Severe Thunderstorm Warning 29, NWS Northern Indiana

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
138 PM EDT MON MAY 31 2010

.AVIATION /18Z TAFS/...

CONVECTION TO CONTINUE THROUGH THE REMAINDER OF THE AFTERNOON WITH
CONTINUED DESTABILIZATION AHEAD OF APPROACHING SURFACE COLD FRONT.
ONE LOOK AT THE EARLY AFTERNOON RADAR SUGGESTS HANDLING THE
SITUATION WITH A TSRA TEMPO GROUP. WILL DO SO AT BOTH TERMINALS
THROUGH 22Z AND COULD SEE THE NEED FOR MORE TSRA MENTION FOR AN
ADDITIONAL 1-2 HRS AT FWA GIVEN CURRENT SPEED OF THE APPROACHING
FRONT. WILL CARRY IFR VSBYS IN THE TSRAS AS THEY HAVE BEEN
ROBUST. SEVERE CONVECTION WILL BE POSSIBLE...BUT ISOLATED IN
NATURE.

THIS EVENING...CLEARING SKIES WILL GRADUALLY WORK IN FROM THE WEST
AND GIVEN THE WIDESPREAD RAINFALL OF THIS AFTERNOON COMBINED WITH
ONLY SLOW LLEVEL DRYING AND RELATIVELY LIGHT LLEVEL WINDS...EXPECT
FOG FORMATION TOWARDS DAYBREAK. WILL CARRY MVFR VSBYS AT THIS
POINT AND SEE HOW THE CONVECTION EVOLVES THIS AFTERNOON. IFR
CERTAINLY NOT OUT OF THE QUESTION...HOWEVER.

VFR DAY ON TAP FOR TUESDAY WITH JUST A FEW POP UP CU.

SOUTHWEST WINDS AROUND 10KTS AHEAD OF THE FRONT WILL SHIFT WEST-
NORTHWEST THIS EVENING 5-10KTS BEHIND THE FRONT BEFORE DIMINISHING
TO LIGHT/VARIABLE AFTER MIDNIGHT. EXPECT WESTERLY WINDS 5KTS AT
SBN ON TUESDAY WITH NORTHWEST WINDS 5KTS AT FWA.

&&

.PREV DISCUSSION... /ISSUED 1002 AM EDT MON MAY 31 2010/

UPDATE...

UPDATE TO TWEAK POPS GIVEN EVOLUTION OF CONVECTION IN POSITIVE
THETAE SURGE AHEAD OF APPROACHING COLD FRONT. THE TWO PRIMARY
CHANGES ARE 1-TO BETTER DELIMIT AREA OF SCT/NUMEROUS SHRA/TSRA
THIS MORNING FROM THE OFFICE NORTH AND EAST...AND THEN EXPAND
LIKELY POPS CWA-WIDE FOR THE AFTERNOON GIVEN SLOWER FRONTAL
ARRIVAL PER 14UTC OBS AND NEAR TERM RUC GUIDANCE WHICH SUGGESTS
ALL AREAS WILL LIKELY SEE ANOTHER BATCH OF STORMS THIS AFTERNOON.

NEAR TERM TEMP TRENDS WILL BE TRICKY GIVEN CONVECTIVE
IMPACTS...BUT OVERALL COULD END UP BEING A FEW DEGREES TOO LOW
OVER NORTHWESTERN AREAS GIVEN ADDITIONAL SUN AHEAD OF APPROACHING
FRONT.

UPDATED GRIDS/PRODUCTS ARE OUT.

