141
FXUS63 KILX 221746
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1246 PM CDT FRI OCT 22 2021
SYNOPSIS
ISSUED AT 1053 AM CDT FRI OCT 22 2021
A BUSY WEEK IS FORTHCOMING AS A PAIR OF STRONG AUTUMN STORM
SYSTEMS LIFT ACROSS CENTRAL ILLINOIS. PERIODS OF HEAVY RAINFALL
AND STRONG THUNDERSTORMS ARE ANTICIPATED ON SUNDAY, AND AGAIN ON
WEDNESDAY. MEANWHILE, TEMPERATURES WILL REMAIN ON THE MILD SIDE AS
FROST AND FREEZE CONCERNS DELAY UNTIL EARLY NOVEMBER.
UPDATE
ISSUED AT 1053 AM CDT FRI OCT 22 2021
SATELLITE IMAGERY SHOWS BREAKS IN THE LOW CLOUDINESS TOWARD THE
ILLINOIS RIVER VALLEY AND NORTHWEST, THOUGH THE BREAKS ARE FILLING
IN WITH CUMULUS SO EVEN THERE ANTICIPATE MORE CLOUDS THAN SUN
THROUGH THIS AFTERNOON. ESPECIALLY EAST OF I-55, LOW CLOUDS ARE
MORE ENTRENCHED WITH EVEN PERIODS OF STEADY DRIZZLE OBSERVED THIS
MORNING. DRIZZLE, CURRENTLY MOST PRONOUNCED FROM NEAR CHAMPAIGN
DOWN TOWARD DECATUR AND TAYLORVILLE, WILL GRADUALLY MOVE OFF TO
THE EAST OVER THE NEXT FEW HOURS BUT WITH COOL TEMPERATURES AND
MOSTLY CLOUDY SKIES CONTINUING.
A FEW MINOR CHANGES WERE MADE INCLUDING TO BUMP UP CLOUD COVER
THROUGH THIS EVENING, BUT OTHERWISE THE GOING FORECAST LOOKS GOOD.
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 237 AM CDT FRI OCT 22 2021
LOW-LEVEL STRATUS WILL KEEP SKIES MURKY THIS MORNING AS PARCELS
REMAIN ADEQUATELY SATURATED IN THE LOWEST 5 KFT. THIS IS A GOOD
DRIZZLE PATTERN WITH THE ABSENCE OF CLOUD ICE AND INCREASING OMEGA
AHEAD OF A MID-LEVEL WAVE EMBEDDED IN CYCLONIC FLOW. PATCHY
DRIZZLE WILL END FROM WEST TO EAST THIS AFTERNOON AS A WEDGE OF
LOW-LEVEL DRY AIR ADVECTS ACROSS THE ILLINOIS RIVER VALLEY.
STILL, SKIES WILL REMAIN MOSTLY CLOUDY LATER THIS AFTERNOON INTO
EARLY EVENING AS ADDITIONAL WAVES RIPPLE THROUGH MID-LEVEL FLOW.
THIS ALL ADDS UP TO A SEASONABLY COOL DAY, WITH AFTERNOON HIGHS
STRUGGLING TO WARM ABOVE THE MID 50S.
THERE IS A LOW-END CHANCE FOR PATCHY FROST LATE TONIGHT, MAINLY
ACROSS THE NORTHERN THIRD OF THE STATE. IF SKIES BECOME CLEAR FOR
A COUPLE HOURS OVERNIGHT, TEMPERATURES WILL FALL INTO THE MIDDLE
30S, IF NOT LOWER. THERE IS REASON TO BELIEVE, HOWEVER, THAT HIGH
CLOUDS WILL LINGER ALL NIGHT AS AN UPPER-LEVEL SPEED MAX MOVES
ACROSS THE REGION. THIS WOULD MITIGATE THE FROST THREAT. BOTTOM
LINE, WE'RE NOT ADVERTISING FROST/FREEZE HEADLINES THIS FAR SOUTH
ACROSS CENTRAL ILLINOIS WHERE OVERNIGHT LOWS ARE FORECAST TO BE IN
THE UPPER 30S TO LOWER 40S; THE GALESBURG AND LACON AREAS BEAR
WATCHING, THOUGH.
LONG TERM
(SATURDAY THROUGH THURSDAY)
ISSUED AT 237 AM CDT FRI OCT 22 2021
THIS PERIOD WILL FOCUS ON:
(1) THE HEAVY RAINFALL AND SEVERE STORM POTENTIAL ON SUNDAY
(2) ADDITIONAL STRONG-TO-SEVERE POTENTIAL ON WEDNESDAY
BY SATURDAY MORNING, GLOBAL MODELS ARE IN EXCELLENT AGREEMENT IN
DEVELOPING A SURFACE LOW IN THE LEE OF THE ROCKIES WITH A BROAD
WARM SECTOR DEVELOPING ACROSS THE SOUTHERN PLAINS. THE SURFACE LOW
WILL BEGIN TO DEEPEN AND LIFT NORTHEASTWARD LATE SATURDAY NIGHT
AS A ROBUST 500-MB SHORTWAVE TROUGH PUSHES ACROSS THE ROCKIES. BY
SUNDAY MORNING, THE CENTER OF LOW PRESSURE WILL BE POSITIONED
OVER NE KANSAS WITH A WARM FRONT EXTENDING EASTWARD INTO MISSOURI
AND ILLINOIS ALONG THE I-70 CORRIDOR.
