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000
FXUS63 KIND 051442
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
942 AM EST THU DEC 5 2013

.UPDATE...

THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 433 AM EST THU DEC 5 2013

A COLD FRONT WILL TRACK SOUTH INTO THE TENNESSEE VALLEY TODAY. A
SERIES OF DISTURBANCES MOVING ALONG THIS BOUNDARY BEGINNING LATER
THIS AFTERNOON INTO FRIDAY WILL SET THE STAGE FOR WHAT WILL BE THE
FIRST SIGNIFICANT WINTER STORM OF THE SEASON ACROSS MUCH OF CENTRAL
INDIANA. AFTER A BRIEF BREAK...ANOTHER WINTRY SYSTEM WILL IMPACT
CENTRAL INDIANA SUNDAY INTO MONDAY. HIGH PRESSURE WILL BRING DRY AND
VERY COLD CONDITIONS FOR THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THIS AFTERNOON/...
ISSUED AT 923 AM EST THU DEC 5 2013

RADAR TRENDS SHOW AN AREA OF FREEZING RAIN OVER EAST CENTRAL
ILLINOIS PUSHING NORTHEAST TOWARD LAFAYETTE AND KOKOMO.
TEMPERATURES IN NW INDIANA CONTINUE TO FALL IN THE WAKE OF THE
COLD FRONT...AND COLDER AIR IS EXPECTED TO ARRIVE AS THE DAY
PROGRESSES. THUS HAVE EXPANDED THE WINTER WEATHER ADVISORY FOR
NORTHWEST PARTS OF CENTRAL INDIANA...AS LIGHT ICING DUE TO THE
FREEZING RAIN MAY RESULT IN SOME ICY SURFACES. AS COLDER AIR
ARRIVES THIS AFTERNOON...A TRANSITION TO ALL SNOW WILL BE
EXPECTED. HAVE TRENDED TEMPERATURES AS FALLING THIS AFTERNOON DUE
TO THE EXPECTED COLD AIR ADVECTION.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
ISSUED AT 433 AM EST THU DEC 5 2013

MAIN FORECAST CHALLENGES REMAIN FOCUSED ON THE IMPENDING WINTER
STORM AND DETAILING SPECIFIC IMPACTS WITH PRECIP TYPE AND SNOW/ICE
ACCUMS. MODEL GUIDANCE HAS TIGHTENED UP A BIT MORE EARLY THIS
MORNING AND WHILE SOME SUBTLE FLUCTUATIONS REMAIN POSSIBLE IN TRACK
AND LOCATION OF THE HEAVIEST SNOWFALL...CONFIDENCE IS HIGH ENOUGH AT
THIS POINT TO UPGRADE HEADLINES FROM THE WATCH IN PLACE. MORE
DISCUSSION ON THIS BELOW.

FRONTAL BOUNDARY WILL SAG SLOWLY SOUTH THROUGH THE TENNESSEE VALLEY
AND INTO THE SOUTHERN APPALACHIANS BY FRIDAY. WINTRY PRECIPITATION
WILL DEVELOP AND IMPACT THE REGION AS TWO DISTINCT WAVES TRAVERSE
THE BOUNDARY TONIGHT AND ON FRIDAY AS PROGRESSIVELY COLDER AIR
SPREADS SOUTH ACROSS CENTRAL INDIANA.

