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000
FXUS63 KIND 031125
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
625 AM EST TUE MAR 3 2015

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

&&

.SYNOPSIS...
ISSUED AT 342 AM EST TUE MAR 3 2015

WINTRY PRECIPITATION DEVELOPING AHEAD OF LOW PRESSURE EARLY THIS
MORNING...WITH SEVERAL HOURS THROUGH LATE MORNING FEATURING THE
THREAT FOR FREEZING RAIN. PRECIPITATION WILL CHANGE OVER TO RAIN
THIS AFTERNOON AND EVENING...BEFORE CHANGING OVER TO SNOW OVERNIGHT
AS A COLD FRONT MOVES THROUGH THE AREA. THE FRONT WILL BECOME NEARLY
STATIONARY OVER THE TENNESSEE VALLEY WEDNESDAY INTO WEDNESDAY
NIGHT...WITH THE POTENTIAL FOR ACCUMULATING SNOW ACROSS PRIMARILY
THE SOUTHERN HALF OF CENTRAL INDIANA. HIGH PRESSURE WILL THEN BUILD
IN THURSDAY WITH DRY CHILLY WEATHER INTO THE WEEKEND.

&&

.NEAR TERM /TODAY/...
ISSUED AT 342 AM EST TUE MAR 3 2015

PRECIP GRADUALLY SPREADING IN FROM THE WEST EARLY THIS MORNING AS
DEEPER MOISTURE ARRIVES. LEADING EDGE OF THE PRECIP LIKELY NOT
REACHING THE GROUND WITH DEWPOINT DEPRESSIONS OF 10-15 DEGREES
ACROSS THE FORECAST AREA. TEMPS WERE GENERALLY IN THE 20S...WITH THE
LOWER WABASH VALLEY NEARING 30 DEGREES.

REALLY FEELS LIKE WE ARE GETTING THE KITCHEN SINK TOSSED AT US OVER
THE NEXT 48 HOURS...WITH FREEZING RAIN...RAIN AND SNOW ALL ON THE
DOCKET. FIRST FOCUS IS ON THE ICING POTENTIAL THROUGH THE MORNING.

OBS ACROSS CENTRAL ILLINOIS NOW REPORTING FREEZING RAIN OR UNKNOWN
PRECIP...WHICH IS PROBABLY A MIX OF FREEZING RAIN AND SLEET. THINK
SLEET IS CERTAINLY A POSSIBILITY AT ONSET AS THE DRIER AIR THROUGH
THE BOUNDARY LAYER ERODES. THERMAL PROFILES HOWEVER ARE STRONGLY
SUPPORTIVE OF FREEZING RAIN QUICKLY BECOMING THE PRIMARY PRECIP TYPE
WITHIN AN HOUR OR TWO OF PRECIP STARTING. SURFACE TEMPS THEN BECOME
THE MAIN FACTOR IN DETERMINING HOW LONG THE FREEZING RAIN LASTS. HI-
RES GUIDANCE HAS INITIALIZED A BIT TOO COOL OVER NORTHERN COUNTIES
BUT IN GENERAL IS DOING A BETTER JOB FURTHER SOUTH. RAP/HRRR/WRF
GUIDANCE ALL SHOWING TEMPS WILL GRADUALLY RISE ABOVE 32F FROM
SOUTHWEST TO NORTHEAST DURING THE MORNING BUT HINTING AT A DELAY
OVER EARLIER GUIDANCE BY AN HOUR OR TWO...ESPECIALLY OVER THE
NORTHERN HALF OF THE FORECAST AREA. STILL APPEARS ENTIRE AREA WILL
BE ABOVE FREEZING BY EARLY AFTERNOON WITH PRECIP FALLING AS RAIN.

