Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KIWX 311941
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
341 PM EDT SUN AUG 31 2014

.SYNOPSIS...
ISSUED AT 1051 AM EDT SUN AUG 31 2014

DRIER AIR WILL FILTER INTO THE AREA THIS AFTERNOON INTO TONIGHT
BEHIND A DEPARTING COLD FRONT AS HIGH PRESSURE BRIEFLY BUILDS INTO
THE GREAT LAKES REGION. ANOTHER COLD FRONT WILL PUSH IN FROM THE WEST
MONDAY INTO MONDAY EVENING BRINGING RENEWED CHANCES FOR SHOWERS
AND THUNDERSTORMS. HIGHS TODAY WILL BE IN THE UPPER 70S TO LOW 80S
TODAY WITH LOWS TONIGHT IN THE UPPER 60S.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 340 PM EDT SUN AUG 31 2014

PESKY STRATUS TRAPPED UNDERNEATH SHALLOW POST FNTL INVERSION WAS SLW
TO BREAKUP THROUGH THIS MORNING BUT WELL UNDERWAY NOW W/CONCURRENT
UPTICK IN POST FNTL MIXING. SUFFICIENT AFTN DIURNAL DESTABILIZATION
HAS OCCURRED WITHIN CONTD WEAKLY CONFLUENT SFC FLW TO YIELD A FEW
ISOLD SHRA ACRS THE CWA AND WILL RIDE A LOW CHC POP MENTION
THROUGH THIS AFTN TO ACCOUNT FOR THAT. OTRWS CONTD WK BUT MOIST
SWRLY FLW REMAINS IN PLACE THROUGH THE OVERNIGHT BFR STRENGTHENING
ON MON AHD OF NXT POTENT UPSTREAM SW EJECTING OUT OF THE NRN
ROCKIES. CLRG COMBINED W/WK GRADIENT FLW PORTENDS A LIKELY
REDVLPMNT OF LOW STRATUS AND PERHAPS SOME FOG AFT MIDNIGHT YET
BELIEVE SFC GRADIENT AND INCREASING HIGH CLDS WILL BE ENOUGH TO
CURTAIL DENSE FOG DVLPMNT.

UPSTREAM ROCKIES SW EJECTS OUT IN SIMILAR FASHION TO LAST TWO
SYS/S...UP THROUGH THE NRN LAKES MON AFTN W/TRAILING SFC TROUGH
STALLING OUT AGAIN DOWN NEAR THE OH RVR ON TUE. SYNOPTIC PATTN
REMAINS PERSISTENT W/A MOIST AND POTENTIALLY UNSTABLE AIRMASS LOCKED
IN ACRS THE SRN LAKES/OH VALLEY COUNTERED BY POOR MID LVL LAPSE
RATES AND GENERALLY POOR PREFNTL BASED FORCING AS LARGER SCALE HGT
FALLS SHIFT WELL NW OF AREA. THUS BELIEVE POPS ON MON ARE OVERDONE
ESP IN LIGHT OF NEW 12Z MODEL CONSENSUS. BASED ON PRIOR TWO
GENERALLY MISHANDLED SYSTEMS HAVE CUT THINGS BACK ESP SE THIRD.
RENEWED DEEP MIXING AND AT LEAST PARTIAL INSOLATION SHLD YIELD CLOSE
TO GOING FCST MAX TEMPS.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 340 PM EDT SUN AUG 31 2014

MAIN FOCUS LIES WITH ONGOING CONVECTION AND HEAVY RAINFALL POTENTIAL
AT THE ONSET OF THE LONG TERM PERIOD MONDAY NIGHT.

SFC COLD FRONT FROM ATTENDANT NRN ONTARIO SFC CYCLONE PROGGED TO BE
JUST WEST OF THE AREA MONDAY NIGHT. ONGOING CONVECTION LIKELY AFTER
00Z ACROSS THE AREA...AS FRONTAL BOUNDARY PUSHES E/SE THROUGH THE
AREA. POTENTIAL SEVERE THREAT AS HIGHLIGHTED BY SPC DY2 OUTLOOK INTO
THE EVENING HOURS...GIVEN 1500-2000 J/KG SBCAPE AND 35-40 KTS OF 0-6
KM BULK SHEAR...MAY BE IN THE LINEAR FROM ALONG/AHEAD OF THE SFC
FRONT WITH DAMAGING WINDS BEING THE PRIMARY HAZARD. AT THIS
POINT...SEVERE POTENTIAL AFTER 00Z WILL BE CONTINGENT ON CONVECTIVE
ACTIVITY DURING THE AFTERNOON HOURS. HOWEVER...AS THE FRONT MOVES
THROUGH THE AREA...DIURNAL STABILIZATION SHOULD YIELD A WANING
SEVERE THREAT HEADING THROUGH THE OVERNIGHT HOURS.

