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077
FXUS63 KIND 221741
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1241 PM EST MON DEC 22 2014

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

&&

.SYNOPSIS...
ISSUED AT 327 AM EST MON DEC 22 2014

AN UPPER TROUGH AND A COUPLE OF AREAS OF LOW PRESSURE WILL BRING
RAIN TO CENTRAL INDIANA TODAY INTO WEDNESDAY...WITH PERHAPS SOME
SNOW WEDNESDAY NIGHT. ANOTHER SYSTEM WILL BRING ADDITIONAL CHANCES
FOR PRECIPITATION FRIDAY AND SATURDAY. NEAR TO ABOVE AVERAGE
TEMPERATURES THIS WEEK WILL RETURN TO COOLER THAN AVERAGE FOR THE
WEEKEND.

&&

.NEAR TERM.../REST OF TODAY/
ISSUED AT 948 AM EST MON DEC 22 2014

.UPDATE...RAISED RAIN CHANCES A LITTLE OVER CENTRAL AND WESTERN
SECTIONS AS RADAR LOOPS HAS SHOWN A PRETTY GOOD PROGRESSION OF LIGHT
RAIN INTO OUR WESTERN SECTIONS AND MODELS SHOW THIS TREND CONTINUING
THIS AFTERNOON.  OTHERWISE...ONLY MINOR TWEAKS MADE TO GRIDS AS
PREVIOUS FORECAST SEEMS TO BE ON TRACK.

PREVIOUS NEAR TERM DISCUSSION FOLLOWS...
ISENTROPIC LIFT WILL INCREASE TODAY AS AN UPPER TROUGH AND SURFACE
WARM FRONT MOVE TOWARD CENTRAL INDIANA. BEST FORCING ARRIVES LATE IN
THE DAY WHEN 850MB WINDS APPROACH 50KT AND AN UPPER JET MOVES CLOSER
TO THE AREA.

ANY PRECIPITATION WILL HAVE TO FIGHT THE DRY LOWER LEVELS OF THE
ATMOSPHERE INITIALLY. SOUTHEAST WINDS AT THE SURFACE WILL AID IN
KEEPING THE LOWER LEVELS DRY. THUS IT WILL TAKE THE ATMOSPHERE A
WHILE TO MOISTEN UP.

GIVEN THE ABOVE...WENT HIGHEST POPS TODAY AT THE END OF THE TODAY
PERIOD. GRADUALLY INCREASED POPS DURING THE DAY. BY LATE DAY WENT
LIKELY POPS FAR WEST...CHANCE CENTRAL...AND SLIGHT CHANCE FAR EAST.

CLOUDS WILL INCREASE/THICKEN THROUGH THE DAY. A BLEND OF MODELS
LOOKS BEST FOR HIGH TEMPERATURES...AND THIS ENDS UP NEAR TO A LITTLE
COOLER THAN MOS SUGGESTS.

&&

.SHORT TERM.../TONIGHT THROUGH WEDNESDAY NIGHT/
ISSUED AT 327 AM EST MON DEC 22 2014

FOCUS IS ON PRECIPITATION CHANCES THROUGH THE PERIOD. THREW OUT THE
NAM AS ITS SOLUTION OF BRINGING A SURFACE LOW NEAR THE APPALACHIANS
LOOKS UNREALISTIC. GFS/ECMWF/CANADIAN MODELS ARE SIMILAR AND LOOK
MORE REASONABLE...SO USED A BLEND OF THEIR SOLUTIONS.

RAIN WILL CONTINUE TO OVERSPREAD CENTRAL INDIANA TONIGHT WITH FIRST
A WARM FRONT THEN A COLD FRONT MOVING THROUGH THE AREA. 850MB JET
WILL PROVIDE GOOD MOISTURE AND FORCING...AND UPPER TROUGH/UPPER JET
WILL BRING ADDITIONAL FORCING. THUS WENT CATEGORICAL POPS ALL AREAS
TONIGHT. LOWERED POPS OVERNIGHT AS SOME DRIER AIR WORKS IN BEHIND
THE COLD FRONT.

