Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 020546
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
146 AM EDT WED SEP 2 2015

.SYNOPSIS...
ISSUED AT 145 AM EDT WED SEP 2 2015

AN UPPER LEVEL DISTURBANCE WILL SLOWLY EXIT THE REGION THROUGH
WEDNESDAY AFTERNOON. AN ISOLATED SHOWER OR THUNDERSTORM IS
POSSIBLE THROUGH THIS AFTERNOON...BUT OTHERWISE HOT AND HUMID
CONDITIONS WILL PERSIST THROUGH MUCH OF THE REMAINDER OF THE WEEK.
HIGH TEMPERATURES THIS AFTERNOON WILL REACH INTO THE UPPER 80S TO
AROUND 90. LOW TEMPERATURES TONIGHT WILL DROP BACK INTO THE MID TO
UPPER 60S.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 345 PM EDT TUE SEP 1 2015

PESKY COMPACT MIDLEVEL VORT MAX CONTINUES TO SWIRL ACROSS CENTRAL
INDIANA THIS AFTERNOON WITH LITTLE FORWARD MOMENTUM. DEWPOINTS IN
THE LOW 70S SUPPORTING SOME DECENT SBCAPE PER SPC/RAP MESOANALYSIS
DESPITE VERY POOR LAPSE RATES ALOFT. DPVA IN THE PRESENCE OF THIS
INSTABILITY IS GENERATING SOME SCT CONVECTION...WITH THE HIGHEST
COVERAGE IN OUR SOUTH CLOSER TO THE HEIGHT ANOMALY AND ALONG REMNANT
OUTFLOW FROM MORNING CONVECTION. EXPECT THIS ACTIVITY TO CONTINUE
THROUGH THE EVENING BUT SHOULD WANE WITH THE LOSS OF DAYTIME
HEATING.

MAIN LINE OF CONVECTION TO OUR W/SW THIS MORNING WAS ACTUALLY BEING
DRIVEN BY FOCUSED 305K ISENTROPIC UPGLIDE ON THE BACKSIDE OF
MIDLEVEL CIRCULATION. SOME OF THE LATEST MODELS (BOTH HI-RES AND
OTHERWISE) SHOW THIS AREA OF ENHANCED ASCENT AND MOISTURE
CONVERGENCE WITH 20-25 KT LLJ SETTING UP AGAIN OVER AT LEAST OUR
SOUTHEAST COUNTIES LATER TONIGHT...PROMPTING CONTINUED LOW CHANCE
POPS IN OUR EAST THROUGH TOMORROW. COVERAGE HIGHLY QUESTIONABLE
GIVEN WEAK FORCING AND INSTABILITY SO WILL MAINTAIN JUST SLIGHT
CHANCE POPS FOR NOW. NO SEVERE WEATHER EXPECTED WITH ANY OF THIS
ACTIVITY GIVEN LIMITED UPDRAFT POTENTIAL AND VIRTUALLY NO FLOW
ALOFT. COROLLARY TO THIS IS THAT ANY CONVECTION THAT DOES MANAGE TO
DEVELOP AND PERSIST WILL MOVE VERY SLOW AND COULD LEAD TO LOCALLY
HEAVY RAINFALL.

OTHER MAIN STORY WILL BE THE HEAT AND HUMIDITY. HIGHS TOMORROW
EXPECTED TO BE A FEW DEGREES WARMER THAN TODAY...APPROACHING 90F.
WITH DEWPOINTS IN THE LOW 70S ONCE AGAIN...HEAT INDICES WILL LIKELY
APPROACH THE MID 90S.

&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 345 PM EDT TUE SEP 1 2015

HOT AND HUMID CONDITIONS TO DOMINATE THE REGION THROUGH THE UPCOMING
HOLIDAY WEEKEND AND BEYOND WITH ONLY MINIMAL CHANCES FOR NEEDED
RAINFALL.

UPPER LEVEL RIDGING WILL CONTINUE TO INFLUENCE THE REGION INTO
FRIDAY WITH A SERIES OF WEAK DISTURBANCES RIDING ITS PERIPHERY. ONE
OF THESE IS POISED TO MOVE NE OUT OF PLAINS AND THEN DROP SE INTO
THE WESTERN GREAT LAKES THURSDAY AND LINGERING INTO FRIDAY. NAM/GFS
SOUNDINGS SUGGEST WE SHOULD BE UNCAPPED WITH AT LEAST LOW TO
MODERATE INSTABILITY AROUND. WILD CARD WILL BE AMOUNT OF SURFACE
CONVERGENCE ASSOCIATED WITH THIS FEATURE AND ITS ABILITY TO SPARK
ISOL TO MAYBE SCT CONVECTION. WILL BE KEEPING POPS SUBDUED FOR THE
TIME BEING IN THE SLGT CHC TO LOW CHC CATEGORY DURING THE
AFTERNOON/EVENING HOURS.

BY SATURDAY...MED RANGE MODELS ALL AGREE ON 588 DM OR HIGHER UPPER
LEVEL HEIGHTS NUDGING INTO THE REGION AND HOLDING TIGHT INTO MONDAY.
THIS WILL RESULT IN HIGHS WELL INTO THE 80S AND POSSIBLY AROUND 90
WITH HEAT INDICIES INTO THE 90S. DEEP LOW PRESSURE WILL MOVE INTO
THE WESTERN STATES SATURDAY AND MAKE AN ATTEMPT TO BREAK DOWN THE
RIDGE FOR THE START OF NEXT WEEK. ECMWF DOES SUGGEST A WEAK
DISTURBANCE WELL SOUTH OF THE MAIN UPPER LOW THAT COULD BRING AN
OUTSIDE CHANCE OF A AFTERNOON/EVENING SHOWER OR STORM TO THE AREA
TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 145 AM EDT WED SEP 2 2015

WATER VAPOR IMAGERY EARLY THIS MORNING INDICATES THE CONTINUED
SLOW EASTWARD PROGRESSION OF OLD VORT MAX WHICH HAS RESIDED ACROSS
THE REGION THE PAST FEW DAYS. WHILE FORCING WITH THIS WAVE IS
MIGRATING EAST OF THE AREA...BROAD ISENTROPIC ASCENT IN THE WAKE
OF THIS WAVE MAY BE ENOUGH TO GENERATE AN ISOLATED SHOWER OR
THUNDERSTORM OVERNIGHT. VERY LIMITED COVERAGE (IF OCCURS)
CONTINUES TO PRECLUDE MENTION IN TERMINAL FORECASTS. FAVORED AREA
OF WEAK ISENTROPIC FORCING SHOULD SHIFT INTO NORTHEAST INDIANA
LATER TODAY...BUT AGAIN DIFFICULT AT THIS TIME TO HAVE ANY
CONFIDENCE FOR TAF INCLUSION GIVEN EXPECTED LIMITED COVERAGE. FOG
POTENTIAL SEEMS TO BE LIMITED FOR TONIGHT AND NO CHANGE TO TEMPO
MVFR VSBYS FOR TERMINALS FOR A BRIEF TIME EARLY THIS MORNING FROM
10-12Z. OTHERWISE...SFC ANTICYCLONE SINKING SOUTH OF THE AREA
SHOULD PROMOTE WESTERLY WINDS AROUND 10 KNOTS THIS AFTERNOON
BACKING LIGHT SOUTHWEST FOR TONIGHT.

&&

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

$$

SYNOPSIS...MARSILI
SHORT TERM...AGD
LONG TERM...FISHER
AVIATION...MARSILI


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