000
FXUS63 KIND 050226
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
925 PM EST WED DEC 4 2013

.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 400 PM EST WED DEC 4 2013

A BOUNDARY WILL DROP THROUGH THE AREA LATE TONIGHT INTO
THURSDAY...BEFORE STALLING ACROSS THE TENNESSEE VALLEY. A SERIES
OF DISTURBANCES MOVING ALONG THIS BOUNDARY LATE TOMORROW INTO
FRIDAY WILL SET THE STAGE FOR WHAT COULD BE THE FIRST SIGNIFICANT
WINTER STORM OF THE SEASON ACROSS MUCH OF CENTRAL INDIANA. AFTER A
BRIEF BREAK...ANOTHER SYSTEM WILL MOVE EAST OF THE AREA LATE
SUNDAY INTO MONDAY...WITH THE POTENTIAL FOR MORE ACCUMULATING
SNOWFALL THEN. TOWARD THE END OF THE PERIOD...DRY CONDITIONS WILL
RETURN BUT TEMPERATURES WILL BE VERY COLD.

&&

.NEAR TERM /TONIGHT/...
ISSUED AT 400 PM EST WED DEC 4 2013

BOUNDARY WILL SINK THROUGH THE AREA BEGINNING LATE TONIGHT...AND
ALTHOUGH ATMOSPHERE WILL BE FAIRLY DRY AT FIRST...AS MOISTURE
MOVES NORTH INTO THE AREA ON A 40KT LOW LEVEL JET MAY SEE SOME
SHOWERS ALONG THE BOUNDARY. WITH MUCH OF THE AREA STILL DEALING
WITH FOG AND LOW LEVEL INVERSION UNLIKELY TO WEAKEN SIGNIFICANTLY
OVERNIGHT...WILL CARRY AREAS OF FOG IN THE FORECAST AS WELL.

ON TEMPS...CONSENSUS APPEARS BEST WITH A BOUNDARY IN THE AREA AND
SIGNIFICANT GRADIENT IN MIN TEMPS LIKELY.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
ISSUED AT 400 PM EST WED DEC 4 2013

SHORT TERM FOCUS IS ON POTENTIALLY SIGNIFICANT WINTER STORM
EARLY THURSDAY EVENING INTO FRIDAY EVENING.

MODELS CONTINUE TO SET THE STAGE FOR A POTENTIAL WINTER STORM. AS
THE BOUNDARY SINKS SOUTH OF THE AREA AND COLD ADVECTION
CONTINUES...A SERIES OF DISTURBANCES MOVING ALONG THE BOUNDARY MAY
ALLOW SIGNIFICANT PRECIPITATION TO OCCUR AT TIMES. AREA WILL BE IN
FAVORABLE POSITION WITH RESPECT TO A 160-170KT UPPER LEVEL
JET AS AMPLE MOISTURE STREAMS NORTHEAST ALONG AND NORTH OF THE
FRONTAL ZONE. MODEL CROSS SECTIONS SHOW INCREASINGLY POTENT
FRONTOGENETIC FORCING THURSDAY EVENING INTO FRIDAY IN A SATURATED
AIRMASS WITH STRONGLY NEGATIVE EQUIVALENT POTENTIAL VORTICITY
VALUES AT TIMES...SUGGESTING THAT MESOSCALE FORCING WILL PICK UP
ANY SLACK FROM MODERATE SYNOPTIC FORCING AND ENHANCE THE POTENTIAL
PRECIPITATION...PERHAPS EVEN RESULTING IN SOME BANDING AT
TIMES...DURING THE STORM.

AT THIS TIME...APPEARS THAT PRECIP THROUGH AT LEAST MIDDAY
THURSDAY WILL BE IN THE FORM OF RAIN. MODEL THERMODYNAMIC PROFILES
SUGGEST A TRANSITION WILL BEGIN AND SWEEP ACROSS THE AREA FROM THE
NORTHWEST TO THE SOUTHEAST LATE TOMORROW AFTERNOON THROUGH
TOMORROW NIGHT. A POTENT WARM LAYER CENTERED AROUND 800-850
MILLIBARS THROWS A COMPLICATING FACTOR INTO THE MIX...AS THIS
COMBINED WITH THE DEPTH AND STRENGTH OF THE LOW LEVEL COLD AIR
SUGGEST A SIGNIFICANT AMOUNT OF SLEET COULD MIX WITH ANY
SNOW...ESPECIALLY THURSDAY EVENING. THIS GREATLY COMPLICATES
RESULTANT SNOWFALL AMOUNTS...BUT AT THIS TIME COMBINED SNOW AND
SLEET AMOUNTS OF THREE TO SIX INCHES WITH SOME HIGHER AMOUNTS
APPEAR LIKELY...WITH THE HIGHEST AMOUNTS SOUTH OF THE INTERSTATE
70 CORRIDOR. A BRIEF PERIOD OF FREEZING RAIN NEAR TRANSITION TIME
MAY OCCUR...BUT THIS WOULD BE TRANSIENT AT BEST AND WILL LEAVE OUT
OF THE GRIDS AT THIS TIME. HAVE GONE WITH A WINTER STORM WATCH
ACROSS THE SOUTHERN HALF OF THE AREA AS A RESULT.

