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 181728
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1228 PM EST THU DEC 18 2014

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

&&

.SYNOPSIS...
ISSUED AT 252 AM EST THU DEC 18 2014

HIGH PRESSURE IS EXPECTED ACROSS THE AREA THROUGH THE END OF THE
WEEK. THE NORTHERN FRINGES OF A LOW PRESSURE SYSTEM PASSING THROUGH
THE GULF COAST STATES MAY AFFECT PARTS OF THE AREA BY THE END OF
WEEK. A SIGNIFICANT LOW PRESSURE SYSTEM MAY MOVE INTO THE AREA BY
THE EARLY TO MIDDLE PARTS OF NEXT WEEK.

&&

.NEAR TERM /THIS AFTERNOON/...

ISSUED AT 956 AM EST THU DEC 18 2014

SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS HIGH PRESSURE IN PLACE
OVER THE UPPER MIDWEST AND THE OHIO VALLEY. RADAR RETURNS SHOW
ECHO ALOFT OVE MUCH OF CENTRAL ILLINOUIS...HOWEVER SURFACE OBS
ONLY REPORT SN FALLING ACROSS WEST CENTRAL ILLINOIS. HRRR TENDS TO
KEEP THE ONGOING PRECIP SOUTH OF CENTRAL INDIANA AND WANES THE
ONGOING PRECIP OVER WESTERN ILLINOIS. ATTM...THE HRRR DOESN/T
APPEAR HANDLE THE ONGOING SITUTAION WELL. GFS 285K ISENTROPIC
SURFACE SHOWS GOOD UPGLIDE ACROSS MISSOURI...HELPING THE ONGOING
SNOW THERE. THIS FEAUTRE HOWEVER DOES NOT TRANSLATE WELL TO
CENTRAL INDIANA AS MODELS SUGGEST THE ISENTROPIC LIFT FAILS TO
REACH INDIANA. TIME HEIGHT SECTIONS CONTINUE TO SUGGEST GOOD MID
AND LOWER LEVEL MOISTURE AVAILABLE BETWEEN 18Z AND 00Z. CONFIDNECE
REMAINS LOW IN THIS EVENT...BUT WILL MONITOR CLOSELY. FOR NOW HAVE
ADDED SLIGHT CHC POPS TO MAINLY THE SOUTHERN PARTS OF THE FORECAST
AREA...WITH FLURRIES ELSEWHERE. WILL BE QUICK TO UPDATE SHOULD
ECHOS OVER ILLINOIS HOLD TOGETHER AND PRECIP BEGINS TO REACH THE
GROUND.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
ISSUED AT 252 AM EST THU DEC 18 2014

MODEL DATA SUGGEST THERE MAY STILL SOME REMNANT ENERGY MOVING
THROUGH THE AREA THIS EVENING ASSOCIATED WITH TODAY/S
DISTURBANCE...SO WILL EXTEND THE FLURRY MENTION INTO THE EVENING
HOURS TONIGHT.

OTHERWISE...A SPLIT FLOW IS EXPECTED TO DEVELOP BY THE END OF THE
WEEK AS THE UPPER BLOCK OVER SOUTHERN CANADA BREAKS DOWN. A SOUTHERN
STREAM DISTURBANCE IS EXPECTED TO SCOOT ALONG THE GULF COAST
STATES...WHILE A DRIER NORTHERN STREAM SYSTEM DIGS INTO THE GREAT
LAKES BY SATURDAY. OPERATIONAL GUIDANCE IS IN PRETTY GOOD AGREEMENT
IN KEEPING THE MAIN PRECIPITATION THREAT TIED UP IN THE SOUTHERN
STREAM AND WELL SOUTH OF THE LOCAL AREA. THERE ARE SOME ENSEMBLES
THAT DRAW ENOUGH MOISTURE NORTH FOR A THREAT FOR LIGHT SNOW AND
MINOR ACCUMULATIONS OVER THE SOUTHERN/SOUTHEASTERN ZONES LATE FRIDAY
NIGHT INTO SATURDAY. TO COVER THIS POSSIBILITY...WILL KEEP SOME
CHANCE POPS GOING FOR LIGHT SNOW DURING THOSE PERIODS OVER ABOUT THE
SOUTHEAST HALF OF THE FORECAST AREA.