WINTER STORM WITH TWO PHASES WILL BE IN ITS INFANCY THIS EVENING
WITH PRECIP ARRIVING. A STRONG LOW LEVEL JET WILL PASS THROUGH THE
TENNESSEE VALLEY OVERNIGHT AND WITH MID LEVEL FRONTOGENESIS AND A
SHARPENING BAROCLINIC ZONE OVER THE REGION...BROAD AREA OF
OVERRUNNING PRECIP WILL BECOME WIDESPREAD. MODEL GUIDANCE HAS
LARGELY COME IN MORE AGGRESSIVE WITH THE COLDER AIR THROUGH THE
BOUNDARY LAYER OVER AS THE NIGHT PROGRESSES OVER THE LAST FEW RUNS.
MODEL SOUNDINGS SHOW A SUBTLE LAYER OF DRIER AIR INFILTRATING THE
BOUNDARY LAYER INITIALLY THAT MAY TAKE A LITTLE TIME TO MOISTEN UP
VIA EVAPORATIVE COOLING PROCESSES. THIS WOULD SUPPORT SLEET MIXING
IN WITH RAIN AND SNOW THROUGH THE EVENING...WITH PRECIP LIKELY
FALLING AS ALL SNOW ALONG AND NORTH OF INTERSTATE 70 AFTER MIDNIGHT.
FURTHER SOUTH...LIGHT RAIN WILL GRADUALLY TRANSITION TO A MIX OF
PRIMARILY SLEET AND SNOW OVERNIGHT...WITH THE SNOW/MIX LINE ALONG
OUR FAR SOUTHERN BORDER BY DAYBREAK FRIDAY. WITH A MORE PRONOUNCED
WARM LAYER OVER SOUTHERN COUNTIES TONIGHT AND SURFACE TEMPS LIKELY
TO FALL BELOW FREEZING BY MIDNIGHT...HAVE INTRODUCED A PERIOD WITH
FREEZING RAIN MIXING IN WITH SLEET AND SNOW LATE TONIGHT IN A THIN
BAND FROM WASHINGTON NORTHEAST TO NEAR SEYMOUR AND GREENSBURG.
BOUNDARY LAYER WILL LIKELY COOL SUFFICIENTLY TO SUPPORT MAINLY SNOW
EVEN ACROSS SOUTHERN COUNTIES AROUND OR SHORTLY AFTER DAYBREAK
FRIDAY.

TAKING INTO CONSIDERATION SNOWFALL RATIOS LIKELY AT 10 TO 1 AND
POSSIBILITY THAT SLEET WILL CUT DOWN ON SNOWFALL AMOUNTS OVER MUCH
OF THE REGION TO SOME DEGREE...POTENTIAL FOR 1 TO 2 INCHES OF SNOW
BY DAYBREAK FRIDAY WITH LOCALLY HIGHER AMOUNTS NEAR OR JUST SOUTH OF
THE I-70 CORRIDOR. SHOULD THE CHANGEOVER HAPPEN A BIT QUICKER
OVERNIGHT...SNOW TOTALS WOULD END UP BEING HIGHER OVER THE SOUTHERN
HALF OF THE FORECAST AREA. LIGHT ICING REMAINS A POSSIBILITY OVER
SOUTHERN COUNTIES AS WELL WITH SLEET AND POCKETS OF FREEZING RAIN
MIXING IN.

PRECIP RATES WILL SLOW DOWN TEMPORARILY FRIDAY MORNING BEFORE ROUND
2 ARRIVES AS ANOTHER WAVE LIFTS OUT OF THE SOUTHERN PLAINS AND RIDES
NORTHEAST INTO THE OHIO VALLEY BY THE AFTERNOON. UPPER DYNAMICS...
MID LEVEL FRONTOGENESIS AND DEFORMATION REMAIN EXTREMELY IMPRESSIVE
AND WILL BE THE MAIN CATALYSTS IN BRINGING WIDESPREAD SNOWFALL
ACROSS MUCH OF THE FORECAST AREA BY MIDDAY FRIDAY. APPEARS THE LOW
LEVEL JET ACCOMPANYING THE SECOND WAVE WILL BE STRONGER THAN THE ONE
PASSING TO OUR SOUTH TONIGHT. COMBINED WITH A RENEWED SURGE OF
FRONTOGENETICAL FORCING NORTH OF THE FRONTAL BOUNDARY AND THE REGION
RESIDING WITHIN THE FAVORABLE RIGHT REAR QUAD OF A 170-180KT UPPER
JET DURING THE AFTERNOON...EXPECT SNOW TO BECOME LOCALLY HEAVY OVER
THE SOUTHERN HALF OF THE FORECAST AREA BY THE AFTERNOON. THE
PRESENCE OF AN INCREASING DENDRITIC GROWTH ZONE TO GO ALONG WITH
NEGATIVE EPV AND THE DEFORMATION AXIS STRONGLY SUGGESTIVE OF A BAND
OR FEW BANDS OF HEAVIER ACCUMS SETTING UP SW TO NE FROM NEAR
VINCENNES E/NE TO BLOOMINGTON/BEDFORD...TO COLUMBUS/SEYMOUR.

