Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 280512
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1212 AM EST SUN DEC 28 2014

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

&&

.SYNOPSIS...
ISSUED AT 324 PM EST SAT DEC 27 2014

A COLD FRONT WILL MOVE EAST ACROSS OUR REGION TONIGHT. A DRY
SECONDARY ARCTIC COLD FRONT WILL MOVE SOUTHEAST ACROSS OUR REGION
AROUND TUESDAY. IN THE LONG TERM AN ARCTIC HIGH PRESSURE SYSTEM WILL
BRING DRY AND COLD WEATHER. HOWEVER MIXED PRECIPITATION IS POSSIBLE
AGAIN THIS FRIDAY THROUGH NEXT SATURDAY AS MODELS SHOW A LOW
PRESSURE SYSTEM MOVING INTO THE LOWER MISSISSIPPI VALLEY.

&&

.NEAR TERM /TONIGHT/...
ISSUED AT 845 PM EST SAT DEC 27 2014

UPDATED TO REFLECT LATEST PROGRESSION OF BAND OF PRECIP INTO THE
NORTHWESTERN FORECAST AREA AND ACROSS THE AREA THIS EVENING INTO
THE OVERNIGHT. EXPECT THERE WILL BE PERIODS OF RAIN AND
SNOW...PERIODS OF EITHER...AND PERHAPS SOME SLEET AS WELL IN MOST
AREAS...BUT WITH LITTLE OR NO ACCUMULATION AS TEMPERATURES REMAIN
ABOVE FREEZING AND MAY DO SO FOR SEVERAL MORE HOURS IF NOT ALL
NIGHT ACROSS SOME PORTIONS OF THE AREA. HAVE ALSO SPED UP ENDING
OF PRECIP A BIT BASED ON LATEST MODEL GUIDANCE. PREVIOUS
DISCUSSION FOLLOWS.

ISSUED AT 324 PM EST SAT DEC 27 2014

TRENDS AMONG THE MODELS REMAIN VIRTUALLY THE SAME...WITH THE EURO
AND NAM BEING MUCH MORE PROGRESSIVE THAN THE GFS AND GEM. AS
USUAL...THE SREF AND HRRR TAKE A DECENT BLEND OF THE FASTER AND
SLOWER SOLUTIONS...SO LEANED HEAVILY TOWARD THIS GUIDANCE WHEN
CREATING THE POPS FOR TONIGHT. ALSO TRIED TO WORK IN WHAT IS
CURRENTLY ON THE RADAR SCOPE WITH ONE WAVE OF LIGHT RAIN MOVING IN
FROM THE SOUTH...WHICH WILL LATER THE EXIT THE FORECAST AREA BY
00Z. WHILE THE MAIN AREA OF PRECIPITATION IS BEGINNING TO APPROACH
THE CENTRAL INDIANA AREA FROM CENTRAL ILLINOIS. THIS AREA WILL
MAKE IT/S WAY THROUGH THE BULK OF CENTRAL INDIANA FROM 00Z TO 08Z.
WITH A FEW COUNTIES TO THE SOUTHEAST COUNTIES SEEING SOME
LINGERING POPS INTO EARLY SUNDAY MORNING.

ATTENTION THEN TURNS TO PRECIP TYPE AND TIMING...BOTH OF WHICH
WILL BE TRICKY. ALL OF THE PRECIP OVER CENTRAL INDIANA WILL BE IN
THE FORM OF RAIN THROUGH THIS EVENING. COLDER AIR WILL BEGIN
WORKING INTO THE NORTHWEST COUNTIES OF THE CWA ABOUT MIDNIGHT AND
PUSH TOWARD THE I-70 CORRIDOR BY 2-3 AM. BEST CHANCE IN TERMS OF
PRECIP TYPE ARE STILL A -RA/SN MIX...CANNOT RULE OUT ANY SLEET
MIXING IN AT TIMES HOWEVER NOT WIDESPREAD ENOUGH TO HAVE THE
CONFIDENCE TO INCLUDE IT IN FORECAST AT THIS TIME. THIS MIX WILL
WORK IT/S WAY TOWARD THE E/SE EARLY SUNDAY MORNING...WHILE PRECIP
BEHIND IT BEGINS TO WIND DOWN AND DRY OUT OVER MOST OF THE
FORECAST AREA BY 12Z SUNDAY MORNING. LOWS 31-36.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
ISSUED AT 324 PM EST SAT DEC 27 2014

AS MENTIONED IN ABOVE DISCUSSION...THERE WILL LIKELY BE SOME REMNANT
MIXTURE OF -RA/SN FOR EARLY SUNDAY MORNING ACROSS SEVERAL OF THE
SOUTHEASTERN COUNTIES BEFORE THAT FRONT MOVES FARTHER FROM THE AREA
AND DRIER AND COLDER AIR FILTERS BACK INTO THE AREA. WILL CONTINUE
LOW CHANCE POPS THERE AT LEAST THROUGH 14-15Z SUNDAY MORNING.

DRY AND COOLER WEATHER WILL PERSIST ACROSS THE REGION FOR THE BETTER
HALF OF THE NEXT WEEK AS A LARGE AREA OF HIGH PRESSURE REMAINS IN
CONTROL OVER THE REGION. MODELS INDICATE HIGHS IN THE UPPER 30S
SUNDAY AND PERHAPS A DEGREE OR TWO WARMER MONDAY. LOWS WILL BE IN
THE MIDDLE TO UPPER 20S SUNDAY NIGHT AND LOWER OR MIDDLE 20S MONDAY
NIGHT AS A DRY SECONDARY COLD FRONT MOVES THROUGH.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
ISSUED AT 240 PM EST SAT DEC 27 2014

MAIN FOCUS FOR THE EXTENDED PERIOD WILL BE POPS AND PRECIPITATION
TYPE STARTING FRIDAY. PRIOR TO THAT...TEMPERATURES WILL BE THE
BIGGEST ISSUE AS STRONG COLD WESTERN CANADIAN HIGH PRESSURE WILL
SETTLE ACROSS THE OHIO VALLEY TO END THE OLD YEAR AND START THE NEW
ONE.

