Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 121640
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1140 AM EST FRI FEB 12 2016

.SYNOPSIS...
ISSUED AT 334 AM EST FRI FEB 12 2016

AN ARCTIC FRONT WILL BRING GUSTY WINDS AND INCREASING CHANCES FOR
SNOW SHOWERS TO THE REGION THIS AFTERNOON. MOST LOCATIONS COULD
SEE A QUICK DUSTING TO HALF INCH OF SNOW...WITH HIGHER AMOUNTS
POSSIBLE IN FAR NORTHERN INDIANA AND LOWER MICHIGAN. HIGHS THIS
AFTERNOON WILL REACH THE LOW TO MID 20S. ARCTIC AIR WILL THEN
CONTINUE TO FILTER IN BEHIND THIS FRONT FRIDAY NIGHT INTO SATURDAY
WITH LOWS INTO THE SINGLE DIGITS ABOVE ZERO TONIGHT...WITH HIGHS
ON SATURDAY ONLY REACHING THE LOW TO MID TEENS. WIND CHILLS
BETWEEN 5 AND 15 BELOW ZERO CAN BE EXPECTED LATER TONIGHT INTO
SATURDAY MORNING. ACCUMULATING LAKE EFFECT SNOW AND BLOWING SNOW
WILL LIKELY CREATE DIFFICULT TRAVEL FRIDAY NIGHT INTO SATURDAY
NEAR LAKE MICHIGAN.

&&

.UPDATE...
ISSUED AT 1056 AM EST FRI FEB 12 2016

ARCTIC FRONT MOVG THROUGH NE IL/SW MI WITH COMPOSITE RADAR
INDICATING AN EXPANDING AREA OF ECHOES ALONG THE FRONT. OBS
INDICATE SNOW REDUCING VSBYS AS LOW AS A 1/4 TO 1/2 MILE IN NE
IL AND 1-2MI IN SRN MICHIGAN. THIS AREA OF SNOW EXPECTED TO MOVE
ACROSS OUR CWA OVER THE NEXT 4-5HRS. BUMPED UP POPS OUTSIDE OF THE
ADVISORY TO LIKELY THIS AFTN WITH A QUICK HALF INCH ACCUM
EXPECTED AS THE FRONT MOVES THROUGH.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 334 AM EST FRI FEB 12 2016

VORT LOBE NEARING WESTERN LAKE SUPERIOR WILL TRANSLATE SOUTHEAST
THROUGH THE GREAT LAKES UNDER A JAMES BAY NEGATIVE HEIGHT ANOMALY
EXPECTED TO DISLODGE SOUTH TOWARD NEW ENGLAND. THIS PROCESS WILL
FORCE AN ARCTIC COLD FRONT THROUGH LOWER MI BY LATE MORNING/EARLY
AFTN AND OUR IN/OH COUNTIES THIS AFTN. LARGE SCALE ASCENT/Q-VECTOR
CONVERGENCE THROUGH A DEEP LAYER AND EXPECTATIONS FOR LAKE PLUME
TO BECOME ENTRAINED INTO FRONTAL ZONE SUPPORT HIGH POPS FOR SNOW
SHOWERS ALONG/BEHIND THIS FEATURE INTO NORTHERN ZONES...WITH LOWER
CHANCES ALONG/SOUTH OF US 30 DIVORCED FROM DEEPER ASCENT AND LAKE
CONTRIBUTION. STEEPENING LAPSE RATES/SATURATION INTO THE DGZ JUST
BEHIND THE ARCTIC FRONT SUGGEST THE POTENTIAL FOR HIGHER
INTENSITY/BRIEF SNOW ALONG THE FRONTAL ZONE...WITH A DUSTING
SOUTH OF US 30 TO AROUND AN INCH OR SO ALONG/NORTH OF THE INDIANA
TOLL ROAD. THIS COMBINED WITH GUSTY WINDS AND SNOW COVER MAY MAKE
FOR HAZARDOUS TRAVEL CONDITIONS LATE MORNING/AFTN ACROSS FAR NRN
IN/SW LOWER MI. OTHERWISE IN THE VERY NEAR TERM (EARLY THIS
MORNING)...COULD SEE SOME LIGHT SNOW (A QUICK DUSTING?) CLIP
AREAS SOUTH OF US 30 IN INDIANA ON THE NORTHERN FRINGE OF A
SEPARATE/WEAK CLIPPER SYSTEM TRACKING INTO THE OH VALLEY.

