Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 090550
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1250 AM EST TUE FEB 9 2016

.SYNOPSIS...
ISSUED AT 349 PM EST MON FEB 8 2016

ACCUMULATING SNOWFALL IS EXPECTED ACROSS MUCH OF THE GREAT LAKES
BEGINNING LATE TONIGHT AND LASTING INTO EARLY THURSDAY. AMOUNTS
DURING ANY ONE PERIOD WILL BE GENERALLY LIGHT BUT THE LONG
DURATION OF THE EVENT MAY ALLOW AREAS NEAR LAKE MICHIGAN TO SEE
BETWEEN 6 AND 12 INCHES OF SNOW BY THE TIME THURSDAY MORNING ROLLS
AROUND. ARCTIC AIR WILL IMPACT THE REGION LATER THIS WEEK
DROPPING HIGHS INTO THE TEENS TO LOW 20S AND LOWS IN THE SINGLE
DIGITS ABOVE ZERO. LOWS TONIGHT WILL RANGE FROM THE UPPER TEENS IN
SOUTHWESTERN INDIANA TO THE MIDDLE 20S IN NORTHWESTERN OHIO.

&&

.UPDATE...
ISSUED AT 838 PM EST MON FEB 8 2016

SEVERAL VORT LOBES ROTATING THROUGH OHIO VALLEY UPPER TROUGH WILL
RESULT IN ONLY VERY SLOW EASTWARD TRANSLATION OF UPPER LEVEL LOW.
AN ELONGATED VORT MAX ACROSS THE WESTERN GREAT LAKES WILL MOVE
VERY LITTLE BUT BECOME INCREASINGLY SHEARED IN NATURE AS IT
APPEARS TO TRY AND PHASE WITH VORT MAX DROPPING ACROSS SOUTHERN
INDIANA THIS EVENING. LOW LEVEL COLD ADVECTION IS BEING SLOWED
SOMEWHAT BY LOW LEVEL THETAE RIDGING EXTENDING BACK NORTHWESTWARD
ACROSS SOUTHERN LOWER MICHIGAN. NEVERTHELESS...SNOW SHOWERS HAVE
EXPANDED IN COVERAGE OVER THE PAST FEW HOURS...LARGELY IN RESPONSE
TO THIS AFOREMENTIONED SYNOPTIC FORCING AND SOME CONVECTIVE
CONTRIBUTION/STEEP LOW LEVEL LAPSE RATES/LAKE ENHANCEMENT. WEAK
LOW LEVEL TROUGH TO DROP SOUTHWARD ACROSS FAR SOUTHERN LAKE
MICHIGAN OVERNIGHT SHOULD ALLOW SNOW SHOWERS TO CONTINUE ALTHOUGH
BETTER ORGANIZATION WILL BE LIMITED BY MODEST SHEAR IN CLOUD
BEARING LAYER. SNOW RATIOS ALSO DO NOT APPEAR TO BE OPTIMAL
OVERNIGHT GIVEN POTENTIAL OF SOME RIMING TO LESSEN RATIOS. 1 TO 3
INCH ACCUMULATIONS APPEAR TO BE POSSIBLE DOWNWIND OF LAKE MICHIGAN
TONIGHT AND NOT MANY CHANGES MADE TO GOING GRIDS. SPS ISSUED
EARLIER TO HIGHLIGHT SLICK ROADS THAT HAVE BEEN REPORTED ACROSS
PORTIONS OF THE AREA DUE TO SOME RE-FREEZING OF EARLIER MELTED
PRECIP AND NEW LIGHT SNOW ACCUMULATIONS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 349 PM EST MON FEB 8 2016

H5 LOW CNTR OVR CNTRL LK MI THIS AFTN WILL ROUND SEWD
INTO WRN LK ER BY TUE AFTN. HWVR ERN EXTENT OF INCOMING LL CAA WING
IS DELAYED UNTIL LT PD COINCIDENT W/EVENTUAL UPSTREAM BACK OF LL
FLW. THUS OVERALL LK RESPONSE TONIGHT XPCD TO BE TEPID UNTIL AFT 06Z
WHEN MOST VIGOROUS MSTR FLUX/VERTICAL ASCENT DVLPS ACRS NW CWA.
REGARDLESS INHERENT SNOW BAND DVLPMNT LT TONIGHT LOOKS TO REMAIN
TRANSITORY WHICH SHLD LIMIT POTENTIAL ACCUMULATIONS IN ANY ONE
LOCALE OUTSIDE PERHAPS NE LAPORTE/WRN ST JOE. AT ANY RATE WILL FOREGO
SHRT DURATIONS HEADLINE NEED LT TONIGHT/ERLY TUE AM TO EVENING SHIFT.

