Tornado and Hail in Illinois, April 2, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
600 PM CDT SUN APR 2 2006

.DISCUSSION FOR AFTERNOON ZFP/GRIDS...
320 PM CDT

MAIN FOCUS THIS AFTN HAS BEEN ON TIMING AND MODE OF CONVECTION AS
STG LO PRES NOW OVR SWRN IA CONTS TO LIFT ENEWD IN CLOSE AGREEMENT
WITH 12Z MODEL RUNS.  VIS SATLT LOOP SHOWS STRONGLY ARCED LINES OF
CONVECTION DVLPG RAPIDLY FROM LOW CENTER...ACRS NRN MO AND ON INTO
THE OZARKS.  GIVEN RAPID INCRS IN LTG AND ANVIL SPREAD WITH THESE
STMS...LOOKS LIKE BIG HULLABALOO WILL BE MOVING INTO WRN IL NXT
COUPLE OF HRS.  INITIAL...MORE SCTD ELEVATED STMS OVR NRN IL ATTM
HAVE PRODUCED SOME SMALL HAIL IN THE DEKALB AREA...AND THREAT THRU
5-6 PM LOOKS LIKE IT WILL BE CONFINED TO HAIL AS MODEL FCST
SOUNDINGS JUMP TOTAL TOTALS INTO UPR 50S BY 00Z ACROSS
RGN...SUGGESTING VERY STG INFLUX OF LLVL MOISTURE IS UNDERWAY. SFC
WARM FRONT WILL MAKE IT ABOUT INTO CENTRAL IL THUS TOR THREAT IS
SOMEWHAT HIER TO S OF CHI FA.  THIS IS ALSO SUPPORTED BY PROFILERS
AND VIS IMAGERY.  AFTER THIS ELEVATED CONVECTION MOVES
THRU...ACTIVITY LIKELY TO BE SUPRESSED UNTIL PRE FRONTAL LN MOVES
THRU DURG 02-05Z TIME FRAME...ACCOMPANIED BY MORE OF A DAMAGING WIND
THREAT AS MID LVL SPEED MAX NOW OVR NERN KS ROTATES ARND BASE OF UPR
LO OVR MN/NWRN IA...AND PUNCHES INTO MID MS VLY THIS EVENING. /SEE
SWODY1 FOR MORE DETAILS ON SVR THREATS/

LOW CENTER TO DEEPEN AS IT HEADS OFF THRU DETROIT AREA MONDAY.  STG
LLVL COLD ADVECTION BHD SYS IN ADDN TO TIGHTENING GRADIENT WILL
PRODUCE ANOTHER ROUND OF BLUSTERY WINDS MON-MON NGT.  FOR NOW WILL
HOLD OFF ON POTL WIND ADVSRY DUE TO INCRSG SVR THREAT THIS EVENING
AND ANTICIPATION OF WW. DONT WANT TO CLUTTER UP FCST WITH MULTIPLE
HEADLINES ATTM AND MOST SURROUNDING FO/S ALREADY BUSY WITH
CONVECTIVE WX.

LTL CHGS TO LATER PERIODS.  TRANQUIL WX PERIOD TUE-WED BEFORE NXT HI
AMP TROF MOVES WRN U.S. BY THUR AND HEADS EWD BY WEEKS END
SUGGESTING DECENT WARM UP LATTER HALF OF WEEK...ALONG WITH TURN TO
WETTER PATN AS UPR LO APCHS.

MERZLOCK

&&

.AVIATION DISCUSSION FOR 00Z TAFS...
600 PM CDT

VERY COMPLICATED FORECAST OVER THE NEXT 24 HRS DUE TO POTENTIAL FOR
+TSRA THIS EVENING.

CIGS HAVE MOSTLY SCT OUT AHEAD OF THE APPROACHING LINE OF TS.
CIGS WILL LIKELY BE QUITE VARIABLE...BOUNCING AROUND BETWEEN VFR
AND MVFR AS THE LINE APPROACHES...BUT SHOULD QUICKLY DETERIORATE TO
IFR INVOF TSRA.  LATEST SATELLITE AND RADAR TRENDS INDICATE THAT THE
LINE OF STORMS SHOULD REACH THE RFD TAF AREA BTWN 00Z AND 01Z AND
THE CHICAGO TAFS SITES BTN 01Z AND 02Z.  IN THE MEAN TIME...SCT
SHRA/TSRA SHOULD MOVE THROUGH NRN IL/NWRN IN.

