Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 012330
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
730 PM EDT MON SEP 1 2014

.SYNOPSIS...
ISSUED AT 123 PM EDT MON SEP 1 2014

SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE AREA THIS
AFTERNOON INTO EARLY EVENING. A COLD FRONT WILL PUSH SOUTH THROUGH
THE AREA TONIGHT...BRINGING A BETTER CHANCE FOR SHOWERS AND
THUNDERSTORMS OVERNIGHT INTO TUESDAY MORNING. HIGH PRESSURE WILL
BUILD INTO THE AREA ON TUESDAY...PROVIDING DRY CONDITIONS AND
COOLER TEMPERATURES THROUGH MIDWEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 320 PM EDT MON SEP 1 2014

CONVECTIVE ACTIVITY ONGOING ACROSS NORTHWEST THIRD OF CWA AS OF
1845Z AS REMNANT OUTFLOW BOUNDARY SLIDES EASTWARD ACROSS THE AREA
AHEAD OF LARGER SCALE FORCING. SEVERE THREAT HAS DIMINISHED FROM THE
EARLY MORNING HOURS AS EXTENSIVE CLOUD COVER HAS KEPT A RELATIVELY
STABILIZED ATMOSPHERE IN PLACE. CANNOT RULE OUT AN ISOLATED STRONG TO
SEVERE STORM THROUGH 00Z...WITH DAMAGING WINDS THE MAIN THREAT...AS
LATE AFTERNOON DESTABILIZATION YIELDING 1500-2000 J/KG SBCAPE EAST OF
U.S. 31 AND 0-6KM BULK SHEAR OF 30-40 KTS ACROSS THE AREA. HOWEVER
POOR MID LEVEL LAPSE RATES AND LACK OF STRONG FORCING SHOULD LIMIT
OVERALL ORGANIZATION. COVERAGE WORDING REFLECTED IN THE FORECAST
THROUGH 00Z.

ATTENTION TURNS TO THE POTENTIAL FOR HEAVY RAINFALL ACROSS SOUTHERN
PORTIONS OF THE AREA OVERNIGHT...AS LARGE SCALE NORTH CENTRAL CONUS
TROF SLIDES EAST TOWARDS THE GREAT LAKES AND SFC COLD FRONT PUSHES
SOUTHEAST THROUGH THE AREA. WIDE SPREAD OF SOLUTIONS AMONG MODEL
GUIDANCE WRT LOCATION/AXIS OF HEAVIEST RAINFALL. AS SFC BOUNDARY
SETTLES SOUTHEAST INTO THE FCST AREA...S/W ENERGY EJECTING THROUGH
THE LARGE SCALE TROF AND 120 KT UPPER JET EJECTING NORTHEAST THROUGH
THE GREAT LAKES WILL PROVIDE STRONG FORCING ACROSS THE REGION.
HIGHER RES GUIDANCE SUCH AS THE ARW-EAST...NMM-EAST AND 4KM SPC
WRF...SUGGEST AFTERNOON/EARLY EVENING CONVECTION REINFORCING THE
FOCUS FOR CONVECTIVE ACTIVITY SOUTH OF THE AREA OVERNIGHT...ROUGHLY
FROM AN EVANSVILLE TO COLUMBUS OH LINE. LOWER RES GUIDANCE SUCH AS
THE NAM/GFS/ECMWF PUTS THE FOCUS OF THE CONVECTION CLOSER TO THE
MAIN SYNOPTIC SFC FORCING...WITH THE HEAVIEST AXIS OF RAINFALL FROM
KIND TO KCLE. THIS SOLUTION WOULD PUT THE FAR SOUTHEAST
COUNTIES...FROM A MARION TO PAULDING LINE AND SOUTHWARD...AT RISK
FOR HEAVY RAINFALL AND LOCALIZED FLOODING AFTER MIDNIGHT INTO EARLY
TUESDAY MORNING. ALTHOUGH CONFIDENCE IS HIGH FOR HEAVIER RAINFALL
EVENT GIVEN RIGHT ENTRANCE REGION OF JET STREAK OVERHEAD...PWAT
VALUES IN TH 1.6-1.8 INCH RANGE...WARM CLOUD DEPTHS AROUND
12KFT...LITTLE CLOUD LAYER SHEAR AND CLOUD LAYER FLOW PARALLEL TO
THE SFC BOUNDARY...UNCERTAINTIES WITH THE LOCATION OF THE RAINFALL
WILL PRECLUDE CATEGORICAL POPS OR HEADLINES OVERNIGHT. WILL
MAINTAIN A MENTION OF HEAVY RAINFALL AND LOCALIZED FLOODING
ROUGHLY ALONG AND SE OF THE U.S. 24 CORRIDOR. WILL CLOSELY MONITOR
TRENDS TONIGHT AND ADJUST FORECAST ACCORDINGLY.