DETERMINISTIC MODELS ARE IN DECENT AGREEMENT THAT AN UPPER LOW WILL
BE OVER NORTHEASTERN ARIZONA DURING THE EVENING OF THE FIRST DAY OF
2015. HOWEVER...THE MODELS THEN DIVERGE RAPIDLY WITH THE MUCH
QUICKER 12Z GFS BRINGING A STRONGER SURFACE SYSTEM BUT WEAK UPPER
WAVE OVER THE OHIO VALLEY FRIDAY NIGHT. MEANWHILE...THE 12Z ECMWF
HAS EVEN A WEAKER BUT MUCH SLOWER WAVE LIFT NORTHEAST TO SOUTHERN
ILLINOIS BY NEXT SATURDAY EVENING. THE EURO ALSO HAS THE MAIN
SURFACE LOW WELL SOUTHWEST OF THE 12Z GFS POSITION SATURDAY EVENING.
THE ECMWF HAS THE SURFACE LOW OVER EASTERN KENTUCKY...WHILE THE GFS
HAS IT OVER SOUTHERN QUEBEC. DESPITE ALL THESE DIFFERENCES...BOTH
MODELS START THE QPF ON FRIDAY WITH THE HEAVIEST PRECIPITATION ALONG
THE OHIO RIVER. MEANWHILE...THE EURO WAS HOLDING MORE QPF AROUND ON
SUNDAY THAN THE GFS. SO...STILL EXPECT THE PRECIPITATION TO SPREAD
NORTHEAST ACROSS THE AREA ON FRIDAY.  WITH CONFIDENCE IN TIMING
LOW...WILL ACCEPT THE REGIONAL BLEND THAT KEEPS DECENT POPS AROUND
NEXT SATURDAY AS HINTED AT BY THE EURO.

REGARDING PRECIPITATION TYPE...WILL NOT MAKE MANY CHANGES WITH THE
MODEL DIFFERENCES. CONFIDENCE NOT GOOD AS TO WHERE THE RAIN/SNOW
LINE WILL BE IN SPACE AND TIME. HOWEVER...NORTHEASTERN PARTS OF THE
FORECAST AREA WILL BE MORE LIKELY TO SEE FROZEN OR MIXED
PRECIPITATION THEN THE SOUTHWESTERN ONES ON FRIDAY BASED ON
THERMAL PROFILES FROM BUFKIT SOUNDINGS AS WELL AS PARTIAL
THICKNESSES. FRIDAY NIGHT AND SATURDAY...THE NORTHWESTERN COUNTIES
WOULD HAVE A HIGHER CHANCE OF MIXED OR FROZEN PRECIPITATION THAN THE
SOUTHEAST AS COLDER AIR MOVES IN FROM THE NORTHWEST IN THE WAKE OF
THE SURFACE SYSTEM. BUFKIT SOUNDINGS EVEN SUGGEST FREEZING RAIN OR
SLEET COULD POSSIBLY MIX IN AT TIMES FRIDAY NIGHT.

GENERALLY ACCEPTED THE REGIONAL BLEND TEMPERATURES. DO NOT FEEL
CONFIDENT ENOUGH TO MAKE CHANGES UNTIL THE MODELS HOPEFULLY COME
CLOSER TOGETHER IN SUBSEQUENT RUNS. AFTERNOON HIGHS IN THE 20S LOOK
GOOD ON NEW YEAR`S DAY WITH HIGHS MOSTLY IN THE 30S THEREAFTER.
MEANWHILE...NEW YEARS EVE NIGHT SHOULD BE THE COLDEST WITH OVERNIGHT
LOWS IN THE TEENS FOR THE FIRST SUNRISE OF THE YEAR. OVERNIGHT LOWS
WILL MOSTLY BE IN THE 20S AND 30S BY LATE WEEK.

&&

.AVIATION /DISCUSSION FOR THE 28/0600Z TAF ISSUANCE/...

ISSUED AT 1211 AM EST SUN DEC 28 2014

WINDS TO REMAIN BELOW 10 KNOTS THROUGH THE FORECAST.

RAIN HAS ENDED AT ALL TAF SITES EXCEPT KBMG BUT SHOULD ALSO END THERE
WITHIN THE HOUR OR AROUND 280700Z.

WITHIN COLD AND DRY AIR ADVECTING IN...VISIBILITY HAS IMPROVED TO 6+
MILES AND WILL REMAIN THAT WAY THROUGH THE FORECAST.

MULTIPLE CLOUD LAYERS HAVE BEEN OBSERVED ACROSS ILLINOIS BUT SEEM TO
BE SETTLING TOWARDS DECKS OF 1800-2200 FEET AND THESE SHOULD PREVAIL
THROUGH THE MORNING.  AS HIGH PRESSURE CONTINUES BUILDING IN AND
SUBSIDENCE BEGINS TO DRY THIS LOWER LAYER EXPECT BREAKS IN THE 2000
FOOT DECK AROUND 281800Z AND EVENTUAL CLEARING OF ALL CLOUDS BY
290000Z.


&&

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

&&

$$

SYNOPSIS...SMF
NEAR TERM...SMF/NIELD
SHORT TERM...SMF
LONG TERM...MK
AVIATION...DT

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