GUIDANCE CONTINUES TO BRING THE SFC LOW ALONG THE WI/IL BORDER...
MOVING OVER SRN LAKE MICHIGAN BY 09Z. AHEAD OF THE LINE OF
TS...WINDS WILL REMAIN SELY...TURNING SWLY WITH THE PASSAGE OF THE
TS BTWN 00Z AND 06Z.  AS THE LOW MOVES N AND E OF THE REGION...WINDS
WILL QUICKLY SHIFT NWLY AND BECOME RATHER GUSTY.  WINDS ARE EXPECTED
TO REMAIN GUSTY OVERNIGHT AND THROUGH THE MORNING HOURS UNDER STRONG
COLD ADVECTION AND A TIGHTENING PRESSURE GRADIENT BEHIND THE EXITING
SFC LOW AND AN APPROCHING SFC HIGH.  WINDS WILL BEGIN TO SUBSIDE
DURG THE AFTERNOON HOURS AS THE SFC HIGH BUILDS INTO NRN IL.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...GALE WRNG LM MON AND TUES.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
430 PM CDT SUN APR 2 2006

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-
019-031030-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
430 PM CDT SUN APR 2 2006

THIS PORTION OF THE HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL
AND NORTHEAST ILLINOIS...AND NORTHWEST INDIANA.

.DAY ONE... TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS
ALL OF NORTHERN ILLINOIS AND NORTHWEST INDIANA.

THE PRIMARY SEVERE THREAT WILL BE LARGE HAIL FROM ELEVATED
THUNDERSTORMS EARLY THIS EVENING.

DEEPENING LOW PRESSURE WILL PASS ACROSS NORTHWEST ILLINOIS THIS
EVENING.  A WARM FRONT EXTENDING SOUTHEASTWARD FROM THIS LOW WILL
RETREAT NORTHWARD INTO CENTRAL ILLINOIS...AND THIS IS EXPECTED TO BE
THE FOCUS FOR MORE SURFACE ROOTED STORMS CARRYING A GREATER TORNADO
THREAT.

HOWEVER...COVERAGE OF STORMS ACROSS NORTHERN ILLINOIS AND NORTHWEST
INDIANA WILL BE INCREASING THIS EVENING...CULMINATING IN A PRE COLD
FRONTAL LINE OF STORMS DUE TO PASS ACROSS THE AREA FROM WEST TO EAST
BETWEEN 8 PM AND MIDNIGHT.  THESE STORMS WILL BRING A THREAT OF
DAMAGING WIND GUSTS ALONG WITH LARGE HAIL.

THE SEVERE WEATHER THREAT WILL END BY MIDNIGHT WITH THE PASSAGE OF
THE COLD FRONT.

.DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY

MORE THUNDERSTORMS ARE POSSIBLE WEDNESDAY NIGHT THROUGH THURSDAY
NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL LIKELY BE NEEDED LATER THIS EVENING.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

LMZ740>745-766-031030-
WINTHROP HARBOR IL TO MICHIGAN CITY IN-
LAKE MICHIGAN-
430 PM CDT SUN APR 2 2006

THIS PORTION OF THE HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS
AND INDIANA WATERS OF LAKE MICHIGAN.

.DAY ONE... TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN
TIP OF LAKE MICHIGAN...MAINLY BETWEEN 800 PM AND MIDNIGHT CDT.
STRONG GUSTY WINDS AND HAIL ARE THE PRIMARY THREATS.

.DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY

NORTHWEST GALES TO 35 KNOTS ARE EXPECTED MONDAY THROUGH MONDAY
NIGHT.

MORE THUNDERSTORMS ARE POSSIBLE WEDNESDAY NIGHT THROUGH THURSDAY
NIGHT.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

MERZLOCK