WITH HIGHER CONFIDENCE IN SIGNIFICANT IMPACTS AND CRITERIA BEING MET
OVER THE SOUTHERN TWO ROWS OF COUNTIES...WILL UPGRADE TO A WARNING.
TOTAL SNOW ACCUMS OF 6 TO 7 INCHES WITH LOCALLY HIGHER AMOUNTS ARE
EXPECTED. FURTHER NORTH WITH SNOWFALL AMOUNTS OF 3 TO 6
INCHES...WILL TRANSITION THE WATCH TO AN ADVISORY AND ADD ANOTHER
ROW OF COUNTIES NORTH. ACROSS FAR NORTHERN SECTIONS OF THE FORECAST
AREA...1 TO 2 INCHES OF SNOW WILL BE POSSIBLE BY FRIDAY EVENING.

THE REMAINDER OF THE SHORT TERM WILL BE COLD AND MAINLY DRY AS
ARCTIC HIGH PRESSURE PASSES THROUGH THE REGION. MOISTURE WILL
QUICKLY RETURN NORTH LATE SATURDAY NIGHT AS AN INVERTED TROUGH SETS
UP ACROSS THE TENNESSEE VALLEY. MAY SEE NORTHERN FRINGE OF THE LIGHT
SNOW EXPAND INTO FAR SOUTHERN COUNTIES TOWARDS DAYBREAK SUNDAY. THE
ACTIVE WINTRY PATTERN CONTINUES.

TEMPS...GENERALLY UNDERCUT MOS GUIDANCE THROUGH THE PERIOD. FRESH
SNOW COVER WILL PRODUCE VERY COLD TEMPS FRIDAY NIGHT WITH SKIES
CLEARING. MANY LOCALES MAY APPROACH 10 DEGREES. HELD HIGHS IN THE
20S ON FRIDAY WITH WIDESPREAD SNOW...WITH HIGHS ONLY IN THE LOW/MID
20S SATURDAY.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
ISSUED AT 433 AM EST THU DEC 5 2013

ENSEMBLES ARE IN GOOD AGREEMENT ON THE SLOW PROGRESSION OF A LARGE
SCALE UPPER TROUGH THROUGH THE PERIOD...WHICH IS EXPECTED TO EXTEND
FROM THE GREAT LAKES BACK INTO THE SOUTHERN PLAINS BY THE MIDDLE OF
NEXT WEEK.

MAJORITY OF THE ENSEMBLES EJECT A DECENT AMOUNT OF ENERGY WILL EJECT
OUT OF THE TROUGH ACROSS THE PLAINS AND INTO THE GREAT LAKES BY
SUNDAY AND EARLY MONDAY. MOST OF THE MEMBERS ARE STILL CLUSTERED
AROUND A TENNESSEE TO WESTERN OHIO SURFACE LOW TRACK...BUT SOME
MEMBERS ARE BEGINNING TO HINT AT AN INVERTED TROUGH EXTENDING
NORTHWEST OF THE SURFACE LOW OR A MORE STRETCHED OUT AREA OF LOW
PRESSURE. THIS IS PROBABLY A REFLECTION OF THE UPPER SYSTEM.
NEVERTHELESS...ALL MEMBERS INDICATE THE 850MB LOW WILL PASS WELL TO
THE NORTHWEST OF THE LOCAL AREA...SO THIS LOOKS MORE LIKE A MIXED
EVENT THAN JUST SNOW. WILL CONTINUE TO CARRY POPS SUNDAY AND
MONDAY...WITH A WINTRY MIX OVER ABOUT THE SOUTHEAST TWO THIRDS OF
THE FORECAST AREA SUNDAY AND SUNDAY NIGHT. COLD ADVECTION SHOULD
CHANGE ANY REMAINING PRECIPITATION TO SNOW LATER SUNDAY NIGHT AND
INTO MONDAY. POTENTIAL CONTINUES FOR SNOW AND ICE ACCUMULATIONS WITH
THIS SYSTEM.

