIS AREA...FROM
CHICAGO SOUTH TO PONTIAC...THE HEAVIEST SNOW IS EXPECTED IN THE
AFTERNOON AND EARLY EVENING. SOUTHEAST OF THE GARY TO PONTIAC LINE WET
SNOW MAY ACCUMULATE A COUPLE INCHES EARLY THIS MORNING THEN THERE WILL
BE A BREAK UNTIL LATE TODAY WHEN SNOW WILL REDEVELOP AND CONTINUE INTO
THE NIGHT. 3 TO 5 INCHES MAY ACCUMULATE FROM THAT EPISODE.

OVERNIGHT...ABOUT THE TIME THE SNOW DIMINISHES TO FLURRIES...STRONG
NORTHWEST WINDS 20 TO 30 MPH AND GUSTY WILL KICK IN.  THIS WILL CAUSE
CONSIDERABLE BLOWING AND DRIFTING SNOW WITH NEAR BLIZZARD CONDITIONS
IN RURAL AREAS. TRAVEL WILL BECOME VERY DIFFICULT OVERNIGHT.

AS IF THAT IS NOT ENOUGH...THE STRONG WINDS WILL BE BRINGING IN
BITTERLY COLD ARCTIC AIR. BY SUNDAY MORNING WIND CHILLS WILL BE AS LOW
AS 20 BELOW IN PARTS OF NORTHERN ILLINOIS. BY MONDAY MORNING ACTUAL
TEMPERATURES WILL LIKELY BE BELOW ZERO ACROSS THE AREA.

THIS MORNING A TROUGH OF LOW PRESSURE LIES FROM NORTHERN ILLINOIS TO
SOUTHERN MISSOURI.  AS THE TROUGH MOVE EAST SLOWLY TODAY...A COUPLE OF
WAVES OF LOW PRESSURE WILL MOVE UP THE FRONT...BEFORE A MAJOR LOW
DEVELOPS OVER SOUTHERN ILLINOIS THIS AFTERNOON...AND DEEPENS AS IT
HEADS FOR LOWER MICHIGAN TONIGHT.

NO SEVERE THUNDERSTORMS ARE EXPECTED TODAY OR TONIGHT.

KAPLAN