OTRWS UPSTREAM MID LVL MSTR PLUME HOLDS WEST ON TUE WHILE LL THERMAL
TROUGH STEADILY GROWS. THIS IS LIKELY TO KEEP LIGHT SHSN GOING
THROUGH THE DAY FAR NW HWVR INLAND REACH MUCH IN DOUBT GIVEN DEGREE
OF MID LVL SUBSIDENCE WITHIN MID LVL DRYSLOT AND WILL TEMPER PRIOR
GRIDDED POPS CONSIDERABLY EAST HALF. AS SUCH WILL AGAIN CONT TO HOLD
OFF ON ANY POTENTIAL HIGHLIGHTS THIS PD AS MORE COMPELLING PERIOD
LIES BEYOND TUE NIGHT AND WED.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 349 PM EST MON FEB 8 2016

FOR TUESDAY NIGHT THROUGH NEXT MONDAY...LAKE EFFECT SNOW WILL
BE ONGOING TUESDAY NIGHT AND SHOULD BE INCREASING AS AN UPPER
LEVEL TROF MOVES INTO THE AREA. MANY FAVORABLE FACTORS WILL COME
TOGETHER FOR ACCUMULATING LAKE EFFECT SNOW TUESDAY NIGHT INCLUDING
A LONG FETCH OVER OPEN WATERS INCLUDING PRECONDITIONING FROM LAKE
SUPERIOR WHICH WAS ONLY 4 PERCENT ICE COVERED. THIS LONG FETCH
COMBINED WITH SYNOPTIC LIFT/UPPER SUPPORT AND VERY LARGE DELTA T
VALUES FROM 20C TO 25C IN THE DENDRITIC GROWTH ZONE FAVOR HEAVY
LAKE EFFECT SNOW FROM NORTHERN LAPORTE COUNTY AND NORTHERN ST
JOSEPH INTO LOWER MICHIGAN INCLUDING BERRIEN AND CASS COUNTIES. A
WINTER HEADLINE WILL LIKELY BE NEEDED AT SOME POINT FOR THIS SNOW.
THE LAKE EFFECT SNOW WILL PERSIST INTO THURSDAY WITH ADDITIONAL
ACCUMULATIONS. INVERSION HEIGHTS FALL BRIEFLY WITH BACKING WINDS
THURSDAY NIGHT AHEAD OF A SECOND STRONG COLD FRONT... ALLOWING
ONLY A SHORT BREAK IN THE SNOW.

LAKE EFFECT SNOW WILL LIKELY DEVELOP AND INCREASE AGAIN FRIDAY
NIGHT...WITH SIGNIFICANT ACCUMULATIONS POSSIBLE AS A SECOND SYSTEM
MOVES INTO THE AREA. HAVE TRENDED TEMPERATURES COLDER FRIDAY THROUGH
SUNDAY. IT LOOKS LIKE LOWS SATURDAY NIGHT WILL BE AROUND ZERO OR
JUST ABOVE ZERO.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1239 AM EST TUE FEB 9 2016

DIFFICULT TAFS THROUGH THE PERIOD ESPECIALLY AT KSBN AS EXACT
LAYOUT OF FORECASTED LAKE EFFECT SNOW BANDS THROUGH THE PERIOD
WILL CAUSE HIGHLY VARIABLE CONDITIONS. CONFIDENCE HIGH IN SNOW
SHOWERS OCCURRING WITH IMPACTS BUT CONFIDENCE LOW TO MEDIUM ON
PLACEMENT OF BANDS WITH RELATION TO TAF SITES.

ONE BAND WAS MOVING EAST OF KBEH AND BASED ON ESE TRAJECTORY MAY
BYPASS KSBN ENTIRELY. HOWEVER HIGH RES MODELS INDICATE SOME
EXPANSION IN COVERAGE IS POSSIBLE BETWEEN 6 AND 12Z TUES. HAVE
TONED DOWN TAFS IN THAT PERIOD AND WILL MONITOR TRENDS. KFWA
SHOULD SEE LITTLE MORE THAN FLURRIES OR LIGHT SNOW SHOWERS WITH
MAINLY MVFR CIGS TO DEAL WITH.

A LULL IN SNOW SHOWERS APPEARS LIKELY AFTER 14Z TUES THROUGH AT
LEAST 00Z WEDS AS DEEPER MOISTURE AND LIFT BRIEFLY WANE.
HOWEVER...LAKE EFFECT SHOULD KICK IN FAIRLY QUICKLY AFTER 00Z WITH
GREATEST IMPACTS BEING SEEN AT KSBN AFTER 2Z AND PERSISTING WELL
THROUGH THE VALID PERIOD. AT KFWA...HAVE KEPT LITTLE MORE THAN
FLURRY MENTION AFTER 14Z WITH TEMPO GROUP TOWARDS THE END OF THE
PERIOD TO HANDLE POTENTIAL FOR LAKE EFFECT SNOW SHOWERS BEGINNING
TO MOVE SE TOWARDS THE SITE.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EST THURSDAY FOR LMZ043-046.

&&

$$

UPDATE...MARSILI
SYNOPSIS...T
SHORT TERM...T
LONG TERM...SKIPPER
AVIATION...FISHER


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