Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 251828
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
228 PM EDT MON AUG 25 2014

.SYNOPSIS...
ISSUED AT 1056 AM EDT MON AUG 25 2014

HOT AND MUGGY CONDITIONS ACROSS THE REGION TODAY INTO TONIGHT.
DEWPOINTS IN THE LOWER 70S WILL CREATE MUGGY CONDITIONS AS HIGH
PRESSURE RETAINS ITS INFLUENCE OVER US. A FRONTAL SYSTEM TO THE
WEST COULD INTRODUCE SOME RAIN TO THE NORTHERN PORTION OF THE
REGION TONIGHT AS IT APPROACHES. HIGH TEMPERATURES TODAY WILL BE IN
THE UPPER 80S TO AROUND 90 WITH THE HEAT INDEX IN THE 90S TO NEAR 100.
LOW TEMPERATURES TONIGHT WILL RANGE FROM THE UPPER 60S NEAR THE
OHIO RIVER TO THE LOWER 70S IN SOUTHERN MICHIGAN.

&&

.UPDATE...
ISSUED AT 1242 PM EDT MON AUG 25 2014

FOCUS FOR THE REMAINDER OF THE AFTERNOON WILL CENTER ON CONVECTIVE
POTENTIAL AND HEAT. RESIDUAL OUTFLOW BOUNDARY FROM UPSTREAM
CONVECTION HAS ALLOWED FOR RENEWED THUNDERSTORM DEVELOPMENT ACROSS
NORTHEAST ILLINOIS. REMNANT OUTFLOW/CONVECTIVE VORT FROM UPSTREAM
CONVECTION WILL HAVE PLENTY OF DOWNSTREAM INSTABILITY TO WORK THIS
AFTERNOON WITH INDICATIONS IN RUC SHORT TERM PROGS OF 3-4K J/KG OF
100 HPA MLCAPES WORKING INTO WESTERN PORTIONS OF THE AREA. DEEP
LAYER SHEAR IS WEAK...BUT GIVEN MAGNITUDE OF INSTABILITY WILL HAVE
TO MONITOR FOR POSSIBILITY OF ISOLATED STRONG/SEVERE STORMS THIS
AFTERNOON. WITH EARLY AFTERNOON UPDATE...WILL GO AHEAD AND MAKE
SOME SOUTHEAST EXPANSION OF SLIGHT CHANCE AND PERHAPS RAISE POPS A
BIT IN THE FAR NORTHWEST DUE TO APPROACH OF OUTFLOW BOUNDARY.
TEMPERATURES/DEW POINTS APPEAR TO BE IN GOOD SHAPE WITH PEAK
AFTERNOON HEAT INDICES STILL LIKELY TO REACH INTO THE UPPER 90S
ACROSS THE WEST. WILL CONTINUE TO GO WITH CURRENT SPS FOR THIS
AFTERNOON TO HIGHLIGHT HAZARDOUS CONDITIONS ASSOCIATED WITH THE
HEAT/HUMIDITY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 404 AM EDT MON AUG 25 2014

FOCUS OF PERIOD WILL BE TWO FOLD...TEMPERATURES/HEAT INDEX ISSUES AND
CHANCES FOR STORMS.

WARM AND MUGGY CONDITIONS WERE IN PLACE ACROSS THE AREA WITH
TEMPERATURES IN THE 70S AND DEWPOINTS IN THE UPPER 60S NE TO LOWER
70S SW WITH MOST UNSTABLE CAPE VALUES IN THE 500 TO 1500 J/KG RANGE.
WITH NO REAL TRIGGER ACROSS THE AREA NO SHOWERS/STORMS HAVE FORMED
THUS FAR. MAIN FOCUS FOR STORMS HAS BEEN FROM NORTHERN WISCONSIN
INTO PORTIONS OF CENTRAL IOWA WHERE 30 TO 35 KT LOW LEVEL JET WAS
AIDING IN DEVELOPMENT AND MAINTENANCE OF A BROKEN LINE OF STRONG
TO LOCALLY SEVERE STORMS. HI RES MODELS ALL SUGGEST THIS LINE WILL
DROP SLOWLY SOUTHEAST BUT VARY IN HOW MUCH HOLD TOGETHER AS WE
APPROACH 12Z MON AND POINTS BEYOND. WOULD SEEM REASONABLE THAT
SOME SORT OF OUTFLOW BOUNDARY OR REMNANT SHOWERS/STORMS COULD
APPROACH NW AREAS THIS AFTERNOON AND THEN STALL SOMEWHERE TONIGHT
BEING REINFORCED SOMEWHAT BY SFC FRONT THAT WILL BE SINKING SOUTH.
ONLY CHANGE TO GRIDS WILL BE REORIENTATION OF SLGT CHC POPS TO
MORE OF A SW TO NE ORIENTATION. IF SUFFICIENT HEATING TAKES PLACE
AND PROGGED INSTABILITY IS AVAILABLE (SURFACE BASED CAPES IN
EXCESS OF 4000 J/KG IN A WEAKLY SHEAR ENVIRONMENT) THEN SOME
STRONGER STORMS COULD BE A CONCERN.

