Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 130319
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1019 PM EST FRI FEB 12 2016

.SYNOPSIS...
ISSUED AT 1016 PM EST FRI FEB 12 2016

ARCTIC AIR WILL CONTINUE TO SPREAD ACROSS THE REGION OVERNIGHT
ACCOMPANIED BY GUSTY WINDS AND NUMEROUS LAKE EFFECT SNOW SHOWERS.
THE LAKE EFFECT SNOW WILL MAINLY IMPACT SOUTHWEST MICHIGAN AND
NORTH CENTRAL INDIANA WHERE 3 TO 6 INCHES OF ADDITIONAL
ACCUMULATION ARE EXPECTED TONIGHT AND SATURDAY. LOWS TONIGHT WILL
BE IN THE SINGLE DIGITS WITH HIGHS SATURDAY NEAR 15.

&&

.UPDATE...
ISSUED AT 734 PM EST FRI FEB 12 2016

POST FNTL SHSN WITHIN EMERGING ARCTIC AIRMASS QUITE INTENSE IN
SPOTS YET THIS EVENING BUT WILL CONT TO DIMINISH AS UNSTABLE SFC
BASED LAPSE RATES DECAY W/SUNSET. REGARDLESS GROWING QUITE CONCERNED
W/UPSTREAM LAKE RESPONSE WITHIN EVOLVING/INTENSIFYING LL THERMAL
TROUGH. GENERAL CONSOLIDATION IN BANDING NOTED OVR THE LAST 3 HOURS
ALG A MUSKEGON TO ALLEGAN LINE...MIMICKING RECENT RAP MODEL
INDICATIONS AS LL FLW VEERS CONSIDERABLY W/UPSTREAM EXTENT. THIS
PRIMARY PLUME XPCD/MODELED TO INTENSIFY AS IT COMES SOUTH THROUGH
LT EVENING BFR LOCKING IN WITHIN ROUGHLY ALG A SOUTH
HAVEN...CASSOPOLIS...ELKHART...WARSAW LINE. BASED ON OBSVD RADAR
TRENDS...SUSPECT NR 1" PER HOUR PEAK SNOWFALL RATES WHICH MAY
REQUIRE SOME FORM OF HEADLINE ADJUSTMENT. WILL ATTM FOLLOW
EVOLUTION OF THIS BAND THROUGH MID EVENING AND MAKE A DECISION IF
NEEDED WELL BFR 11 PM.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 306 PM EST FRI FEB 12 2016

CDFNT MOVG RAPIDLY E-SE ACROSS THE CWA THIS AFTN ACCOMPANIED BY A
BAND OF SNOW SHOWERS. LAKE EFFECT SNOW SHOWERS DVLPG BEHIND THE
FRONT SHOULD GRDLY INTENSIFY THIS EVE AS CAA CONTS AND WINDS VEER
FROM AROUND 300 DEGREES TO 340 DEGREES AS A SECONDARY CDFNT
CURRENTLY OVER NRN LWR MI MOVES THROUGH OUR AREA. INVERSION BASE
FORECAST TO PEAK LATE THIS EVE AROUND 6500FT WITH SIGNIFICANT LAKE
INDUCED INSTABILITY (0-2KM THETA-E LAPSE RATES OVER THE LAKE
AROUND -2.5C/KM). CONVECTION ALLOWING MODELS SUGGEST A DOMINANT
BAND OR TWO WILL SET UP AROUND THIS TIME IMPACTING NORTHWEST
PORTION OF OUR CWA. HWVR, THESE OPTIMAL CONDITIONS FOR LES SHOULD
BE SHORT LIVED AS INVERSION FCST TO LOWER/LAKE INDUCED INSTABILITY
DECREASE LATE TONIGHT AND THROUGH THE DAY SATURDAY. DGZ WILL ALSO
BE VERY LOW GIVEN ARCTIC AIRMASS MOVG IN WHICH SHOULD LIMIT ACCUMS
BLO WHAT OTRWS MIGHT BE EXPECTED. ONLY MINOR CHANGE MADE TO
PREVIOUS FCST ACCUMS WITH TOTALS TONIGHT AND SATURDAY EXPECTED TO
BE IN THE 3-6" RANGE IN THE ADVISORY AREA WITH 1-3" IN COUNTIES
SURROUNDING ADVISORY AND <1" OVER THE REST OF THE CWA. LOCALLY
HIGHER AMOUNTS PSBL IF DOMINANT BAND PERSISTS OVER ANY GIVEN AREA
VERY LONG THIS EVENING. BOUNDARY LAYER WINDS FCST 15-25KT TONIGHT
WHICH SHOULD CAUSE CONSIDERABLE BLOWING DRIFTING OF THE POWDERY
LES, MAINLY IN THE NW ADVISORY AREA. LITTLE CHANGE MADE TO TEMPS
WITH LOWS TONIGHT IN THE 0-5 RANGE NE AND SW WHERE SOME PARTIAL
CLEARING EXPECTED AND 5-10 UNDER THE LAKE EFFECT CLOUD PLUME OVER
MOST OF THE REST OF THE CWA, WITH HIGHS SATURDAY ONLY 12-16.
MINIMUM WIND CHILLS TONIGHT AND SATURDAY MORNING EXPECTED TO BE IN
THE -5 TO -15 RANGE.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 306 PM EST FRI FEB 12 2016

