Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 010636
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
136 AM EST SUN FEB 1 2015

.SYNOPSIS...
ISSUED AT 427 PM EST SAT JAN 31 2015

A COLD FRONT WILL MOVE SOUTH FROM THE GREAT LAKES TO THE OHIO
VALLEY TONIGHT. A STRENGTHENING LOW PRESSURE SYSTEM WILL MOVE EAST
ALONG THE FRONT THROUGH THE OHIO VALLEY SUNDAY AND SUNDAY NIGHT.
SNOW WILL OVERSPREAD OUR AREA TONIGHT AND BECOME HEAVY ON SUNDAY.
WINDS WILL INCREASE SUNDAY AND SUNDAY NIGHT CAUSING BLOWING AND
DRIFTING SNOW MAKING TRAVEL DIFFICULT...IF NOT IMPOSSIBLE. LOWS
TONIGHT WILL PRIMARILY BE IN THE 20S..WITH LITTLE IF ANY
TEMPERATURE RISE ON SUNDAY. MUCH COLDER TEMPERATURES ARE IN STORE
FOR SUNDAY NIGHT AND MONDAY.

&&

.UPDATE...
ISSUED AT 645 PM EST SAT JAN 31 2015

NO SGFNT CHANGES TO EARLIER ZONES ATTM. PRECIP LIFTING NE TOWARD
THE AREA BEING FORCED BY WK LEAD SHRTWV MOVG INTO THE UPR MS
VALLEY/MIDWEST. ALL RAIN UPSTREAM ACROSS IL ATTM BUT AMDAR
SOUNDINGS EAST OF CHICAGO SUGGEST A PROFILE SUPPORTIVE OF SNOW.
MAINTAINED GOING MIXED PRECIP WX GRIDS ACROSS SWRN PORTION OF THE
CWA THIS EVE... WITH JUST SNOW ACROSS THE REST OF THE AREA. 18Z
MODELS CONT TO SUPPORT FCST OF A MAJOR WINTER STORM IMPACTING THE
CWA LATE TONIGHT THROUGH SUNDAY NIGHT AS MAIN UPR TROF DIGS SE
INTO THE MIDWEST PRECEDED BY STRONG MOISTURE TRANSPORT FROM THE SW
AND ACCOMPANIED BY A DEEPENING SFC LOW MOVG EAST FROM KS THROUGH
THE OH VALLEY RESULTING IN INCREASING WINDS AND SGFNT DRIFTING
SNOW FOR THE LATTER HALF OF THE EVENT.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 418 PM EST SAT JAN 31 2015

INCREASED CONFIDENCE THROUGHOUT THE DAY WRT QUITE SIGNIFICANT
WINTER WX EVENT TARGETING CWA. WV IMAGERY AND UPSTREAM
PRECONDITIONING SETS STAGE FOR DEEP WALL OF MOISTURE
ADVECTION/MFLUX CONVERGNECE FOR PROLONGED PERIOD INTO CWA. PWAT
VALUES OVR CNTL PLAINS ON ORDER OF 200-300 PERCENT OF NORMAL.
EXPANSIVE BREADTH OF BULK MOISTURE WITH CONSISTENT 0.5 TO 0.65
INCH PWAT PIVOTING SLOWLY THROUGH SRN TWO THIRDS CWA THROUGH THE
EVENT...WITH CULMINATING 0.9 INCH PWAT TAP ACRS SWRN OH SUN
EVENING...ON ORDER OF 2 SD ABOVE CLIMATOLOGICAL
MEAN...IMPLICATING THIS EVENT WITH HIGH POTENTIAL FOR BEING SIG
OUTLIER TO CLIMATOLOGY. HIGHLY CONFLUENT/RAMPING I285/I290K ISENT
UPGLIDE OVER SERN MISSOURI THIS EVENING...TO 50-55KT LOW LEVEL
JET ENTERING FAR SRN IN BY SUN AFTN. STRONG TRAILING MID LEVEL
DEFORMATION WITH PROLONGED PERIOD OF SYSTEM RELATIVE ISENT
UPGLIDE PERSISTING THROUGH 06 UTC MONDAY...LENDING TO EXT IN TIME
TO ERN CWA UNTIL 12 UTC. BLSN TO IMPACT HIGHLY...ESPCLY ACRS E-W
ROADS ACRS NRN CWA WHERE EVENT SLR TO BE HIEST. 7H CLOSED LOW
TRACK ALONG WITH TROWAL/DEFORMATION AXIS PORTENDS TO AXIS OF
HEAVIEST SNOW FROM ABOUT KNOX TO TOLEDO...WITH A FAIRLY BROAD
20-30 MILES EITHER SIDE...BEFORE SIG SNOW TOTAL GRADIENTS FOUND.
EXTREME DEEPENING WITH SENSATIONAL MID TROPOPHERIC HEIGHT FALLS
RAMPING IN EXCESS OF 200M/12 HR THROUGH AS IT TRACKS EWD THROUGH
MID/OHIO VALLEY SUN NIGHT...AND MORE STRONGLY CLOSED 7H TRACK AND
PRESENCE OF DECREASED STATIC STATIC STABILITY SUN AFTERNOON INTO
EARLY EVENING GIVES CONCERN FOR POSSIBLE MESOBANDING LEADING TO
AMOUNTS UPWARDS OF 15 INCHES THROUGH FAR NRN IN ALONG NORTH OF
ROUTE 30...TO SCNTL LWR MI/EXTREME NWRN OH. 18 UTC NAM EVEN
GENERATING POCKETS OF 30-80 J/KG MUCAPE ACRS NRN TWO THIRDS CWA
SUNDAY INTO EARLY SUN NIGHT...PERHAPS POINTING TO CONVECTIVE
ELEMENTS...COMMENSURATE SNOWFALL RATES WOULD THEN LIKELY PEAK AT
2-4 INCHES PER HOUR...ALBEIT BRIEFLY.

