Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 170828
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
326 AM EST WED DEC 17 2014

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

&&

.SYNOPSIS...
ISSUED AT 254 AM EST WED DEC 17 2014

HIGH PRESSURE IS EXPECTED TO BUILD INTO THE AREA FOR THE NEXT FEW
DAYS. A LOW PRESSURE SYSTEM MAY AFFECT THE AREA BY THE END OF THE
WEEK. A STRONGER SYSTEM MAY AFFECT THE AREA BY THE EARLY TO MIDDLE
PARTS OF NEXT WEEK.

&&

.NEAR TERM /TODAY/...
ISSUED AT 254 AM EST WED DEC 17 2014

STILL SOME AREAS OF FREEZING DRIZZLE/FLURRIES AROUND BASED ON RADAR
AND SURFACE OBSERVATIONS...MAINLY OVER THE EASTERN ZONES. SHORT TERM
MODELS SUGGEST THERE MAY BE A LOW LEVEL VORTICITY LOBE ASSOCIATED
WITH THIS PRECIPITATION...WHICH THE MODELS MOVE EAST OF THE FORECAST
AREA PRIOR TO SUNRISE. AS A RESULT...THINK ANY PRECIPITATION THAT
MAY BE LEFT DURING THE PRE DAWN HOURS WILL BE OVER BY SUNRISE.

OTHERWISE...MODELS INDICATE A STOUT SUBSIDENCE INVERSION WILL
CONTINUE TODAY...SO EXPECTING LITTLE IN THE WAY OF CLEARING. THE FAR
SOUTHWEST ZONES MAY SEE SOME BREAKS AROUND SUNSET...BUT THAT WOULD
BE ABOUT IT.

GIVEN COLD ADVECTION AND CLOUD COVER...THE GFS MOS HIGHS FOR TODAY
ARE PROBABLY TOO WARM. WILL CUT THE HIGHS BY A CATEGORY.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
ISSUED AT 254 AM EST WED DEC 17 2014

UPPER BLOCK OVER SOUTHERN CANADA EXPECTED TO BREAK DOWN DURING THIS
PERIOD...AS A NORTHERN STREAM DISTURBANCE DIGS INTO THE NORTHERN
MIDWEST BY FRIDAY NIGHT AND SOUTHERN STREAM SYSTEM SCOOTS ALONG THE
GULF COAST STATES.

MODELS CONTINUE TO SUGGEST THERE MAY BE SOME LIFT DEVELOPING OVER
THE SURFACE HIGH PRESSURE RIDGE ON THURSDAY. THE PRECIPITATION
BEARING LAYER APPROACHES SATURATION ON THURSDAY...BUT THE LIFT LOOKS
RATHER WEAK AND THERE IS QUITE A BIT OF DRY AIR BELOW THE
PRECIPITATION BEARING LAYER. AT THIS TIME...IF ANYTHING HAPPENS IT
LOOKS MORE LIKE A FLURRY OR TRACE EVENT...WITH THE CHANCES FOR
MEASURABLE TOO LOW TO MENTION.

SOME LIFT IS EXPECTED TO MOVE BACK INTO THE AREA BY FRIDAY NIGHT AND
THE NORTHERN AND SOUTHERN STREAM SHORT WAVE TROUGHS APPROACH. MODEL
DATA SUGGEST THE SOUTHERN ZONES WILL HAVE THE BEST CHANCE FOR
SATURATION OF THE PRECIPITATION BEARING LAYER...SO WILL GO WITH
CHANCE POPS FOR LIGHT SNOW BY LATE FRIDAY NIGHT IN THOSE AREAS.

APPEARS THERE WILL BE QUITE A BIT OF CLOUD COVER AROUND OVER THE
NEXT FEW DAYS. AS A RESULT...WILL NARROW THE DIURNAL RANGE OF THE
GFS MOS TEMPERATURE GUIDANCE ALL PERIODS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
ISSUED AT 312 AM EST WED DEC 17 2014

MAIN FOCUS ON THE EXTENDED WILL BE FIRST ON A DEPARTING SYSTEM THIS
WEEKEND AND THEN AN APPROACHING WHEN EARLY NEXT WEEK THAT COULD
IMPACT THE HOLIDAY TRAVEL.

