Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 011153
AFDIWX

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

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

A MAJOR WINTER STORM WILL CONTINUE TO TAKE SHAPE TODAY...BRINGING
HEAVY SNOW ALONG WITH BLOWING AND DRIFTING SNOW TO MUCH OF THE
REGION THROUGH TONIGHT. TRAVEL WILL BECOME DIFFICULT TO IMPOSSIBLE
ACROSS THE REGION THIS AFTERNOON INTO THIS EVENING. SNOW WILL
DIMINISH LATE TONIGHT AS THE SYSTEM PULLS OFF TO THE EAST WITH
SOME LINGERING LAKE EFFECT SNOW SHOWERS POSSIBLE ACROSS SOUTHWEST
LOWER MICHIGAN AND NORTHWEST INDIANA ON MONDAY. ANOTHER SYSTEM MAY
BRING ADDITIONAL SNOW ACCUMULATIONS TO PORTIONS OF THE SOUTHERN
GREAT LAKES REGION TUESDAY NIGHT INTO EARLY WEDNESDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 524 AM EST SUN FEB 1 2015

MERGER OF NORTHERN STREAM AND SOUTHERN STREAM SYSTEMS NOW COMPLETE
OVER THE CENTRAL CONUS...WITH THIS STORM HEADED FOR THE OHIO VALLEY
AND WESTERN GREAT LAKES REGIONS. HEAVY SNOW ALONG WITH BLOWING AND
DRIFTING SNOW EXPECTED AS ADVERTISED LAST WEEK. A PLUME OF MID AND
UPPER LEVEL MOISTURE SPREADING INTO THE AREA AHEAD OF THIS SYSTEM
WILL HELP ENHANCE SNOWFALL AMOUNTS. THE RIBBON OF -2C TO -5C AT 850
MB FAVORABLE FOR HEAVIER SNOW WILL CONTINUE OVER MOST OF THE AREA
FOR THE DURATION OF THE EVENT. THE OVERALL TREND OF THE GFS IS
FAVORED WITH A GRADUAL NORTH SHIFT OF THE SFC LOW TRACK. FORECAST
THERMAL PROFILES ALONG THE EXTREME SOUTH PART OF THE FORECAST AREA
VERY CLOSE TO A RAIN/SNOW MIX. GIVEN THE NORTHERN MODEL SHIFT AND
THE POTENTIAL FOR A RAIN/SNOW MIX OVER THE FAR SOUTH...RAISED
SNOWFALL AMOUNTS OVER FAR SOUTHWEST LOWER MICHIGAN AND LOWERED
AMOUNTS SLIGHTLY FROM MARION TO PORTLAND. STILL EXPECT HEAVY SNOW
WITH BLOWING SNOW THIS AFTERNOON. THE COLD AIR WAS ALREADY SPREADING
SOUTHWEST OUT OF LOWER MICHIGAN WHERE TEMPERATURES WERE FALLING
RAPIDLY. THE TEMPERATURES DROP WAS MORE ACUTE THAN ADVOCATED BY THE
GFS...WHICH LENDS CREDENCE TO STRONGER WINDS THIS AFTERNOON INTO
EARLY TONIGHT. EXPECT SUBSTANTIAL BLOWING AND DRIFTING SNOW BY LATE
AFTERNOON...CAUSING SOME ROADS TO BECOME IMPASSIBLE. KEPT SNOWFALL
TOTALS IN THE DOUBLE DIGITS ALONG AND NORTH OF HIGHWAY 30.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 524 AM EST SUN FEB 1 2015