ANOTHER NW FLOW LAKE EFFECT EVENT REMAINS THE LARGER STORY INTO
TONIGHT AND SATURDAY AS ARCTIC AIRMASS OVERSPREADS POST-FRONTAL.
TRAJECTORIES TONIGHT FAVOR A LAKE SUPERIOR CONNECTION...WHICH WHEN
COMBINED WITH LAKE-800 MB TEMP DIFFERENTIALS PUSHING WELL INTO THE
20S (INVERSION HEIGHTS TO 8-10 KFT, LAKE INDUCED CAPE TO 6-7K J/KG)
HIGHLIGHT THE POTENTIAL FOR MOD-HVY LAKE EFFECT SNOW SHOWERS IN
FAVORED NW FLOW BELTS. ORGANIZATION/INTENSE BANDING OVER ONE AREA
SHOULD BE LIMITED BY STRONGER FLOW AT LEAST INTO THE EVENING/EARLY
OVERNIGHT. A PLETHORA OF NEEDLE GENERATION ALSO SEEMS LIKE A GOOD
BET WITH BULK OF ASCENT/SATURATION OCCURRING JUST ABOVE THE DGZ.
THIS ALL POINTS TO ANOTHER SOLID ADVISORY EVENT LATE MORNING
THROUGH SATURDAY...ALTHOUGH GUSTY WINDS/BLSN AND MORE ORGANIZATION
THAN CURRENTLY EXPECTED WOULD BE PROBLEMATIC FOR MORE SIGNIFICANT
SNOW RATES/ACCUMS AND IMPACTS.

DRYING/SUBSIDENCE AND BACKING WINDS IN RESPONSE TO RIDGE BUILDING
INTO THE UPPER/MIDDLE MS VALLEY WILL GRADUALLY TAKE ITS TOLL ON
INVERSION HEIGHTS SATURDAY. THE RESULT WILL BE A TREND TOWARD LOWER
INTENSITY LAKE EFFECT SNOW INTO WNW FLOW BELTS...WITH DIURNAL
COMPONENT/BACKING LIKELY ALLOWING SCT FLURRIES OR LIGHT SNOW SHOWERS
TO FILL INTO EASTERN PORTIONS OF THE FORECAST AREA DURING THE AFTN.
WINDS WILL ALSO BE MUCH LIGHTER WHICH WILL REDUCE THE BLOWING SNOW
POTENTIAL ACROSS NW IN/SW LOWER MI. COULD STILL SEE SOME DECENT
ADDITIONAL SNOW ACCUMS (1-3 INCHES) IN THE ADVISORY AREA INTO AT
LEAST THE FIRST HALF OF SATURDAY AS DIMINISHED FLOW/SUPERSATURATION
WRT ICE MORE FOCUSED INTO DGZ POSSIBLY SURPRISES (BETTER
RATIOS/ORGANIZATION/TROUGHING). COLD OTHERWISE WITH WIND CHILLS
LATER TONIGHT/SATURDAY MORNING PROGGED INTO THE 5 TO 15 BELOW ZERO
RANGE (ADVISORY CRITERIA LOCALLY IS 15 BELOW ZERO OR COLDER).

