Area Forecast Discussion
Issued by NWS Indianapolis, IN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KIND 211420
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
920 AM EST SUN DEC 21 2014

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

&&

.SYNOPSIS...
ISSUED AT 301 AM EST SUN DEC 21 2014

A LOW PRESSURE SYSTEM WILL BRING PRECIPITATION TO CENTRAL INDIANA
MONDAY THROUGH WEDNESDAY. AFTER A DRY CHRISTMAS...CHANCES FOR
PRECIPITATION WILL RETURN FRIDAY WITH A WEAKER SYSTEM. WARM AIR
AHEAD OF THE FIRST SYSTEM COULD BRING THE WARMEST READINGS OF
DECEMBER ON TUESDAY...THEN TEMPERATURES WILL RETURN TO CLOSER TO
AVERAGE BY CHRISTMAS.

&&

.NEAR TERM.../TODAY/
ISSUED AT 301 AM EST SUN DEC 21 2014

SKIES HAVE CLEARED ACROSS A GOOD PORTION OF CENTRAL INDIANA EARLY
THIS MORNING...BUT ADDITIONAL LOW CLOUDS WERE NEAR THE
ILLINOIS/INDIANA BORDER AND MOVING SLOWLY EAST.

CLOUD COVER WILL BE TOUGH TO PIN DOWN TODAY AND ONCE AGAIN
CONFIDENCE IS LOW IN THE DETAILS. LOW CLOUDS WILL MARCH INTO WESTERN
AND NORTHWESTERN SECTIONS OF THE AREA THIS MORNING. HOWEVER DRIER
AIR WILL FLOW INTO THE AREA AS WINDS INCREASE OUT OF THE SOUTHEAST.

FOR NOW WILL GO MOSTLY CLOUDY ACROSS THE NORTHWEST FORECAST
AREA...WITH SKIES REMAINING/BECOMING PARTLY CLOUDY ELSEWHERE.
ADJUSTMENTS WILL LIKELY HAVE TO BE MADE LATER THIS MORNING AS THE
EVOLUTION OF THE CLOUDS BECOMES CLEARER.

TEMPERATURES HAVE COOLED MORE THAN EXPECTED EARLY THIS MORNING DUE
TO THE PARTIAL CLEARING. THIS COLD START WILL HELP KEEP TEMPERATURES
BELOW MAV MOS AND CLOSER TO THE MET MOS TODAY.

&&

.SHORT TERM.../TONIGHT THROUGH TUESDAY NIGHT/
ISSUED AT 301 AM EST SUN DEC 21 2014

FOCUS IS ON CHANCES FOR PRECIPITATION THROUGH THE PERIOD. MODELS ARE
SHOWING DIFFERENCES AS WOULD BE EXPECTED WITH THE INCOMING SYSTEM
NOT FULLY SAMPLED YET. CANADIAN LOOKS TOO STRONG WITH THE
SYSTEM...WHILE THE LARGER CHANGE IN SOLUTIONS BETWEEN THE 12Z/00Z
ECMWF LEADS TO LOWER CONFIDENCE IN ITS SOLUTION THIS RUN. WILL USE A
BLEND OF REMAINING MODELS.

CLOUDS WILL INCREASE TONIGHT AS THE SYSTEM APPROACHES FROM THE WEST.
WILL GO A LITTLE WARMER THAN MAV MOS MOST AREAS.

ON MONDAY ISENTROPIC LIFT INCREASES DURING THE AFTERNOON. HOWEVER
DEEPER MOISTURE WILL BE SLOWER TO RETURN THANKS IN PART TO SOUTHEAST
WINDS IN THE LOWER LEVELS. WILL KEEP THE MORNING DRY AND GO WITH
SLIGHT CHANCE TO CHANCE POPS IN THE AFTERNOON. WITH THE CLOUDS AND
SOUTHEAST FLOW...MOS LOOKS TOO WARM FOR HIGHS. WILL CUT SOME.

MONDAY NIGHT AND TUESDAY FORCING RAMPS UP WITH SURFACE FRONT MOVING
INTO THE AREA...850MB WINDS APPROACHING 50KT...AND AN UPPER JET
MOVING IN. THUS WENT LIKELY POPS MOST AREAS BY LATE MONDAY NIGHT AND
LIKELY TO CATEGORICAL POPS ON TUESDAY.

