Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 100216
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
916 PM EST TUE FEB 9 2016

.SYNOPSIS...
ISSUED AT 258 PM EST TUE FEB 9 2016

LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY LATE THIS AFTERNOON AND THIS EVENING. THE SNOW SHOWERS
WILL BE HEAVIEST LATE TONIGHT INTO WEDNESDAY MORNING WITH 1 TO 2
INCH PER HOUR RATES IN THE STRONGEST BANDS. THEN THE SNOW SHOWERS
WILL LESSEN IN INTENSITY BUT STILL PERSIST ALL THE WAY INTO MIDDAY
THURSDAY. WHILE MOST LOCATIONS SHOULD SEE AT LEAST SOME MEASURABLE
SNOWFALL DURING THIS PERIOD...THE MORE SIGNIFICANT AMOUNTS AND
GREATEST IMPACTS WILL BE CONFINED TO THE FAVORED LAKE EFFECT
REGION SOUTHWESTERN LOWER MICHIGAN AND THE ADJACENT COUNTIES IN
NORTHERN INDIANA. LOWS TONIGHT WILL BE IN THE TEENS WITH HIGHS
WEDNESDAY IN THE UPPER TEENS AND LOWER 20S.

&&

.UPDATE...
ISSUED AT 830 PM EST TUE FEB 9 2016

LOW LEVEL COLD ADVECTION WILL CONTINUE TO INCREASE OVER THE NEXT
SEVERAL HOURS...WITH LAKE RESPONSE STARTING TO BECOME MORE
APPARENT VIA OBSERVATIONS AND REGIONAL RADAR IMAGERY. RAP BUFR
SOUNDINGS CONTINUE TO INDICATE RISING INVERSION HEIGHTS THROUGH
AROUND 09Z. NATURE OF LAKE EFFECT HAS BEEN CELLULAR MULTIBAND
THIS EVENING AND WOULD SUSPECT INTENSITY TO PICK UP LATE EVENING
AS SYNOPTIC UPPER TROUGH APPROACHES. WEAK TO MODERATE SHEAR IN
CLOUD BEARING LAYER MAY CONTINUE TO PROMOTE MORE OF A MULTIBAND
SETUP THROUGH MUCH OF THE EARLY PART OF THE OVERNIGHT HOURS.
CONCERN THAT A MORE DOMINANT BAND MAY SETUP LATE TONIGHT INTO
EARLY WEDNESDAY MORNING PER RECENT HRRR TRENDS AS WEAK SYNOPTIC
TROUGH DEPARTS SOUTH OF THE LAKE ALLOWING SLIGHTLY MORE FAVORABLE
WIND FIELD ALONG WITH A PEAK IN LAKE INDUCED INSTABILITY.
CURRENTLY HAVE NO PLANS FOR HEADLINE CHANGES AT THIS TIME DUE TO
UNCERTAINTY IN POTENTIAL MORE DOMINANT PLACEMENT/INTENSITY LATE
TONIGHT/EARLY WEDNESDAY MORNING. ALSO HAVE NOT MADE SIGNIFICANT
CHANGES IN FORECASTED SNOW ACCUMS. ACCUMULATION EFFICIENCY HAS
STRUGGLED AWAY FROM THE LAKE THIS EVENING...ALTHOUGH INCREASING
MORE FAVORABLE THERMO PROFILES FOR SNOW GROWTH SHOULD BEGIN TO
COME INTO PLAY LATE EVENING/OVERNIGHT...AND THUS HESITANT TO
LOWER AMOUNTS TOO MUCH AT THIS TIME.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 258 PM EST TUE FEB 9 2016

