000
FXUS63 KIND 112234
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
533 PM EST WED DEC 11 2013

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

&&

.SYNOPSIS...
ISSUED AT 321 PM EST WED DEC 11 2013

VERY COLD TEMPERATURES ARE EXPECTED TONIGHT AS A RENEWED SURGE OF
ARCTIC AIR OVERSPREADS THE REGION. COLD AND DRY CONDITIONS WILL
CONTINUE INTO FRIDAY AS HIGH PRESSURE PASSES THROUGH THE REGION. A
SERIES OF UPPER WAVES WILL TRACK THROUGH THE OHIO VALLEY FRIDAY
NIGHT AND SATURDAY...BRINGING ACCUMULATING SNOW TO MUCH OF THE
REGION. COLDER AIR WILL RETURN IN THE WAKE OF THIS SYSTEM BY LATE
WEEKEND...BEFORE RISING TO NEAR NORMAL BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /TONIGHT/...
ISSUED AT 520 PM EST WED DEC 11 2013

UPDATED GRIDS AND HAZARDOUS WEATHER OUTLOOK FOR THE SNOW SHOWERS
THAT WERE OCCURING ACROS THE METRO WITH SMALL CHANCE POPS THROUGH
23Z. THEN...DIURNAL ACTIVITY SHOULD END WITH SUNSET.

PREVIOUS DISCUSSION FOLLOWS...

COLD FRONT TRACKING THROUGH THE REGION AS OF 19Z. SNOW ASSOCIATED
WITH THE CLIPPER SYSTEM REMAINS LARGELY NORTH OF THE FORECAST
AREA...JUST GRAZING FAR NORTHERN/NE COUNTIES FROM KOKOMO TO MUNCIE.
TEMPS WERE IN THE 20S NORTH OF I-70 AND UPPER 20S TO LOWER 30S
FURTHER SOUTH.

MAIN FOCUS FOR TONIGHT WILL BE TEMPS AND WIND CHILLS...AS
REINFORCING BLAST OF BITTERLY COLD AIR POISED TO ADVECT INTO THE
REGION ONCE THE COLD FRONT PASSES BY LATE AFTERNOON.

AS MENTIONED ABOVE...LIGHT SNOW SHOWERS WILL IMPACT THE EXTREME
NORTHEAST PART OF THE FORECAST AREA OVER THE NEXT FEW HOURS AS THE
CLIPPER SYSTEM QUICKLY SHIFTS INTO THE EASTERN GREAT LAKES. ANY
LIGHT SNOW SHOWERS OR FLURRIES WILL BE EAST OF THE FORECAST AREA BY
LATE AFTERNOON. CLOUDS INITIALLY WILL LIMIT TEMP FALLS LATE THIS
AFTERNOON AND EARLY EVENING BUT MODEL SOUNDINGS AND RH PROGS
INDICATE SKIES WILL BECOME CLEAR AS THE EVENING PROGRESSES AND WILL
REMAIN SO THROUGH THE OVERNIGHT OUTSIDE OF A FEW MID/HIGH LEVEL
CLOUDS DRIFTING INTO THE REGION FROM THE NORTHWEST. GUSTY WINDS
DIRECTLY BEHIND THE FRONT WILL IMPACT CENTRAL INDIANA INTO THE EARLY
EVENING...WITH NORTHWEST WINDS DECREASING TO LESS THAN 10KTS LATE AS
HIGH PRESSURE CENTERS OVER THE MID MISSISSIPPI VALLEY.

TEMPS...SET TO EXPERIENCE OUR COLDEST NIGHT FOR MANY LOCATIONS
POTENTIALLY IN CLOSE TO THREE YEARS. COMBINATION OF STRENGTHENING
COLD ADVECTION...THE SNOWPACK FOR MUCH OF THE AREA AND CLEARING
SKIES BY MID EVENING WILL SET THE STAGE FOR NEAR IDEAL CONDITIONS
FOR VERY COLD TEMPS. THE POSSIBILITY THAT WINDS STAY UP JUST A TOUCH
OVERNIGHT MAY KEEP TEMPS FROM COMPLETELY BOTTOMING OUT IN SOME
LOCATIONS...BUT STILL AM HIGHLY CONFIDENT IN UNDERCUTTING ALL
GUIDANCE ON LOWS. GOING RIGHT AT ZERO DEGREES AT INDY...WHICH WOULD
MAKE FOR THE COLDEST NIGHT SINCE FEB 10 2011. MANY RURAL LOCALES
LIKELY TO SLIP BELOW ZERO. MIN WIND CHILLS ANTICIPATED AROUND -15 TO
-10F...AND WILL CARRY AN SPS TO HIGHLIGHT THE COLD.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
ISSUED AT 324 PM EST WED DEC 11 2013

