Severe Thunderstorm Warning 108, NWS Northern Indiana

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1155 AM EDT SUN JUL 18 2010

.AVIATION/UPDATE...
MCV/STORM COMPLEX ACROSS SOUTHERN IL AND EASTERN MO WAS HAVING A
MAJOR IMPACT ON AVIATION AND FCST ISSUES FOR THE FORECAST AREA.
HAVE UPDATED GRIDS/FCST TO GO WITH A LATER TIMING OF STORMS TODAY.
SUBSIDENCE ON THE NORTH SIDE OF THE COMPLEX WAS LIMITING STORM
DEVELOPMENT. THE COMPLEX SHOULD CONTINUE TO MOVE SOUTH THIS
AFTERNOON AS THE ATMOSPHERE DESTABILIZES OVER N INDIANA AND
SURROUNDING AREAS. OLDER 4KM WRF RUN HAS BEEN HANDLING THIS
SCENARIO WELL...AND INDICATES STORMS SHOULD DEVELOP IN THE SFC
THETA E RIDGE OVER N INDIANA BY 21Z. HAVE UPDATED THE TAFS AND
FORECAST IN THIS REGARD. HAVE ALSO LOWERED HIGH TEMPERATURES
TODAY...ESPECIALLY OVER WEST AREAS GIVEN HIGH CLOUD CANOPY.

&&

.PREV DISCUSSION... /ISSUED 654 AM EDT SUN JUL 18 2010/

SHORT TERM... MIDDAY SEVERE CONVECTION LARGELY DEPENDENT UPON AM
CONVECTIVE TRENDS. HOWEVER...NRN BRANCH OF LLJ INTO CNTL WI TO
CONT VEERING PROVIDING FOCUS FOR ELEVATED NON-SEVERE CONVECTION
ACRS ECNTL WI AND CRNTLY CROSSING LK MI. DOWNWIND STEERING FLOW
SHOULD CONT TO BACK SLIGHTLY AS NEW ENGLAND VORTEX CONTS TO ROTATE
THROUGH ERN CAN TROF...KEEPING FOCUS LARGELY TO NORTH OF CWA...AND
ALONG WITH STORMS OUTRIDING MIDLVL LAPSE RATE PLUME/GRDLY INCRSG
STABILITY TOWARD DAYBREAK/SBCIN WITH TIME...SUGGESTS IR SAT TRENDS
TO CONT SLOW DEMISE. MEANWHILE 35-40 KT LLJ ACRS ERN KS TO FAVOR
CONTD MCS MAINTENANCE ACRS NRN MO/NE KS/SERN IA WITH SIG PLUME OF
8-9 C/KM MIDLVL LAPSE RATES FIRMLY TAPPED WITH 3000-4000 J/KG
MLCAPE YET AT 08 UTC. THIS MCS TO RIDE SW OF CWA....LEAVING SRN
GRTLKS PRIMED FOR STRONG SFC HEATING/DESTABILIZATION BY MIDDAY. IN
ADDITION...PLUME OF SIG HIR SFC DPS IN LWR/MID 70S POOLED AHEAD OF
COLD FNT FM UPR MS VLY INTO CNTL PLAINS TO ADVECT INTO CWA BY THIS
AFTN IN INCRSD SWRLY LLVL FLOW. STRONG DESTABILIZATION WITH
MODIFIED NAM POINT SOUNDINGS YIELDING 4000-4500 J/KG ACRS CWA AND
SREF INDICATING MLCAPES GT 4000 J/KG INTO SWRN CWA. COMPARABLY
SIMILAR TO LAST THURSDAY...HOWEVER WITH THIS EVENT CORE OF MUCH
STRONGER WNWLY MIDLVL FLOW FURTHER SOUTH INTO LWR MI TO ENHANCE
DEEP LAYER SHEAR...PROGGED BY 18 UTC IN PREFRONTAL TROF FM 45-50
KTS NORTH TO 30 KTS SWRN CWA AND 06 UTC NAM ABOUT 5 KTS
LESS...THOUGH STILL APPRECIABLY MORE THAN THU. MAX DESTAB/SHEAR
ENVIRON COINCIDING ABOUT TIME OF REACHING CONVECTIVE TEMPERATURE.
OF NOTE MODEL DCAPE QUITE STRONG SIGNAL WITH 1500-2000 J/KG IN
PREFRONTAL TROF AND IMMEDIATELY AHEAD OF SFC FNT. HOWEVER...SOME
CONCERN THAT LESSER BULK SHEAR/STABILITY MAY KEEP SECONDARY
CONVECTION LINE LESS PRONE TO SEVERE. SVRL DERECHO CLIMO
PARAMETERS MET ALONG WITH 5H COOL POOL INTO NRN CWA AND PRONOUNCED
DRY ENVIRONMENTAL AIR IN 600-400 MB LYR WITH MDPI GT 1.25/WINDEX
55-65 KTS...WITH SHEAR TO AID IN ORGANIZATION COULD SEE CLUSTERS
QUICKLY DVLP INTO SERIAL TYPE DERECHO/LEWP ACRS NRN IL/NWRN IN BY
MIDDAY...AND PROGRESS RAPIDLY EWD. PRECIP LOADING WITH PWAT
RAPIDLY INCRS TO 1.75-2 INCHES AND MORE FAVORABLE WB0 HEIGHTS IN
11.5-12.5 KFT RANGE...FZLVL AROUND 15KFT FOR LARGE HAIL PRODUCTION
IN STRONGER/ORGANIZED UPDRAFTS...THOUGH WIND BY FAR SHOULD BE
LARGEST RISK TODAY. CONTD SCAT WORDING WITH UNCERTAINTIES IN
OVERALL COVERAGE/MESOSCALE OUTCOMES. LESSENING TO LWR CHC POPS NW-
SE OVERNIGHT. MSTR/INSTABILITY WELL RAKED OUT TO SOUTH ON MONDAY
FOR DRY/COOLER LESS HUMID DAY. HIGH THETA-E RIBBON LAID OUT WEST
TO EAST WITH ADDNL SHORTWAVES EMANATING FM NRN ROCKIES EMBEDDED IN
RAPID ZONAL FLOW WITH CNTL ROCKIES EML PLUME ADVANCING WELL EAST
INTO MID MS VLY FOR CONTD UPSTREAM CONVECTION DVLPMNT
MONDAY...TRANSLATING INTO CWA MONDAY NIGHT...TIMING OF WHICH
SUGGESTS A LESSER RISK OF SVR.