LONG DURATION LAKE EFFECT SNOW EVENT BEGINNING LATE THIS AFTN AS
STRENGTHENING LOW LEVEL NW FLOW AND CAA OVERSPREADS LAKE MICHIGAN
AND NW PORTION OF OUR CWA. FAVORABLE FACTORS FOR LES TONIGHT INCLUDE
A DEEP MOIST LAYER FROM THE SFC-700MB, LITTLE SFC-850MB LAYER SHEAR,
A SHRTWV MOVG ACROSS THE AREA CAUSING INVERSION HEIGHTS TO RISE TO
AROUND 6KFT AND PROVIDING WK SYNOPTIC SCALE LIFT. SFC TROF
REFLECTION SHOULD ALSO MOVE SE ACROSS SRN LAKE MICHIGAN OVERNIGHT
STRENGTHENING BANDS AS LOW LEVEL CONVERGENCE ENHANCED, BUT ALSO
PSBLY CAUSING DOMINANT BANDS TO BECOME SOMEWHAT TRANSITORY.
MAIN NEGATIVE FACTOR OVERNIGHT AND THROUGH THE ENTIRE EVENT IS WK
LAKE INDUCED INSTABILITY OF <500J/KG. HIGH RES MODELS IN DECENT
AGREEMENT ON A COUPLE OF DOMINANT BANDS IMPACTING THE AREA, ONE
THROUGH CASS COUNTY MI AND SECOND IMPACTING SW BERRIEN, NW ST JOE
INDIANA, AND PSBLY NE LAPORTE. EXPECT GENERAL 2-4" SNOWFALL ACCUMS
IN THE ADVISORY AREA TONIGHT WITH LOCALLY HIGHER AMOUNTS PSBL IN
AREAS WHERE DOMINANT BANDS PERSIST THE LONGEST.

LOW LEVEL CAA EXPECTED TO CONT WED AS 850MB THERMAL TROF WITH -21C
AIR MOVES OVER THE LAKE. DESPITE THIS, LITTLE CHANGE IN LAKE INDUCED
INSTABILITY FCST AS WARMING OCCURS ABOVE INVERSION BASED AROUND
4.5KFT. WITH SOME DRYING OF THE COLUMN ALSO OCCURRING WED/WED NGT,
EXPECT ACCUMS IN THE ADVISORY AREA WILL BE A LITTLE LIGHTER THAN
TONIGHT, GENERALLY IN THE 1-3" RANGE EACH PERIOD. LAKE EFFECT SHOULD
FINALLY WIND DOWN THU AS SFC RIDGE BUILDS IN, INVERSION LOWERS, AND
LOW LEVELS CONT TO DRY OUT WITH ADDITIONAL ACCUMS EXPECTED TO BE <1"
IN THIS PERIOD. THUS, CONTD WITH A WINTER WX ADVISORY FOR THIS LAKE
EFFECT SNOW EVENT AS 12-24HR AMOUNTS EXPECTED TO GENERALLY BE BLO
WARNING CRITERIA, THOUGH STORM TOTALS (INCLUDING LAST NIGHT`S
SNOWFALL) WILL PRBLY BE CLOSE TO A FOOT IN PORTIONS OF THE ADVISORY
AREA.

FOR THE REST OF THE CWA, BRISK CYCLONIC NW FLOW SHOULD SUPPORT LAKE
EFFECT SNOW BANDS PENETRATING WELL INLAND TONIGHT THROUGH THURSDAY.
HWVR, TYPICAL OF LAKE EFFECT, ACCUMS WILL BE LESS FARTHER INLAND,
THOUGH SOME COUNTIES BORDERING THE ADVISORY MAY HAVE 3-5" STORM
TOTALS.

