Area Forecast Discussion
Issued by NWS Indianapolis, IN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 201927
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
227 PM EST SAT DEC 20 2014

.UPDATE...
THE SYNOPSIS...NEAR TERM AND SHORT TERM SECTIONS HAVE BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 226 PM EST SAT DEC 20 2014

HIGH PRESSURE IN PLACE OVER THE EASTERN GREAT LAKES AND INDIANA
THROUGH SUNDAY WILL KEEP DRY WEATHER IN PLACE ACROSS CENTRAL
INDIANA THROUGH THE WEEKEND. BY SUNDAY NIGHT...THE HIGH WILL REACH
NEW ENGLAND AND WARMER...SOUTHERLY FLOW WILL RETURN TO INDIANA AND
THE OHIO VALLEY.

HIGH CLOUDS ARE EXPECTED TO ARRIVE ON SUNDAY NIGHT AHEAD OF A WARM
FRONT...AS LOW PRESSURE BUILDS ACROSS THE PLAINS STATES. A WARM
FRONT WILL THEN SURGE INTO INDIANA BY MONDAY NIGHT AND TUESDAY
PROVIDING GOOD CHANCES FOR RAIN.

LOW PRESSURE WILL THEN MOVE THROUGH THE TENNESSEE AND OHIO RIVER
VALLEYS ON CHRISTMAS EVE...BRINGING CHANCES FOR LIGHT SNOWFALL
ACROSS CENTRAL INDIANA FOR MID WEEK. DRY BUT COLDER WEATHER IS
EXPECTED FOR CHRISTMAS.

&&

.NEAR TERM /TONIGHT/...

ISSUED AT 226 PM EST SAT DEC 20 2014

SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS WEAK HIGH PRESSURE IN
PLACE ACROSS INDIANA. IR IMAGES CONTINUE TO SHOW EXTENSIVE
CLOUDINESS ACROSS CENTRAL INDIANA AND THE ENTIRE MIDWEST. RADAR
WAS QUIET.

MAIN FORECAST CHALLENGE TONIGHT WILL BE TEMPS. CLOUDY SKIES WILL
BE EXPECTED THROUGH THE NIGHT. TIME HEIGHT SECTIONS CONTINUE TO
SHOW PLENTY OF LOWER LEVEL MOISTURE LINGERING THROUGH THE NIGHT.
GIVEN THIS AND OUR SATELLITE IMAGES...EXPECT CLOUDY SKIES TO
REMAIN THROUGH THE NIGHT. TEMPERATURE ADVECTION THROUGH THE NIGHT
APPEARS RATHER NEUTRAL. THUS WILL TREND LOWS AT OR ABOVE
MAVMOS...CLOSER TO PERSISTENCE.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...

ISSUED AT 226 PM EST SAT DEC 20 2014

MAIN FORECAST CHALLENGE WILL BE TEMPS INITIALLY...FOLLOWED BY
PRECIP CHANCES ON MONDAY INTO TUESDAY.

DRY WEATHER IS EXPECTED THROUGH AT LEAST MONDAY AS MODELS SUGGEST
WEAK RIDGING IN PLACE ALOFT AS TROUGHING BUILDS ACROSS THE
CENTRAL PLAINS. LITTLE IN THE WAY OF UPPER SUPPORT APPEARS TO
PASS THROUGH THE OHIO VALLEY ON SUNDAY AND SUNDAY NIGHT. TIME
HEIGHT SECTIONS CONTINUE TO SHOW LOWER LEVEL SATURATION LINGERING
ON SUNDAY AND SUNDAY NIGHT. EVEN IF THE STRATUS DOES BEGIN TO
BREAK UP ON SUNDAY AFTERNOON...THE START OF WARM AIR ADVECTION ON
SUNDAY NIGHT AND MONDAY ON THE BACKSIDE OF THE HIGH SHOULD RESULT
IN A RETURN OF HIGH CLOUD. THUS THE OUTLOOK FOR SUNSHINE IS LOW.
WILL TREND TOWARD MOSTLY CLOUDY SUNDAY AND SUNDAY NIGHT. AS FOR
TEMPS...GIVEN THE ONGOING WARM AIR ADEVCTION ON THE BACKSIDE OF
THE HIGH AS 850MB TEMPS RISE TOWARD 0C BY 12Z MONDAY WILL TREND
HIGHS SUNDAY COOLER THAN MAVMOS WITH CLOUDS AND LOWS SUNDAY NIGHT
WARMER THAN MAVMOS.

ON MONDAY AND MONDAY NIGHT GFS AND NAM SUGGESTS A DEEP TROUGH
DIGGING OVER THE CENTRAL PLAINS AS TE SURFACE HIGH REACHES NEW
ENGLAND. STRONG WARM AIR ADVECTION BEGINS TO TAKE SHAPE ON MONDAY
AS SOUTHEAST WINDS DEVELOP ACROSS THE STATE. BY MONDAY
AFTERNOON...FORECAST SOUNDINGS ARE HINTING AT DEEP SATURATION AS
IN INITIAL SHORT WAVE IS PUSHED ACROSS CENTRAL INDIANA AS IT IS
EJECTED OUT OF THE TROUGH TO THE WEST. MEANWHILE THE 295K GFS
ISENTROPIC SURFACE CONTINUES TO SHOW VERY STRING UPGLIDE STARTING
MONDAY AFTERNOON WITH SPECIFIC HUMIDITIES IN EXCESS OF 3 G/KG.
THUS FEEL GOOD INGREDIENTS ARE AVAILABLE FOR PRECIP ON MONDAY
AFTERNOON. WILL TREND POPS HIGHER THAN MAVMOS AND ALSO TREND TEMPS
HIGHER ALSO GIVEN.

ON MONDAY NIGHT AND TUESDAY...STRONG ISENTROPIC LIFT IS EXPECTED
TO CONTINUES AS THE STRONG TROUGH ALOFT DIGS THROUGH THE CENTRAL
PLAINS MEANWHILE FORECAST SOUNDINGS CONTINUE TO SHOW GOOD
SATURATION. BEST SATURATION APPEARS ON TUESDAY AFTERNOON AS STRONG LOW
PRESSURE PUSHES INTO THE MISSISSIPPI RIVER VALLEY AND A SURGE OF
WARM AIR ARRIVES IN CENTRAL INDIANA. FURTHERMORE THE GFS SUGGESTS
A 50 KNTS LLJ PROVIDING ADDITIONAL LIFT. THUS WITH ALL THESE
INGREDIENTS WILL AGAIN TREND POPS UPWARDS...AND AGAIN TREND TEMPS
WARMER ON LOWS AND COOLER ON HIGHS. FURTHERMORE...BEING IN THE
WARM SECTOR...AND FORECAST SOUNDINGS SOLIDLY ABOVE
FREEZING...PRECIP TYPE WILL BE RAIN.

&&

.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 20/1800Z TAF ISSUANCE/...

ISSUED AT 1232 PM EST SAT DEC 20 2014

PERSISTENT LOW LEVEL CLOUD DECK CONTINUES TO AFFECT TAF SITES.
MVFR/VFR CONDITIONS WILL PREVAIL FOR DURATION OF TAF PERIOD
DESPITE HIGH PRESSURE OVER THE AREA. TIME CROSS SECTIONS CONTINUE
TO SHOW SUBSTANTIAL LOW LEVEL MOISTURE. VARIABLE WINDS WILL BECOME
MAINLY SOUTHEASTERLY TONIGHT WITH SUSTAINED SPEEDS OF 2 TO 4 KTS.


&&

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

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM....RYAN
AVIATION...TDUD

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.