Damaging Winds in Illinois, June 8, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
647 AM CDT WED JUN 8 2005

.AVIATION DISCUSSION FOR 18Z TAFS...

WINDS AND THUNDERSTORM POTENTIAL REMAIN MAIN TAF CONCERNS.

THE OUTFLOW BOUNDARY HAS PUSHED INTO THE ROCKFORD AREA AND SCATTERED
CONVECTION HAS INITIATED AT 18Z.  THE TSRA ACTIVITY IS EXPECTED TO
REMAIN WIDELY SCATTERED OR IN SMALL CLUSTERS...SO WILL NOT GO
PREVAILING TS IN THE TAFS INITIALLY...VCTS SHOULD BE SUFFICIENT.
WINDS LOOKING TO GO GUSTY SW TO W FOR A COUPLE HOURS FOLLOWING THE
PASSAGE OF THE BOUNDARY BEFORE SETTING BACK TO GENERALLY SOUTHERLY.
EXCEPT INVOF TS...CIGS/VIS SHOULD REMAIN VFR INTO THE EVENING.
CONVECTIVE ACTIVITY SHOULD CONTINUE THROUGH SUNSET AND AFTER
MIDNIGHT...WINDS SHOULD GO NEAR CALM...AND WITH RESIDUAL LOW LEVEL
MOISTURE...LOOKING FOR MVFR VISIBILITIES IN HAZE INTO THE MORNING
HOURS.

...WILL KEEP PREVIOUS DISCUSSION FOR 12Z TAFS HERE AS TIME IS SHORT
DUE TO INCREASING TS ACTIVITY...

CONVECTION EARLIER IN THE NIGHT HAS PUSHED A WEAK OUTFLOW BOUNDARY
INTO THE FORECAST AREA EARLY THIS MORNING WITH 88D...LOCAL MESONET
AND METARS PLACING WIND SHIFT ROUGHLY FROM NORTH OF KRFD...TO NEAR
KPWK...TO ABOUT THE FORMER KCGX. BOUNDARY APPEARS TO HAVE STALLED
AND MAY BE DRIFTING BACK NORTH...WITH SOME SOUTHERLY COMPONENT TO
WIND FIELD AT ALL TAF SITES. QUESTION ARISES WITH WEAK GRADIENT AND
CONVECTIVELY DISTURBED LIGHT WIND FIELD THIS MORNING AS TO WHETHER
LAKE BREEZE/OUTFLOW WILL BE ABLE TO PUSH A BIT FARTHER INLAND THAN
OTHERWISE EXPECTED. NAM/GFS/RUC ALL INDICATE 950 HPA WINDS FROM
SOUTH AT 10-14 KTS TODAY...WHICH WOULD SUGGEST WEAK SOUTHEAST LAKE
BREEZE INTO LAKE CO IL...BUT REMAINING EAST OF KORD/KMDW. SOME
RECOVERY TO SOUTH FLOW BEHIND OUTFLOW ALREADY...SO FOR NOW WILL
CONTINUE IDEA OF NO LAKE BREEZE INTO KORD/KMDW TODAY.

ATTENTION THEN TURNS QUICKLY TO CONVECTIVE POTENTIAL. AIRMASS AGAIN
EXPECTED TO BE MODERATELY UNSTABLE TODAY...WITH SFC TEMPS AROUND 90
AND DEWPOINTS IN MID 60S AGAIN YIELDING SBCAPES IN 1800-2300 J/KG
RANGE AND LITTLE/NO CIN INDICATED BY FCST SOUNDINGS AFTER 18Z OR SO.
INITIALLY...LARGER SCALE FORCING APPEARS MARGINAL WITH WEAK SHORT
WAVE TROUGH MOVING ACROSS IL DURING THE MORNING...THOUGH A COUPLE OF
OTHER WEAK MID LEVEL TROUGHS APPROACHING IN SOUTHWEST FLOW ALOFT.
OTHER CONCERN IS LINEAR MCS MOVING SOUTHEAST OUT OF MN/IA THIS
MORNING. BEST INSTABILITY/SHEAR REMAINS TO OUR WEST OVER IA THROUGH
THE DAY...THOUGH WOULD NOT BE SURPRISED TO SEE TSTMS CONTINUE TO
PROPAGATE SOUTHEAST TOWARD NRN IL AS AIRMASS DESTABILIZES. MESO-ETA
(NAM) AND UCAR 4KM WRF BOTH BRING THIS ACTIVITY SOUTHEAST ACROSS
FCST AREA THIS AFTN...THOUGH BOTH APPEAR A LITTLE SLOWER THAN
CURRENT 88-D MOSAIC SHOWS. CONSIDERING EXPECTED
INSTABILITY...NAM/WRF SIGNALS AND POTENTIAL OUTFLOW BOUNDARY FOCUS
FROM BOTH ADVANCING MCS AND AFOREMENTIONED NE IL REMNANT...WILL
INDICATE VCTS IN TERMINALS THIS AFTN...AS EARLY AS 17Z AT KRFD BASED
ON MN MCS...AND AFTER 20Z CHI AREA TERMS FOR PEAK DIURNAL HEATING
HOURS. DAY SHIFT CAN FINE TUNE TIMING AND UPGRADE TO TEMPO OR
PREVAILING IF NEEDED. EXPECTING ANY ACTIVITY TO DIMINISH/MOVE
SOUTH/EAST OF TERMINALS THIS EVENING AS LLJ REFOCUSES NOCTURNAL
ACTIVITY BACK INTO THE PLAINS TO OUR WEST. LIGHT WIND
FIELD...SLIGHTLY HIGHER DEW POINTS AND POTENTIAL FOR WET GROUND FROM
ANY AFTN TSTMS SUGGESTS MORE OF A HZ POSSIBILITY TNGT AND HAVE
HINTED AT.