NOW FOR TEMPERATURES...THE WARM START TO THE MORNING SHOULD ALLOW
TEMPERATURES TO QUICKLY CLIMB INTO THE 80S BY NOON TIME AND POSSIBLY
CLOSE TO 90 IN WESTERN AREAS. DEWPOINTS IN WESTERN AREAS LOOK TO
CLIMB INTO THE MIDDLE 70S IN SOME SPOTS WHICH IF TEMPS DO APPROACH
90 WILL EDGE REAL CLOSE TO HEAT ADVISORY LEVELS (EVEN BRIEFLY TOUCH
IN FAR WEST). WILL HANDLE WITH HWO AND SPS FOR NOW AND LET DAY SHIFT
ASSESS THINGS AFTER SUNRISE AS TO EXTENT OF CLOUD COVER AND POSSIBLE
INFLUENCE FROM UPSTREAM CONVECTION. LOWS TONIGHT WILL DROP BACK INTO
THE UPR 60S TO LOWER 70S.

&&

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 404 AM EDT MON AUG 25 2014

LOW OVER SRN MANITOBA THIS MORNING EXPECTED TO LIFT NE INTO QUEBEC
TUESDAY WITH TRAILING CDFNT MOVG INTO OUR CWA. WK FORCING ALONG THE
FRONT COMBINED WITH SOME CAPPING ASSOCIATED WITH UPR RIDGE OVER THE
OH/MID MS VALLEY LIMITS TSTM POTENTIAL TO CHC DESPITE AT LEAST
MODERATE INSTABILITY IN PLACE OVER THE AREA. TEMPS WILL REMAIN ABOVE
NORMAL WITH HIGHS IN THE UPPER 80S AND PM HEAT INDEX READINGS IN THE
90S.

CDFNT EXPECTED TO SAG SOUTH INTO CENTRAL OH/IN TUE NGT. POTENTIAL
FOR TSTMS INCREASES A BIT IN THIS TIMEFRAME AS A SHRTWV CURRENTLY
OVER WRN CANADA MOVES TO THE UPR GRTLKS RESULTING IN MINOR HEIGHT
FALLS AS FAR SOUTH AS OUR CWA. WK CAA SHOULD ALLOW FOR LOWS TO FALL
INTO THE M-U60S ACROSS THE AREA.

RAIN CHANCES DIMINISH WED-WED NGT AS FRONT CONTS TO SAG SOUTH TO THE
OH VALLEY AND SFC HIGH MOVES ESE INTO THE UPR GRTLKS. TEMPS SHOULD
FALL BACK CLOSER TO NORMAL WITH HIGHS IN THE L80S AND LOWS IN THE
L-M60S.

FRONTAL SYSTEM EXPECTED TO LIFT BACK NORTH INTO OUR AREA THU-THU NGT
AS SFC HIGH MOVES TO THE MID ATLANTIC/NORTHEAST U.S.. DVLPG SPLIT
FLOW CUT-OFF LOW OVER THE WRN U.S. BY MID WEEK IS EXPECTED TO MOVE
SLOWLY EAST TO THE CENTRAL PLAINS FRIDAY AND INTO THE MID MS VALLEY
BY SUNDAY WHILE SFC BOUNDARY LINGERS OVER THE AREA... ENHANCING TSTM
POTENTIAL ACROSS OUR AREA OVER THE LABOR DAY WEEKEND... WHILE TEMPS
REMAIN CLOSE TO NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 200 PM EDT MON AUG 25 2014

AN OUTFLOW BOUNDARY ASSOCIATED WITH OVERNIGHT UPSTREAM CONVECTION
HAS BEEN A TRIGGER MECHANISM FOR SHOWERS AND THUNDERSTORMS ACROSS
NORTHEAST ILLINOIS AND SOUTHERN LOWER MICHIGAN. THIS BOUNDARY
SHOULD CONTINUE TO DROP INTO NORTH CENTRAL INDIANA BY 20Z. A
STRONGLY UNSTABLE ENVIRONMENT EXISTS ACROSS THE AREA...WITH MAIN
NEGATIVE FACTOR TO SOUTHEAST EXPANSION OF THE SHOWERS AND STORMS
IS BACKGROUND WEAK UPPER FORCING AND PRESENCE OF MID/UPPER LEVEL
RIDGING. HAVE CARRIED A VCTS MENTION AT KSBN FROM 20Z-22Z AND WILL
BE MONITORING TRENDS OVER NEXT HOUR OR SO FOR POSSIBLE TSRA
INCLUSION. SOUTH WINDS AT KSBN MAY BECOME NORTHWEST FOR A TIME IN
THE 20Z-22Z TIMEFRAME DUE TO THE PASSAGE OF THE OUTFLOW
BOUNDARY...OR VARIABLE IN NATURE. A SHEARED UPPER VORT MAX FROM
CENTRAL WISCONSIN INTO EASTERN IOWA WILL TRACK INTO NORTHWEST
INDIANA THIS EVENING WITH SOME POSSIBILITY OF ADDITIONAL ISOLATED
THUNDERSTORMS. OTHER THAN PASSAGE OF THIS WEAK WAVE THIS
EVENING...FORCING WILL BE SOMEWHAT WEAK WITH LOW CONFIDENCE IN
TIMING AND WILL KEEP TAFS DRY THROUGH THE END OF THE PERIOD.
CHANCES OF THUNDER MAY INCREASE LATE TONIGHT INTO TUESDAY MORNING
AS LOW LEVEL FRONT BEGINS TO APPROACH THE AREA...BUT CONFIDENCE
REMAINS LOW IN TIMING/COVERAGE.

&&

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

$$

UPDATE...MARSILI
SYNOPSIS...LOTHAMER
SHORT TERM...FISHER
LONG TERM...JT
AVIATION...MARSILI


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