Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 201428
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
928 AM EST SAT DEC 20 2014

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

&&

.SYNOPSIS...
ISSUED AT 300 AM EST SAT DEC 20 2014

HIGH PRESSURE WILL KEEP DRY CONDITIONS ACROSS MUCH OF THE AREA
THROUGH THE WEEKEND. A POTENT LOW PRESSURE SYSTEM WILL BRING
PRECIPITATION TO CENTRAL INDIANA MONDAY THROUGH CHRISTMAS EVE NIGHT.
ANOTHER SYSTEM WILL BRING A CHANCE FOR MORE PRECIPITATION LATE NEXT
WEEK. ABOVE NORMAL TEMPERATURES EARLY IN THE WEEK WILL RETURN TO
AROUND NORMAL BY CHRISTMAS.

&&

.NEAR TERM.../TODAY/
ISSUED AT 300 AM EST SAT DEC 20 2014

FORCING FROM AN UPPER WAVE IS CREATING SOME LIGHT PRECIPITATION
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA AT THE MOMENT. THE
MAJORITY OF THIS PRECIPITATION IS NOT REACHING THE GROUND PER
SURFACE OBSERVATIONS. THIS IS DUE TO THE DRY AIR NEAR THE SURFACE.

FORCING WITH THIS UPPER WAVE WILL BE EAST OF THE AREA BY 12Z SO WILL
HAVE NO MENTION OF SNOW THEN. ANOTHER UPPER WAVE WILL MOVE ACROSS
NORTHERN INDIANA DURING THE DAYLIGHT HOURS TODAY...BUT AGAIN
MOISTURE IS LACKING. FORCING IS WEAK AS WELL. THUS WILL KEEP
FORECAST DRY THROUGH THE DAY.

FOCUS THEN SHIFTS TO SKY COVER. SATELLITE SHOWS EXTENSIVE CLOUD
COVER STRETCHING ALL THE WAY BACK TO KANSAS. WITH THE UPPER WAVE
MOVING ACROSS TODAY SEE NO REASON FOR SKIES TO BE ANYTHING OTHER
THAN MOSTLY CLOUDY TO CLOUDY.

WITH THE CLOUDS AROUND WENT COOLER THAN MAV MOS FOR HIGHS...CLOSER
TO THE COOLER MET MOS.

&&

.SHORT TERM.../TONIGHT THROUGH MONDAY NIGHT/
ISSUED AT 300 AM EST SAT DEC 20 2014

FOCUS IS ON SKY COVER AND CHANCES FOR RAIN THROUGH THE PERIOD.
MODELS ARE CLOSE ENOUGH THAT A BLEND WAS USED.

MODELS TRY AND CLEAR THINGS OUT TONIGHT. CANNOT REALLY SEE THIS
HAPPENING PER RECENT EXPERIENCE AND NOTHING COMING IN TO SCOUR OUT
THE CLOUDS. WILL ONCE AGAIN GO MOSTLY CLOUDY MOST AREAS. WITH THE
CLOUDS WENT CLOSER TO OR EVEN ABOVE THE WARMEST MOS FOR LOWS.

SUNDAY SOME BREAKS IN THE CLOUDS MAY APPEAR ACROSS THE SOUTHERN
TWO-THIRDS OF THE FORECAST AREA AS FLOW BECOMES SOUTHEAST.
CONFIDENCE IS LOW IN THIS THOUGH. SINCE WENT WITH MORE CLOUDS THAN
MODELS SUGGEST...WENT COOLER THAN MAV MOS FOR HIGHS.

DRY CONDITIONS WILL CONTINUE SUNDAY NIGHT AHEAD OF THE APPROACHING
SYSTEM...BUT CLOUDS WILL INCREASE/THICKEN. FORCING INCREASES DURING
THE DAY MONDAY AS ONE UPPER IMPULSE MOVES THROUGH. WENT CHANCE
POPS...HIGHEST IN THE AFTERNOON.

