Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 311004
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
504 AM 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.

&&

.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 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1239 AM EST SAT JAN 31 2015

LIGHT SOUTHWEST FLOW THROUGH THIS AFTERNOON AS LOW LEVEL RIDGE
AXIS CONTINUES TO DROP SOUTHEAST ACROSS THE MID ATLANTIC STATES.
SOME INCREASE IN MID LEVEL WAA CLOUDS EXPECTED THIS MORNING...AND
SCT-BKN HIGH CLOUDINESS...BUT MVFR CIGS SHOULD HOLD OFF UNTIL
TONIGHT. LEAD UPPER VORT MAX ASSOCIATED WITH NEXT SIGNIFICANT
SYSTEM TO IMPACT THE AREA COMBINED WITH ISENTROPIC UPGLIDE WILL
ALLOW SNOW TO OVERSPREAD TERMINALS IN THE EVENING AND HAVE
INTRODUCED IFR VSBYS TOWARD THE END OF THIS PERIOD. SNOWFALL
INTENSITY/CIGS/VSBYS TO DETERIORATE MORE SIGNIFICANTLY AFTER THIS
FORECAST VALID PERIOD AND ESPECIALLY AFTER 12Z SUNDAY AS PRIMARY
UPPER LEVEL TROUGH APPROACHES FROM THE WEST.

&&

.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 WATCH FROM THIS EVENING THROUGH LATE SUNDAY NIGHT
     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.
&&

$$

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


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