Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 311722
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1222 PM EST SAT JAN 31 2015

.SYNOPSIS...
ISSUED AT 501 AM EST SAT JAN 31 2015

A WINTER STORM WILL IMPACT THE REGION BEGINNING TONIGHT AND
CONTINUING INTO SUNDAY NIGHT. THE HEAVIEST SNOW WITH THIS SYSTEM
IS EXPECTED SUNDAY MORNING THROUGH EARLY SUNDAY EVENING...WITH
BLOWING AND DRIFTING SNOW ALSO BECOMING A CONCERN SUNDAY
AFTERNOON AND EVENING. AFTER MILDER CONDITIONS TODAY INTO THE
30S...MUCH COLDER TEMPERATURES ARE IN STORE FOR SUNDAY NIGHT AND
MONDAY.

&&

.UPDATE...
ISSUED AT 825 AM EST SAT JAN 31 2015

DISCONTENT WITH MICHIGAN COUNTIES UNDER WATCH ESPECIALLY GIVEN 03
UTC SREF/06 UTC NAM ALONG WITH WPC CONTINUING TO PEG NRN THIRD
WITH HIEST SNOW SWATH. DEGREE OF ISENT MOISTURE FLUX
CONVERGENCE/ADVECTION INTO SRN LWR MI TO EASILY OVERWHELM/SHUNT
NWD ANY DRY AIR ENTRAINMENT ISSUES. REVERT TO BROAD 6 TO 12 INCH
ACCUMS AND AWAIT 12 UTC MODEL SUITE/09 UTC SREF OUTPUT BEFORE
FINE TUNING WITH APPLICATION OF GREATER MESOSCALE DETAIL/WARNING
SEGMENTATION. ACTUALLY RIGHT NOW AM MORE CONCERNED WITH
DIMINISHED AMOUNTS FAR SWRN/SRN IN COUNTIES OWING TO MAGNITUDE OF
WARM WET BULB WEDGE EXTRUDED NWD THROUGH INDIANA. 1KFT PLUS 1C
WET BULB PER KGUS 06 UTC NAM PROFILE...WOULD SUGGEST AT LEAST A
PARTIAL MELT OVERNIGHT...LENDING TO LOWER SLR FOR FIRST 6-9 HOURS
OF EVENT.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 501 AM EST SAT JAN 31 2015

FORECAST CONCERNS FOR THE SHORT TERM WILL CENTER ON SNOW
OVERSPREAD THE AREA TONIGHT WHICH WILL LEAD INTO POTENTIALLY HIGH
IMPACT SNOW EVENT FOR THE AREA INTO SUNDAY NIGHT COVERED IN THE
LONG TERM SECTION BELOW. A WINTER STORM WARNING WILL BE IN EFFECT
FROM 00Z THIS EVENING THROUGH 09Z MONDAY MORNING WITH A WINTER
STORM WATCH IN EFFECT FOR SOUTHERN LOWER MICHIGAN COUNTIES FOR
THE SAME TIMES.

QUIET WEATHER EXPECTED TO CONTINUE THROUGH MOST OF THE DAY WITH
SOME MID LEVEL WAA INDUCED CLOUDINESS ACROSS NORTHERN ILLINOIS
THIS MORNING EXPECTED TO SHIFT ACROSS NORTHERN INDIANA OVER THE
NEXT FEW HOURS. AN UPPER LEVEL SHORT WAVE TRACKING ACROSS THE
NORTHERN GREAT LAKES MAY ALLOW SOME LOW CLOUDS TO PUSH ACROSS THE
FAR NORTH...BUT MOST LOCATIONS SHOULD BE PARTLY CLOUDY AT LEAST
THROUGH EARLY AFTERNOON. AN INCREASE IN MID AND HIGH LEVEL CLOUDS
IS EXPECTED LATER THIS AFTERNOON AS PRIMARY SHORT OF INTEREST FOR
UPCOMING SNOW EVENT BEGINS TO DIG ACROSS THE CENTRAL ROCKIES.
HIGH TEMPERATURES THIS AFTERNOON SHOULD BE 3 TO 6 DEGREES WARMER
THAN YESTERDAY INTO THE LOWER AND MID 30S.

FOR TONIGHT A SHEARED UPPER LEVEL SHORT WAVE WILL LIFT INTO THE
SOUTHERN GREAT LAKES REGION DOWNSTREAM OF PRIMARY VORT MAX. BROAD
SYNOPTIC SUPPORT FOR UVM WILL ALSO INCREASE AS LOCAL AREA BECOMES
POSITIONED IN FAVORABLE RIGHT ENTRANCE OF UPPER JET. ISENTROPIC
ASCENT PER 290K SFC ALSO TO SIGNIFICANTLY RAMP UP TOWARD DAYBREAK
SUNDAY. OVERALL EXPECTING LIGHT SNOWFALL AMOUNTS IN THE 1 TO 3
INCH RANGE FOR TONIGHT...WHICH WILL LEAD INTO PERIOD OF GREATEST
IMPACTS WITH THIS WINTER STORM ON SUNDAY/SUNDAY NIGHT DISCUSSED
IN LONG TERM SECTION BELOW AS STRONGER MID/UPPER LEVEL FORCING
APPROACHES THE REGION.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 501 AM EST SAT JAN 31 2015

