Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 310453
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1153 PM CDT SUN AUG 30 2015

.UPDATE...
ISSUED AT 900 PM CDT SUN AUG 30 2015

THE STATIONARY FRONT ACROSS THE AREA, ROUGHLY ALONG I-72, WAS
A FOCUS FOR MOISTURE POOLING THIS AFTERNOON. THE RESIDUAL HIGH RH
IN THE BOUNDARY LAYER WILL SET THE STAGE FOR FOG FORMATION AFTER
MIDNIGHT. SKIES ARE PRIMARILY CLEAR, WHICH WILL AID RADIATIONAL
COOLING AND INCREASE POTENTIAL FOR FOG. SOME FOG COULD BECOME
LOCALLY DENSE, ESPECIALLY NORTH OF THE FRONT. WILL ADD SOME DENSE
FOG WORDING TO THE WEATHER GRIDS N OF I-74.

A FEW VERY ISOLATED SHOWERS DEVELOPED IN BETWEEN SPRINGFIELD AND
DECATUR OVER THE LAST COUPLE OF HOURS. FORECAST SOUNDINGS INDICATE
THERE WILL BE SUFFICIENT INSTABILITY OVERNIGHT JUST SOUTH OF THE
FRONT FOR SHOWERS TO BUBBLE UP PERIODICALLY. WILL KEEP THE SLIGHT
CHANCE POPS GOING IN THE SOUTH HALF OF THE FORECAST AREA THE REST
OF TONIGHT.

LOW TEMPS LOOK ON TRACK IN THE MID TO UPPER 60S. UPDATED
WEATHER INFO WILL BE AVAILABLE SHORTLY.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 237 PM CDT SUN AUG 30 2015

REMNANTS OF STALLED FRONTAL BOUNDARY STILL PROVIDING A FOCUS FOR
SHOWER DEVELOPMENT THIS AFTERNOON IN CENTRAL ILLINOIS. PLENTY OF
LLVL MOISTURE IN THE BOUNDARY LAYER NOT MIXING OUT ENTIRELY UNDER
STRATUS AND FOG NW OF THE BOUNDARY THIS MORNING, AND OTHER AREAS TO
THE SOUTH AND EAST REMAINING PARTLY CLOUDY THROUGH THE AFTERNOON.
POOLED MOISTURE AT THE SFC RICH ON BOTH SIDES OF THE BOUNDARY AND
TEMPS TONIGHT DROPPING WITH LIGHT WINDS AND CLEARING SKIES.  FOG
DEVELOPMENT EXPECTED FOR MOST OF CENTRAL ILLINOIS TONIGHT, MAINLY
AFTER MIDNIGHT.

.LONG TERM...(MONDAY THROUGH SUNDAY)
ISSUED AT 237 PM CDT SUN AUG 30 2015

THE EXTENDED LOOKS WARM AND DRY AS UPPER-LEVEL RIDGING DOMINATES THE
EASTERN CONUS THROUGH THE END OF THE WEEK.  A SLIGHT WEAKNESS IN THE
RIDGE APPEARS TO DEVELOP ACROSS ILLINOIS INTO THE OHIO RIVER
VALLEY...POTENTIALLY TRIGGERING ISOLATED AFTERNOON/EVENING
CONVECTION TUESDAY THROUGH FRIDAY.  HOWEVER...MID-LEVEL WARMING
BENEATH THE RIDGE WILL LIKELY LEAD TO CAPPING AND AN OVERALL
SUPPRESSION OF CONVECTION. THEREFORE...WILL MAINTAIN A DRY FORECAST
THROUGH THE WEEK. THE NEXT SIGNIFICANT CHANCE FOR PRECIPITATION WILL
LIKELY HOLD OFF UNTIL LATE IN THE WEEKEND AND EARLY NEXT WEEK WHEN A
SHORT-WAVE TROUGH GRADUALLY FLATTENS THE PREVAILING RIDGE AND PUSHES
A COLD FRONT INTO THE REGION.  MODELS ARE IN CLOSE AGREEMENT
CONCERNING TIMING THIS FAR OUT...BUT TYPICAL TREND IN THIS TYPE OF
SCENARIO IS USUALLY SLOWER.  AS A RESULT WILL MAINTAIN DRY WEATHER
THROUGH SUNDAY FOR NOW.

WITH RIDGING IN PLACE...HIGH TEMPERATURES SHOULD CLIMB INTO THE
UPPER 80S AND LOWER 90S EACH DAY.  WITH DEWPOINTS IN THE UPPER 60S
THROUGH THE PERIOD...SOME HUMID CONDITIONS CAN BE EXPECTED...THOUGH
HEAT INDEX VALUES SHOULD REMAIN BELOW 100.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1153 PM CDT SUN AUG 30 2015

FOG AND LOW CLOUD FORMATION LATER TONIGHT REMAIN THE PRIMARY
CONCERNS. THE STALLED OUT FRONTAL BOUNDARY ACROSS CENTRAL IL IS
BEGINNING TO WASH OUT, BUT RESIDUAL MOISTURE IN THE BOUNDARY LAYER
HAS ALLOWED DEWPOINTS TO LINGER IN THE UPPER 60S TO LOW 70S
THROUGH THE EVENING. THE POTENTIAL FOR MVFR FOG IS HIGH IN A
MAJORITY OF THE AREA OVERNIGHT. HRRR/RAP OUTPUT ARE POINTING
TOWARD THE POTENTIAL OF LOCALIZED VLIFR FOG NEAR PIA AND BMI, AND
TO SOME EXTENT SPI AND DEC. THE NAM FORECAST SOUNDINGS SHOW AT
LEAST AN MVFR CLOUD LAYER WILL DEVELOP LATER TONIGHT AT MOST TAF
LOCATIONS. HAVE INCLUDED LIFR FOG AT PIA AND BMI WITH VLIFR CIGS
AT BMI. WILL CONTINUE WITH ONLY IFR FOG LATER TONIGHT FOR SPI, DEC
AND CMI, FOR NOW.

FOG SHOULD DISSIPATE BY MID MORNING, WITH MVFR CLOUDS POSSIBLY
LINGERING TO AROUND 17-18Z. VFR CONDITIONS SHOULD DEVELOP AT ALL
TAF SITES FOR THE AFTERNOON AND THROUGH THE EVENING.

WINDS WILL REMAIN LIGHT AND VARIABLE THE REST OF THE NIGHT, WITH
A PREVAILING S-SW WIND DEVELOPING AFTER SUNRISE TOMORROW. WIND
SPEEDS DURING PEAK MIXING TOMORROW SHOULD REMAIN 10KT OR LESS.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...HJS
LONG TERM...AUTEN
AVIATION...SHIMON



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