Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 211755
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
155 PM EDT THU AUG 21 2014

.SYNOPSIS...
ISSUED AT 154 PM EDT THU AUG 21 2014

SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE REGION WILL BECOME
MORE LIKELY TONIGHT AS A COUPLE OF UPPER LEVEL DISTURBANCES
APPROACH. HIGHS TODAY WILL BE IN THE LOWER TO MID 80S. LOWS THE
NEXT SEVERAL NIGHTS WILL BE AROUND 70. HIGHS THIS WEEKEND WILL BE
AROUND 90 DEGREES.

&&

.UPDATE...
ISSUED AT 1128 AM EDT THU AUG 21 2014

BROAD ISENTROPIC LIFT/LOW LEVEL MOISTURE TRANSPORT WILL CONTINUE
THROUGH THIS AFTERNOON FROM THE MID MS RIVER VALLEY EXTENDING
EASTWARD TO THE OHIO RIVER VALLEY. RUC INITIALIZATION SUPPORT
CONVECTIVE ENHANCEMENT TO SMALL SCALE VORT MAX TRACKING ACROSS
SOUTH/SOUTHEAST PORTIONS OF THE AREA THIS MORNING...WITH SOME
INDICATIONS OF MCV HAVING ALSO FORMED ACROSS FAR NORTH CENTRAL
INDIANA. A BRIEF LULL IN PRECIP IS POSSIBLE IN WAKE OF THIS
FEATURE OVER NEXT FEW HOURS...BUT A STEADY STREAM OF SMALLER SCALE
WAVES EMBEDDED IN NORTHWEST UPPER FLOW AND POOLED LOW LEVEL
MOISTURE AXIS ACROSS MUCH OF LOCAL AREA WILL SUPPORT AT LEAST
CHANCE TSRA MENTION THROUGH THE REMAINDER OF THE AFTERNOON.
SLIGHTLY MORE STABLE CONDITIONS ASSOCIATED WITH MORNING
CLOUDS/PRECIP MAY TEMPER SEVERE THREAT AT LEAST THROUGH MUCH OF
THE AFTERNOON HOURS. POCKET OF STRONGER MID/UPPER FLOW IS EXPECTED
TO OVERSPREAD THE AREA THIS EVENING AND THIS MAY SUPPORT SOUTHEAST
PROPAGATION OF POTENTIAL CONVECTIVE SYSTEM FORMING UPSTREAM OF
LOCAL AREA TONIGHT. RADAR ESTIMATES THAT MANY LOCATIONS FROM
WESTERN STARKE COUNTY INTO GRANT COUNTY HAVE EXPERIENCED 1 TO 2
INCHES OF RAINFALL WITH MORNING STORMS...AND SOME HYDRO CONCERNS
MAY EVOLVE TONIGHT DEPENDING ON UPSTREAM LATE AFTERNOON/EVENING
CONVECTIVE EVOLUTION...BUT WILL HOLD OFF ON ANY HYDRO HEADLINES AT
THIS TIME.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 449 AM EDT THU AUG 21 2014

UPPER LEVEL JET DYNAMICS COMBINED WITH THE LEADING EDGE OF THETA E
CONVERGENCE WAS HELPING TO TRIGGER ISOLATED STORMS AND AN AREA OF
SHOWERS NORTH OF THE FRONT. THE STORMS WERE HIGH BASED EARLY THIS
MORNING...BUT SHOULD BECOME MORE SURFACE BASED AS THE FRONT MOVES
NORTH AND AS THE ATMOSPHERE DESTABILIZES WITH DAYTIME HEATING LATER
TODAY. THETA E FLUX WILL INCREASE TONIGHT...WITH A BETTER CHANCE FOR
SHOWERS AND STORMS AS AN UPPER LEVEL DISTURBANCE TOPS THE UPSTREAM
RIDGE AND MOVES INTO THE WESTERN GREAT LAKES REGION. THE 12KM NAM
APPEARED TO HAVE A REASONABLE HANDLE ON THE TIMING OF THIS UPSTREAM
SYSTEM AND THE TRACK OVER THE UPPER LEVEL RIDGE...SO HAVE LIKELY
THUNDERSTORM CHANCES LATER TONIGHT. SEVERE STORMS ARE POSSIBLE GIVEN
DEEP LAYER SHEAR TOPPING OUT AT 30 TO 40 KNOTS. HAVE RAISED HIGHS
TODAY. THE NAM/MET HAS RAISED HIGHS TODAY 5 DEGREES AT SBN AND
APPEARS ON TRACK...COMING MORE IN LINE WITH THE GFS/MAV. 850 MB
TEMPS WILL BE BETWEEN 18C AND 19C TODAY...AND SOME SUN TODAY SHOULD
ALLOW HIGHS TO RISE TO BETWEEN 82F AND 86F.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 449 AM EDT THU AUG 21 2014