CONTINUED LIKELY TO CATEGORICAL POPS TUESDAY NIGHT AS A SURFACE LOW
RIDES ALONG THE FRONT TOWARD CENTRAL INDIANA. LOOKS LIKE COLDER AIR
WILL BE SLOWER TO ARRIVE THAN PREVIOUSLY THOUGHT...SO WENT ALL RAIN
THROUGH TUESDAY NIGHT.

THE SYSTEM LOOKS TO BRING ENOUGH WARM UP INTO THE AREA ON TUESDAY
FOR HIGHS IN THE LOWER TO MIDDLE 50S...WHICH WILL BE THE WARMEST AIR
THIS MONTH ACROSS THE AREA.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
ISSUED AT 328 AM EST SUN DEC 21 2014

FOCUS FOR THE EXTENDED REMAINS ON POTENTIAL IMPACTS FROM A
STRENGTHENING LOW PRESSURE FOR CHRISTMAS EVE...FOLLOWED BY ANOTHER
STORM SYSTEM BRINGING PRECIPITATION TO THE OHIO VALLEY FRIDAY AND
FRIDAY NIGHT.

LEAD PORTION OF THE POWERFUL UPPER JET APPROACHING THE PACIFIC
NORTHWEST IS STARTING TO BE SAMPLED BY THE RAOB NETWORK.
HOWEVER...THAT HAS DONE LITTLE TO AID IN DEVELOPING A STRONGER
CONSENSUS FOR THE PHASED LOW PRESSURE SYSTEM TO IMPACT THE REGION
WEDNESDAY AS 00Z MODEL SUITE FRANKLY INTRODUCING MORE QUESTIONS THAN
ANSWERS. THE ECMWF AND OP GFS ARE BOTH SLOWER WITH PHASING THE
POLAR AND SUBTROPICAL JETS ALOFT...WITH THE STRENGTHENING UPPER
TROUGH NOT TAKING ON A NEGATIVE TILT UNTIL LATER ON WEDNESDAY AS THE
FEATURE PASSES CENTRAL INDIANA. CONSEQUENTLY THE DEEPENING SURFACE
LOW IS ALSO SLOWER TO TAKE PLACE...OCCURRING OVER THE EASTERN GREAT
LAKES BY EARLY CHRISTMAS MORNING. GFS ENSEMBLE MEMBERS STILL HAVE
QUITE A BIT OF SPREAD AND IT SHOULD BE NOTED THAT A COUPLE MEMBERS
REMAIN DEEPER AND FURTHER WEST WITH THE SURFACE WAVE TRACK.

TAKING INTO CONSIDERATION THAT MODEL SPREAD REMAINS LARGER THAN
DESIRED AND WITH BOTH THE OP GFS AND ECMWF SHIFTING THE LOW TRACK
FURTHER EAST WITH A SLOWER ENERGY PHASE...IT REMAINS PREMATURE TO
LATCH ONTO A SPECIFIC SOLUTION. 12Z RUNS TODAY AND DEFINITELY THE
00Z RUNS TONIGHT SHOULD GET FULL SAMPLING OF THE STRONG UPPER JET
ENERGY COMING INTO THE PACIFIC NORTHWEST. WITH THIS FEATURE SET TO
BE A MAJOR PLAYER INT HE EVOLUTION OF THE STORM SYSTEM...MAY
FINALLY START TO SEE A SLOW INCREASE IN MODEL CONSENSUS.

DO PLAN TO SLOW THE ARRIVAL OF THE COLDER AIR ON WEDNESDAY WITH RAIN
GRADUALLY CHANGING TO SNOW ON WEDNESDAY AFTERNOON AND EVENING.
CANNOT RULE OUT LIGHT ACCUMS BUT ATTEMPT TO EMPLOY ANY MORE DETAIL
WOULD BE FUTILE WITH SUCH TRACK UNCERTAINTY TO THE SURFACE WAVE. IF
THE WAVE TRACKS CLOSER TO THE FORECAST AREA VERSUS FURTHER
EAST...POTENTIAL FOR LIGHT ACCUMS WOULD BE GREATER WITH THE MID
LEVEL DEFORMATION BAND ALIGNING IN SOME MANNER OVER THE FORECAST
AREA. AS IT STANDS...WILL MAINTAIN CHANCE POPS THROUGH WEDNESDAY
NIGHT WITH STRONG WIND GUSTS BEING THE PRIMARY IMPACT...AND
POTENTIAL LIGHT ACCUMS AS A SECONDARY IMPACT. THE THREAT FOR TRAVEL
DISRUPTIONS REMAINS GREATEST DURING THIS TIME PERIOD...AND THOSE
WITH TRAVEL PLANS ARE ENCOURAGED TO MONITOR FORECASTS OVER THE NEXT
FEW DAYS.