RATZER

&&

.DISCUSSION FOR MORNING ZONES/GRIDS...
CONVECTION FIRED UP OVER NW IN AND LOWER MI DURING THE OVERNIGHT
HOURS MOVING E. EARLIER MCS OVER NRN WIS HAS DISSIPATED FOR THE MOST
PART EXCEPT FOR SMALL CLUSTER OF ACTIVE STORMS WEST CENTRAL WIS.
HOWEVER OUTFLOW BOUNDARY SEEN IN MKX RADAR AND SFC OBS...DROPPING
SOUTH TOWARD NRN IL. LATEST RUC TRIES TO WASH THIS OUT RATHER
QUICKLY AND SLY FLOW TAKES OVER AGAIN. FEW STORMS TRYING TO FORM
ALONG AND N OF THE BOUNDARY BUT SEEM TO BE DYING AS QUICKLY AS THEY
FORM. WILL KEEP FORECAST DRY THROUGH THE MORNING.

AMS SHOULD HEAT UP INTO LOWER 90S AGAIN TODAY WITH SFC DEW POINTS IN
MID 60S. THIS WILL BE SIMILAR SCENARIO TO TUES WITH GOOD
INSTABILITY...WEAK SHEAR AND NO ORGANIZED LIFTING MECHANISM. EXPECT
DISORGANIZED WIDELY SCATTERED AFTERNOON TSTMS AGAIN JUST ABOUT
ANYWHERE. SSW LOW LEVEL WINDS SHOULD LIMIT LAKE BREEZE TO THE NORTH
SHORE AREA OF IL SIMILAR TO TUES...ALTHOUGH WIS OUTFLOW BOUNDARY MAY
ENHANCE THE LAKE BREEZE SOMEWHAT. THE LAKE BREEZE/REMNANTS OF WIS
OUTFLOW COULD BE FOCUS FOR MORE ORGANIZED STORMS. TRAILING VORT LOBE
ASSOCIATED WITH NEB SQUALL LINE COULD MOVE ACROSS IL THIS AFTERNOON
AND EVE TO ENHANCE TSTM CHANCES AS WELL. EXPECT STORM CHANCES TO
DIMINISH RAPIDLY AFTER DARK AS ACTION REFOCUSES OVER CENTRAL PLAINS.

THEN A SERIES OF DISTURBANCES MOVING ALONG NEARLY STATIONARY
BOUNDARY FROM PLAINS INTO THE GREAT LAKES THROUGH MONDAY. GFS
APPEARS TO BE THROWING A TROPICAL DISTURBANCE INTO THE MIX THIS
WEEKEND...MOVING IT FROM THE CENTRAL GULF COAST INTO THE LOW MS VLY
AND TN VLY. WILL KEEP TSTM CHANCES GOING THROUGH MON. PATTERN SHIFT
MON NIGHT/TUES STILL APPEARS TO BE ON TRACK WITH DRYING FOR MID
WEEK.

ALLSOPP

&&

.LOT...WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LK MI...NONE.

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1140 AM CDT WED JUN 8 2005

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-
019-091100-
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-
1140 AM CDT WED JUN 8 2005

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

.DAY ONE... TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON.
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP EARLY THIS AFTERNOON
AND CONTINUE INTO THE EARLY EVENING HOURS. THE MAIN THREATS WITH
THESE STORMS ARE DAMAGING WINDS AND HAIL. THERE IS ALSO THE
POTENTIAL FOR HEAVY DOWNPOURS WHICH MAY RESULT IN SOME LOCALIZED
FLOODING OF ROADWAYS AND LOW LYING AREAS THIS AFTERNOON AND EARLY
EVENING.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS AGAIN THURSDAY AND
FRIDAY. THUNDERSTORMS ARE POSSIBLE THROUGH MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MIGHT BE NEEDED TODAY THROUGH FRIDAY.

&&

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

LMZ740>745-766-091100-
WINTHROP HARBOR IL TO MICHIGAN CITY IN-
LAKE MICHIGAN-
1140 AM CDT WED JUN 8 2005

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

.DAY ONE... TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON.
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP EARLY THIS AFTERNOON
AND CONTINUE INTO THE EARLY EVENING HOURS. THE MAIN THREATS WITH
THESE STORMS ARE DAMAGING WINDS AND HAIL.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS AGAIN THURSDAY AND
FRIDAY. THUNDERSTORMS ARE POSSIBLE THROUGH MONDAY.

&&

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