MAIN CONCERN THIS PERIOD IS POTENTIAL FOR EXCESSIVE HEAT AS STRONG
UPR LEVEL RIDGE BUILDS INTO THE AREA RESULTING IN HEAT INDEX
READINGS IN THE 90S EACH AFTN. ALTHOUGH THESE READINGS ARE A BIT
BLO OUR ADVISORY CRITERIA... IMPACTS MAY BE GREATER THAN USUAL DUE
TO EXPECTED RATHER LONG DURATION OF THE HEAT WAVE... AND
DIFFICULTY FOR PEOPLE TO BECOME ACCLIMATED TO THE HEAT GIVEN
ABNORMALLY COOL TEMPS THUS FAR THIS SUMMER.

CONVECTION AT NOSE OF A WK WLY LLJ MAY BE ONGOING IN OUR AREA AT
THE START OF THE PERIOD FRIDAY MORNING. WK LOW LEVEL WAA PATTERN
AND STNRY SFC BOUNDARY DRAPED ACROSS NERN PORTION OF THE CWA
EXPECTED FRI WHICH MAY PROVIDE FOCUS FOR REDEVELOPMENT IN THE AFTN
AS AIRMASS DESTABILIZES. THIS BOUNDARY EXPECTED TO REMAIN OVER THE
AREA FRI NGT WITH NOSE OF WSWLY LLJ OVER THE MID MS VALLEY
PROVIDING FORCING FOR CONVECTION UPSTREAM OVERNIGHT WHICH COULD BE
SUSTAINED INTO OUR AREA GIVEN LINGERING WK/MODERATE ELEVATED
INSTABILITY. RATHER STRONG NWLY UPR LEVEL FLOW ON EAST SIDE OF MS
VALLEY RIDGE WILL PROVIDE DECENT DEEP LAYER SHEAR FRI/FRI
NGT...ESPECIALLY OVER ERN PORTIONS OF THE CWA WHICH ALSO COULD AID
IN CONVECTIVE PERSISTENCE AS WELL AS SUPPORT A FEW STRONG/SVR
STORMS AROUND PEAK HEATING FRI AFTN/EVE. DOUBT CONVECTION WILL BE
SUFFICIENTLY WIDESPREAD OR LAST LONG ENOUGH TO HOLD TEMPS DOWN
SIGNIFICANTLY FRIDAY. GIVEN H85 TEMPS PROGGED IN THE 19-20C RANGE
STAYED CLOSE TO PREVIOUS FCST WITH HIGHS RANGING FROM THE M80S NE
TO AROUND 90 SW. DWPTS SHOULD ALSO BE RISING TO THE L-M70S WHICH
WILL RESULT IN AFTN HEAT INDICES ABOUT 5-10F HIGHER THAN TEMPS.
LIGHT WINDS FRI NGT SHOULD ALLOW FOR SOME RADIATIONAL COOLING SO
EXPECT MINS TO BE IN THE U60S NE AND L70S SW.

SIMILAR CONDITIONS EXPECTED SATURDAY. UPR RIDGE AXIS SHOULD MOVE
SLIGHTLY EAST INTO OUR AREA AS STRONG TROF MOVES ACROSS THE NRN
ROCKIES. E-W ORIENTED SURFACE BOUNDARY WILL LIKELY REMAIN OVER THE
AREA PROVIDING SOME FOCUS FOR CONVECTION AS AIRMASS DESTABILIZES
DURING THE DAY. WK LOW LEVEL GRADIENT WINDS AND VERY MOIST AIRMASS
OVER THE AREA SHOULD AGAIN LIMIT HEATING BUT EXPECT SUFFICIENT
MIXING TO ALLOW FOR HIGHS CLOSE TO FRIDAYS READINGS AS SUGGESTED BY
MAV MOS TEMPS.