HEAVY SNOW IS EXPECTED EARLY SUNDAY...CONTINUING THROUGH SUNDAY
EVENING BEFORE ENDING EARLY MONDAY. SEVERAL FAVORABLE FACTORS
COMING TOGETHER FOR A WINTER STORM WITH HEAVY SNOW AND BLOWING
SNOW. MOISTURE LADEN SUBTROPICAL MOISTURE IN THE MID TO UPPER
LEVELS WILL ARRIVE IN TANDEM AS THE NORTHERN STREAM SYSTEM AND
THE SOUTHERN STREAM PHASE. PRECIPITATION EFFICIENCY WITH THIS
SETUP SHOULD BE VERY GOOD. FOR THIS EVENT...FAVORED A GFS
SOLUTION. THE GFS HAS BEEN TRENDING TOWARD A SLOWER AND MORE
NORTHERN TRACK AND A RELATIVELY LONG DURATION EVENT. ALSO...THIS
GFS SEEMS TO BE HANDLING ALL OF THE SIGNIFICANT PARAMETERS FOR
THIS WINTER STORM REASONABLY WELL. THE 290K GARCIA/MIXING RATIO
METHOD RENDERS 8 TO 12 INCHES OF SNOW...WITH LESSER AMOUNTS OVER
FAR SOUTHERN LOWER MICHIGAN. STILL SOME UNCERTAINTY OVER THIS FAR
NORTHERN PORTION OF THE AREA GIVEN LOWER MIXING RATIOS AND A
GREATER CHANCE FOR DRY AIR ENTRAINMENT WITH LOW LEVEL/DRIER
NORTHEAST FLOW DURING THE SECOND HALF OF THE EVENT. THEREFORE...
AFTER COORDINATION WITH SURROUNDING OFFICES... KEPT LOWER
MICHIGAN IN A WINTER STORM WATCH FOR NOW AND DEFERRED TO THE NEXT
SHIFT THE OPTION TO UPDATE. WAS HESITANT TO RAISE HIGH END
SNOWFALL AMOUNTS IN LIGHT OF CLIMATE DATA...ALTHOUGH GFS...ECMWF
AND NAM ALL SUPPORT SNOWFALL TOTALS OF 12 TO 15 INCHES ACROSS
NORTHERN INDIANA AND NORTHWEST OHIO. CLIMATE PERCENTAGES AT BOTH
FT WAYNE AND LAFAYETTE INDICATE A TWO DAY SNOWFALL TOTAL OF 8
INCHES OR MORE IS RARE...IT ONLY HAPPENS ON AVERAGE OF ONCE EVERY
5 TO 6.5 YEARS. FURTHERMORE...A SNOWFALL OF 12 INCHES OR MORE
HAPPENS ONLY ONCE IN EVERY 15 TO 25 YEARS. GIVEN THESE
FACTORS...AND CONSIDERING THE ABOVE...KEPT ONGOING SNOWFALL
AMOUNTS CLOSE TO THE ONGOING/INHERITED AMOUNTS...WITH THE LATEST
THINKING THAT TOTAL SNOWFALL AMOUNTS FROM THIS STORM SHOULD RANGE
FROM 7 TO 11 INCHES. SIGNIFICANT TRAVEL IMPACTS WILL BE MOUNTING
SUNDAY NIGHT AS WINDS INCREASE WITH BLOWING AND DRIFTING SNOW.
RAISED WIND SPEEDS CONSIDERABLY SUNDAY EVENING GIVEN THE NEW AND
FARTHER NORTH AND DEEPER GFS LOW WITH A TIGHT SURFACE PRESSURE
GRADIENT OVER THE AREA. OTHERWISE...SNOWFALL SHOULD END FROM WEST
TO EAST LATE SUNDAY NIGHT. SNOW DRIFTS ON UNPLOWED ROADS WILL
LIKELY MAKE SOME ROADS IMPASSIBLE. WIND CHILLS DROPPING WELL BELOW
ZERO EARLY MONDAY MORNING ARE EXPECTED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1217 PM EST SAT JAN 31 2015

HIGH CONFIDENCE FOR DETEORATION INTO LONG LIVED LIFR EVENT DURING
DAYTIME HOURS SUNDAY. INCREASED CONFIDENCE WITH RESPECT TO MULTI
MODEL CONSENSUS FOR ALL SNOW EVENT/HEAVY AT TIMES SUNDAY. LATER
FORECAST ITERATIONS WILL INCLUDE BLSN AS SFC WINDS WILL BEGIN TO
BACK AND RAMP CONSIDERABLY LT SUNDAY AFTN INTO NIGHT.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER STORM WARNING FROM 7 PM EST /6 PM CST/ THIS EVENING TO 4
     AM EST /3 AM CST/ MONDAY FOR INZ003>009-012>018-020-022>027-
     032>034.

MI...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 AM EST MONDAY
     FOR MIZ077>081.

OH...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 AM EST MONDAY
     FOR OHZ001-002-004-005-015-016-024-025.

LM...NONE.
&&

$$

UPDATE...MURPHY
SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MURPHY


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