GIVEN THE DEGREE OF CLOUD COVER EXPECTED OVER THE NEXT COUPLE OF
DAYS...WILL CONTINUE TO NARROW THE DIURNAL RANGE OF THE GFS MOS
TEMPERATURE GUIDANCE THROUGH THE PERIOD.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
ISSUED AT 340 AM EST THU DEC 18 2014

EXTENDED MODELS AND ENSEMBLES AGREE THAT STRONG PACIFIC JET...ARCING
OVER A HIGH AMPLITUDE WEST COAST UPPER RIDGE...WILL DIVE SOUTHEAST
OVER THE CENTRAL UNITED STATES DURING THE EARLY AND MIDDLE PART OF
NEXT WEEK RESULTING IN AN UPPER TROUGH CLOSING INTO AN UPPER LOW AND
INTENSIFYING INTO A VERY STRONG SYSTEM BEFORE IT MOVES INTO
SOUTHEASTERN CANADA ON CHRISTMAS. MODELS WERE NOT TOO FAR OFF
REGARDING STRENGTH AND TIMING OF THIS SYSTEM...SO A BLEND OF THE
FURTHER NORTH 00Z GFS AND FURTHER SOUTH 12Z ECMWF LOOKS GOOD.

00Z MODELS ARE SHOWING AN UPPER TROUGH OVER SOUTHEASTERN SOUTH
DAKOTA OR NORTHWESTERN IOWA AT 00Z TUESDAY WITH BROAD AREA OF UPPER
DIFFLUENT FLOW ALOFT OVER THE OHIO VALLEY AND GREAT LAKES.
MEANWHILE...LOW LEVEL FLOW WILL BE SOUTHERLY BY MONDAY AND OPEN THE
OHIO VALLEY AND GREAT LAKES TO THE GULF RESULTING IN DEEPENING
MOISTURE TO GO ALONG WITH THE UPPER FORCING. THIS WILL BRING RAIN TO
THE AREA BY MONDAY AS WELL AS ABOVE NORMAL TEMPERATURES. THE WARMER
TEMPERATURES AND RAIN WILL BE SHORT-LIVED...HOWEVER AS COLDER AIR
RUSHES IN FROM THE NORTHWEST ON THE BACK END OF THE SYSTEM LATE
TUESDAY OR TUESDAY NIGHT. ALONG WITH THE COLDER AIR...UPPER IMPULSES
WILL MOVE ACROSS THE AREA IN THE CYCLONIC FLOW IN THE WAKE OF THE
DEPARTING STACKED LOW THAT SHOULD MOVE INTO QUEBEC EARLY CHRISTMAS.
THIS SHOULD GENERATE SOME SNOW WITH LIGHT ACCUMULATION POSSIBLE BY
CHRISTMAS EVE.

00Z GFS ENSEMBLE MOS TEMPERATURES LOOK TOO WARM THIS WEEKEND.
STRONGLY PREFER THE COOLER 00Z DECEMBER 17 EUROPEAN ENSEMBLE MEAN
TEMPERATURES.

&&

.AVIATION /DISCUSSION FOR THE 18/1800Z TAF ISSUANCE/...

ISSUED AT 1208 PM EST THU DEC 18 2014

FLIGHT CONDITIONS WILL HOVER RIGHT AROUND THE MVFR/VFR MARK INTO
THE NIGHT. HOWEVER...TIME CROSS SECTIONS ARE LEANING TOWARD DRIER
CONDITIONS AT ALL LEVELS EARLY TOMORROW MORNING. SO...ANTICIPATE
SCATTERING SOME TIME BETWEEN FRI 09-15Z...WHICH IS REFLECTED IN
TAFS. AT THAT POINT...VFR SHOULD BE THE PREVAILING FLIGHT CATEGORY
THROUGH THE REMAINDER OF TAF PERIOD. NORTHWEST WINDS WILL VEER
SLIGHTLY TO THE NORTHEAST LATE TONIGHT...BUT WILL REMAIN LIGHT.

&&

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

&&

$$

SYNOPSIS...JAS
NEAR TERM...PUMA
SHORT TERM...JAS
LONG TERM...MK
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.