CHRISTMAS DAY LOOKS TO BE QUIET AS THE SURFACE WAVE QUICKLY LIFTS
AWAY FROM THE REGION WITH SURFACE RIDGING DEVELOPING OVER THE OHIO
VALLEY. HIGHLY AMPLIFIED FLOW ALOFT WILL MAINTAIN AN ACTIVE
PATTERN...WITH ANOTHER SURFACE LOW TRACKING OUT OF THE CENTRAL
PLAINS AND INTO THE GREAT LAKES ON FRIDAY. STILL A LOT OF MODEL
VARIANCE WITH THIS SYSTEM...AND THAT IS NOT LIKELY TO CHANGE UNTIL
MODELS CAN GAIN A BETTER CONSENSUS ON THE CHRISTMAS EVE STORM. WILL
CARRY CHANCE POPS FOR FRIDAY AND FRIDAY NIGHT...WITH RAIN ON FRIDAY
TRANSITIONING TO LIGHT SNOW FRIDAY NIGHT BEFORE ENDING. SURFACE HIGH
PRESSURE WILL RETURN FOR THE WEEKEND...WITH CHILLY AND MAINLY DRY
CONDITIONS AS A SHARP UPPER TROUGH ESTABLISHES OVER THE GREAT
LAKES.

&&

.AVIATION /DISCUSSION FOR 211500Z IND TAF UPDATE/...
ISSUED AT 920 AM EST SUN DEC 21 2014

ONLY INSIGNIFICANT MINOR CHANGE TO VFR CONDITIONS.

PREVIOUS DISCUSSION FOLLOWS...

MVFR CONDITIONS POSSIBLE AT TIMES THIS MORNING...OTHERWISE VFR
CONDITIONS EXPECTED.

MUCH OF THE FORECAST AREA REMAINS UNDER MOSTLY CLEAR SKIES WITH A
LIGHT HAZE FROM LINGERING MOISTURE LEFT UNDER THE REMNANT
INVERSION PRODUCING VISIBILITIES IN THE 4-6SM RANGE. STRATUS
REMAINS ACROSS FAR NORTHERN COUNTIES BACK INTO ILLINOIS...BUT HAS
LARGELY SHOWN AN INABILITY TO EXPAND BACK INTO THE REGION OVER THE
LAST SEVERAL HOURS. RAP INDICATING S/SE FLOW IN THE 925-850MB
LAYER WHICH IS LIKELY KEEPING THE THICKER CLOUDS FROM RETURNING TO
THE REGION. MODEL SOUNDINGS AND RH PROGS INDICATE THAT THIS IS
LIKELY TO CONTINUE FOR MOST OF THE DAY WITH INCREASINGLY DRIER AIR
SLIPPING INTO THE BOUNDARY LAYER. GROWING OPTIMISM THAT THE REGION
WILL ENJOY THE MOST SUNSHINE SEEN IN MORE THAN A WEEK. ENOUGH LOW
LEVEL MOISTURE PRESENT THAT COULD SEE SCATTERED STRATOCU DEVELOP
THIS AFTERNOON. SOUTHEAST WINDS WILL BE 5-10KTS TODAY.

MAINLY CLEAR SKIES WILL CONTINUE THIS EVENING WITH A SLOW
INCREASE IN MID LEVEL CLOUDS AS A WARM FRONT APPROACHES FROM THE
WEST. LOW LEVEL RH PROGS SHOW THE LOWER STRATUS DECK IS LIKELY TO
MAKE A RETURN TOWARDS DAYBREAK MONDAY AS WELL WITH INCREASING
MOISTURE ADVECTING INTO THE OHIO VALLEY. LIGHT SOUTHEAST WINDS
WILL CONTINUE OVERNIGHT.

&&

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

&&

$$

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

VISIT US AT HTTP://WWW.WEATHER.GOV/IND

FOLLOW US ON FACEBOOK...TWITTER AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSINDIANAPOLIS
WWW.TWITTER.COM/NWSINDIANAPOLIS
WWW.YOUTUBE.COM/NWSINDIANAPOLIS










USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.