Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 132037
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
337 PM EST SAT FEB 13 2016

.SYNOPSIS...
ISSUED AT 331 PM EST SAT FEB 13 2016

HIGH PRESSURE WILL MOVE ACROSS OUR AREA TONIGHT CAUSING LAKE
EFFECT SNOW SHOWERS TO DIMINISH. A WEAK LOW PRESSURE SYSTEM
WILL MOVE EAST FROM THE PLAINS SUNDAY CAUSING LIGHT SNOW TO
SPREAD INTO OUR AREA. TEMPERATURES WILL CONTINUE BELOW
NORMAL WITH LOWS TONIGHT AROUND ZERO AND HIGHS ON SUNDAY
AROUND 20.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 331 PM EST SAT FEB 13 2016

LAKE EFFECT SNOW SHOWERS WILL DIMINISH IN COVERAGE AND INTENSITY
LATE THIS AFTN AND THIS EVE AS HIGH PRESSURE MOVES ACROSS THE
AREA REDUCING CROSS LAKE FETCH WITH SUBSIDENCE/WAA ALOFT LOWERING
INVERSION HEIGHTS. WITH LITTLE ADDITIONAL ACCUM EXPECTED, HAVE CANCELLED
ADVISORY. STRATO CU SHOULD ALSO DIMINISH THIS EVENING PROVIDING
EXCELLENT RADIATIONAL COOLING CONDITIONS TONIGHT, THOUGH SOME HIGH
CLOUDS AHEAD OF SHRTWV APCHG FROM THE PLAINS SHOULD MOVE INTO OUR
AREA AFTER MIDNIGHT. ONLY MINOR ADJUSTMENTS TO GOING MINS WHICH
ARE AT OR A BIT BLO LATEST LOWEST GUIDANCE IN MOST OF THE AREA.

&&

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 331 PM EST SAT FEB 13 2016

MODERATING TEMPS AND TWO CHANCES FOR SNOW ARE THE MAIN STORIES
FOR THIS LONG TERM PERIOD. THE FIRST CHANCE OF SNOW WILL ARRIVE
TOMORROW AND PERSIST THROUGH MONDAY MORNING. HEALTHY MIDLEVEL
SHORTWAVE CURRENTLY SEEN EXITING THE NORTHERN ROCKIES ON WV
IMAGERY WILL DIVE SOUTHEAST BY TOMORROW AND CROSS OUR AREA.
HOWEVER...HIGHLY CONFLUENT MID/UPPER LEVEL FLOW WILL SHEAR OUT
THIS WAVE WITH RAPID WEAKENING EXPECTED BY THAT TIME. THERE WILL
BE A DECENT MOISTURE SURGE WITH 850-700MB MIXING RATIOS OVER 2
G/KG AND SOME GENTLE/BROAD ISENTROPIC ASCENT THAT WILL GENERATE
SOME LIGHT SNOW BUT NEAR TOTAL COLLAPSE OF SUPPORTING MID/UPPER
LEVEL DYNAMICS SUGGESTS QPF WILL BE VERY LIMITED...AN IDEA
SUPPORTED BY LATEST HI-RES MODELS. NAM BUFR SOUNDINGS STILL
INDICATE A DEEP ISOTHERMAL LAYER IN THE -12 TO -15C RANGE BUT GFS
SOUNDINGS ARE A BIT WARMER AND WOULD SUGGEST LOWER OVERALL RATIOS.
FOR NOW...WENT WITH JUST SLIGHTLY HIGHER THAN CLIMO...GENERATING
1-2" FOR MOST OF THE AREA BY MON MORNING. BEST CHANCE FOR HIGHER
AMOUNTS IS STILL IN OUR SOUTHWEST WHERE BETTER MOISTURE AND
FORCING RESIDE. MAY SEE UP TO 3" IN A FEW SPOTS BUT CONFIDENCE AND
EXPECTED IMPACTS ARE NOT NEARLY HIGH ENOUGH FOR AN ADVISORY.