MODELS IN DECENT AGREEMENT THAT AN UPPER SYSTEM WILL BE MOVING
THROUGH THE GREAT LAKES AND OHIO VALLEY ON SATURDAY. REGIONAL BLEND
WITH CHANCE POPS LOOK GOOD. CRITICAL THICKNESS PROGS SUGGEST MOSTLY
SNOW BUT THAT SOME RAIN COULD MIX IN SOUTH OF INTERSTATE 70 DURING
THE AFTERNOON.

HIGH PRESSURE WILL BRING DRY WEATHER TO THE AREA THE REST OF THE
WEEKEND. THEN...BUILDING WEST COAST UPPER RIDGE WILL ALLOW A BROAD
UPPER TROUGH TO DIG SOUTHEAST ACROSS WESTERN CANADA AND INTO THE
PLAINS AND MISSISSIPPI VALLEY ON TUESDAY. THE GFS WAS ONCE AGAIN
QUICKER WITH THIS SYSTEM AND CONSEQUENTLY BRINGS THE COLD AIR IN
QUICKER. VARIOUS WAVES AHEAD OF THE TROUGH WILL RESULT IN RAIN
CHANCES STARTING MONDAY ACROSS WEST CENTRAL INDIANA AND SPREADING
EAST ACROSS THE AREA ON MONDAY NIGHT AND TUESDAY. FOR NOW ...WILL
KEEP IT ALL RAIN THROUGH TUESDAY AFTER WHICH IT SHOULD CHANGE TO
SNOW AND COULD BRING AN ACCUMULATION TO CENTRAL INDIANA IN TIME FOR
CHRISTMAS.

NEAR NORMAL REGIONAL BLEND TEMPERATURES WITH NEAR NORMAL
TEMPERATURES AND AFTERNOON HIGHS IN THE 30S EXCEPT PERHAPS A BIT
WARMER ON TUESDAY AS WARM AIR MOVES IN AHEAD OF THE APPROACHING
DIGGING SYSTEM.

&&

.AVIATION /DISCUSSION FOR 170900Z IND TAF UPDATE/...

ISSUED AT 326 AM EST WED DEC 17 2014

WILL GO WITH IFR CEILINGS IN SNOW THROUGH 10Z BASED ON TRENDS.

PREVIOUS DISCUSSION FOLLOWS...

A MIXTURE OF IFR/MFVR CONDITIONS WILL CONTINUE THROUGH THE EARLY
OVERNIGHT PERIOD...THEN EXPECT GRADUAL IMPROVEMENTS IN CEILINGS
TO LOW END MVFR BY LATE THIS MORNING. AND POSSIBLY VFR AT A FEW OF
THE SITES (NAMELY KLAF) BY LATER THIS AFTERNOON...FOR A VERY BRIEF
PERIOD BEFORE AN INVERSION DEVELOPS AGAIN BY THE EVENING AND ALL
SITES MAINTAIN AN MVFR STRATUS DECK ONCE AGAIN. LEANED CLOSER TO
THE NAM GUIDANCE WHICH MORE ACCURATELY DEPICTS THIS HAPPENING AS
OPPOSED TO THE OVERLY OPTIMISTIC MAV/GFS WHICH IS COMMON DURING
THIS TIME OF YEAR.

GUSTS WILL CONTINUE TO DIMINISH TOWARD THE START OF THIS TAF
PERIOD...WITH W/NW WINDS PERSISTING AROUND 10KTS FOR MUCH OF THE
REST OF THE FORECAST PERIOD...UNTIL LATE THIS EVENING WHEN WINDS
BECOME LIGHTER...AOB 5KT OUT THE NW.

-SHSN SHOULD BE COMING TO AN END AT THE EASTERN MOST TAF SITES
(KIND/KBMG) BY 8/9Z.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....MK
AVIATION...SMF/MK

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