ATTENTION THEN TURNS TO HEAVY RAINFALL THREAT AFTER 03Z. AS SFC
FRONT PUSHES THROUGH THE LOCAL AREA...BOUNDARY WILL BEGIN TO SLOW
AND ORIENT WSW TO ENE ACROSS THE SOUTHEAST THIRD OF THE FORECAST
AREA. AS BROAD NORTH CENTRAL CONUS UPPER TROUGH TRANSLATES EASTWARD
INTO THE GREAT LAKES...AN UPPER DISTURBANCE WILL EJECT NORTHEAST
ALONG THE FRONTAL BOUNDARY. ALONG AND AHEAD OF THE BOUNDARY...PWAT
VALUES IN EXCESS OF 1.75 INCHES...WARM CLOUD LAYER GREATER THAN
11KFT...MODEST MUCAPE VALUES AROUND 1000-1500 J/KG W/ LONG AND
SKINNY CAPE SOUNDING PROFILE...SHOULD YIELD THE POTENTIAL FOR
EFFICIENT RAINFALL PROCESSES AND HEAVY RAINFALL. WITH UNIDIRECTIONAL
WIND PROFILE ORIENTED SOMEWHAT PARALLEL TO THE FRONT...SMALL SPEED
DIFFERENCE BETWEEN 850MB AND 500MB...ALONG WITH REGION UNDER THE
RIGHT ENTRANCE REGION OF GREAT LAKES UPPER JET...SHOULD ALLOW THE
FOCUS OF TRAINING CONVECTION ALONG AND JUST AHEAD OF THE FRONTAL
BOUNDARY. THIS COULD BE ENHANCED IF LOW LEVEL JET KICKS UP INTO THE
AREA...HOWEVER FOCUS OF THE JET WILL REMAIN SOUTHEAST OF THE
FORECAST AREA. CONTEMPLATED ADDING HEAVY RAINFALL MENTION INTO
FORECAST OVERNIGHT INTO TUESDAY MORNING...HOWEVER UNCERTAINTIES WILL
THE POSITION OF THE SYNOPTIC FRONT WILL PRECLUDE MENTION AT THIS
TIME...AS FOCUS FOR HEAVY RAINFALL COULD BE JUST SOUTH OF THE
FORECAST AREA...ESPECIALLY IF 00Z-06Z CONVECTION REINFORCES A
COMPOSITE OUTFLOW SOUTH OF THE AREA. WILL KEEP POPS IN THE LIKELY
CATEGORY MONDAY NIGHT GIVEN UNCERTAINTIES AND CONVECTIVE NATURE OF
THE PRECIPITATION.

FRONTAL BOUNDARY SLOWLY PUSHES SOUTH OF THE AREA ON TUESDAY.
LINGERING SHOWERS AND STORMS POSSIBLE INTO THE AFTERNOON HOURS
ACROSS THE EXTREME SOUTHEAST PART OF THE FORECAST AREA. HIGH
PRESSURE WILL BUILD EAST ACROSS THE AREA TUESDAY NIGHT THROUGH
THURSDAY...BRINGING COOLER AND DRIER CONDITIONS TUESDAY AND
WEDNESDAY. AS UPPER EASTERN CONUS RIDGE BUILDS AND SFC RIDGE AXIS
SHIFTS EAST OF THE REGION...RETURN FLOW WILL BRING WARMER AND MORE
HUMID AIR TO THE AREA THURSDAY THROUGH FRIDAY. UPPER LEVEL FLOW WILL
BECOME MORE ZONAL AS NORTHERN TIER SHORTWAVE/ATTENDANT SFC CYCLONE
PUSHES A SLOW MOVING COLD FRONT SOUTH INTO THE AREA.
THEREFORE...CONTINUED WITH LOW CHANCE POPS THURSDAY NIGHT THROUGH
SATURDAY AS PROVIDED BY ALLBLEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 154 PM EDT SUN AUG 31 2014

PESKY STRATUS FINALLY BREAKING UP EARLY THIS AFTN W/RECENT UPTICK
IN LL MIXING AND XPC THIS TREND WILL CONT THROUGH LT AFTN. AN
ISOLD SHRA INBTWN THE TERMINALS REMAINS PSBL YET THIS AFTN WITHIN
WEAK SFC CONFLUENCE BUT TAF MENTION OMITTED FROM THE TERMINALS FOR
18Z ISSUANCE. PRIMARY PROB LIES W/LIKELY RENEWED STRATUS/FOG
REDVLPMNT OVERNIGHT W/PERSISTENT SOUPY AIRMASS IN PLACE. PER
GENERALLY WK GRADIENT FLW AND AT LEAST EARLY CLRG MVFR VSBY
RESTRICTIONS AFT MIDNIGHT LIKELY YET BELIEVE MORE SIG ISSUE WILL
BE IFR CIGS DVLPMNT AS STRATUS REFORMS. REGARDLESS THIS WILL BURN
OFF/MIX OUT MON MORNING AS LLJ FLW RAMPS SIGLY AHD OF SW TROUGH
EJECTING THROUGH THE PLAINS.


&&

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

$$

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


VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSNORTHERNINDIANA
WWW.TWITTER.COM/NWSIWX
WWW.YOUTUBE.COM/NWSNORTHERNINDIANA





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.