OVERALL QPF VALUES FALLING AS FREEZING RAIN SHOULD BE 0.10 TO 0.15
INCHES WITH HIGHEST AMOUNTS OVER THE NORTHEAST HALF OF THE FORECAST
AREA. THESE AMOUNTS WILL CERTAINLY CAUSE LIGHT ICE TO ACCUMULATE ON
ROADS AND ELEVATED SURFACES AND THE TIMING COULD NOT BE WORSE AS THE
MORNING RUSH WILL BE IMPACTED. IN AN EFFORT TO HEIGHTEN AWARENESS OF
THE IMPACTS...GOING TO SWITCH THE WINTER WEATHER ADVISORY TO A
FREEZING RAIN ADVISORY AND STRESS THE ICING POTENTIAL. IMPACTS WILL
LIKELY BE GREATEST THROUGH ABOUT 13-14Z. EVEN AS TEMPS RISE ABOVE
32F...THE FROZEN GROUND WILL LIKELY LEND TO AT LEAST SOME ICING TO
CONTINUE UNTIL THE SURFACE TEMP CAN GET TO 33-34F LATER IN THE
MORNING. AT THE SAME TIME...SOLAR RADIATION WILL WORK AS AN OPPOSING
FORCE TO MINIMIZE ICING AS THE MORNING PROGRESSES...AS EARLY MARCH
LEVELS ARE FAIRLY EFFICIENT. WILL MAINTAIN THE ADVISORY THROUGH 17Z
TO ACCOUNT FOR THE UNCERTAINTIES.

REMAINDER OF THE DAY WILL SEE RAIN FALL AS MOISTURE SPREADS NORTH
ALONG AND AHEAD OF THE COLD FRONT. RECENT TRENDS CONTINUE TO FOCUS
THE HEAVIER RAINFALL FURTHER SOUTH CLOSER TO THE OHIO RIVER WHERE
FORCING AND AVAILABLE MOISTURE WILL BE GREATER. AMOUNTS WILL RANGE
FROM A QUARTER INCH NORTHWEST TO THREE QUARTERS OF AN INCH OVER THE
SOUTH BY EARLY EVENING. THIS WILL CREATE RUNOFF INTO AREA STREAMS
CONSIDERING THE FROZEN GROUND AND AMBIENT SNOWPACK WHICH WILL AT
LEAST PARTIALLY MELT. LOCALIZED AREAS OF FLOODING REMAIN CONCERNS
GOING FORWARD. ADDITIONALLY...REMAINING SNOW AND ICE MAY CLOG STREET
DRAINS AND RESULT IN URBAN FLOODING ALONG ROADWAYS.

TEMPS...UTILIZED RAP/HRRR BLEND FOR HOURLY TEMPS THROUGH MIDDAY.
TRENDED TOWARDS THE COOL END OF GUIDANCE FOR HIGHS THIS AFTERNOON.
DESPITE THE WARM ADVECTION...SNOWPACK WILL LIKELY HOLD TEMPS DOWN A
BIT WITH UPPER 30S NORTH AND 40S SOUTH.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
ISSUED AT 342 AM EST TUE MAR 3 2015

FORECAST CHALLENGES FOCUS ON POTENTIAL FOR ADDITIONAL SNOW
ACCUMULATIONS AS A SECONDARY WAVE RIDES THE DEPARTING FRONTAL
BOUNDARY LATE WEDNESDAY THROUGH WEDNESDAY NIGHT. BITTERLY COLD AIR
THEN RETURNS FOR THE REMAINDER OF THE EXTENDED.

PRECIP WILL GRADUALLY SHIFT SOUTH TONIGHT WITH THE FRONT...MIXING
WITH THEN CHANGING OVER TO SNOW AFTER MIDNIGHT AS COLDER AIR ADVECTS
IN BEHIND THE FRONT. ANY ACCUMS SHOULD BE MINOR...ON THE ORDER OF A
TENTH OR TWO OF AN INCH AT BEST. SCATTERED LIGHT SNOW WILL CONTINUE
WEDNESDAY MORNING OVER FAR SOUTHERN COUNTIES WITH DRY COLD
CONDITIONS ELSEWHERE.

