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000
FXUS63 KIWX 211449
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1049 AM EDT TUE MAY 21 2013

.SYNOPSIS...
ISSUED AT 1042 AM EDT TUE MAY 21 2013

LOW PRESSURE OVER THE UPPER MIDWEST WILL TRACK EAST INTO THE GREAT
LAKES REGION TOMORROW. THIS SYSTEM WILL BRING INCREASING CHANCES
FOR SHOWERS AND THUNDERSTORMS TO THE AREA...MAINLY LATER TONIGHT
INTO WEDNESDAY. A FEW THUNDERSTORMS MAY BECOME STRONG TO SEVERE. A
FEW SHOWERS MAY LINGER INTO THURSDAY...WITH COOLER AND DRIER AIR
FORECAST TO SETTLE INTO THE REGION LATE THIS WEEK INTO THE
HOLIDAY WEEKEND.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 442 AM EDT TUE MAY 21 2013

OUTFLW DOMINANT CONVN CONTS TO PROGRESS SLOWLY ACRS
WRN PORTION OF CWA THIS MORNING YET CONTS TO FESTER WITHIN AS YET
FVRBLY UNSTABLE LL THETA-E RIDGE. HWVR UPSTREAM STRATIFORM ACRS WRN
IN/ERN IL DECAYING RAPIDLY W/WARMING CLOUD TOPS NOTED IN IR AND
MARKS XPCD RAPID EWD DOWNTREND THROUGH DAYBREAK.

STABILIZATION OCCURRING IN WAKE OF THIS LINE AND SUSPECT LTL IF ANY
REDVLPMNT IN THE CARDS UNTIL VRY LT THIS AFTN/EARLY EVE IN ASSOCN/W
EWD TRANSLATION OF SFC LOW INTO NE WI BY 00Z. HWVR NWD REDVLPMNT OF
PREFERRED LL THETA-E RIDGE LIKELY DELAYED TO WELL AFT DARK TIMED
W/NWD EXPANSION OF LLJ TIED TO EJECTING CONV INDUCED SW TROUGH OUT
OF OK. THUS DELAYED OVERNIGHT RAMP TO PRIOR POPS TWD WINDOW OF
GREATER MODEL CONSENSUS IMPLIED FORCING AFT MIDNIGHT.

INBTWN XPC CLDS TO SCT OUT BY LT MORNING/EARLY AFTN W/ANOTHER VRY
WARM DAY IN STORE PER MODEST MIXING WITHIN LL THERMAL RIDGE.

&&

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 442 AM EDT TUE MAY 21 2013

AN UPPER LOW WILL LIFT NORTHEAST WEDNESDAY...ACCOMPANIED BY A COLD
FRONT. THE RIGHT ENTRANCE REGION OF AN UPPER LEVEL JET WILL PASS
OVER THE SOUTHEAST PORTION OF THE FORECAST AREA WEDNESDAY INCLUDING
MOST OF NW OHIO. HOWEVER...GIVEN VERY LIMITED CAPE AND A RATHER
UNIDIRECTIONAL WIND PROFILE...CURRENT THINKING IS SEVERE STORM
POTENTIAL IS MARGINAL. MUCH COOLER AIR WILL SPREAD INTO THE AREA
BEHIND THE COLD FOR LATE THIS WEEK. FAVORED THE GFS MEAN ENSEMBLE
MOS WHICH HAS BEEN GENERALLY TRENDING A LITTLE COLDER LATE THIS
WEEK...OTHERWISE...HAS BEEN CONSISTENT FOR THE PAST FEW 00Z RUNS.
KEPT THE FORECAST DRY AFTER THURSDAY AS AN UPPER LEVEL RIDGE BUILDS
UPSTREAM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 442 AM EDT TUE MAY 21 2013

DIFFICULT FORECAST WITH RESPECT TO CONVECTIVE PROBABILITIES THROUGH
THE FORECAST PERIOD AND EARLY FAILURE. AMID A STRONGLY DIVERGENT
BOUNDARY LAYER AXIS PER VIS SAT IMAGERY LYING ACROSS NERN IL/NWRN IN
PAST FEW HOURS PROVING TO BE STRONGLY DETRIMENTAL. THIS DESPITE
MODERATE SURFACE BASED INSTABILITY POOL SITUATED ACROSS NORTHERN
INDIANA/SOUTHERN LOWER MICHIGAN THIS EVENING. A WELL SCOURED/DEEPLY
MIXED ENVIRONMENT ACROSS NORTHERN/CENTRAL ILLINOIS WITH PUTRID
MID/UPR 50S DPS THIS AFTERNOON...REMOVES ANY IMMEDIATE CONCERN FOR
INITIATION NEXT FEW HOURS. THIS IMMEDIATE UPSTREAM ENVIRON WAS
WITHIN WAKE OF EARLY AFTERNOON SHORTWAVE...THAT INITIATED
STRONG/SEVERE CONVECTION MIDDAY ACROSS YOOP/NORTHERN LOWER MICHIGAN.
EASTERN FRINGE OF EML ENVIRONMENT WITH 7.5-8.25 C/KM MID LEVEL LAPSE
RATES TO LIKELY KEEP UPDRAFTS IN CHECK/ISOLATED REMAINDER OF THE
EVENING. WILL MAINTAIN THAT ANY SIG CHANCE FOR CONVECTION TO BE
ASSOCIATED WITH WELL UPSTREAM CONVECTION ACROSS EAST CENTRAL
MO...WITH SEVERAL HOUR WAIT UNTIL MORE VIGORED UPSTREAM 925-8H WIND
FIELD WITH PRESENT FOCUS OVER THE OZARKS/NORTHERN ARKANSAS SHIFTS
NORTHEASTWARD OVERNIGHT INTO SRN/CENTRAL ILLINOIS AND VEERS/RAMPS TO
45-55KTS...FINALLY NOSING INTO KLAF VCNTY AROUND 09-12 UTC PER
RAP/ARW...AND A SIGNIFICANTLY POOR/LAGGARD HRRR3KM RECENTLY COMING
IN LINE TO REALITY. SUFFICIENT PREPARATORY CONDITIONING OF
ENVIRONMENT VIA MOISTURE FLUX CONVERGENCE SFC-900MB TO MAINTAIN
MUCAPE POOL OF 1200-2000 J/KG ACROSS FORECAST AREA. THIS SHOULD
ALLOW DECENT MAINTENANCE OF CONVECTIVE COMPLEX WITH ACROSS MISSOURI
TO REACH NORTHERN INDIANA WELL AFTER MIDNIGHT INTO KSBN AND NEAR
DAYBREAK AT KFWA. DISFAVORED TIMING/PARCEL ASCENT BECOMING LESS
SURFACE BASED WITH TIME AND MODEST DEEP LAYER SHEAR TO LARGELY
PRECLUDE SEVERE POTENTIAL...THOUGH HAVE CONTD TO ACK THAT STRONGEST
CELLS MAY APPROACH LOW END SEVERE LIMITS IN HWO.


&&

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

$$

SYNOPSIS...STEINWEDEL
SHORT TERM...T
LONG TERM...SKIPPER
AVIATION...T


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