MODELS NOW SHOWING A DRY SLOT ACROSS CENTRAL INDIANA FOR MUCH OF
TUESDAY. THIS SEEMS REASONABLE WITH FIRST SURFACE AND UPPER SYSTEMS
MOVING OFF THE NORTH...AND NEXT UPPER LOW AND SURFACE LOW STILL
ORGANIZING TO THE SOUTH/SOUTHWEST. HOWEVER DO NOT BELIEVE THE VERY
DRY GFS GIVEN THAT ANY WEAK UPPER IMPULSES COULD GENERATE SOME
SHOWERS.

THUS WENT MAINLY CHANCE POPS THROUGH THE DAY TUESDAY ACROSS THE
AREA. KEPT HIGHER POPS EAST DURING THE MORNING TO ACCOUNT FOR RAIN
ALONG THE EXITING SURFACE FRONT.

TUESDAY NIGHT POPS WILL INCREASE ONCE AGAIN AS THE NEXT SYSTEM
APPROACHES FROM THE SOUTH. BY 06Z WENT LIKELY POPS MOST AREAS.

ON WEDNESDAY A SURFACE LOW WILL MOVE THROUGH THE AREA. MODELS STILL
UNCERTAIN ON EXACT PATH...BUT IT SHOULD BE IN THE GENERAL AREA OF
CENTRAL INDIANA TO WESTERN OHIO. WENT HIGH END LIKELY POPS...AND MAY
NEED TO UP THEM TO CATEGORICAL AS WE GET CLOSER.

WITH THE MORE WESTERN TRACKS OF THE MODELS GAINING FAVOR /GFS
ENSEMBLE MEAN AND PARALLEL GFS ARE FARTHER WEST THAN OPERATIONAL GFS
AND ECMWF/ FEEL THAN RAIN WILL BE THE PRIMARY PRECIPITATION TYPE
THROUGH THE DAY WEDNESDAY. WENT WITH CHANCE OF SNOW MIXING IN ACROSS
ROUGHLY THE WEST HALF OF CENTRAL INDIANA IN THE LATE AFTERNOON AS
COLDER AIR STARTS TO WORK IN.

MOST OF THE FORCING WILL BE OFF TO THE EAST WEDNESDAY NIGHT SO WENT
CHANCE POPS. WILL HAVE TO WATCH CLOSELY THOUGH IN CASE DEFORMATION
ZONE OR EVEN A TROWAL BRING BETTER CHANCES. WENT SNOW AS THE
PRECIPITATION TYPE WITH COLDER AIR QUICKLY MOVING IN. AT THE MOMENT
WILL KEEP ANY SNOWFALL AMOUNTS LESS THAN AN INCH.

FOR TEMPERATURES THROUGH THE PERIOD GENERALLY STUCK WITH A BLEND OF
GFS/ECMWF/MOS.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
ISSUED AT 253 AM EST MON DEC 22 2014

STRONG SYSTEM SET TO IMPACT THE REGION CHRISTMAS EVE WILL LIFT INTO
QUEBEC BY EARLY CHRISTMAS MORNING...WILL ANY LEFTOVER LIGHT SNOW
SHOWERS DEPARTING AROUND OR SHORTLY BEFORE DAYBREAK. SURFACE RIDGING
WILL IMMEDIATELY EXPAND INTO THE OHIO VALLEY ON THURSDAY WITH CLOUDS
GRADUALLY DIMINISHING AS WINDS TURN SOUTHERLY. FOCUS SHIFTS ABRUPTLY
TO NEXT SURFACE WAVE EJECTING OUT OF THE CENTRAL PLAINS AS YET
ANOTHER SHARP UPPER TROUGH DIVES INTO THE NORTHERN ROCKIES. OVERALL
MODEL CONSENSUS IS NOT TOO BAD AT THIS POINT WITH RESPECT TO THE
SURFACE LOW TRACK INTO THE WESTERN GREAT LAKES BY FRIDAY NIGHT.
SOUTHERLY FLOW AND WARM ADVECTION AHEAD OF THIS FEATURE WILL BRING
MILDER AIR NORTH WITH ANY PRECIPITATION FALLING AS RAIN INTO FRIDAY
EVENING. COLDER AIR WILL SPILL IN LATE AS A COLD FRONT PASSES
THROUGH THE REGION...WITH PRECIP POSSIBLY MIXING WITH OR CHANGING TO
LIGHT SNOW INTO SATURDAY BEFORE ENDING.

