Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 221752
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
152 PM EDT FRI AUG 22 2014

.SYNOPSIS...
ISSUED AT 310 PM EDT THU AUG 21 2014

A WEAK UPPER LEVEL DISTURBANCE MOVING ALONG A STALLED FRONTAL
BOUNDARY ACROSS THE REGION WILL RESULT IN SHOWERS AND
THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL MAINLY ACROSS SOUTHERN
PORTIONS OF THE AREA THIS MORNING. WITH DAYTIME HEATING... THERE
IS A CHANCE OF THUNDERSTORMS REDEVELOPING THIS AFTERNOON AND
LINGERING INTO TONIGHT. HIGHS TODAY WILL BE IN THE MID 80S WITH
LOWS TONIGHT IN THE UPPER 60S AND LOWER 70S.

&&

.UPDATE...
ISSUED AT 1145 AM EDT FRI AUG 22 2014

AN UPPER LEVEL SHORT WAVE DROPPING ACROSS NORTHERN INDIANA WILL
CONTINUE TO SAG INTO THE OHIO RIVER VALLEY THIS AFTERNOON
PROVIDING A LULL IN HIGHER PRECIPITATION CHANCES. ELEVATED
INSTABILITY ACROSS THE MID MISSISSIPPI RIVER VALLEY HAS ALLOWED
FOR SOME RENEWED CONVECTION TO DEVELOP ACROSS THE QUAD CITIES AREA
EARLIER THIS MORNING...BUT HAS SHOWN SOME WEAKENING TRENDS
RECENTLY. GIVEN THE EXCESSIVE AMOUNT OF RECENT RAIN ACROSS
PORTIONS OF SOUTHWEST/SOUTH CENTRAL PORTIONS OF THE AREA...THIS
WILL NEED TO BE WATCHED THROUGH THE REMAINDER OF THE LATE
MORNING/EARLY AFTERNOON HOURS. MID LEVEL RIDGING IN STILL EXPECTED
TO AMPLIFY SOMEWHAT THROUGH THIS AFTERNOON...WHICH EFFECTIVELY
SHOULD RESULT IN AN INCREASINGLY SOUTHEAST PROPAGATION TO
UPSTREAM CONVECTION THIS AFTERNOON. CONFIDENCE IS LOW IN ON
RECEIVING ADDITIONAL SIGNIFICANT RAINFALL ACROSS THE AREA THIS
AFTERNOON...ALTHOUGH GIVEN RAINFALL PAST 24 HOURS...WILL BE
MONITORING THIS SITUATION CLOSELY. SOME DOWNWARD ADJUSTMENTS MAY
BE NEEDED TO TEMPERATURES WHICH WILL LIKELY BE ADDRESSED WITH
MIDDAY UPDATE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 434 AM EDT FRI AUG 22 2014

...INCREASED FLASH FLOOD THREAT IN LOCALIZED AREAS NEXT 3 TO 6
HOURS...

MAIN FOCUS OF FORECAST WILL BE ON NEAR TERM WITH EXPANDING AREA OF
SHOWERS AND THUNDERSTORMS IMPACTING PORTIONS OF NORTHERN INDIANA
WITH POTENTIAL TO SPREAD INTO PORTIONS OF SOUTHERN LOWER MI AND NW
OHIO. BAND OF SLOW MOVING SHOWERS/STORMS WAS LOCATED FROM THE
CHICAGO SUBURBS INTO NW INDIANA SOUTHEAST INTO PORTIONS OF WEST
CENTRAL OHIO. LOTS OF BACKBUILDING HAS BEEN OCCURRING WITH CORFIDI
VECTORS SHOWING ONLY SLOW ESE MOVEMENT. HIGH RES MODELS EARLIER THIS
EVENING KEYED IN ON THIS AND ARE COMING TO FRUITION. EXPECTED THIS
TO CONTINUE THROUGH 12Z WITH A DECREASE IN COVERAGE AND INTENSITY AS
MODELS SUGGEST 30 KT LOW LEVEL JET BEGINS TO WEAKEN AND WEAK
MID/UPPER LEVEL DISTURBANCE MOVING THROUGH THE SOUTHERN GREAT LAKES
EXITS. DISCUSSION HAS TAKEN PLACE REGARDING THE NEED FOR A
FLOOD/FLASH FLOOD WATCH. HEAVIEST POCKETS OF RAINFALL HAVE BEEN
CONFINED TO NARROW BANDS BUT HAVE BEEN OCCURRING OVER THE SAME AREAS
IMPACTED YESTERDAY. GIVEN EVENT IS ONGOING...SEE NO MAJOR VALUE IN
HOISTING A WATCH WHEN POTENTIAL EXISTS FOR LITTLE OR NO ADDITIONAL
RAINFALL IN MANY AREAS UNTIL MAYBE TONIGHT. EVEN THIS SCENARIO IS
UNCERTAIN WITH MANY QUESTIONS AS TO WHERE THE STATIONARY FRONT WILL
LIE AFTER BEING MODULATED SOUTHWARD FROM ONGOING CONVECTION. SPC 4KM
WRF 00Z ACTUALLY HAD A DECENT HANDLE ON CURRENT SETUP AND PUSHES
FRONT WELL SOUTH OF THE AREA. OTHER MODELS VARY FROM ADDITIONAL RAIN
LATER TODAY/TONIGHT TO NOTHING. WILL DEFER ANY WATCHES TO DAY SHIFT
AND HANDLE IMMEDIATE CONCERNS WITH ADVISORIES AND WARNINGS AS NEEDED.