CONSENSUS TEMPS APPEAR CLOSE TO WETBULB DURING PRECIP TIMES AND
THIS WILL BE ACCEPTABLE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
ISSUED AT 209 PM EST WED DEC 4 2013

ECMWF AND GFS AGREE THAT A COLD PATTERN IS EXPECTED TO PERSIST FOR
THIS PERIOD. COLD...ARCTIC HIGH PRESSURE IS EXPECTED TO BUILD INTO
THE OHIO VALLEY ON SATURDAY AS THE PRECEDING STORM SYSTEM DEPARTS
FARTHER SOUTH. WITH NEW SNOW PACK ON THE GROUND ALONG WITH COLD AIR
ADVECTION AMID COLD NORTH TO NORTHEAST FLOW...WILL TREND TEMPS
LOWER THAN GUIDANCE WITH A DRY FORECAST.

GFS AND ECMWF SUGGEST A CONTINUE VERY QUICK FLOW ALOFT ON SUNDAY
INTO MONDAY AS ANOTHER TROUGH ALOFT OVER THE CENTRAL PLAINS SAGS
EASTWARD AND PASSES ACROSS THE OHIO VALLEY ON MONDAY. THIS WILL NOT
ONLY GIVE US ANOTHER SHOT AT SNOW...BUT IN IT/S WAKE PROVIDE YET
ANOTHER REINFORCING BLAST OF COLD AIR AS BY TUESDAY A BROAD TROUGH
OF LOW PRESSURE ALOFT WILL ALLOW VERY COLD AIR OUT OF THE CANADIAN
NORTHWEST TO STREAM INTO THE OHIO VALLEY. WITH THE COLD...DRY AIR
MASS IN PLACE...NO PRECIP WILL BE EXPECTED ON TUESDAY AND
WEDNESDAY...HOWEVER WILL CONTINUE TO TREND TEMPERATURES COOLER THAN
ALLBLEND WHERE POSSIBLE.

&&

.AVIATION /DISCUSSION FOR 050300Z TAF ISSUANCE/...

ISSUED AT 925 PM EST WED DEC 4 2013

UPDATED CURRENT CONDITIONS. PREVIOUS DISCUSSION FOLLOWS...

A WARM FRONT HAS LIFTED NORTH OF THE SITES AND THIS IS ALLOWING
FOR IMPROVEMENT IN FLYING CONDITIONS...WITH THE SITES ALL VFR AT
23Z. THINK THIS WILL PERSIST FOR A BIT BEFORE MVFR CEILINGS AND
VISIBILITIES REDEVELOP ON A 40 KT 850 JET THAT WILL BRING IN SOME
MORE MOISTURE AND LIFT. THIS WILL PRODUCE SOME WIND SHEAR FOR A
FEW HOURS AS IT MOVES NORTH ACROSS THE STATE FROM AROUND 0-4Z.
WITH THE PREVIOUS 2 NIGHTS OF LIFR AND VLIFR CONDITIONS IN MIND
WILL BRING IN IFR AFTER 6Z. WITH THE WARM FRONT TO THE NORTH AND
EXTRA MIXING FROM THE JET DO NOT EXPECT THINGS TO GET WORSE THAN
THAT. COLD FRONT WILL PASS 9-14Z OR SO AND THEN THURSDAY SHOULD SEE
RAIN DEVELOP BY AFTERNOON AND CHANGEOVER TO SLEET THEN SNOW THURSDAY
EVENING.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THURSDAY EVENING THROUGH FRIDAY EVENING
FOR INZ042-045>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...NIELD
NEAR TERM...NIELD
SHORT TERM...NIELD
LONG TERM....PUMA
AVIATION...CP

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