Severe Thunderstorm Warning 54, NWS Northern Indiana

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
313 PM EST MON JUN 11 2001

TWO MAIN FCST PROBLEMS THIS AFTN. FIRST IS CONVECTION FIRING ON OLD
BOUNDARY IN SRN CWA THIS AFTN. SECOND IS MCS OVR MN/IA AND ITS
MOVEMENT TONIGHT. MODELS HAVE SIGNIFICANT DIFFERENCES WRT TRACK OF
CONVECTIVE S/W TONIGHT. AVN AND RUC40 HAVE BEEN FCSTG THIS AFTNS
CONVECTION OVR CWA...BUT BOTH ALSO TRYING TO MOVE CONVECTIVE
COMPLEX EAST AS UPPER RIDGE BUILDS IN FROM SOUTH. NGM DIVES MCS SE
TONIGHT ALONG FAVORABLE THICKNESS LINES...AND ETA IS IN BETWEEN
WITH COMPLEX MOVING INTO ERN MI. WL BE TRYING TO MESH MODELS AND
REMOTE SENSING DATA INTO FCST FOR FIRST TWO PERIODS.

BEGINNING WITH THE BOUNDARY THIS AFTN...IMPRESSIVE INSTABILITY WITH
LAPS AND GOES SOUNDINGS SHOWING CAPES IN EXCESS OF 4000 J/KG AND
LI/S NEAR -10. SOUNDINGS ALSO SHOWING CAP ALMOST GONE AND HENCE
CONVECTIVE DEVELOPMENT PER 88D/S. WITH HIGH INSTABILITY AND
MOISTURE...BOUNDARY SHOULD REMAIN ACTIVE FOR MOST OF EARLY EVENING
HOURS.

FOCUS SHIFTS TO MCS OVR MN CONTS TO BE IMPRESSIVE WITH RAPID
DEVELOPMENT ON SRN BOUNDARY AS HIGH INSTABILITY AND LOW LEVEL THTA E
AIR ADVECTS IN. 18Z SOUNDINGS IMPRESSIVE WITH INSTABILITY AND
INSTABILITY/MOISTURE AXIS LIES FM MN TO INDIANA. FAVORED THICKNESS
PATTERNS ALSO INDICATE MCS TO TAKE A TURN SOUTHEAST AND DIVE INTO
INDIANA. NEGATIVE FACTOR REMAINS UPPER LEVEL RIDGE AND ITS IMPACT.
AS MENTIONED...RUC40 AND AVN TRYING TO BUILD RIDGE FROM SOUTH
TONIGHT BUT ETA AND NGM ALLOW STRONG COMPLEX TO MOVE SOUTHEAST AND
IMPEDE ITS NWRD PROGRESS. WITH SUCH A MASSIVE SYSTEM...LEANING
TOWARD THE ETA/NGM SOLUTIONS WITH ARRIVAL INTO NRN CWA AROUND
MIDNIGHT AND SRN CWA WELL AFTER MIDNIGHT. WL KEEP POPS IN THE CHC
CATEGORY DUE TO UNCERTAINTY WITH TRACK...BUT HIGHER THAN FWC. WL
ALSO HAVE MORNING MENTION OF THUNDER TO ACCOUNT FOR EXITING SYSTEM.

REMAINDER OF SHORT TERM FCST TO SEE RIDGE BUILD AND MCS ACTIVITY
MOVING AROUND RIDGE NORTH OF FA. DO NOT PLAN TO INTRODUCE POPS BACK
INTO FCST FOR TUE AND WED WITH RIDGE OVERHEAD...BUT AGAIN...IF
BOUNDARIES EXIST AND CAN OVERCOME CAP IN AFTN...SCT CONVECTION
POSSIBLE. NOT MANY CHANGES TO EXTENED. GENERALLY WL FOLLOW HPC
GUIDANCE. WEAK FRONT SUN AND MON BUT CHC/S TOO SMALL FOR ADDITION
RIGHT NOW.

.IWX...NONE.

LASHLEY

INZ003>009-012>018-020-022>027-032>034-MIZ077>081-OHZ001-002-004-005-
015-016-024-025-120000-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1245 PM EST MON JUN 11 2001

...SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON AND AGAIN TONIGHT...

THE STORM PREDICTION CENTER HAS INDICATED A SLIGHT RISK FOR SEVERE
THUNDERSTORMS THIS AFTERNOON AND TONIGHT OVER NORTHWEST
INDIANA AND SOUTHWEST LOWER MICHIGAN. THE SLIGHT RISK
AREA IS ROUGHLY ALONG AND WEST OF A LINE FROM COLDWATER MICHIGAN TO
PERU INDIANA. THE PRIMARY THREAT FROM THESE THUNDERSTORMS WILL BE
DAMAGING WIND. HEAVY RAINFALL IS ALSO POSSIBLE.

THE ATMOSPHERE WILL BE VERY UNSTABLE THIS AFTERNOON...BUT WARMER AIR
IN THE MIDDLE ATMOSPHERE WILL ACT TO PROHIBIT THUNDERSTORM
DEVELOPMENT. IF THIS WARMER AIR CAN BE OVERCOME...STRONG TO SEVERE
THUNDERSTORMS WILL BE POSSIBLE LATE THIS AFTERNOON.

A LARGE THUNDERSTORM COMPLEX IN THE UPPER MIDWEST THIS AFTERNOON WILL
BEGIN MOVING SOUTHEAST...AND COULD MOVE ACROSS SOUTHWEST LOWER
MICHIGAN...NORTHERN INDIANA LATE TONIGHT. SEVERE THUNDERSTORMS WITH
DAMAGING WIND WOULD BE POSSIBLE WITH THIS COMPLEX. WHILE NORTHWEST
OHIO AND EASTERN INDIANA ARE NOT IN A SLIGHT RISK OUTLOOK AT THIS
TIME...ANY EASTWARD MOVEMENT OF THIS COMPLEX COULD BRING IT INTO THE
AREA OVERNIGHT.

SPOTTER ACTIVATION MAY BE NEEDED LATER TONIGHT. THUNDERSTORM
DEVELOPMENT THIS AFTERNOON WILL BE SCATTERED AND SOME SPOTTERS MAY
BE NEEDED IF THUNDERSTORMS DEVELOP. STAY TUNED TO THIS STATION FOR
UPDATES.