STNRY SFC BOUNDARY SHOULD LIFT NORTH OF OUR CWA SAT NGT-SUNDAY AS
SFC LOW DEEPENS OVER THE NRN PLAINS. THIS SHOULD RESULT IN MAINLY
DRY CONDITIONS BY SUNDAY WITH TEMPS CONTG TO SLOWLY WARM. NRN PLAINS
LOW EXPECTED TO LIFT NE-E INTO ONTARIO MONDAY AND TO QUEBEC TUE WITH
TRAILING WK CDFNT DROPPING SOUTH INTO OUR AREA BY THAT TIME. SOME
SUPPRESSION OF UPR RIDGE PER ECMWF SOLUTION SEEMS APPROPRIATE AS
SHRTWV BREAKS OVER THE TOP ACROSS THE UPR GRTLKS...  SO WKNG CAPPING
INVERSION/CHC TSTMS... AND SLIGHTLY LOWER TEMPS FCST BY TUE. MEDIUM
RANGE MODELS DIFFERING SOLUTIONS WRT PERSISTENCE OF UPR RIDGE TUE
LEADING TO EVEN GREATER DIFFERENCES BY WED WITH ECMWF SUGGESTING
RIDGING BUILDING BACK INTO OUR REGION AS CLOSED LOW DEVELOPS IN
THE WRN U.S., WHILE GFS FCSTG MORE PROGRESSIVE WRN TROF WITH A STRONG
SHRTWV APPROACHING THE MIDWEST BY WED EVE. GIVEN LARGE DIFFERENCES
STAYED CLOSE TO PREVIOUS FCST WHICH WAS FOR CONTD SLOW COOLING
TREND AND A LOW CHC OF TSTMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 129 PM EDT THU AUG 21 2014

FIRST WAVE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE TO EXIT
NORTHEAST INDIANA OVER THE NEXT FEW HOURS...WITH ATTENTION FOR
REMAINDER OF AFTERNOON AND EVENING TURNING UPSTREAM WITH A COUPLE
OF ADDITIONAL SHORT WAVE PROGRESSING THROUGH UPPER RIDGE. SOME
LINGERING IFR CONDITIONS WILL PERSIST OVER THE NEXT HOUR OR TWO
BEFORE IMPROVING AFTER 20Z. THE NEXT SHORT WAVE ACROSS SOUTHERN
WISCONSIN SHOULD ALLOW SHOWERS TO MOVE BACK INTO NORTH CENTRAL
INDIANA LATE THIS AFTERNOON. A RELATIVE STABLE BUBBLE PERSISTS
ACROSS NORTH CENTRAL INDIANA IN REGARDS TO SFC BASED CONVECTIVE
POTENTIAL...BUT SUSPECTING ENOUGH ELEVATED INSTABILITY WILL BE
PRESENT FOR SOME THUNDER POTENTIAL AS THE SRN WISCONSIN SHORT
WAVE SHIFTS EASTWARD THIS AFTERNOON. BETTER CHANCE OF THUNDER
STILL APPEARS TO BE IN STORE FOR LATE EVENING INTO THE OVERNIGHT
AS NEXT UPSTREAM IOWA SHORT WAVE APPROACHES THE AREA WITH
PERSISTENT ISENTROPIC UPGLIDE ASSOCIATED WITH LOW LEVEL BOUNDARY
ACROSS THE REGION. HAVE KEPT IN VCSH MENTION AFTER 12Z WITH A MORE
MUDDLED PICTURE AT THIS FORECAST DISTANCE IN TERMS OF LATCHING
ONTO ANY SIGNIFICANT ADDITIONAL SHORT WAVES. GRADUALLY MID LEVEL
HEIGHT RISES TOWARD THE END OF THE PERIOD SHOULD DIMINISH
CONVECTIVE POTENTIAL LATER FRIDAY AFTERNOON.

&&

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

$$

UPDATE...MARSILI
SYNOPSIS...MARSILI
SHORT TERM...SKIPPER
LONG TERM...JT
AVIATION...MARSILI


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