LONG TERM...

TUESDAY THROUGH SATURDAY

VERY LITTLE CHANGE TO THE PREVIOUS FORECAST AS FORECAST MODEL
CONSENSUS GROWS TOWARD AN ACTIVE PATTERN IN THE SOUTHERN GREAT
LAKES. THE TREND CONTINUES TO BE TOWARD FLATTER MID LEVEL HEIGHTS IN
THE NORTHERN CONUS...A SOLUTION THAT IS PREFERRED GIVEN THE NEGATIVE
HEIGHT ANOMALY IN SE CANADA AND DOWNSTREAM RIDGE BLOCKING. TIGHT MID
LEVEL HEIGHT GRADIENT INTO THE REGION THROUGH MOST OF THE PERIOD
WILL OFFER FAST MID LEVEL FLOW WITH SEVERAL IMPULSES EXPECTED
THROUGH THE FLOW GIVEN AN ANCHORED NW CONUS TROUGH. DEEP
MOISTURE WILL BE OVER THE REGION WITH SFC DEWPOINTS EXPECTED INTO AT
LEAST THE LOWER 70S MOST PLACES...SUPPORTING AMPLE INSTABILITY AHEAD
OF ANY APPROACHING IMPULSE. IN ADDITION...A LINGERING STATIONARY
FRONTAL BOUNDARY IS EXPECTED OVER THE REGION OR VERY
NEAR...SUPPORTING THE ADDED CONVERGENCE AND BACKED SFC WINDS/WAA
REGIME FAVORABLE FOR AN MCS CORRIDOR. DID ADJUST POPS IN THE
PERIOD...ADJUSTING NUMBERS UP EARLY IN THE PERIOD...WITH
INTRODUCTION IN LATER PERIODS. THERE STILL REMAINS SOME UNCERTAINTY
PER THE DEGREE OF RIDGE FLATTENING AND THE ORIENTATION AND PLACEMENT
OF THE UPPER RIDGE CENTER...NOT TO MENTION DETAILS PER THE
SPEED/TIMING OF INDIVIDUAL IMPULSES. MODEL CONSENSUS DOES SUPPORT
INCREASED CONFIDENCE IN THE PERIOD...AND SO FEEL POP RAISES WERE
WARRANTED...ALTHOUGH DID NOT MATCH THE HIGH MEX NUMBERS GIVEN THE
PERIOD AND INHERENT UNCERTAINTY. DID CONTINUE A TREND TO A DRY
FORECAST AT THE END OF THE PERIOD GIVEN THE CURRENT FAVORED EJECTION
OF THE WESTERN CONUS UPPER TROUGH AND ASSOCIATED DOWNSTREAM RIDGING.
HOWEVER...MODEL SOLUTIONS DIVERGE BY NEXT WEEKEND WITH TROUGH
EJECTION TIMING VARYING GREATLY. GIVEN THE PATTERN AND THE
SEASON...A MUCH SLOWER EJECTION IN LINE WITH 12Z AND 00Z ECMWF PROGS
IS FAVORED. GIVEN THE DEGREE OF FAST MID LEVEL FLOW WITH 50+ KNOTS
SUPPORTING AMPLE DEEP SHEAR FOR STORM ORIGINATION...SEVERE CHANCES
WILL BE ELEVATED WITH EACH IMPULSE...PARTICULARLY THE THREAT FOR
DAMAGING SFC GUSTS GIVEN FAVORED STORM SCALE ORGANIZATION INTO A
BOWING LINEAR CONVECTIVE COMPLEX. HEAVY RAIN WILL ALSO BR A CONCERN
WITH EACH COMPLEX...AND IF SUCCESSIVE COMPLEXES TRACK OVER THE SAME
AREAS...AREAL AND RIVER FLOODING MAY OCCUR. THIS WILL NEED TO BE
WATCHED. DETAILS PER IMPULSE ARRIVAL TIME IS NEARLY IMPOSSIBLE ATTM
GIVEN MESOSCALE CONVECTIVE INFLUENCES AND CURRENT POOR WAVE
STRUCTURE DETAILS AND WILL CONTINUE TO BE VERY GENERAL WITH POP
PERIODS.