AS FRONTAL WAVE PUSHES NORTHEAST OF THE AREA TUESDAY MORNING AND SFC
BOUNDARY SLIDES SOUTHEAST OF THE AREA...PRECIP CHANCES WILL WANE
FROM NW TO SE THROUGH THE DAY. POP TRENDS FOR THE TUESDAY PERIOD
STILL IN LINE FROM PREVIOUS FCST...SO NO MAJOR CHANGES WITH THIS
ISSUANCE. NO MAJOR CHANGES TO TEMPS TONIGHT AND TUESDAY.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 320 PM EDT MON SEP 1 2014

PERTURBED NRN STREAM FLW ACRS SRN CANADA OVERTOP FLAT CONUS RIDGING
WILL CONT THIS PD. HIGH PRES BLDS EWD OUT OF THE PLAINS TO START THE
PD TUE NIGHT IN WAKE OF LEAD SW LIFTING UP THROUGH NRN QB. HWVR
SHALLOW CAA WING GIVES WAY QUICKLY AS FLW BACKS DURING THE DAY WED
IN RESPONSE TO ANOTHER UPSTREAM VIGOROUS SYS EJECTING EWD THROUGH
SRN AB. THIS SYS WILL CONT TO STREAK EWD THROUGH FRI AS ATTENDANT
SFC BNDRY SAGS SWD INTO THE LWR LAKES/OH VALLEY. HWVR AS HAS BEEN
THE CASE W/MOST OF THESE SYS/S...HGT FALLS ARE CONFINED WELL NORTH
W/TRAILING SFC FNTL BNDRY WKNG THROUGH TIME. AS SUCH AND IN
REFLECTION OF MOST 12Z MED RANGE MODEL GUIDANCE...NOTHING MORE THAN
A LOW CHC POP WARRANTED LATE WEEK.

BEYOND THAT SERN US/WRN ATL UPR RIDGE LOOKS TO FLATTEN FURTHER
W/SECONDARY SW AMPLIFYING THROUGH JAMES BAY NXT WEEKEND. THIS WILL
ALLOW A BIT COOLER CANADIAN AIRMASS TO DRIVE SEWD ACRS THE LAKES/NEW
ENGLAND W/SEASONABLY PLEASANT AND DRY WX XPCD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 730 PM EDT MON SEP 1 2014

CONVECTION ASSOCIATED WITH WEAK PREFRONTAL TROUGH HAS CURRENTLY
EXITED THE AREA. MAIN COLD FRONT IS STILL WELL TO OUR WEST THOUGH
AND WILL CROSS THE REGION LATER TONIGHT. A FEW SHOWERS MAY BE
POSSIBLE AROUND KSBN BUT INSTABILITY WILL BE VERY LIMITED AND HAVE
THEREFORE REMOVED THUNDER MENTION. SOME BRIEF MVFR CONDITIONS MAY
BE POSSIBLE JUST BEFORE SUNRISE BUT OTHERWISE VFR CONDITIONS
EXPECTED. BETTER CHANCES FOR THUNDER AND MVFR CONDITIONS WILL BE
AT KFWA. CONVECTION CURRENTLY OVER MISSOURI WILL EXPAND NORTHEAST
IN RESPONSE TO STRENGTHENING UPPER LEVEL JET. STILL SOME QUESTION
AS TO EXACTLY HOW FAR NORTH THIS PRECIP WILL REACH BUT CURRENT HI-
RES MODELS SUGGEST KFWA WILL GET CLIPPED AROUND 09-12Z TOMORROW
MORNING. NOT CONFIDENT ENOUGH IN CEILING HEIGHTS TO GO WITH FUEL
ALTERNATE CONDITIONS BUT WILL CONTINUE TO MONITOR OBSERVATIONAL
TRENDS OVERNIGHT. DRIER AIR AND VFR CONDITIONS EXPECTED AT KFWA BY
LATE TOMORROW MORNING.

&&

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

$$

SYNOPSIS...NG
SHORT TERM...NG
LONG TERM...T
AVIATION...AGD


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