Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 172025
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
325 PM 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 NIGHT THROUGH WEDNESDAY/...

ISSUED AT 135 PM EST WED DEC 17 2014

THE INITIALIZATION FROM THE REGIONAL MODEL WILL BE ACCEPTED...BUT
THIS IS A VERY LOW CONFIDENCE FORECAST.

THE EUROPEAN MODEL AND THE GFS BOTH DEVELOP VERY STRONG SYSTEMS
ALOFT AND AT THE SURFACE BY MIDWEEK.  WITH SUCH SYSTEMS EVEN A SMALL
DIFFERENCE IN LOCATION COULD HAVE A BIG IMPACT ON THE SENSIBLE
WEATHER.

DIFFERENCES BETWEEN THE MODELS ARE GREAT. DEPENDING ON WHAT IS
CORRECT...INDIANA COULD HAVE A MAJOR WINTER STORM OR A MUCH LESSER
EVENT THE MIDDLE OF NEXT WEEK. IT PROBABLY WONT BE POSSIBLE TO MAKE
A HIGH CONFIDENCE FORECAST UNTIL SUNDAY OR EVEN MONDAY. UNTIL THEN
THE BEST STRATEGY MAY BE TO PLAN FOR THE WORST AND HOPE FOR THE BEST.

&&

.AVIATION /DISCUSSION FOR 172100Z TAF ISSUANCE/...

ISSUED AT 325 PM EST WED DEC 17 2014

UPDATED CURRENT CONDITIONS ONLY. PREVIOUS DISCUSSION FOLLOWS...

MVFR CEILINGS WILL PERSIST INTO THURSDAY MORNING. A COLD CYCLONIC
FLOW IS GOING TO MAINTAIN AN INVERSION A FEW THOUSAND FEET ABOVE
GROUND LEVEL...TRAPPING MOISTURE NEAR THE SURFACE.

THURSDAY MORNING THE INVERSION SHOULD BREAK DUE TO THE ACTION OF AN
APPROACHING UPPER LEVEL DISTURBANCE. THIS WILL CAUSE THE MVFR DECK
TO SCATTER OUT AND BE REPLACED BY CEILINGS NEAR 10 THOUSAND FEET.

WEST TO NORTHWEST WINDS NEAR 10 KNOTS ARE EXPECTED THIS AFTERNOON.
WINDS SHOULD BE TOO LIGHT TO IMPACT OPERATIONS TONIGHT AND TOMORROW
AS THE CYCLONIC FLOW SLOWLY WEAKENS.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....JK
AVIATION...JK/CP

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