Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 092007
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
307 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.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
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 MONDAY)
ISSUED AT 459 AM EST TUE FEB 9 2016

LAKE EFFECT SNOW SHOWERS SHOULD DIMINISH AS INVERSION HEIGHTS
LOWER AND WINDS BACK IN RESPONSE TO THE NEXT WAVE RAPIDLY MOVING
SE TOWARDS THE REGION. LIGHT ACCUMULATIONS MAY BE IN STORE DURING
THE DAY FRIDAY WITH TRANSITION BACK TO LAKE EFFECT SNOW SHOWERS
FRIDAY NIGHT.

MORE PRONOUNCED LAKE RESPONSE WILL LIKELY TAKE PLACE SATURDAY
INTO MONDAY AS ARCTIC LOW DROPS INTO NEW ENGLAND FOR THE WEEKEND
AND SENDS TEMPERATURES PLUMMETING ACROSS THE AREA. MODELS NOW SEEM
TO BE IN AGREEMENT ON BULK OF COLDEST AIR STAYING EAST OF HERE,
BUT STILL PLENTY LOW ENOUGH TO END UP WITH HIGHS IN THE LOW TO MID
TEENS FOR SATURDAY. POTENTIAL EXISTS FOR ACCUMULATING SNOWFALL
AGAIN ACROSS THE AREA...BUT GIVEN CONCERNS AS TO EXACTLY HOW
MOISTURE PROFILES AND TRAJECTORIES WILL SET UP...LITTLE MORE THAN
CHC POPS WARRANTED.

WITH TRENDS BEING FURTHER EAST WITH THE COLDER AIR...MOS GUIDANCE
HAS TRIED TO INCREASE TEMPERATURES SEVERAL DEGREES. HAVE WENT WITH
BLEND OF PREVIOUS FORECAST AND NEW SUPERBLEND DATA TO HOLD DOWN
MASSIVE CHANGES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1153 AM EST TUE FEB 9 2016

-SHSN DIMINISHING LATE THIS MORNING AS VORT MAX WHICH MOVED
THROUGH THE AREA OVERNIGHT DIVES SSE INTO THE OH VALLEY, BUT
CONDITIONS SHOULD PERSIST BLO FUEL ALTERNATE THIS AFTN. LOW LEVEL
CAA WILL CAUSE LAKE EFFECT SHSN TO INCREASE IN COVERAGE/INTENSITY
THIS EVE WITH LIFR CONDITIONS AT SBN AND OCNL IFR AT FWA. LITTLE
OR NO IMPROVEMENT EXPECTED THROUGH THE END OF THE TAF PERIOD AS NW
FLOW CONTS.


&&

.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.

&&

$$

SYNOPSIS...JT
SHORT TERM...JT
LONG TERM...FISHER
AVIATION...JT


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