LONG TERM PERIOD TO BEGIN WITH CONCERN FOR LAKE EFFECT SNOW
SHOWERS...PRIMARILY ACROSS NORTHWEST INDIANA PORTIONS OF THE
FORECAST AREA WITH A PRIMARILY NORTHERLY FETCH. LIMITED/LOWERING
INVERSION HEIGHTS AND INCREASING MID LEVEL SYNOPTIC SCALE SUBSIDENCE
ALONG WITH BACKING LOW LEVEL WINDS SHOULD LIMIT ANY ADDITIONAL
ACCUMULATIONS TO LESS THAN AN INCH. DID MAINTAIN CHANCE OF LIGHT
SNOW ACROSS THE FAR EAST MONDAY MORNING GIVEN RECENT TREND TO
SLOWER/MORE AMPLIFIED SOLUTION REGARDING EXITING WINTER STORM SUNDAY
NIGHT. OTHERWISE...DECREASING CLOUDS EXPECTED ON TUESDAY OUTSIDE OF
LAKE EFFECT CLOUDINESS WHICH WILL BE ADVANCING EASTWARD WITH THE
BACKING WIND PROFILES. NEW SNOW COVER AND LOW LEVEL THERMAL
TROUGHING ACROSS THE AREA WILL KEEP MAX TEMPS IN THE TEENS.

AN ACTIVE NORTHWEST FLOW PATTERN IS IN STORE FOR MUCH OF THE
REMAINDER OF THE UPCOMING WEEK WITH A WEAK CLIPPER SYSTEM TRACKING
INTO THE AREA LATE MONDAY NIGHT/EARLY TUESDAY...BUT WITH ONLY A
BRIEF WINDOW OF DEEPER MOISTURE ASSOCIATED WITH THIS WAVE WILL KEEP
LOW CHANCE ACROSS MAINLY THE NORTHWEST. A MORE PRONOUNCED WAVE IN
NORTHWEST FLOW WILL REACH THE UPPER MS VALLEY LATE TUESDAY/WEDNESDAY
WITH A BROAD ZONE OF ISENTROPIC UPGLIDE ASSOCIATED WITH RETREATING
COLD AIR DOME. GIVEN FAIRLY GOOD AGREEMENT WITH OPERATIONAL EC/GFS
AND BROAD NATURE OF FORCING HAVE INCREASED TO POPS TO LIKELY FOR
TUESDAY NIGHT WITH EARLY INDICATIONS SUGGESTING A 1-3 OR 2-4 INCH
TYPE ACCUMULATION POSSIBLE. ANY MODERATION IN TEMPERATURES IN WAA
REGIME IN ADVANCE OF THIS WAVE WILL BE SHORT LIVED AS PASSAGE OF
PRIMARY UPPER WAVE USHERS IN ANOTHER ARCTIC FRONTAL BOUNDARY ACROSS
THE AREA...WHICH MAY ALSO SERVE AS A FOCUS FOR MORE LIGHT SNOW LATER
WEDNESDAY. NOT SIGNIFICANT CHANGES MADE TO THE REMAINDER OF THE
FORECAST WITH MODERATION IN TEMPERATURES EXPECTED AGAIN FOR
FRIDAY/SATURDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 642 AM EST SUN FEB 1 2015

SNOW TO INCREASE IN INTENSITY...ESPECIALLY FROM MID MORNING TO
EARLY AFTERNOON AS ISENTROPIC LIFT CONTINUES TO STRENGTHEN AND AS
PRIMARY UPPER LEVEL TROUGH APPROACHES THE MID MS RIVER VALLEY.
LIFR CONDITIONS ARE EXPECTED THROUGH OF THE LATE MORNING THROUGH
EARLY EVENING PERIOD DUE TO THE COMBINATION OF HEAVY SNOW AND
INCREASING NORTHEAST WINDS (GUSTING TO AROUND 25 KNOTS) RESULTING
IN BLOWING SNOW/REDUCED VISIBILITIES. DEFORMATION FORCING TO ALLOW
SNOW TO CONTINUE INTO TONIGHT...BEFORE DIMINISHING DURING THE
OVERNIGHT HOURS. CONDITIONS TO IMPROVE TOWARD THE END OF THE
FORECAST VALID 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.
&&

$$

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


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