LAKE EFFECT SNOW WILL TAPER OFF SATURDAY EVENING AS LOW LEVEL RIDGE
AXIS SHIFTS OVERHEAD AND INVERSION HEIGHTS LOWER. DGZ REMAINS ACTIVE
IN THE 00-06Z TIMEFRAME SO SOME LIGHT FLURRIES/SNOW SHOWERS EXPECTED
BUT ANY ADDITIONAL ACCUMULATION WILL BE VERY LIGHT. MAIN STORY FOR
SATURDAY NIGHT WILL BE VERY COLD TEMPS. LIGHT WINDS...PARTIALLY
CLEAR SKIES...AND FRESH SNOW WILL SUPPORT GOOD RADIATIONAL COOLING
POTENTIAL IN SPOTS. GRADIENT WIND/WAA AND CLOUDS BEGIN TO INCREASE
TOWARD 12Z BUT SHOULD STILL BE ENOUGH TIME FOR TEMPS TO DROP. KEPT
CLOSE TO INHERITED FORECAST...WHICH IS ON THE COLD SIDE OF
GUIDANCE...WITH LOWS AROUND ZERO. WILL LIKELY BE A HIGH DEGREE OF
VARIANCE IN FINAL NUMBERS THOUGH...DEPENDING ON EXACT CLOUD TRENDS.

CHANCE FOR LIGHT SNOW THEN QUICKLY RETURNS LATE SUNDAY AS NEXT
SHORTWAVE ROTATES THROUGH THE REGION. CONFLUENT FLOW OVER THE
EASTERN CONUS WILL INCREASINGLY SHEAR OUT AND WEAKEN THIS WAVE. CVA
BECOMES NEGLIGIBLE BY SUNDAY NIGHT WITH JUST SOME BROAD/WEAK 280-
285K ISENTROPIC ASCENT. DO SEE A DECENT MOISTURE SURGE THOUGH WITH
MIXING RATIOS OVER 2 G/KG. GIVEN STEADY...ALBEIT WEAK...ASCENT AND
POTENTIAL FOR HIGHER THAN CLIMO SNOW RATIOS...COULD CHURN OUT 1-2"
BY LATE MONDAY MORNING. BEST CHANCES FOR HIGHER AMOUNTS WILL BE IN
OUR SOUTHWEST WHERE BETTER MOISTURE AND FORCING RESIDE.

AFTER A BRIEF BREAK MONDAY NIGHT...THERE IS ANOTHER CHANCE FOR SNOW
TUESDAY/TUESDAY NIGHT AS POTENT NORTHERN STREAM SHORTWAVE DIVES
SOUTHEAST AND STRENGTHENS EAST COAST LOW. MODELS HAVE BEEN KEEPING
PRECIP SHIELD OF PRIMARY LOW JUST EAST OF OUR CWA BUT CONTINUE TO
STRUGGLE IMMENSELY WITH EXACT TRACK OF SECONDARY VORT MAX.
CONFIDENCE IN SNOW CHANCES REMAINS LOW AT THIS POINT WITH PARENT JET
ENERGY STILL WELL OUT OVER THE DATA-SPARSE NORTH PACIFIC. WILL
CONTINUE TO WATCH THIS PERIOD AND ADJUST AS MODELS GET A BETTER
HANDLE ON SITUATION. SOME MINOR LAKE EFFECT THEN POSSIBLE WEDNESDAY
WITH MUCH WARMER TEMPS (AND POTENTIAL FOR RAIN) STILL EXPECTED BY
THE END OF THE WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 651 PM EST FRI FEB 12 2016

PRIMARY LAKE SNOW BANDING ALREADY WELL UNDERWAY FROM STONY POINT
SWD TO NR SAUGATUCK INLINE W/RAP TRENDS AS LL FLW CONTS TO VEER IN
WAKE OF SW PASSAGE. GIVEN GOOD CONTINUITY OF NR TERM MODEL SIGNALS
HAVE SHIFTED FWD TIME OF GREATEST IMPACT INVOF OF KSBN AND FULLY
XPC A PD OF LIFR CONDS TO MANIFEST AFT 06Z. INLAND REACH OF THIS
PRIMARY BAND MAY AFFECT FWA TERMINAL BRIEFLY PRIOR TO 06Z BUT OF
QUITE LIMITED DURATION AND LEFT OUT ATTM. WILL AMEND ACCORDINGLY
AS NEEDED.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 4 PM EST /3 PM CST/ SATURDAY FOR
     INZ003>005.

MI...WINTER WEATHER ADVISORY UNTIL 4 PM EST SATURDAY FOR MIZ077>079.

OH...NONE.
LM...HEAVY FREEZING SPRAY WARNING UNTIL 7 AM EST SATURDAY FOR LMZ043-
     046.

     GALE WARNING UNTIL 7 AM EST SATURDAY FOR LMZ043-046.

&&

$$

UPDATE...T
SYNOPSIS...JT/SKIPPER
SHORT TERM...JT
LONG TERM...AGD
AVIATION...T



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