FROM 03/09 UTC SREF WITH ITS INCREASED CLUSTERING OVER NRN/CNTL
CWA TO 12/18 UTC MODEL SUITE CONSISTENT MESSAGE APPEARS.
REMARKABLY EVEN THE LOWEST OUTLIER IN 09 UTC SREF MEMBERS ACRS
NRN CWA PEGGED AT 8-10 INCHES...WITH CONSENSUS MEANS ABOUT 6-8
INCHES HIR. IDYLLIC DEEP DGZ ALONG NORTH OF ROUTE 30...WITH
NAM/ARW DEPICTING 7-9KFT DGZ LAYER. STILL MINOR CONCERN WITH
SUPERSATURATION ABOVE TO INTRODUCE PLATES/NEEDLES FOR FINER SIZED
FLAKES...BUT CONCEDE QPF/DYNAMICS OF SYSTEM TO OFFSET. KSBN TO
KJYM MOST CONSTERNATION ACRS FAR SWRN/SRN INDIAN COUNTIES WHERE
INITIAL WARM 0-2KM WET BULB INTRUSION LENDING POSSIBLE MIX AT
ONSET AND LESSENED SLR THEREAFTER WITH PARTIAL MELT.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 418 PM EST SAT JAN 31 2015

ONE OR MORE LAKE EFFECT SNOW BANDS WILL RESIDE NEAR OR JUST WEST
OF THE FORECAST AREA ACROSS LAKE AND PORTER COUNTIES. HI RES
MODELS TREND THIS FEATURE SLOWLY EAST THROUGH THE MORNING AND
THEN DISSIPATE AS IT SHIFTS ACROSS NORTHERN INDIANA. DESPITE WHAT
SHOULD BE A WELL FORMED BAND THAT MAY EXTEND THE LONG AXIS OF LK
MI...INVERSION HGTS WILL BE LOWERING AND MSTR WILL BE SOMEWHAT
LIMITED. ALSO EXACT EVOLUTION OF THE BAND WILL BE DETERMINED BY
ANY POTENTIAL INTENSIFICATION OF THE SFC LOW AND ITS FINAL TRACK.
AS A RESULT HAVE NOT MADE MANY CHANGES OTHER THAN TO INCREASE
POPS SLIGHTLY IN FAR NW AREAS AND TRY TO BRING THE BAND SOMEWHAT
EAST BEFORE WEAKENING.

ALTHOUGH NO BIG SYSTEMS ARE DURING THE PERIOD...A WEAK SYSTEM
WILL DROP SE TOWARDS THE REGION TUESDAY INTO EARLY WEDNESDAY.
LIGHT SNOW WILL BE POSSIBLE WITH THIS FEATURE FOLLOWED BY ANOTHER
BRIEF SHOT OF COLD AIR BEFORE SOME MODERATION AGAIN LATE WEEK
INTO THE WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 132 AM EST SUN FEB 1 2015

LEAD UPPER LEVEL SHORT WAVE HAS ALLOWED LIGHT SNOW TO OVERSPREAD
TERMINALS OVER PAST SEVERAL HOURS...AND WITH ISENTROPIC UPGLIDE
AND LOW LEVEL FGEN FORCING INCREASING OVER THE NEXT SEVERAL
HOURS....SNOW INTENSITY SHOULD PICK UP...PARTICULARLY TOWARD
DAYBREAK. AN EXTENDED PERIOD OF LIFR CONDITIONS EXPECTED AS POTENT
UPPER LEVEL SYSTEM BEGINS TO APPROACH MID MS RIVER VALLEY ON
SUNDAY WITH PERIODS OF HEAVY SNOW SUNDAY/SUNDAY EVENING BEFORE
DIMINISHING. DEEPENING SFC REFLECTION TRACKING SOUTH OF THE AREA
WILL ALLOW NORTHEAST WINDS TO INCREASE WITH SIGNIFICANT BLOWING
AND DRIFTING SNOW AND REDUCED VISIBILITIES. SNOW TO WIND DOWN IN
INTENSITY TOWARD THE END OF THIS FORECAST VALID PERIOD...ALTHOUGH
GUSTY NORTHEAST WINDS TO 25 TO 30 KNOTS WILL RESULT IN CONTINUED
BLOWING SNOW THROUGH END OF THE FORECAST PERIOD.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER STORM WARNING UNTIL 4 AM EST /3 AM CST/ MONDAY FOR
     INZ003>009-012>018-020-022>027-032>034.

MI...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR MIZ081.

     WINTER STORM WARNING UNTIL 4 AM EST MONDAY FOR MIZ077>080.

OH...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR OHZ001-002-004-
     005-015-016-024-025.

LM...NONE.
&&

$$

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


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