PREV DISCUSSION... /ISSUED 702 AM EDT MON MAY 31 2010/

SHORT TERM...
STORM CLUSTER OVR CHICAGO EARLY THIS MORNING A LIKELY HARBINGER OF
THINGS TO COME BY AFTN W/APCH OF SFC FNTL BNDRY EXTENDING SWWD FM
POTENT SW TROUGH EJECTING EWD THROUGH SRN CANADA. ALTHOUGH SW PROGGED
TO DEAMPLIFY EWD INTO DOWNSTREAM FLATTENING MID LVL RIDGE...IT STILL
RETAINS SOME MEASURE OF MID LVL HGT FALLS ACRS NRN IN/SRN MI THIS
AFTN AND COMBINE THAT W/LIKELY MOD DESTABILIZATION OFFERS WHAT
SHLD BE FAIRLY WIDESPREAD CONVN SE HALF INVOF OF SFC BNDRY THROUGH
THE AFTN AND INTO EARLY EVENING. MBE VELOCITIES ARE QUITE SLOW
OWING TO WEAKNESS IN MID LVL FLW AND GIVEN DEGREE OF MID LVL MSTR
ADVTN OUT OF THE MID MS VALLEY OVERNIGHT SHLD SEE SOME PRETTY
HEFTY RAINFALL AMTS FOR SOME. IN ADDN...A LOW END RISK FOR A SVR
MULTICELL CLUSTER OR TWO AS EVIDENT W/IMPRESSIVE STORM OVR CHICAGO
THIS MORNING. OTHERWISE TEMP GRIDS TDA LOOK IDEAL W/A WARM AND
MUGGY DAY FOR MOST.

SFC BNDRY WILL WORK CLEAR SERN AREAS BY MID EVENING W/ROBUST DRYING
INTO TUE FOLLOWING IN BEHIND SFC RIDGING THAT QUICKLY BLDS EWD OUT
OF THE PLAINS. HWVR LTL CHG IN LL THERMAL RIDGE AND GIVEN DEGREE OF
INSOLATION XPCD WILL REORIENT TEMPS A BIT SW-NE AND STILL WELL ABV
NORMAL.

SFC RIDGE SHIFTS EWD OF CWA TUE NIGHT W/STG RTN FLW DVLPG IN
RESPONSE TO UPSTREAM SW OVR THE CNTRL ROCKIES THIS AM STEAMING EWD
IN PROGRESSIVE MID LVL FLW REGIME. TEMPTED TO ADD A POP MENTION AFT
MIDNIGHT PER FVRBL INCREASE IN LL MSTR FLUX/THETA-E ADVTN AHD OF
EJECTING SW WELL OUT INTO THE PLAINS BY THAT TIME. HWVR PLACEMENT OF
IMPLIED STORMS QUITE UNCERTAIN OWING TO LIKELY UPSCALE MCS DVLPMNT
UPSTREAM ANYWHERE FM ERN NE INTO SE MN. GFS BRINGS MCS EWD THROUGH
CNTRL LWR MI...LOCAL WRF INTO NE IL/SW MI AND NAM INTO ERN IL/WRN
IN. CERTAINLY PER FLAT PATTN ALOFT...QUICKER EWD ARRIVAL OF MCS XPCD
AND WILL TAKE A STAB AT IT NOW W/LOW CHC POP INTRODUCTION WRN
THIRD LATE.

LONG TERM...

