Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 011157
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
657 AM CDT TUE SEP 1 2015

.SHORT TERM...(TODAY)
ISSUED AT 315 AM CDT TUE SEP 1 2015

LATEST UPPER AIR ANALYSIS CONTINUES TO SHOW A LARGE RIDGE OF HIGH
PRESSURE EXTENDING FROM THE SOUTHERN PLAINS TO THE EASTERN GREAT
LAKES...HOWEVER A WEAKNESS IN THE RIDGE IS NOTED FROM INDIANA
SOUTHWESTWARD TO THE OZARKS.  07Z/2AM WATER VAPOR IMAGERY SHOWS A
VIGOROUS WAVE OVER NORTH-CENTRAL INDIANA...WHICH WILL LIKELY TRIGGER
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS EAST-CENTRAL ILLINOIS
TODAY.  MODELS DISAGREE ABOUT THE AREAL COVERAGE OF PRECIP...WITH
THE NAM KEEPING MOST OF IT ACROSS INDIANA.  MEANWHILE...HIGHER-RES
MODELS SUCH AS THE RAPID REFRESH AND HRRR ARE QUITE AGGRESSIVE IN
DEVELOPING CONVECTION ACROSS THE E/SE KILX CWA OVER THE NEXT COUPLE
OF HOURS THEN LINGERING IT THROUGH EARLY AFTERNOON.  GIVEN CURRENT
RADAR/SATELLITE TRENDS...THINK THIS MAY BE A BIT OVERDONE...HOWEVER
PRONOUNCED FEATURE ON WATER VAPOR IMAGERY DEFINITELY SUPPORTS POPS.
HAVE THEREFORE INCLUDED 20-30 POPS EAST OF I-55 TODAY AS THE WAVE
INTERACTS WITH A VERY WARM/HUMID AIRMASS.  AFTERNOON HIGH
TEMPERATURES WILL BE COOLEST ACROSS THE EAST WHERE CLOUDS AND
SCATTERED THUNDERSTORMS WILL KEEP READINGS IN THE MIDDLE 80S.
FURTHER WEST ACROSS THE REMAINDER OF THE AREA...HIGHS WILL REACH THE
UPPER 80S TO AROUND 90 DEGREES.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 315 AM CDT TUE SEP 1 2015

INDIANA SHORT-WAVE WILL LIFT TO THE NORTHEAST ON WEDNESDAY...TAKING
ANY UPPER SUPPORT FOR CONVECTION INTO THE GREAT LAKES.  AS A
RESULT...AM EXPECTING A HOT AND DRY DAY ACROSS THE BOARD WITH HIGH
TEMPERATURES CLIMBING INTO THE LOWER 90S.  NEXT POTENTIAL FLY-IN-THE-
OINTMENT WILL BE A SECOND SHORT-WAVE TROUGH CURRENTLY EVIDENT ON
WATER VAPOR IMAGERY OVER WYOMING/COLORADO.  THIS FEATURE WILL TRACK
INTO THE UPPER MIDWEST ON WEDNESDAY...THEN DROP E/SE INTO THE
EASTERN GREAT LAKES BY THURSDAY.  00Z SEP 1 NAM TAKES THE WAVE MUCH
FURTHER SOUTH AND GENERATES CONVECTION ACROSS NORTH-CENTRAL ILLINOIS
ON THURSDAY...HOWEVER THE NAM IS THE ODD MODEL OUT AS BOTH THE GFS
AND ECMWF KEEP IT FURTHER NORTH.  WILL KEEP AN EYE ON THE TRACK OF
THE WAVE OVER THE NEXT 24-36 HOURS...BUT WILL FOLLOW THE GFS/ECMWF
CONSENSUS AND KEEP THURSDAY DRY FOR NOW.

THE PREVAILING UPPER RIDGE WILL CONTINUE TO BE THE DOMINANT WEATHER
FEATURE THROUGH THE WEEKEND...ENSURING A CONTINUATION OF VERY WARM
CONDITIONS WITH HIGHS IN THE LOWER 90S FRIDAY THROUGH SUNDAY.  MAIN
QUESTION FOR EARLY NEXT WEEK WILL BE HOW QUICKLY THE RIDGE WILL
BREAK DOWN AS AN UPPER LOW APPROACHES FROM THE WEST.  AS
EXPECTED...MODEL TRENDS HAVE BEEN SLOWER WITH THIS PROCESS...WITH
EVEN THE FASTER GFS SLOWING ITS SOLUTION TO LOOK MORE LIKE THE
ECMWF/GEM. THERE ARE EVEN SOME INDICATIONS THAT THE WESTERN UPPER
LOW WILL LIFT INTO SOUTHERN CANADA WHILE ITS ASSOCIATED COLD FRONT
DISSIPATES BEFORE PASSING THROUGH CENTRAL ILLINOIS.  GFS CONTINUES
TO BE MORE AGGRESSIVE WITH FROPA LATE MONDAY INTO TUESDAY...HOWEVER
ECMWF SUGGESTS FRONT MAY ESSENTIALLY WASH OUT OVER CENTRAL ILLINOIS
TUESDAY.  GIVEN BETTER MODEL CONSENSUS ON TIMING...HAVE REMOVED POPS
FROM SUNDAY AND SUNDAY NIGHT AND HAVE FOCUSED HIGHEST RAIN CHANCES
LATE MONDAY INTO TUESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 652 AM CDT TUE SEP 1 2015

ASIDE FROM SOME EARLY MORNING FOG, AND LATE NIGHT FOG ONCE AGAIN
WEDNESDAY MORNING, PREDOMINANTLY VFR CONDTIONS ARE EXPECTED ACROSS
THE CENTRAL ILLINOIS TERMINALS THROUGH THE 12Z TAF VALID TIME.
CIGS ARE MOST LIKELY TODAY AT KCMI AND POSSIBLY KDEC/KBMI WITH AN
UPPER LEVEL DISTURBANCE IN THE VICINITY. THIS DISTURBANCE WILL
ALSO PRODUCE A FEW THUNDERSTORMS AT KCMI FOR THE NEXT FEW HOURS
AND POSSIBLY INTO THE AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...BARNES
AVIATION...BAK


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