MONDAY NIGHT THE FRONTAL SYSTEM GETS CLOSE TO THE AREA...AND AN
UPPER JET PROVIDES ADDITIONAL FORCING. SOUTHERLY FLOW WILL BRING IN
DECENT MOISTURE...SO WENT LIKELY POPS ALL AREAS.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
ISSUED AT 330 AM EST SAT DEC 20 2014

ACTIVE WEATHER PATTERN THROUGH THE EXTENDED WITH FOCUS REMAINING ON
EXPECTED DEVELOPMENT OF AN INTENSE STORM SYSTEM OVER THE GREAT LAKES
BY WEDNESDAY BRINGING A MYRIAD OF WEATHER IMPACTS TO CENTRAL INDIANA
JUST IN TIME FOR CHRISTMAS.

SHARP UPPER RIDGE AXIS WILL BE ALIGNED JUST OFF THE PACIFIC COAST
TUESDAY MORNING...AND THIS WILL ENCOURAGE AMPLIFICATION OF A
DOWNSTREAM TROUGH EAST OF THE ROCKIES AS A POWERFUL POLAR JET RIDES
OVERTOP OF THE RIDGE AND CARVES OUT A PROGRESSIVELY DEEPER TROUGH.
THE POLAR JET ENERGY WILL INTERACT WITH THE SUBTROPICAL JET LIFTING
OUT OF THE GULF OF MEXICO BY TUESDAY NIGHT...PROMPTING RAPID
CYCLOGENESIS OVER THE REGION AS LOW PRESSURE OVER THE GREAT LAKES
LINKS UP WITH A SECONDARY LOW LIFTING NORTHEAST FROM THE LOWER
MISSISSIPPI VALLEY.

THE PRESENCE OF THE PRIMARY LOW APPROACHING FROM THE NORTHWEST AND
SOUTHERLY FLOW AHEAD OF IT WILL TRANSPORT DEEP MOISTURE INTO THE
OHIO VALLEY WITH WIDESPREAD RAIN ANTICIPATED ALL DAY TUESDAY. THE
PHASING OF THE JET ENERGY ALOFT WILL BEGIN LATE TUESDAY WITH A FULL
MERIDIONAL UPPER TROUGH QUICKLY TAKING ON A NEGATIVE TILT. AS STATED
ABOVE...THIS WILL PROMPT A RAPID INTENSIFICATION OF THE SECONDARY
LOW AS IT LIFTS NORTH AND ABSORBS THE GREAT LAKES SURFACE WAVE.

INDIVIDUAL MODELS STILL MAINTAIN DIFFERENCES WITH RESPECT TO HOW
QUICKLY THE PHASING OCCURS...RESULTING IN DIFFERENT TRACKS OF THE
SURFACE LOW. GGEM APPEARS TO BE THE FASTEST TO PHASE AND
STRENGTHEN...FOLLOWED BY THE ECMWF WITH THE OP GFS AND MAJORITY OF
ITS ENSEMBLE MEMBERS LAGGING BY 6 HOURS OR SO. TIMING OF THE PHASE
WILL BE CRITICAL IN DETERMINING HOW QUICKLY COLDER AIR CAN ARRIVE
AND CHANGE PRECIPITATION TO SNOW. A FASTER PHASED SYSTEM WILL PULL
THE TRACK OF THE LOW LEFT OR FURTHER WEST PER THE GGEM...WHILE A
SLOWER PHASE WOULD KEEP THE TRACK EAST AS PER THE ECMWF AND OP GFS.
THOSE DETAILS ARE STILL PROBABLY 36 TO 48 HOURS AWAY AT A MINIMUM
FROM BEING ENTIRELY WORKED OUT...BUT OVERALL MODEL CONSENSUS
SUPPORTS SLOWING THE P-TYPE TRANSFER TO LATE TUESDAY NIGHT/WEDNESDAY
MORNING.