FORECAST BECOMES MORE INTERESTING WEDNESDAY AFTERNOON AND EVENING AS
A SURFACE WAVE RIDES THE BOUNDARY FROM EAST TEXAS INTO THE SOUTHERN
APPALACHIANS BY EARLY THURSDAY. MODELS CONTINUE TO DIFFER ON THE
DEGREE OF IMPACTS THIS SYSTEM MAY HAVE FOR PARTS OF THE REGION...BUT
AN INCREASING CONCERN FOR ACCUMULATING SNOW IS A CLEAR TREND.
NAM/WRF/UKMET ALL REMAIN FURTHER NORTH WITH THE TRACK OF THE SURFACE
LOW AND LOCATION OF THE FRONT WHICH WOULD SUPPORT MORE SNOW FOR
CENTRAL INDIANA. OP GFS CONTINUES TO BE MORE SUPPRESSED WITH A MORE
PROGRESSIVE UPPER FLOW SETUP. THE SREF/ECMWF/GGEM ARE ALL IN
BETWEEN.

A CONSERVATIVE APPROACH IS WARRANTED RIGHT NOW CONSIDERING THE LACK
OF MODEL CONSENSUS. AT THE SAME TIME...RULING OUT THE MORE NORTHERN
NAM/WRF/UKMET GROUP COMPLETELY WOULD BE FOOLISH...ESPECIALLY
CONSIDERING HOW THE UKMET HAS PERFORMED AS OF LATE. PRESENCE OF
DEFORMATION BANDING AHEAD OF THE POSITIVELY TILTED UPPER WAVE AND A
STRONG PHASED UPPER JET STRUCTURE WEDNESDAY NIGHT BOTH ARGUE IN A
MORE NORTHERN SOLUTION THAN THE OP GFS. THE LOCATION OF THE UPPER
JET TO OUR N/NW SHOULD ENHANCE FORCING AS WELL ON WEDNESDAY EVENING.
HIGHER RATIOS ON THE ORDER OF 15/20 TO 1 WOULD ALSO HAVE AN IMPACT
ON POTENTIAL ACCUMS.

TAKING THIS ALL INTO CONSIDERATION...HAVE INCREASED POPS AND
SNOWFALL AMOUNTS ALONG AND SOUTH OF THE I-70 CORRIDOR WEDNESDAY
NIGHT. INITIAL THINKING IS A SHARP CUTOFF ALIGNING SOMEWHERE OVER OUR
NORTHERN COUNTIES...INCREASING TO 1 TO 3 INCHES ALONG AND JUST SOUTH
OF THE I-70 CORRIDOR. TAKE AMOUNTS ALL THE WAY UP TO 5 TO POSSIBLY 6
INCHES IN FAR SOUTHERN COUNTIES FROM BEDFORD TO SEYMOUR. SHOULD THE
CONSENSUS TREND TOWARDS THE NORTHERN CAMP...AMOUNTS WILL NEED TO BE
RAISED OVER THE ENTIRE AREA. WILL INTRODUCE A WINTER STORM WATCH OVER
FAR SOUTHERN ROW OF COUNTIES WHERE CONFIDENCE IS HIGHEST AT THIS
TIME IN SNOW AMOUNTS APPROACHING 6 INCHES. SHOULD THE CONSENSUS
TREND TOWARDS THE NORTHERN MODEL CAMP...AMOUNTS WILL NEED TO BE
RAISED. STAY TUNED AS THIS SETUP REMAINS FLUID AND IS LIKELY TO
CHANGE FURTHER IN THE COMING 24-36 HOURS.

ANY SNOW WILL END BY EARLY THURSDAY WITH ANOTHER ARCTIC HIGH TAKING
OVER THE REST OF THE SHORT TERM. DRY AND BITTERLY COLD WEATHER IS
EXPECTED THURSDAY AND THURSDAY NIGHT.

TEMPS...TRENDED TOWARDS THE COOLER MAVMOS WEDNESDAY...THEN TOOK A
BLEND FOR THURSDAY HIGHS. NEAR MAV FOR LOWS TONIGHT THEN UNDERCUT
WEDNESDAY/THURSDAY NIGHTS. STRONG LIKELIHOOD ANOTHER RECORD FALLS AT
INDY. LOW MAX OF 18 (1960) ON THURSDAY IN DANGER. MAYBE EVEN MORE
IMPRESSIVE..COULD SEE OUR FIRST MARCH SUBZERO MORNING IN 31 YEARS ON
FRIDAY MORNING.

