000
FXUS63 KIND 041707
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1207 PM EST WED DEC 4 2013

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

&&

.SYNOPSIS...
ISSUED AT 352 AM EST WED DEC 4 2013

SCATTERED SHOWERS WILL BE POSSIBLE TODAY AND TONIGHT AS A STRONG
COLD FRONT MOVES THROUGH THE REGION. THE FRONT WILL BECOME NEARLY
STATIONARY OVER THE OHIO AND TENNESSEE VALLEYS ON THURSDAY. SEVERAL
WAVES WILL RIPPLE ALONG THE BOUNDARY LATE THURSDAY INTO FRIDAY AND
WITH INCREASINGLY COLDER AIR OVER CENTRAL INDIANA...A WINTRY MIX OF
PRECIP WILL TRANSITION TO ALL SNOW BY EARLY FRIDAY...POTENTIALLY
BECOMING HEAVY DURING THE DAY. AFTER A BRIEF BREAK SATURDAY...
ANOTHER WINTER STORM WILL IMPACT THE REGION SUNDAY AND MONDAY WITH A
MESSY WINTRY MIX. BEHIND THIS SYSTEM...HIGH PRESSURE WILL BRING DRY
AND VERY COLD WEATHER FOR THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /TODAY/...
ISSUED AT 1010 AM EST WED DEC 4 2013

HELD ONTO PATCHY DENSE FOG IN THE GRIDS UNTIL NOON AS FOG REMAINS
THICK IN SPOTS ACROSS THE AREA. PREVIOUS DISCUSSION FOLLOWS.

ISSUED AT 352 AM EST WED DEC 4 2013

CLOUDS WITH SOME FOG ACROSS THE REGION EARLY THIS MORNING. TEMPS
WERE IN THE 40S AT 08Z WITH A MILD SOUTHEAST FLOW AND WARM ADVECTION
INCREASING.

FOG WILL BE THE INITIAL ISSUE AS MODEL SOUNDINGS INDICATING A DECENT
INVERSION PRESENT AROUND 2-3KFT. AS WARM ADVECTION INCREASES THROUGH
THE MORNING...THE INVERSION MAY ACTUALLY STRENGTHEN. THIS SHOULD
KEEP A SOLID DECK OF STRATUS ACROSS THE FORECAST AREA AND AT LEAST
THROUGH MID MORNING...WILL MAINTAIN FOG WITH SOME LOCALLY DENSE FOG
OVER THE WABASH VALLEY. WILL CONTINUE TO MONITOR BUT HAVE NO PLANS
FOR AN ADVISORY AT THIS TIME.

LOW PRESSURE ORGANIZING OVER THE SOUTHERN PLAINS EARLY THIS MORNING
WILL PINWHEEL INTO THE WESTERN GREAT LAKES THIS EVENING AS A DOUBLE
BARRELED UPPER LOW ROTATES THROUGH THE NORTHERN PLAINS. COULD SEE A
FEW ISOLATED SHOWERS BY MIDDAY CONTINUING THROUGH THE AFTERNOON AS
WEAK FORCING ALOFT INCREASES...BUT NOTHING SUBSTANTIAL IN THE
ABSENCE OF DEEPER MOISTURE.

TEMPS...DESPITE THE STRONG WARM ADVECTION...MOS GUIDANCE APPEARS
AGGRESSIVE WITH WARMING CONSIDERING THE LOW CLOUDS AND MORNING FOG.
GENERALLY UNDERCUT BY A DEGREE OR TWO MOST LOCATIONS WHICH WILL
STILL END UP IN THE UPPER 50S AND LOWER 60S. THIS WILL BE THE
WARMEST DAY BY FAR FOR THE FORESEEABLE FUTURE.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
ISSUED AT 352 AM EST WED DEC 4 2013

FORECAST CHALLENGES FOCUS ON PRECIP TYPE INITIALLY...THEN AMOUNT AND
DURATION OF SNOWFALL THURSDAY NIGHT THROUGH FRIDAY NIGHT AS SIGNS
CONTINUE TO GROW TOWARDS THE FIRST SIGNIFICANT WINTER SYSTEM TO
IMPACT THE REGION THIS SEASON.

MODEL GUIDANCE IN GOOD AGREEMENT ON BRINGING THE FRONTAL BOUNDARY
ACROSS THE REGION OVERNIGHT TONIGHT. MOISTURE REMAINS LIMITED UNTIL
LATE TONIGHT AS THE FRONT INTERACTS WITH GULF MOISTURE ADVECTING
NORTH INTO THE OHIO VALLEY. WILL MAINTAIN CHANCE POPS TONIGHT...
PLACING HIGHEST POPS OVER SOUTHEAST COUNTIES LATE AS THE MOISTURE
PLUME LIFTS INTO THE REGION. MORE WIDESPREAD RAIN HOWEVER SHOULD
REMAIN JUST SOUTH OF THE FORECAST AREA INTO THURSDAY...GRADUALLY
SHIFTING FURTHER SOUTH WITH THE FRONT BY EARLY AFTERNOON.