SECOND...AND POTENTIALLY MORE INTERESTING...CHANCE OF SNOW ARRIVES
LATE TUESDAY. 180+ KT JET CURRENTLY OVER THE NORTH PACIFIC WILL MOVE
ONSHORE AND EVENTUALLY CARVE OUT A FAIRLY DEEP TROUGH OVER THE
SOUTHEAST CONUS. MODELS CONTINUE TO KEEP PRIMARY SURFACE LOW/PRECIP
SHIELD TO OUR E/SE BUT CONTINUE TO FLIRT WITH THE IDEA OF A
SECONDARY (VERY HEALTHY) PV ANOMALY/JET STREAK DIGGING THROUGH THE
BACKSIDE OF THIS TROUGH AND POTENTIALLY PROVIDING SOMEONE IN THE
OHIO VALLEY WITH A QUICK BURST OF MODERATE SNOW. 12Z MODEL SUITE IN
GENERAL AGREEMENT ON THIS SCENARIO BUT STILL VARY WITH REGARD TO
EXACT TRACK. ECMWF AND GEM ARE FURTHER SOUTH THAN THE NCEP MODELS.
GIVEN THE COMPACT NATURE OF THIS WAVE...MINOR TRACK DIFFERENCES WILL
RESULT IN LARGE DIFFERENCES IN SNOW AMOUNTS/IMPACTS FOR ANY GIVEN
LOCATION AND CONFIDENCE IS LOW AT THIS POINT. UPPER JET WILL START
TO GET SAMPLED BY NOAM UPPER AIR NETWORK TOMORROW SO HOPE TO HAVE A
BETTER HANDLE ON THE SITUATION BY THEN. CERTAINLY SOMETHING TO WATCH.

OTHER STORY WILL BE MODERATING TEMPS. AFTER A COLD START
SUNDAY...HIGHS WILL MODERATE INTO THE MID 30S FOR MON-THURS.
THIS WILL POSE SOME POTENTIAL FOR A RN/SN MIX IN OUR SOUTHERN
COUNTIES WITH THE TUESDAY SYSTEM BUT FORECAST SOUNDINGS CURRENTLY
SUGGEST PRIMARILY SNOW IF PRECIP DOES OCCUR WITH JUST SOME LOWER
RATIOS/MELTING POTENTIAL IN OUR SOUTH. VERY WARM TEMPS STILL
EXPECTED ON FRIDAY AS DEEP S/SW FLOW PUSHES HIGHS TO AROUND 50F.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1223 PM EST SAT FEB 13 2016

LAKE EFFECT SNOW BANDS CONTINUING TO IMPACT SW MI AND FAR NRN
INDIANA EARLY THIS AFTN. -SHSN EXPECTED TO REMAIN NORTH OF FWA BUT
WILL BE CLOSE SO CONTD WITH A VCSH THERE FOR THIS AFTN. MVFR/OCNL
IFR CONDITIONS SHOULD CONT AT SBN UNTIL THIS EVE WHEN BACKING
WINDS AND LOWERING INVERSION SHOULD CAUSE LAKE BANDS TO SHIFT
NORTH AND WEAKEN. VFR CONDITIONS WITH LIGHT/VARIABLE WINDS AS SFC
RIDGE MOVES EAST ACROSS INDIANA. HIGH/MID CLOUDS WILL OVERSPREAD
THE AREA SUNDAY MORNING AND GRDLY LOWER AS A SHRTWV MOVES ESE FROM
THE NRN PLAINS. DETERIORATING AVIATION CONDITIONS IN -SN WILL
LIKELY OVERSPREAD THE AREA JUST BEYOND THIS PERIOD, SUNDAY AFTN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR LMZ043-
     046.

&&

$$

SYNOPSIS...JT
SHORT TERM...JT
LONG TERM...AGD
AVIATION...JT


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