WEDNESDAY THROUGH SUNDAY

POWERFUL UPPER FLOW ASSOCIATED WITH THE MASSIVE HEIGHT SINK OVER THE
NORTHERN PAC WILL SUPPORT A VERY ACTIVE START TO JUNE. FAST
LATITUDINAL FLOW WILL SUPPORT NUMEROUS EJECTING SMALL SCALE
DISTURBANCES WITH ONE LARGE MID LEVEL SHORT WAVE EXPECTED BY THE
LATTER PORTION OF THE PERIOD. COMPLICATED AND POORLY SAMPLED FLOW
OVER THE PAC SOURCE REGION COUPLED WITH POOR HANDLING OF THE EASTERN
CANADIAN NEG HEIGHT ANOMALY CONTINUES TO SUPPORT EXTREMELY POOR
MODEL PERFORMANCE AND CONTINUITY IN THE PERIOD. THIS IS SUPPORTING
WAVERING OF THE LL BAROCLINIC ZONE DEMARKING HIGH THETA-E AIR IN
ADDITION TO ADVECTING CONUS MID LEVEL BAROCLINIC WAVE
TRACK/SPEED/AND INTENSITY. THE OVERALL TREND THIS SPRING HAS BEEN
FOR A NORTHERN BIAS TO THE LL THETA-E GRADIENT...AND WILL CONTINUE
TO TREND TO DETERMINISTIC SOLUTIONS THAT FAVOR THIS SCENARIO. THE
ECMWF HAS BEEN THE MODEL OF CHOICE FOR SEVERAL FORECAST
PERIODS...BUT IT SEEMS IT TOO MAY BE TOO AGGRESSIVE WITH HEIGHT
FALLS AND COOLING IN THE GREAT LAKES BY THE END OF THE PERIOD AND
BEYOND. NOT TO MENTION GIVEN THE INCREASED LL INSTABILITY AND
SEASONAL BIAS TOWARD MCS SYSTEMS...HIRES MODEL SOLUTIONS BEYOND DAY
2 WILL BE UTILIZED VERY CAUTIOUSLY GIVEN CONVECTIVE FEEDBACK ISSUES
THAT BECOME PROBLEMATIC. A GOOD EXAMPLE OF THIS CAN BE SEEN IN THE
NAM12/S DAY 3 PROGS OVER THE MIDWEST. SIMILAR TO LAST NIGHT/S
FORECAST...ONLY SMALL CHANGES AND TRENDS IN THE PERIOD...WITH THE
ECMWF FAVORED THROUGH THE MAJORITY OF THE PERIOD...TRENDING TO
BIASED MEAN DETERMINISTIC SYNOPTIC FIELDS BY DAY 6-7.

WED-THU...THE FIRST IN A POTENTIAL SERIES OF DISTURBANCES IS
EXPECTED TO AFFECT THE REGION IN THIS PERIOD. EXPECTED MCS ACTIVITY
FROM INITIAL CENTRAL PLAINS ELEVATED THETA-E ADV WILL LIKELY PUSH
QUICKLY EAST INTO THE UPPER MIDWEST WITH A NORTHERN BIAS TO THE
TRACK EXPECTED GIVEN A WEAK NEG THETA-E PUSH FROM THE MON-TUE
DEPARTING SYSTEM...LIKELY FAVORING NORTHERN IL/WI/SOUTHERN
MI/NORTHERN IN AND NW OH. WITH A GOOD SETUP FOR MCS ACTIVITY...WED
HAVE RAISED POPS TO 40 ACROSS THE NORTH WHERE THE BEST OVERLAP OF
INCREASED MID LEVEL FLOW/POS THETA-E ADV WILL RESIDE GIVEN H85-3
THICKNESS CONTOURS. DO FAVOR THE SLOWER BIASED ECMWF AND UKMET PER
UPPER WAVE AND ASSOCIATED SFC REFLECTION...WHICH STILL SUPPORTS
INCREASED POPS THROUGH THUR AFTERNOON. SEVERE POTENTIAL WILL BE
ELEVATED IN THIS PERIOD GIVEN AMPLE INSTABILITY/STRONG FORCING PER
INCREASED UPPER FLOW. DAMAGING WINDS WOULD BE THE MAIN THREAT GIVEN
STORM ENVIRONMENT FAVORING AN OUTFLOW DOMINATE FORWARD PROPAGATING
CONVECTIVE SYSTEM. NO CHANGE TO FORECAST TEMPS GIVEN CONCERNS ON
CLOUDS AND PRECIP. MODEL THERMAL FIELDS CERTAINLY SUPPORT CURRENT
FORECAST NUMBERS ALTHOUGH INSOLATION WILL PLAY A LARGE ROLE IN
RESULTANT NUMBERS.

FRI-SUN...MUDDLED FORECAST DETAILS IN THIS PERIOD GIVEN POOR MODEL
CONFIDENCE. CURRENT FORECAST ENCOMPASSES ALL CONCERNS WITH A BIAS
TOWARD CLIMO GIVEN LOOMING UNCERTAINTY. DID ADD POPS TO SAT NIGHT
GIVEN A VERY REAL POTENTIAL FOR AN MCS CORRIDOR RESIDING OVER THE
REGION. FORECAST MODELS STILL OFFER A SIG NORTHERN STREAM WAVE BY
DAY 7-8 AND GIVEN CONCERNS ON A NORTHERN BIAS...CURRENT TEMPS IN THE
GRIDDED DATABASE ARE LIKELY TOO LOW. CONCERNS ON FAST FLOW MID LEVEL
IMPULSES IN THE PRESENCE OF AMPLE LL HEAT/MOISTURE CERTAINLY
SUPPORTS CURRENT FORECAST POP NUMBERS...WITH WAVE TIMING/TRACK/AND
ORGANIZATION FAR FROM BEING RESOLVED AT THIS POINT. EXPECT ABOVE
NORMAL TEMPS IN THE PERIOD WITH ABOVE NORMAL CHANCES FOR PRECIP.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