TEMPS WILL BE ON A GENERAL SLOW DECLINE OVER THE NEXT 36HRS AS
THERMAL TROF MOVES INTO THE AREA. LOWS TNGT SHOULD GENERALLY BE IN
THE TEENS WITH HIGHS WED IN THE UPPER TEENS TO L20S, AND LOWS WED
NGT AROUND 10 ABOVE. TEMPS SHOULD MODERATE SLIGHTLY THU AS WK WAA
DVLPS, WITH HIGHS EXPECTED IN THE L20S ACROSS THE AREA.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 343 PM EST TUE FEB 9 2016

A VERY DEEP COLD CORE LOW WILL BE IN THE VICINITY OF JAMES BAY
NEAR FAR SOUTHERN HUDSON BAY BY EARLY FRIDAY. THE GFS AND GFS
ENSEMBLES ALONG WITH THE ECMWF HAVE COME INTO GOOD AGREEMENT WITH
THIS SYSTEM BRINGING ANOTHER STRONG COLD FRONT ACROSS THE AREA
FOLLOWED BY LAKE EFFECT SNOW. DELTA T VALUES MAY EXCEED 25C
SATURDAY AS A FAVORABLE LAKE FETCH DEVELOPS. THE FETCH SHOULD BE
MORE NORTH/SOUTH THAN THIS ONGOING EVENT... WITH THE HEAVIEST
SNOWFALL OVER NORTHWEST INDIANA. HAVE RAISED SNOW CHANCES SATURDAY
IN THIS REGARD. THE RIDGE AXIS WILL TRANSLATE ACROSS THE AREA
SATURDAY NIGHT...CAUSING LAKE EFFECT SNOW TO SHIFT WEST.

KEPT TEMPERATURES VERY COLD FRIDAY NIGHT AND SATURDAY NIGHT...WITH
LOWS NEAR ZERO SATURDAY NIGHT WHERE SKIES ARE ABLE TO CLEAR OVER
FRESH SNOW COVER. MILDER WEATHER IS EXPECTED BY TUESDAY AS THE UPPER
FLOW BECOMES MORE HIGH ZONAL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 656 PM EST TUE FEB 9 2016

LAKE EFFECT SNOW SHOWERS WILL CONTINUE TO AFFECT THE TERMINALS
THROUGH THIS FORECAST VALID PERIOD. EXPECTING IFR VSBYS IN THE 1-2
MILE RANGE TO CONTINUE AT KSBN THROUGH MUCH OF THE EVENING...WITH
SOME LOWER END PROBABILITY OF LIFR VSBYS. NEXT SYNOPTIC TROUGH IS
EXPECTED TO REACH THE WESTERN GREAT LAKES DURING THE OVERNIGHT
HOURS...WITH MORE ORGANIZED BANDING POSSIBLE IN WAKE OF THIS WEAK
TROUGH LATE TONIGHT INTO WEDNESDAY MORNING. DID MAINTAIN TEMPO
LIFR CONDITIONS AT KSBN AFTER 07Z GIVEN MORE SUBSTANTIAL LAKE
EFFECT PARAMETERS BY THIS TIME. AT LEAST IFR VSBYS WILL LIKELY
PERSIST THROUGH MUCH OF THIS FORECAST VALID PERIOD AT
KSBN...ALTHOUGH GREATEST SNOWFALL RATES MAY BE CONFINED TO THE
LATE TONIGHT THROUGH MIDDAY WEDNESDAY PERIOD. CONFIDENCE REMAINS
SOMEWHAT LESS AT KFWA WHERE IFR VSBYS WILL BE
POSSIBLE...ESPECIALLY LATE TONIGHT GIVEN THE SYNOPTIC TROUGH
CONTRIBUTION OVERNIGHT ALLOWING SOME BETTER INLAND PENETRATION OF
MORE SUBSTANTIAL SNOW SHOWERS. NOT MUCH CHANGE ANTICIPATED TO
WINDS THROUGH THE PERIOD...GENERALLY WESTERLY IN THE 15G20-25 KNOT
RANGE.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 10 AM EST /9 AM CST/ THURSDAY FOR
     INZ003>005.

MI...WINTER WEATHER ADVISORY UNTIL 10 AM EST THURSDAY FOR MIZ077>079.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EST THURSDAY FOR LMZ043-046.

&&

$$

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


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