WITH THE ABOVE CONCERNS...POPS HAVE BEEN LEFT IN THE SLGT CHC TO CHC
RANGE WITH HIGH TEMPERATURES TODAY HIGHLY DEPENDENT ON AMOUNT OF
CLOUD COVER REMAINING IN THE WAKE OF CURRENT CONVECTION. BEHIND ALL
THE CONVECTION A LOT OF LOW CLOUDS AND FOG WAS NOTED ACROSS NW
ILLINOIS AND EASTERN IOWA THAT COULD POSE AN ISSUE DURING THE DAY
FRIDAY.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 434 AM EDT FRI AUG 22 2014

UPR LEVEL RIDGE OVER THE MS VALLEY THIS MORNING EXPECTED TO EXPAND
NORTHWARD AND SHIFT EAST INTO THE WRN GRTLKS/LWR OH VALLEY ON SATURDAY.
ROUGHLY E-W ORIENTED SFC BOUNDARY WHICH HAS LINGERED OVER THE AREA
IS EXPECTED TO SHIFT SOUTH INTO THE OH VALLEY BY SATURDAY AS WK
LOW PRESSURE OVER THE UPR MIDWEST DIMINISHES AND A NEW STRONGER
LOW DEVELOPS OVER THE CENTRAL PLAINS. THIS SHOULD LEAD TO GRDLY LESS
FAVORABLE CONDITIONS FOR CONVECTION IN OUR AREA OVER THE WEEKEND
DESPITE CONSIDERABLE DIURNAL INSTABILITY. TEMPS SHOULD RESPOND TO
APCHG UPR RIDGE... RISING INTO THE U80S/L90S OVER SWRN PORTIONS
OF THE AREA AND M-U80S NE OVER THE WEEKEND.

RIDGE AXIS WILL PIVOT TO AN OH VALLEY TO NEW ENGLAND LINE BY MONDAY
AS A STRONG SHRTWV EJECTS FROM THE ROCKIES TO ONTARIO... RESULTING
IN CONTD ABOVE NORMAL TEMPS/HUMIDITY ACROSS OUR AREA. TRAILING CDFNT
ASSOCIATED WITH THIS SYSTEM SHOULD SAG INTO OUR AREA BY TUE BRINGING
A RENEWED TSTM POTENTIAL. FRONT WILL LIKELY STALL OVER THE AREA AS
IT ENCOUNTERS THE STRONG RIDGE IN PLACE... WITH A SECOND SHRTWV MOVG
EAST ACROSS THE GRTLKS WED-THU PUSHING THE FRONT SOUTH OF THE AREA
BY THE END OF THE PERIOD AND ALLOWING TEMPS TO FALL BACK TO NORMAL
OR SLIGHTLY BLO BY THAT TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 150 PM EDT FRI AUG 22 2014

A MID/UPPER LEVEL SHORT WAVE HAS DROPPED SOUTHEAST OF THE AREA
THIS AFTERNOON ALLOWING FOR A LULL IN PRECIP CHANCES. SCATTERED
SHOWERS AND STORMS HAVE BEEN REGENERATING BACK ACROSS WEST CENTRAL
ILLINOIS IN ELEVATED WAA REGIME. WATER VAPOR IMAGERY SUGGESTS
ANOTHER SHORT WAVE ROUNDING THE UPPER LEVEL RIDGE ACROSS SOUTHERN
IOWA WHICH SHOULD EVENTUALLY WORK INTO THE SOUTHERN GREAT LAKES
THIS EVENING. MODERATELY UNSTABLE CONDITIONS WILL DEVELOP THIS
AFTERNOON WITH MAIN QUESTION ON PRECIP CHANCES DEALING WITH
FORCING MECHANISM. RESIDUAL OUTFLOWS FROM MORNING CONVECTION MAY
TEND TO FOCUS LATE AFTERNOON/EVENING THUNDERSTORM CHANCES...ALONG
WITH THE POSSIBILITY OF WEAK CONVERGENT AXIS DOWNWIND OF LAKE
MICHIGAN SERVING AS ANOTHER FOCUS. EXPECTED COVERAGE/CONFIDENCE OF
OCCURRENCE IS TOO LOW TO INCLUDE TS FOR THE 18Z TAFS AT THIS TIME.
HAVE MAINTAINED TREND TO IFR/LIFR CONDITIONS LATE TONIGHT IN FOG
WITH VERY WEAK GRADIENT AND PLENTY OF LOW LEVEL MOISTURE
LINGERING. IF STRATUS/FOG DOES MATERIALIZE...THE IFR/LIFR
CONDITIONS SHOULD IMPROVE TO MVFR TOWARD MID MORNING SATURDAY.

&&

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

$$

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


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