ISENTROPIC ASCENT NORTH OF THE WARM FRONT WILL LEAD TO SHOWERS
AND ELEVATED THUNDERSTORMS LATE SATURDAY NIGHT INTO SUNDAY MORNING
FOR PORTIONS OF CENTRAL AND WEST CENTRAL ILLINOIS. RAINFALL RATES
MAY BE HEAVY IN SPOTS, BUT THE HEAVIER RAINFALL RATES WILL COME
LATER SUNDAY MORNING ONCE THE WARM FRONT LIFTS NORTHWARD ACROSS
CENTRAL ILLINOIS. AS UNSEASONABLY HIGH PWATS IMPINGE ON THE
SHARPENING WARM FRONT, THERE WILL LIKELY BE SOME FRONTOGENETIC
FORCING INVOLVED TO HELP ENHANCE RAINFALL RATES TO 1.00" +/HR AT
TIMES. THIS MAY LEAD TO SOME FLASH FLOODING, AS COLLABORATED AND
MESSAGED BY WPC.
THE SEVERE RISK APPEARS TO COME LATER IN THE EVENING ON SUNDAY AS
A 40-50 KT LLJ VEERS INTO THE REGION AHEAD OF THE SURFACE COLD
FRONT. PLENTY OF FORCING AND UPPER-LEVEL SUPPORT WILL BE PRESENT
BY THAT TIME AS THE LEFT EXIT REGION OF THE UPPER-LEVEL SPEED MAX
NOSES ACROSS THE MID-MISSISSIPPI VALLEY IN TANDEM WITH A STRONG
500-MB SHORTWAVE TROUGH. ALL SEVERE WEATHER THREATS WILL BE
POSSIBLE ACROSS CENTRAL ILLINOIS GIVEN THE HIGHLY SHEARED
ENVIRONMENT JUXTAPOSED TO A MOIST AND MODESTLY UNSTABLE BOUNDARY
LAYER. WITH THE TRIPLE POINT OF THE FRONTAL SYSTEM NEARBY,
FORECAST HODOGRAPHS EXHIBIT SIGNIFICANT TURNING IN THE LOWEST FEW
KILOMETERS, FURTHER SUPPORTING THE NOTION OF ORGANIZED SEVERE
CONVECTION. THE SPC HAS COLLABORATED AND MESSAGED A SLIGHT RISK
ACROSS MUCH OF THE FORECAST AREA SUNDAY EVENING.
GUSTY WINDS AND SCATTERED SHOWERS WILL LINGER INTO MONDAY AS THE
DYNAMIC STORM SYSTEM MAKES ITS DEPARTURE. LARGE SCALE SUBSIDENCE
WILL BEGIN TO WORK IN BEHIND THE DEPARTING WAVE, AS AN AMPLIFIED
RIDGE OF HIGH PRESSURE QUICKLY BUILDS ACROSS THE REGION ON
TUESDAY.
ANOTHER DYNAMIC STORM SYSTEM LOOKS TO LIFT ACROSS THE MISSISSIPPI
VALLEY ON WEDNESDAY, WITH NOTABLE DIFFERENCES AMONG GLOBAL AND
ENSEMBLE GUIDANCE. REGARDLESS OF THE TRACK OF THE SURFACE LOW,
THERE WILL LIKELY BE ANOTHER GOOD SURGE OF GULF MOISTURE INTO
SOUTHERN AND/OR CENTRAL ILLINOIS AHEAD OF THE COLD FRONT.
INSTABILITY IS THE BIGGEST QUESTION AT THIS JUNCTURE, BUT THE
SHEAR WILL BE THERE TO SUPPORT A FEW STRONG-TO-SEVERE STORMS.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1235 PM CDT FRI OCT 22 2021
OBSERVATIONAL TRENDS AND SHORT-TERM GUIDANCE INDICATE THAT CLOUD
BASES SHOULD GRADUALLY INCREASE THROUGHOUT THE AFTERNOON INTO THE
EVENING. SUB-VFR CEILINGS MAY PERSIST AS LATE AS 00Z AT CMI AND
OTHER LOCATIONS NEAR THE IN STATE LINE. OTHERWISE, AT LEAST SOME
PERIODS OF VFR CIG/VSBY ARE EXPECTED FROM THIS AFTERNOON
ESPECIALLY NEAR/WEST OF A LINE FROM KBMI-KDEC. VFR CONDITIONS ARE
EXPECTED OVERNIGHT INTO SATURDAY MORNING EXCEPT PERHAPS FOR SOME
MVFR/IFR VISIBILITY IN THE VICINITY OF KOLY/KAJG.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...AAT
SYNOPSIS...AAT
SHORT TERM...MJA
LONG TERM...MJA
AVIATION...AAT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page