FORECAST CHALLENGES FOCUS ON THE ARRIVAL AND IMPACTS FRIDAY NIGHT
AND SATURDAY FROM THE NEXT WINTER STORM IN THE PIPELINE. MODEL
CONSENSUS STARTING TO SHOW BETTER AGREEMENT ON TIMING AND ON LOW
LEVEL THERMAL PROFILES WHICH WILL BE CRITICAL IN DETERMINING PRECIP
TYPE FOR SOUTHERN PORTIONS OF THE FORECAST AREA.

PRIOR TO THE WINTER STORM...DRY CHILLY WEATHER EXPECTED INTO FRIDAY
AS STRONG HIGH PRESSURE TRACKS FROM THE MID MISSISSIPPI VALLEY INTO
THE CAROLINAS. OTHER THAN PERIODS WITH THIN MID/HIGH LEVEL
CLOUDS...SHOULD SEE ABUNDANT SUNSHINE THURSDAY WITH MAINLY CLEAR
SKIES CONTINUING THURSDAY NIGHT. SHARP SURFACE PRESSURE GRADIENT
WILL CREATE A FAVORABLE SET UP FOR GUSTY WINDS THURSDAY AFTERNOON AS
THE CENTER OF THE HIGH PASSES TO OUR SOUTH.

WARM ADVECTION BEGINS LATE THURSDAY AND CONTINUES INTO FRIDAY AS
ENERGY ASSOCIATED WITH AN UPPER LOW EJECTS OUT OF THE SOUTHERN
ROCKIES. THIS LEAD WAVE ALOFT WILL QUICKLY TRACK E/NE INTO THE OHIO
VALLEY BY EARLY SATURDAY...DRAWING LOW LEVEL MOISTURE NORTH INTO THE
REGION AS LOW PRESSURE TRACKS ACROSS THE LOWER MISSISSIPPI VALLEY.
SUBTLE RIDGING AHEAD OF THE WAVE WILL ALLOW FOR WARMER AIR TO LIFT
INTO THE FORECAST AREA FRIDAY AFTERNOON. NAM/GFS/ECMWF ALL
INDICATING ISENTROPIC UPGLIDE COMMENCING BY LATE AFTERNOON ACROSS
THE REGION AS DEEPER MOISTURE ARRIVES. EVAPORATIVE COOLING PROCESSES
WILL BE KEY FOR THE INITIAL STAGES OF PRECIP LATE FRIDAY AFTERNOON
AND EVENING...AS NEAR 0C TEMPS THROUGH THE BOUNDARY LAYER WILL
QUICKLY COOL WITH THE ONSET OF MOISTURE ADVECTION. WHILE THE
POTENTIAL FOR A RA/SN MIX OR SOME FORM OF A WINTRY MIX SEEMS
PLAUSIBLE OVER SOUTHERN PORTIONS OF THE FORECAST AREA AT PRECIP
ONSET...EXPECT SNOW TO QUICKLY BECOME THE PREDOMINANT PRECIP TYPE
FRIDAY EVENING.

COOLING 850MB TEMPS OVERNIGHT FRIDAY NOW STRONGLY SUPPORTIVE OF SNOW
OVER THE ENTIRE FORECAST AREA LATE FRIDAY NIGHT. PRECIP RATES
EXPECTED TO INCREASE LATE FRIDAY NIGHT INTO EARLY SATURDAY MORNING
DURING PERIOD OF STRONGEST ISENTROPIC LIFT AND COINCIDENT WITH SOME
MID LEVEL DEFORMATION. LOW LEVEL THERMALS AGAIN WILL BECOME CRITICAL
FOR FAR SOUTHERN COUNTIES SATURDAY AS A SURGE OF WARM ADVECTION
LIFTS INTO THE OHIO VALLEY. MODEL SOUNDING ANALYSIS SUGGESTIVE OF
POTENTIAL FOR RAIN TO MIX IN WITH SNOW SOUTH OF A WASHINGTON-
BLOOMINGTON-COLUMBUS LINE SATURDAY. FURTHER NORTH HOWEVER...COLD AIR
WILL REMAIN FIRMLY ENTRENCHED WITH PRECIP CONTINUING TO FALL AS
SNOW. PRECIP RATES WILL LIGHTEN SATURDAY AFTERNOON BUT EVEN AS
ISENTROPIC LIFT DIMINISHES...MID LEVEL FORCING WILL PERSIST FOR MUCH
OF THE DAY AHEAD OF A SECONDARY UPPER WAVE.