FOCUS WILL THEN TURN TO A WINTER STORM WITH TWO PARTS THAT WILL
IMPACT CENTRAL INDIANA BEGINNING THURSDAY EVENING AND CONTINUING
THROUGH FRIDAY EVENING.

THE FIRST WAVE WILL QUICKLY EXPAND NORTHEAST FROM THE SOUTHERN
PLAINS LATE THURSDAY AFTERNOON...GRADUALLY EXPANDING ACROSS THE
FORECAST AREA THURSDAY EVENING. MODEL SOUNDINGS SHOW A SUBTLE LAYER
OF DRIER AIR INFILTRATING THE BOUNDARY LAYER INITIALLY THAT MAY TAKE
A LITTLE TIME TO MOISTEN UP. WITH SURFACE TEMPS FALLING BELOW
FREEZING DURING THE EVENING...WARM LAYER AT 850MB WILL REMAIN BUT
GRADUALLY GIVE WAY THROUGH THE NIGHT FROM THE NORTHWEST AS COLD
ADVECTION INTENSIFIES ALOFT. SOUNDING PROFILES AND THE LIKELIHOOD
THAT SOME EVAPORATIVE COOLING OCCURS INITIALLY SUPPORT SLEET MIXING
IN WITH RAIN AND SNOW THROUGH THE EVENING...WITH PRECIP LIKELY
FALLING AS ALL SNOW ALONG AND NORTH OF INTERSTATE 70 BY OR SHORTLY
AFTER MIDNIGHT. FURTHER SOUTH...A MIX OF PRIMARILY SLEET AND SNOW
WILL SHIFT SOUTH THROUGH THE OVERNIGHT...WITH THE SNOW/MIX LINE
BEING SOMEWHERE ACROSS FAR SOUTHERN COUNTIES BY DAYBREAK FRIDAY.
CANNOT ENTIRELY RULE OUT FREEZING RAIN MIXING IN WITH THE SLEET OVER
FAR SOUTHERN COUNTIES FOR A PERIOD OF TIME...BUT CONFIDENCE IN THAT
HAPPENING REMAINS LOW ENOUGH TO KEEP ANY MENTION OUT OF THE
FORECAST. 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 POSSIBLY 2
INCHES OF SNOW BY DAYBREAK FRIDAY WITH LIGHT ICING OVER SOUTHERN
COUNTIES.

PRECIP RATES WILL SLOW DOWN EARLY FRIDAY MORNING AS THE LEAD WAVE
SHIFTS EAST AND THE STRONGER LOW LEVEL JET ACCOMPANYING IT FOLLOWS
SUIT. THE LULL IN PRECIP LIKELY TO BE SHORT LIVED AS YET ANOTHER
WAVE LIFTS OUT OF THE SOUTHERN PLAINS AND RIDES NORTHEAST INTO THE
OHIO VALLEY BY THE AFTERNOON. UPPER DYNAMICS ARE EXTREMELY
IMPRESSIVE ACCOMPANYING THE SECOND WAVE...WITH A PHASED JET
STRUCTURE IN EXCESS OF 150KT CUTTING ACROSS THE REGION. THE TRACK OF
THE JET WILL PLACE THE FORECAST AREA IN THE FAVORABLE RIGHT REAR
QUAD AND ENHANCE LIFT. COMBINED WITH A RENEWED SURGE OF
FRONTOGENETICAL FORCING NORTH OF THE FRONTAL BOUNDARY AND AN EVEN
STRONGER LOW LEVEL JET INTERACTING WITH AN INTENSIFYING BAROCLINIC
ZONE OVER THE OHIO VALLEY...WIDESPREAD PRECIP WILL RETURN IN EARNEST
BY MIDDAY FRIDAY AND COULD BECOME LOCALLY HEAVY THROUGH THE
AFTERNOON. NO QUESTION ABOUT THE THERMAL PROFILES WITH THE SECOND
WAVE AS PRECIP WILL FALL AS ALL SNOW FROM MID MORNING ON ACROSS THE
FORECAST AREA WITH INCREASINGLY COLDER AIR OVERSPREADING THE REGION.