CHRISTMAS EVE APPEARS TO BE THE POTENTIAL TRAVEL TROUBLE DAY AT THIS
POINT AS LOW LEVEL THERMALS AND BOUNDARY LAYER TEMPS CRASH WITH
COLDER AIR WRAPPING AROUND THE INTENSIFYING NORTHWARD MOVING LOW
TRACKING INTO THE GREAT LAKES. STILL QUITE A BIT OF UNCERTAINTY AS
TO HOW ROBUST PRECIP RATES WILL BE WITHIN THE COLD POOL WEDNESDAY...
ESPECIALLY WITH DEEPEST FORCING ALOFT ACCOMPANYING THE SURFACE WAVE
AND SETTING UP NORTHEAST OF THE FORECAST AREA. IT REMAINS PREMATURE
TO ADDRESS ANY SNOWFALL ACCUMULATIONS AT THIS TIME...BUT AN INCH OR
TWO CERTAINLY APPEAR PLAUSIBLE WITH THE SCENARIO PRESENTED ABOVE. AS
HAS BEEN MENTIONED...WIND IS LIKELY TO BE THE MORE SIGNIFICANT
IMPACT WITH SUCH AN INTENSE SURFACE LOW MOVING THROUGH THE REGION.
WIND DRIVEN SNOW SHOWERS WITH FALLING TEMPS WEDNESDAY INTO WEDNESDAY
NIGHT IS LIKELY TO CREATE DIFFICULT CONDITIONS FOR TRAVEL ACROSS THE
REGION. THOSE WITH TRAVEL PLANS DURING THIS TIME PERIOD ARE
ENCOURAGED TO STAY TUNED IN THE COMING DAYS.

CHRISTMAS DAY LOOKS TO BE QUIET AS HIGH PRESSURE FINALLY ARRIVES IN
THE WAKE OF THE STRONG LOW PRESSURE. YET ANOTHER STORM SYSTEM
DEVELOPING OVER THE HIGH PLAINS WILL SWING INTO THE MIDWEST FOR
FRIDAY. MODELS ARE ALL OVER THE PLACE WITH THE EVOLUTION OF THIS
SYSTEM...BUT RECENT TRENDS SUGGEST THIS FEATURE TO TRACK NORTHWEST
OF THE FORECAST AREA AS WARMER AIR AND RIDGING ALOFT QUICKLY
RETURNS TO CENTRAL INDIANA. WILL CARRY CHANCE POPS FRIDAY FOR RAIN
AS TEMPS RETURN TO THE 40S...WITH COLDER AIR BEING DRAWN BACK INTO
THE OHIO VALLEY NEXT WEEKEND AS THE SYSTEM PASSES.

TO SUM UP IMPACTS AT THIS POINT...RAIN TUESDAY/WIND AND SNOW
WEDNESDAY/QUIET THURSDAY/RAIN FRIDAY. LONG RANGE MODEL TRENDS
SUGGEST ACTIVE PATTERN WILL CONTINUE BEYOND THE 7 DAY.

&&

.AVIATION /DISCUSSION FOR THE 20/1500Z TAF UPDATE/...

ISSUED AT 924 AM EST SAT DEC 20 2014

UPDATE...
CONDITIONS CONTINUE TO HOVER AT THE MVFR/VFR MARK AT KIND.

PREVIOUS DISCUSSION...
MVFR/VFR STRATUS TO PERSIST THROUGH THIS EVENING.

WEAK WAVE ALOFT QUICKLY SHIFTING EAST OF THE REGION EARLY THIS
MORNING AFTER PRODUCING A FEW HOURS OF LIGHT SNOW AT KBMG. DESPITE
SURFACE HIGH PRESSURE BUILDING INTO THE REGION TODAY...THICK
STRATUS DECK SHOWING NO SIGNS OF ABATING. LIGHT NORTHEAST FLOW
THROUGH THE BOUNDARY LAYER AND PRESENCE OF A LOW LEVEL INVERSION
WILL HELP TO MAINTAIN THE CLOUD DECK ALL DAY...WITH CEILINGS
VARYING BETWEEN 2500-3500FT IN GENERAL. DRIER AIR TRIES TO BUILD
INTO THE NEAR SURFACE LAYER TONIGHT...AND AT THE VERY LEAST SHOULD
ENABLE SOME SCATTERING OF THE STRATUS DECK TO A HIGHER CLOUD BASE.
LIGHT AND VARIABLE WINDS EXPECTED THROUGH THE PERIOD.

&&

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

&&

$$

SYNOPSIS...50
NEAR TERM...50
SHORT TERM...50
LONG TERM....RYAN
AVIATION...RYAN/TDUD

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