&&

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 334 AM EST FRI FEB 12 2016

EXPANSIVE AREA OF HIGH PRESSURE WILL MOVE ACROSS THE AREA SATURDAY
NIGHT. LAKE EFFECT WILL BE ENDING AS RIDGE MOVES IN AND FLOW WEAKENS
WHILE BECOMING SOUTHERLY OVERNIGHT. CLEARING SKIES AND LIGHT WINDS
EXPECTED TO PROVIDE A BRIEF WINDOW OF GOOD RADIATIONAL COOLING
BEFORE MID AND HIGH LEVEL CLOUDS AHEAD OF NEXT CLIPPER APPROACH.
TEMPS WILL BE TRICKY IN THIS REGIME BUT ANY SHORT DURATION OF
RADIATIONAL COOLING IN AREAS WITH FRESH AND DEEP SNOWPACK TO YIELD
SHARP DROPS IN TEMPS. CONTINUED TO UNDERCUT MOS TEMPS WITH LOWS
AROUND ZERO AND BELOW ZERO TEMPS WHERE IDEAL CONDITIONS COME
TOGETHER.

FAST MOVING WEAK CLIPPER TO MOVE THROUGH SUNDAY WITH MODELS
INDICATING WEAK LIFT AND LIMITED MOISTURE. SNOW RATIOS REMAIN NEAR
20 TO 1 SO AN INCH OR TWO LOOKS PLAUSIBLE AT THIS TIME ACROSS THE
AREA. FOCUS THEN SHIFTS TO SOUTHERN STREAM WAVE THAT INDUCES
CYCLOGENESIS MONDAY NIGHT AND TUESDAY OVER THE SOUTHEAST CONUS.
MODELS HAVE TIGHTENED THE DEFORMATION AREA AND NOW KEEP MOST PCPN
JUST SOUTHEAST OF OUR AREA. MAINTAINED LOW CHANCE POPS FROM
SUPERBLEND INIT FOR NOW DUE TO MODEL UNCERTAINTY.

ANOTHER WEAK SHORT WAVE AND SFC FRONT TO MOVE THROUGH LATE TUESDAY
BRINGING A LAST SHOT OF COLDER AIR FOR WEDNESDAY BEFORE WHAT APPEARS
TO BE A NICE WARM UP TO END THE WEEK. COULD BE SOME LAKE EFFECT SNOW
SHOWERS WEDNESDAY BEFORE ANOTHER LARGE AREA OF HIGH PRESSURE MOVES
IN. RETURN FLOW BEHIND THIS RIDGE BRINGS VERY WARM AIR ALOFT INTO
THE GREAT LAKES TO END THIS PERIOD AND JUST BEYOND WITH A MORE ZONAL
MID LEVEL FLOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1139 AM EST FRI FEB 12 2016

BAND OF SNOW ALONG THE ARCTIC FRONT EXTENDING FM SW MI TO NE IL
SHOULD IMPACT THE TERMINALS WITH OCNL IFR CONDITIONS THIS AFTN.
W-NW WINDS ALSO INCRSG ALONG THE FRONT WITH GUSTS TO 25-30KT
EXPECTED THIS AFTN/EVE. LAKE EFFECT SNOW WILL DEVELOP BEHIND THE
FRONT AND SHOULD IMPACT SBN WITH IFR/OCNLY LIFR CONDITIONS
TONIGHT. INITIAL LAKE EFFECT BANDS MAY IMPACT FWA WITH MVFR
CONDITIONS THIS EVE BUT WINDS SHOULD VEER TO A MORE NORTHERLY
DIRECTION OVERNIGHT RESULTING IN BANDS PRBLY STAYING WEST OF FWA
INTO SAT MORNING.

&&

.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 FROM 7 PM THIS EVENING TO 7 AM EST
     SATURDAY FOR LMZ043-046.

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

&&

$$

UPDATE...JT
SYNOPSIS...STEINWEDEL
SHORT TERM...STEINWEDEL
LONG TERM...LASHLEY
AVIATION...JT


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