GAVE STRONG CONSIDERATION TO HOISTING A WINTER STORM WATCH THIS
MORNING BUT AFTER DISCUSSION WITH SURROUNDING NWS OFFICES...HAVE
CHOSEN TO HOLD OFF FOR ANOTHER SET OF RUNS LATER TODAY. CONFIDENCE
IS GROWING IN ADVISORY CRITERIA BEING MET OVER ALL BUT THE NORTHWEST
CORNER OF THE FORECAST AREA WITH POTENTIAL FOR A BAND OF BORDERLINE
WARNING CRITERIA BY FRIDAY NIGHT. AS IT STANDS NOW HOWEVER...THERE
IS STILL SOME UNCERTAINTY WITH RESPECT TO WHERE THE BAND LAYS
OUT...LIKELY SOMEWHERE IN THE SOUTHERN HALF OF THE FORECAST AREA.
ULTIMATELY...ANOTHER SET OF MODEL RUNS LATER TODAY WILL ALLOW FOR
SOME ADDITIONAL DETAILS TO BE EMPLOYED TO ASSIST IN PLACEMENT OF
POTENTIAL HEADLINES. THINK MOST AREAS ALONG AND SOUTH OF A TERRE
HAUTE-NOBLESVILLE-MUNCIE LINE WILL SEE AT LEAST 4 INCHES BY FRIDAY
NIGHT...WITH AS MENTIONED ABOVE...AN ENHANCED SOUTHWEST TO NORTHEAST
BAND WITH HIGHER AMOUNTS NEAR WARNING CRITERIA. WILL BE ISSUING AN
SPECIAL WEATHER STATEMENT TO HIGHLIGHT POTENTIAL IMPACTS IN
GREATER DETAIL.

TEMPS...QUITE THE TEMP SWING THROUGH THE PERIOD EXPECTED. WENT
SLIGHTLY ABOVE GUIDANCE FOR LOWS TONIGHT. HIGHS FOR THURSDAY WILL BE
AT DAYBREAK...WITH STEADILY FALLING TEMPS ALL DAY AS COLDER AIR
ARRIVES. TRENDED TOWARDS WARMER MET THURSDAY NIGHT...THEN COOLER MAV
FRIDAY WITH WIDESPREAD PRECIP. ANTICIPATE MOST LOCATIONS WILL REMAIN
BELOW 30 DEGREES ON FRIDAY. UNDERCUT ALL TEMP GUIDANCE FRIDAY NIGHT
AS FRESH SNOWPACK IN MANY LOCALES COMBINED WITH CLEARING SKIES LATE
WILL SUPPORT LOWS APPROACHING 10 DEGREES BY DAYBREAK SATURDAY.
WELCOME TO WINTER.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
ISSUED AT 352 AM EST WED DEC 4 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.

ENSEMBLES ARE TRENDING MORE TOWARDS A BIGGER CHUNK OF ENERGY
EJECTING OUT OF THE WESTERN TROUGH INTO THE PLAINS ON
SUNDAY...REACHING THE GREAT LAKES BY NEXT MONDAY. ALL ENSEMBLES KEEP
THE LOCAL AREA ON THE COLD SIDE OF THE SURFACE LOW...BUT WITH THE
UPPER SYSTEM PASSING SO FAR TO THE NORTHWEST...THERE IS CONCERN FOR
WARMER AIR ADVECTING INTO THE AREA ALOFT RESULTING IN MORE OF MIXED
PRECIPITATION EVENT RATHER THAN JUST SNOW. WILL GO WITH POPS
STARTING SATURDAY NIGHT AND CONTINUE THEM INTO MONDAY NIGHT. AS FAR
AS PRECIPITATION TYPE...WILL GO WITH A WINTRY MIX FOR ABOUT THE
SOUTHEAST TWO THIRDS OF THE FORECAST AREA FOR SUNDAY INTO SUNDAY
NIGHT...WHEN MODELS SUGGEST THE STRONGEST WARM ADVECTION WILL BE.
WILL CHANGE THINGS BACK TOWARDS ALL SNOW BY MONDAY UNDER COLD
ADVECTION. POTENTIAL FOR ACCUMULATING SNOW OR ICE CONTINUES WITH
THIS SYSTEM.

&&

.AVIATION /DISCUSSION FOR THE 041800Z TAFS/...

ISSUED AT 1152 AM EST WED DEC 4 2013

IFR OR WORSE CONDITIONS ARE EXPECTED FOR MUCH OF THIS TAF PERIOD.

OBSERVATIONS ACROSS THE FORECAST AREA SHOW PLENTY OF IFR OR WORSE
CONDITIONS. LOW CIGS AND VISIBILITIES CONTINUE TO HOLD IN PLACE.
SURFACE ANALYSIS LATE THIS MORNING SHOWS A SUBTLE WARM FRONT JUST
SOUTH OF THE TAF SITES WHERE CIGS AND VISIBILITIES IMPROVE TO VFR.

LITTLE OVERALL CHANGE IS EXPECTED IN THE AIR MASS OVER THE NEXT 18
HOURS AND HAVE USED A PERSISTENCE TYPE FORECAST AGAIN TONIGHT AS
WEAK WARM AIR ADVECTION CONTINUES AND DAYTIME HEATING IS LOST.
FORECAST SOUNDINGS AND TIME HEIGHTS CONTINUE TO SUGGEST LOWER
LEVEL MOISTURE REMAINS ACROSS THE TAF SITES.

AS THE COLD FRONT PASSES ON THURSDAY...CIGS ARE EXPECTED TO IMPROVE
TO MVFR AS MIXING IMPROVES AHEAD OF THE COLD FRONT...ALONG WITH
STRONGER LIFT APPROACHING THE AREA.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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

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