ENSEMBLES INDICATE LITTLE THREAT FOR PRECIPITATION AFTER MONDAY AS
BROAD UPPER TROUGH GRADUALLY SHIFTS EAST.

&&

.AVIATION /DISCUSSION FOR THE 05/15Z TAF UPDATE/...
ISSUED AT 942 AM EST THU DEC 5 2013

AS COLD ADVECTION PROCEEDS...PERHAPS A BIT QUICKER THAN INITIALLY
SUSPECTED...AND BASED ON RADAR TRENDS...HAVE BUMPED ONSET OF PRECIP
UP A FEW HOURS AT IND. THINK THAT A MIX OF RAIN AND SLEET MAY OCCUR
INITIALLY IN A SHOWERY FASHION BEFORE THE GRADUAL TRANSITION BEGINS
LATE THIS AFTERNOON INTO THE EVENING. PREVIOUS DISCUSSION FOLLOWS.

ISSUED AT 535 AM EST THU DEC 5 2013

WIDESPREAD MVFR CEILINGS AROUND 015 UPSTREAM IN THE POST FRONTAL
ZONE...SO EXPECTING CEILINGS AROUND THIS LEVEL INTO THE AFTERNOON
HOURS. MODEL DATA SUGGEST ORGANIZED LIFT FROM APPROACHING SYSTEM
OVER THE SOUTHERN PLAINS WILL BEGIN MOVING INTO THE AREA THIS
AFTERNOON HELPING TO MIX OUT THE LOWER CEILINGS...SO SHOULD SEE THE
MVFR CEILINGS BEGIN TO SCATTER OUT AFTER ABOUT 052000Z FROM
SOUTHWEST TO NORTHEAST.

THE LIFT SHOULD HELP TO GENERATE SOME PRECIPITATION OVER THE MORE
SOUTHERN TAF SITES...KBMG/KHUF/KIND...LATER THIS AFTERNOON. HOWEVER
IT APPEARS THE STRONGER LIFT WILL HOLD OFF UNTIL AFTER 060000Z...SO
THINK THE PRECIPITATION THIS AFTERNOON WILL BE RATHER LIGHT AND NOT
RESTRICT VISIBILITIES TOO MUCH.

MODEL DATA SUGGEST MAINLY RAIN/ICE PELLETS THIS AFTERNOON...WITH A
TENDENCY TOWARDS SNOW AFTER SUNSET. HOWEVER...IF THE COLD AIR COMES
IN FASTER THAN EXPECTED...THERE MAY BE A PERIOD OF FREEZING RAIN
LATE THIS AFTERNOON.

SOME SURFACE WIND GUSTS 15-20 KTS FROM 280-300 DEGREES EXPECTED
EXPECTED TO DIMINISH BY THIS AFTERNOON AS PRESSURE GRADIENT RELAXES.

WIDESPREAD IFR/POSSIBLY LIFR VISIBILITY RESTRICTIONS EXPECTED AFTER
060000Z DUE TO SNOW/ICE PELLETS IN THE KHUF/KIND AREAS...WITH
FREEZING RAIN POSSIBLE AT KBMG.

&&

.IND WATCHES/WARNINGS/ADVISORIES...

WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST FRIDAY NIGHT FOR
INZ021-028>031-035>049-051>057.

WINTER STORM WARNING FROM 10 PM THIS EVENING TO MIDNIGHT EST
FRIDAY NIGHT FOR INZ060>065-067>072.

&&

$$

SYNOPSIS...RYAN
NEAR TERM...PUMA
SHORT TERM...RYAN
LONG TERM....JAS
AVIATION...JAS/NIELD

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