Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 311600
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1100 AM CDT MON AUG 31 2015

.UPDATE...
ISSUED AT 1049 AM CDT MON AUG 31 2015

WEAK REMNANTS OF THE BOUNDARY IN THE REGION FROM YESTERDAY
PROVIDING JUST ENOUGH OF A FOCUS FOR SHOWERS AND THUNDERSTORMS
THIS MORNING. SOME INTENSE PRECIPITATION RATES COMBINED WITH
A LACK OF SIGNIFICANT STORM MOTION HAS RESULTED IN HIGH RAINFALL
TOTALS UNDER THE NEARLY STATIONARY STORMS. HAVE HAD TO SENT OUT
UPDATES FOR PRECIP IN THE SOUTHEAST. ENOUGH GAPS IN THE CLOUD
COVER OVER THE SE THAT NO RUSH TO KNOCK DOWN THE MAX TEMPS FOR
TODAY...BUT WILL KEEP AN EYE ON THE AREA. OTHERWISE, A WARM A
MUGGY DAY FOR CENTRAL ILLINOIS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 317 AM CDT MON AUG 31 2015

08Z/3AM SURFACE ANALYSIS SHOWS DISSIPATING FRONTAL BOUNDARY
EXTENDING FROM NORTHERN INDIANA INTO CENTRAL ILLINOIS...GENERALLY
ALONG A FORT WAYNE TO QUINCY LINE.  AS WAS THE CASE LAST
NIGHT...QUITE A BIT OF FOG IS DEVELOPING ALONG/NORTH OF THE BOUNDARY
WHERE WINDS ARE NEARLY CALM AND LOW-LEVEL MOISTURE IS ABUNDANT.
LATEST OBS SHOW LOWEST VISBYS CONCENTRATED ALONG THE SOUTHERN SHORE
OF LAKE MICHIGAN ACROSS NORTHERN INDIANA INTO THE CHICAGO AREA.
HRRR HAS BEEN CONSISTENTLY SPREADING THIS THICKER FOG W/SW ALONG THE
FRONT INTO THE NORTHERN KILX CWA OVER THE NEXT COUPLE HOURS...AND AM
BEGINNING TO SEE THIS UNFOLDING WITH VISBY NOW DOWN TO 1/4SM AS FAR
SW AS KIKK.  FOLLOWING THE HRRR TREND...WILL MENTION AREAS OF DENSE
FOG ALONG/NORTHEAST OF A GALESBURG TO BLOOMINGTON-NORMAL LINE EARLY
THIS MORNING...WITH PATCHY/AREAS OF FOG ELSEWHERE AROUND THE AREA.

HIGH-RES MODELS SUCH AS THE HRRR AND RAPID REFRESH ARE SUGGESTING
THAT ISOLATED CONVECTION MAY DEVELOP ACROSS SOUTHEAST ILLINOIS OVER
THE NEXT COUPLE OF HOURS.  LATEST RADAR IMAGERY IS CLEAR...HOWEVER
SCATTERED MID-LEVEL CLOUDS ARE BEGINNING TO DEVELOP ON IR SATELLITE
IMAGERY ALONG/SOUTH OF I-70...SO HAVE OPTED TO CARRY SLIGHT CHANCE
POPS HERE EARLY THIS MORNING.  LATEST WATER VAPOR IMAGERY SHOWS A
SMALL BUT VIGOROUS SHORT-WAVE DROPPING SOUTHWESTWARD FROM NORTHEAST
INDIANA.  THIS FEATURE WILL LIKELY INTERACT WITH THE DECAYING FRONT
TO TRIGGER ISOLATED CONVECTION FURTHER NORTH INTO THE CWA THIS
AFTERNOON.  MOST MODELS ARE HINTING AT LEAST SOME QPF ACROSS THE
SOUTHERN TWO-THIRDS OF THE AREA...SO HAVE ADDED SLIGHT CHANCE POPS
ALONG/SOUTH OF A JACKSONVILLE TO BLOOMINGTON-NORMAL LINE FOR THE
AFTERNOON.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 317 AM CDT MON AUG 31 2015

MAIN WEATHER STORY THROUGH THE EXTENDED WILL BE THE VERY WARM AND
HUMID CONDITIONS THAT ARE EXPECTED TO PERSIST THROUGH EARLY NEXT
WEEK.  HIGH TEMPERATURES ON TUESDAY WILL REACH THE UPPER 80S TO
AROUND 90 DEGREES...THEN READINGS WILL CLIMB INTO THE LOWER 90S FOR
THE REMAINDER OF THE PERIOD.  DRY WEATHER WILL GENERALLY BE THE
RULE...HOWEVER ISOLATED CONVECTION CANNOT BE RULED OUT...ESPECIALLY
TUESDAY AFTERNOON AS A WEAKNESS IN THE MEAN 500MB RIDGE AXIS REMAINS
IN THE VICINITY.  MODELS ARE HINTING AT SOME QPF ACROSS THE E/NE CWA
AS THIS FEATURE GRADUALLY SHIFTS INTO THE GREAT LAKES BY WEDNESDAY.

THE NEXT SIGNIFICANT CHANCE FOR RAIN WILL NOT ARRIVE UNTIL EARLY
NEXT WEEK...WHEN A STRONG SHORT-WAVE FLATTENS THE UPPER RIDGE AND
PUSHES A COLD FRONT INTO THE REGION.  MODELS ARE IN DISAGREEMENT
CONCERNING THE SPEED OF THIS PROCESS...WITH THE GFS BEING ABOUT 24
HOURS FASTER THAN THE ECMWF/GEM.  THE 00Z AUG 31 GFS SHOWS THE COLD
FRONT PASSING THROUGH CENTRAL ILLINOIS LATE SUNDAY NIGHT INTO
MONDAY...WHILE THE ECMWF/GEM HAVE DELAYED FROPA UNTIL LATE MONDAY
NIGHT INTO TUESDAY.  GIVEN PERSISTENT AND HIGHLY AMPLIFIED RIDGE
POSITIONED ACROSS THE MIDWEST...THINK A SLOWER BREAK DOWN TO THE
PATTERN IS PRUDENT.  HAVE THEREFORE TRENDED THE FORECAST TOWARD THE
SLOWER ECMWF/GEM CONSENSUS.  AS A RESULT...AM EXPECTING DRY
CONDITIONS THROUGH SUNDAY NIGHT...WITH HIGHER RAIN CHANCES ARRIVING
BY LATE MONDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 653 AM CDT MON AUG 31 2015

ASIDE FROM SOME EARLY MORNING IFR/MVFR FOG TODAY AND AGAIN LATE
TONIGHT, PREDOMINANTLY VFR CONDITIONS EXPECTED ACROSS THE CENTRAL
ILLINOIS TERMINALS THROUGH THE 12Z TAF VALID TIME. DIURNALLY
DRIVEN CU WILL POP THIS MORNING, WITH ISOLATED SHOWER/STORMS
POSSIBLY DEVELOPING. HOWEVER, SHOWER/STORM COVERAGE IS EXPECTED TO
BE TOO LOW TO MENTION AT THIS TIME. WINDS SHOULD CONTINUE TO BE
LIGHT OVERALL.


&&

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

$$

UPDATE...HJS
SHORT TERM...BARNES
LONG TERM...BARNES
AVIATION...BAK


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