REMAINDER OF THE EXTENDED QUITE A BIT MORE CONVOLUTED AS MODELS
EXHIBITING DIFFERENCES IN HANDLING OF SUBSEQUENT WAVES ALOFT
TRAVERSING THE LOWER 48. THE ECMWF AND GGEM STARTING TO FAVOR
SECONDARY SURFACE WAVE DEVELOPMENT ON THE TRAILING PART OF THE
AFOREMENTIONED COLD FRONT...BRINGING THE FEATURE NORTHEAST OUT OF
THE WESTERN GULF OF MEXICO UP INTO THE OHIO AND TENNESSEE VALLEYS BY
EARLY SUNDAY IN TANDEM WITH THE WAVE ALOFT. NOT SURPRISINGLY...OP
GFS/PARALLEL GFS AND PRETTY MUCH ALL OF THE GFS ENSEMBLE MEMBERS
PAINT A COMPLETELY DIFFERENT PICTURE...WITH ANY SECONDARY WAVE
DEVELOPMENT ON THE FRONT BEING SUPPRESSED ALONG THE GULF COAST WITH
NO UPPER SUPPORT PRESENT.

WILL MAINTAIN A DRY CHILLY FORECAST FOR THE SECOND HALF OF THE
WEEKEND TO MAINTAIN CONTINUITY FROM PREVIOUS FORECASTS...BUT IT WILL
BE INTERESTING TO SEE IF THE GLOBAL MODELS MAINTAIN THIS NEW IDEA OF
BRINGING A SECONDARY WAVE NORTH WITH POTENTIALLY ADDITIONAL
OPPORTUNITIES FOR WINTRY PRECIP SATURDAY NIGHT AND SUNDAY. NOT
ANTICIPATING ANY BETTER MODEL CONSENSUS FOR AT LEAST A FEW MORE
DAYS...ESPECIALLY CONSIDERING THE CHAOTIC MODEL PERFORMANCE
RECENTLY. DEFINITELY SOMETHING TO MONITOR GOING FORWARD.

&&

.AVIATION /DISCUSSION FOR 221800Z TAF ISSUANCE/...

ISSUED AT 1231 PM EST MON DEC 22 2014

QUICKLY DETERIORATING FLYING CONDITIONS WITH RAIN IMPACTING THE
TERMINALS THIS AFTERNOON INTO TONIGHT. WIDESPREAD MVFR WILL BECOME
IFR NOW OR SHORTLY...THEN IMPROVE BACK TO MVFR BY TUE MORNING.
POSSIBLY EVEN VFR BY LATER TUESDAY AFTERNOON OR EVENING.

LOW PRESSURE AND ITS ASSOCIATED WARM FRONT ARE APPROACHING THE
REGION INTO THE EVENING. EXPECT WIDESPREAD RAIN AND IFR
CONDITIONS TO DEVELOP (IF NOT ALREADY SUCH AS AT SITE KLAF) OVER
CENTRAL INDIANA. SOUTHEAST WINDS WILL STEADILY INCREASE TO
10-15KTS BY THIS EVENING...EVENTUALLY VEERING TO A MORE SOUTHERLY
DIRECTION AND BECOMING GUSTY UP TO 18 TO 20 KT BY DAYBREAK
TUESDAY AS THE WARM FRONT PASSES THROUGH THE FORECAST AREA. RAIN
WILL DECREASE IN COVERAGE AFTER 06Z AS THE SURFACE LOW LIFTS INTO
NORTHERN ILLINOIS...BUT LOW STRATUS WILL PERSIST AS MODEL
SOUNDINGS AND 925/950MB RH PROGS MAINTAIN DEEP LOW LEVEL MOISTURE
BENEATH AN INVERSION. AFTER THE RAIN ENDS...THE INVERSION IS
FORECAST PER MODEL XSECTIONS TO LIFT BY TUESDAY AFTERNOON...AND
VFR CONDITIONS ARE THEN FORECAST FOR A BRIEF PERIOD...BEFORE THE
NEXT SYSTEM IS SET TO IMPACT THE REGION LATER IN THE NEXT AVIATION
FORECAST PERIOD.

&&

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

$$

SYNOPSIS...50
NEAR TERM...50/JH
SHORT TERM...50
LONG TERM....RYAN
AVIATION...SMF

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