&&

.LONG TERM /FRIDAY THROUGH NEXT TUESDAY/...
ISSUED AT 227 AM EST TUE MAR 3 2015

ENSEMBLES INDICATE A SLOWLY PROGRESSIVE NATURE TO THE LONG WAVE
FEATURES DURING THIS PERIOD. MEAN TROUGHING INITIALLY OVER THE
EASTERN PARTS OF THE COUNTRY IS EXPECTED TO LIFT OFF TO THE
NORTHEAST BY EARLY NEXT WEEK AS AN UPPER RIDGE MOVES INTO THE
PLAINS.

A COUPLE OF SHORT WAVE TROUGHS MAY PASS THROUGH THE AREA DURING THIS
PERIOD...ONE AROUND SATURDAY AND ANOTHER AROUND SUNDAY NIGHT INTO
NEXT MONDAY. A FEW ENSEMBLE MEMBERS INDICATE VERY LIGHT QPF WITH
EACH OF THESE FEATURES...SUGGESTING MINOR CHANCES FOR SOME LIGHT
SNOW. HOWEVER...CHANCES FOR MEASURABLE NOT HIGH ENOUGH TO INCLUDE
IN THE FORECAST AT THIS TIME. WILL KEEP THE EXTENDED DRY.

INITIALLY COLD TEMPERATURES SHOULD MODERATE WITH TIME AS HEIGHTS
GRADUALLY RISE.

&&

.AVIATION /DISCUSSION FOR THE 031200Z TAFS/...
ISSUED AT 533 AM EST TUE MAR 3 2015

INITIAL AREA OF FREEZING RAIN CURRENTLY MOVING OFF TO THE EAST OF
THE TAF SITES. SHORT TERM MODEL GUIDANCE SUGGESTS THERE MAY BE SOME
PATCHY AREAS OF LIGHT FREEZING RAIN IN THE VICINITY OF THE TAF SITES
THROUGH ABOUT THE MID TO LATE MORNING HOURS...BEFORE PRECIPITATION
BECOMES MORE WIDESPREAD WITH BETTER LIFT MOVING IN.

LOWER CONFIDENCE IN THE TIMING OF THE CHANGE OVER FROM FREEZING RAIN
TO RAIN GIVEN THE WARM SURGE AT THE SURFACE WILL LIKELY BE SLOWED BY
SNOWPACK. BEST ESTIMATES AT THIS TIME WOULD BE IN THE
031500Z-031800Z TIME FRAME FROM SOUTHWEST TO NORTHEAST.

CEILINGS EXPECTED TO GRADUALLY FALL INTO THE IFR CATEGORY AROUND
MIDDAY OR EARLY AFTERNOON AS SUSTAINED WARM/MOIST ADVECTION
CONTINUES OVER SNOWPACK. LIFR CONDITIONS PROBABLE LATER THIS
AFTERNOON AS ABOVE FREEZING SURFACE DEWPOINTS BEGIN ADVECTING IN
OVER SNOWPACK...ENHANCING THREAT FOR FOG/LOW CEILINGS.

MODEL DATA SUGGEST A 60-65 KT LOW LEVEL JET WILL BE MOVING INTO THE
AREA BY LATE MORNING AND CONTINUING THROUGH THE AFTERNOON. A NEAR
SURFACE INVERSION WILL PROBABLY LINGER THROUGHOUT THE DAY DUE TO
THE SNOWPACK...RESULTING IN A LOW LEVEL WIND SHEAR THREAT. WILL ADD
THIS TO THE FORECAST.

SURFACE WINDS 130-160 DEGREES AT 8-12 KTS EXPECTED TO GRADUALLY VEER
AROUND TO 180-200 DEGREES AT 12-15 KTS BY THIS AFTERNOON. SOME
LOCALIZED SURFACE GUSTS 20-25 KTS POSSIBLE IN AREAS WHERE THE LOW
LEVEL JET CAN BREAK THROUGH THE SURFACE INVERSION.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR INZ021-028>031-
035>049-051>057-060>065-067>072.

WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR INZ067>072.

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN
SHORT TERM...RYAN
LONG TERM....JAS
AVIATION...JAS

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