976
FXUS63 KILX 201128
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
628 AM CDT THU SEP 20 2018
SHORT TERM
(TODAY THROUGH FRIDAY)
ISSUED AT 317 AM CDT THU SEP 20 2018
MAJORITY OF THE SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE NEXT
WEATHER SYSTEM TO IMPACT CENTRAL IL ARE CURRENTLY NORTH OF THE
AREA. WINDS INCREASING OUT OF THE SOUTHWEST TODAY WILL PICK UP AND
PUSH THE DIFFUSE SFC REFLECTION OF A WARM FRONT FURTHER NORTH
QUICKLY TODAY. CENTRAL IL WILL REMAIN FIRMLY IN A WARM SECTOR
ENVIRONMENT, WITH HOT AND HUMID AIR IN PLACE. TEMPS WILL WARM
QUICKLY TODAY, WITH GUSTY SOUTHWESTERLY WINDS. EARLY LLVL
MOISTURE WILL RESULT IN SOME HEAT INDEXES IN THE UPPER 90S/LOW
100S BY THE EARLY AFTERNOON BEFORE MIXING OUT TO A CERTAIN EXTENT.
WITH THE STRONG WARM AIR ADVECTION MOVING INTO THE REGION,
DIURNAL DEVELOPMENT WILL BE ISOLATED AT BEST WITH RATHER LACKING
LAPSE RATES. HOWEVER, YESTERDAYS AFTERNOON ACTIVITY WAS ENOUGH TO
WARRANT A VERY LOW POP AHEAD OF THE APPROACHING COLD FRONT LATER
TONIGHT.
THE NEXT LOW WILL MOVE ACROSS THE PLAINS AND INTO THE MIDWEST
TONIGHT AND INTO TOMORROW MORNING, DRAGGING A COLD FRONT THROUGH
THE REGION. EVEN THIS CLOSE TO THE ARRIVAL OF THE FRONT, THE
MODELS ARE STILL HAVING INCONSISTENT TIMING. THE GFS IS MORE QUICK
WITH THE PASSAGE OF THE BOUNDARY, THE ECMWF AND NAM SLIGHTLY
SLOWER. BOTH, HOWEVER, BRING THE FRONT THROUGH MAINLY IN THE
OVERNIGHT HOURS, LIMITING THE CONVECTIVE ACTIVITY OVER CENTRAL IL
AND ALSO THE SEVERE WEATHER THREAT. WITH THE POTENTIALLY SLOWER
PROGRESSION OF THE BOUNDARY, THE POTENTIAL FOR SOME SEVERE WEATHER
MAY OCCUR TOMORROW ON A REFIRE OF THE BOUNDARY SOUTH OF I-70. THAT
AREA IS IN A MARGINAL RISK FOR FRIDAY AFTERNOON. IN THE MEANTIME,
MUCH OF THE INITIAL CONVECTION ALONG AND AHEAD OF THE BOUNDARY
FALLS APART IN THE CAMS AS THE PRECIP APPROACHES THIS EVENING.
EVEN SO, BUFKIT SOUNDINGS HAVE ENOUGH WIND BELOW 5KFT TO BRING
SOME VERY GUSTY WINDS WITH EVEN WEAKER SHOWERS THIS EVENING,
SHOULD THEY TRANSLATE TO THE SURFACE. TEMPS TOMORROW CONSIDERABLY
COOLER BEHIND THE BOUNDARY AND DIMINISHING PRECIP. LOCATION OF
THAT FRONT IS QUESTIONABLE, AND COULD RESULT IN SOME CONTINUED HOT
AND MUGGY CONDITIONS SOUTH OF A LINE ROUGHLY FROM EFFINGHAM TO
PARIS.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 317 AM CDT THU SEP 20 2018
FRONT STALLS SOMEWHAT IN THE OHIO RIVER VALLEY, BUT HOLDS MOST OF
THE PRECIP CHANCES SOUTH OF THE REGION. WEEKEND FORECAST IS THEN
LOOKING INCREASINGLY DRIER AND TEMPS MUCH COOLER ON SATURDAY. BY
SUNDAY, HOWEVER, THOSE MIDLEVELS THAT DID NOT QUITE GET THE COOLER
TEMPS WITH THE FRONT START TO DOMINATE AGAIN, AND SOUTHWESTERLY
FLOW HELPS PICK UP YET ANOTHER WARMING TREND FOR TEMPS IN THE
UPPER 70S BY SUNDAY IN WESTERN IL...SPREADING ACROSS CENTRAL IL
FOR MONDAY.
ANOTHER PATTERN SHIFT TO MORE FALL LIKE TEMPERATURES SETTING UP
FOR EARLY IN THE WEEK. MODELS HAVING TROUBLE WITH RESOLVING THE
POPS/SPEED OF THE PRECIP AHEAD OF THE SHOWERS OVERNIGHT MONDAY
INTO TUESDAY NIGHT. BUT HIGH TEMPERATURES ON THE OTHER SIDE OF THE
PRECIP DROP INTO THE LOW 70S BY MIDWEEK.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 615 AM CDT THU SEP 20 2018
PATCHY 5-6SM IN GROUND FOG TIL 13Z, OTHERWISE, VFR CONDITIONS
EXPECTED THIS FORECAST PERIOD. MAIN FORECAST CHALLENGE WILL BE
WITH COVERAGE OF ANY TSRA TODAY AND ESPECIALLY AFTER 03Z TONIGHT
AS A COLD FRONT PUSHES TOWARDS OUR AREA. SCATTERED CUMULUS EXPECTED
TODAY WITH BASES AROUND 5000 FEET WITH FORECAST SOUNDINGS INDICATING
SOUTHERLY WINDS SHOULD START TO INCREASE BY LATE MORNING INTO THE
AFTERNOON HOURS WITH GUSTS UP TO AROUND 20 KTS AT PIA, BMI AND SPI
WITH DEC AND CMI HAVING THE GUSTS MAINLY THIS AFTERNOON. NOT MUCH,
IF ANY DROP OFF IN THE GUSTY SOUTH WINDS TONIGHT AS A COLD FRONT
APPROACHES THE AREA FROM THE WEST. IT APPEARS COVERAGE OF ANY TSRA
THIS AFTERNOON WILL ONCE AGAIN BE TOO LIMITED TO INCLUDE IN THE
TAFS.
WILL CONTINUE TO INCLUDE LLWS IN THE WESTERN TAF SITES THIS EVENING
WITH 1500-2000 FOOT WINDS FROM THE SOUTH TO SOUTHWEST INCREASING
TO 45 KTS. HOWEVER, AT THE SAME TIME, CONVECTION CHANCES AHEAD OF
THE COLD FRONT WILL START TO INCREASE AFTER 03Z WEST OF THE MISSISSIPPI
RIVER. HOWEVER, LATEST MODEL GUIDANCE CONTINUES TO WEAKEN THE BAND OF
STORMS BEFORE IT GETS INTO OUR AREA LATE TONIGHT SO WILL NOT INCLUDE
IN THIS SET OF TAFS AND HIGHLIGHT THE LLWS THREAT IN PIA, BMI AND SPI
LATE THIS EVENING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...SMITH
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