POTENTIAL FOR SNOW ACCUMS FOR MUCH OF THE AREA FRIDAY NIGHT INTO
SATURDAY BASED ON ABOVE THOUGHTS...AND SUSPICION THAT MODELS ARE
UNDERDOING THE DEPTH OF THE COLD AIR PRECEDING THE WINTER STORM.
INITIAL THOUGHTS REGARDING ACCUMS BY SATURDAY EVENING AT THIS TIME
IS POTENTIAL FOR 3 TO 5 INCHES FOR MUCH OF THE NORTHERN 2/3 OF THE
FORECAST AREA. SNOW AMOUNTS WILL BE DIMINISHED OVER FAR SOUTHERN
COUNTIES DUE TO POTENTIAL FOR MIXING OF OTHER PRECIP TYPES AND ON
SATURDAY RAIN...BUT EVEN HERE THINK 1 TO 2 INCHES IS A POSSIBILITY.
WILL HIGHLIGHT POTENTIAL SNOW ACCUMS IN THE HWO WITH MORE DETAIL
FORTHCOMING OVER THE NEXT DAY OR TWO AS MODEL CONSENSUS ALIGNS EVEN
FURTHER.

TEMPS...LEANED MUCH CLOSER TO THE COOLER MAVMOS GUIDANCE THROUGH
MUCH OF THE PERIOD AS IT SEEMS TO HAVE A BETTER HANDLE ON THE COLD
AIRMASS THURSDAY/FRIDAY. LOWS FRIDAY NIGHT LIKELY TO BE EARLY...WITH
SLOWLY RISING TEMPS INTO SATURDAY. AS STATED ABOVE...MODEL GUIDANCE
IN GENERAL LOOKS TOO WARM SATURDAY AND UNDERCUT BY A DEGREE OR TWO
ACROSS THE BOARD FOR HIGHS.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
ISSUED AT 203 PM EST WED DEC 11 2013

THE EUROPEAN AND GFS MODELS CONTINUE TO HOLD ON TO THE LATEST
TREND OF A 2-3 WAVE PATTERN OVER THE POLAR REGION WITH SLIGHTLY
POSITIVE ANOMALIES OVER THE INTERMOUNTAIN WEST. ONE STORM SYSTEM
WILL BE MOVING EASTWARD AT THE START OF THE PERIOD...WITH HIGH
PRESSURE MOVING OVER THE AREA MONDAY WITH AN ALBERTA CLIPPER
MOVING OVER THE NORTHERN GREAT LAKES. AT THIS TIME...LOOKS LIKE
ANY PRECIPITATION WILL MOVE ACROSS THE NORTHERN COUNTIES ON
MONDAY/EARLY TUESDAY.

TEMPERATURES LOOK TO MODERATE JUST A BIT LIMITED BY THE PERSISTENT
SNOW COVER ON THE GROUND ACROSS MUCH OF THE FORECAST AREA. NORMALS
FOR THE EXTENDED PERIOD ARE IN THE UPPER 30S DURING THE DAY AND
MID 20S AT NIGHT. THUS..TEMPERATURES WILL STILL BE AROUND 5 DEG
COOLER THAN NORMAL FOR THE MOST PART DURING THE PERIOD.

&&

.AVIATION /DISCUSSION FOR 120000Z TAFS/...
ISSUED AT 533 PM EST WED DEC 11 2013

AREAS OF MVFR CEILINGS/VISIBILITY RESTRICTIONS IN SCATTERED LIGHT
SNOW SHOWERS HAVE DEVELOPED IN THE POST FRONTAL ZONE. SOME BRIEF IFR
RESTRICTIONS NOTED IN THE HEAVIER SHOWERS. SATELLITE LOOPS INDICATE
THE BACK EDGE OF THESE CONDITIONS SHOULD BE AROUND KLAF BY ISSUANCE
TIME...AND BY 120100Z-120200Z AT THE REMAINDER OF THE TAF SITES.
ONCE THESE LOWER CLOUDS DISSIPATE...NO SIGNIFICANT CLOUD COVER
EXPECTED FOR THE REST OF THE NIGHT.

ANY LINGERING SURFACE WIND GUSTS EXPECTED TO DIMINISH OVER THE NEXT
COUPLE OF HOURS.

&&

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

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/MK
SHORT TERM...RYAN
LONG TERM....DWM
AVIATION...JAS

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