SHORT TERM...T
LONG TERM...JC
AVIATION...ARNOTT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1257 PM EDT MON MAY 31 2010

INZ003>009-012>018-020-022>027-032>034-LMZ043-046-MIZ077>081-OHZ001-
002-004-005-015-016-024-025-011700-
LA PORTE-ST. JOSEPH IN-ELKHART-LAGRANGE-STEUBEN-NOBLE-DE KALB-STARKE-
PULASKI-MARSHALL-FULTON IN-KOSCIUSKO-WHITLEY-ALLEN IN-WHITE-CASS IN-
MIAMI-WABASH-HUNTINGTON-WELLS-ADAMS-GRANT-BLACKFORD-JAY-
NEW BUFFALO MI TO ST JOSEPH MI-MICHIGAN CITY IN TO NEW BUFFALO MI-
BERRIEN-CASS MI-ST. JOSEPH MI-BRANCH-HILLSDALE-WILLIAMS-FULTON OH-
DEFIANCE-HENRY-PAULDING-PUTNAM-VAN WERT-ALLEN OH-
INCLUDING THE CITIES OF...MICHIGAN CITY...LA PORTE...SOUTH BEND...
MISHAWAKA...ELKHART...GOSHEN...LAGRANGE...TOPEKA...ANGOLA...
KENDALLVILLE...LIGONIER...AUBURN...GARRETT...KNOX...NORTH JUDSON...
WINAMAC...FRANCESVILLE...PLYMOUTH...BREMEN...ROCHESTER...WARSAW...
WINONA LAKE...COLUMBIA CITY...SOUTH WHITLEY...FORT WAYNE...
MONTICELLO...BROOKSTON...LOGANSPORT...PERU...WABASH...
NORTH MANCHESTER...HUNTINGTON...BLUFFTON...OSSIAN...DECATUR...
BERNE...MARION...HARTFORD CITY...MONTPELIER...PORTLAND...NILES...
BENTON HARBOR...ST. JOSEPH...BUCHANAN...DOWAGIAC...CASSOPOLIS...
STURGIS...THREE RIVERS...COLDWATER...HILLSDALE...BRYAN...WAUSEON...
ARCHBOLD...DEFIANCE...NAPOLEON...PAULDING...ANTWERP...OTTAWA...
PANDORA...VAN WERT...DELPHOS...LIMA
1257 PM EDT MON MAY 31 2010 /1157 AM CDT MON MAY 31 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST OHIO...
NORTHERN INDIANA...SOUTHWEST LOWER MICHIGAN AND THE NEARSHORE WATERS
OF SOUTHEASTERN LAKE MICHIGAN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS ARE LIKELY THIS AFTERNOON INTO THIS EVENING. WHILE
THE PRIMARY THREAT FROM THESE STORMS WILL BE HEAVY RAINFALL AND
LOCALIZED FLOODING...A FEW SEVERE STORMS...WITH DAMAGING WINDS
AND LARGE HAIL...ARE ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SEVERAL ROUNDS OF THUNDERSTORMS ARE POSSIBLE IN THIS PERIOD. THE
BEST CHANCE FOR ORGANIZED SEVERE WEATHER WILL BE WEDNESDAY INTO
THURSDAY...WITH ANOTHER EPISODE OF SEVERE WEATHER POSSIBLE THIS
WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE THROUGH AFTERNOON INTO EARLY
EVENING.

&&

STAY TUNED TO NOAA WEATHER RADIO FOR FURTHER DETAILS OR UPDATES...OR
CHECK OUR WEB SITE AT WEATHER.GOV/IWX

ARNOTT

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