TEMP CONCERNS REMAIN GIVEN QUESTIONS ON THE LOCATION OF THE EXPECTED
STATIONARY FRONT IN ADDITION TO TS OUTFLOW INFLUENCE AND RAINFALL.
DID TREND T/S DOWN A FEW DEGREES IN EARLY PERIODS WHERE A HIGHER
CONFIDENCE IN PRECIP AND CLOUDS LIES...OPTING TO DEFER ANY MAJOR
CHANGES UNTIL BETTER CONFIDENCE IN SYNOPTIC DETAILS IS MET.

&&

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

SHORT TERM...MURPHY
LONG TERM...JC
AVIATION...SKIPPER
UPDATE...SKIPPER

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE NORTHERN INDIANA
954 AM EDT SUN JUL 18 2010

INZ003>009-012>018-020-022>027-032>034-MIZ077>081-OHZ001-002-004-005-
015-016-024-025-191400-
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-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
954 AM EDT SUN JUL 18 2010 /854 AM CDT SUN JUL 18 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST OHIO...
SOUTHWEST LOWER MICHIGAN AND NORTHERN INDIANA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP BY MID AFTERNOON
AND PERSIST INTO THIS EVENING. SOME OF THE STORMS MAY BE SEVERE WITH
DAMAGING WIND GUSTS THE PRIMARY THREAT. HAIL TO ONE INCH IN
DIAMETER IS POSSIBLE WITH THE STRONGER STORMS. HEAVY DOWNPOURS
WHICH MAY CAUSE LOCALIZED FLOODING ARE ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT THROUGH THURSDAY AS AN
ACTIVE PATTERN SETTLES INTO THE GREAT LAKES REGION. THE THREAT FOR
SEVERE WEATHER WILL BE ELEVATED IN THIS PERIOD...WITH DAMAGING
WINDS BEING THE PRIMARY THREAT. HEAVY RAINFALL WILL ALSO BE A
POSSIBILITY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED TODAY

&&

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

LMZ043-046-191400-
NEW BUFFALO MI TO ST JOSEPH MI-MICHIGAN CITY IN TO NEW BUFFALO MI-
954 AM EDT SUN JUL 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE NEARSHORE WATERS OF
SOUTHEASTERN LAKE MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TODAY. SOME OF THE STORMS
MAY BE SEVERE WITH WIND GUSTS TO 50 KNOTS WITH LOCALLY HIGHER
WAVES NEAR STORMS THE PRIMARY THREAT. HAIL TO ONE INCH IN
DIAMETER IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT THROUGH THURSDAY AS AN
ACTIVE PATTERN SETTLES INTO THE GREAT LAKES REGION. THE THREAT FOR
SEVERE WEATHER WILL BE ELEVATED IN THIS PERIOD...WITH DAMAGING
WINDS BEING THE PRIMARY THREAT.

&&

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

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