383
FXUS63 KDVN 302253
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
553 PM CDT SUN AUG 30 2026
KEY MESSAGES
- HEAT AND HUMIDITY WILL BUILD ACROSS THE AREA MONDAY THROUGH THURSDAY
THIS WEEK. HEAT INDICES OF 95 TO 100+ ARE EXPECTED, HIGHEST
FOR AREAS SOUTH OF I-80. A HEAT ADVISORY HAS BEEN ISSUED FOR
AREAS ALONG AND SOUTH OF I-80 FOR MONDAY THROUGH WEDNESDAY.
- HOW HOT CONDITIONS GET THIS WEEK WILL DEPEND ON WHERE ANY
SHOWERS/STORMS DEVELOP.
- THERE IS A NEAR-DAILY RISK OF SHOWERS AND STORMS POSSIBLE
MORE LIKELY FOR AREAS ALONG AND NORTH OF I-80.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 219 PM CDT SUN AUG 30 2026
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE ACROSS MUCH OF
THE AREA THIS AFTERNOON AS A MID-LEVEL SHORTWAVE CONTINUES TO SWEEP
OVER THE AREA ON THE NORTHERN SIDE OF A HEAT DOME. THIS HEAT DOME
WILL SUPPORT VERY WARM AND MUGGY CONDITIONS FOR MUCH OF THE AREA
THIS WEEK (MORE ON THAT IN JUST A BIT!). STRONG TO SEVERE STORMS ARE
NOT ANTICIPATED WITH THIS ACTIVITY, GIVEN MEAGER MID-LEVEL LAPSE
RATES AND SBCAPE VALUES OF ONLY 500 TO 1000 J/KG PER THE SPC
MESOANALYSIS PAGE. THIS WILL STILL BE AMPLE INSTABILITY FOR SOME
ISOLATED STORMS THIS AFTERNOON, MOST LIKELY ALONG AND NORTH OF
HIGHWAY 30.
TONIGHT WILL LIKELY BE NEARLY A CARBON-COPY OF THIS MORNING'S
CONDITIONS, WITH ADDITIONAL CHANCES (10-40%) OF SHOWERS AND STORMS
DEVELOPING AS A NOCTURNAL SOUTHWESTERLY 30 TO 40 KNOT LOW-LEVEL JET
(LLJ) BUILDS, ENHANCING CONVERGENCE ALONG IT. AT THIS TIME, THE MORE
LIKELY AREAS TO SEE THIS ACTIVITY CONTINUES TO BE OVER NORTHWESTERN
ILLINOIS AND ADJACENT AREAS OF EASTERN IOWA, CLOSER TO THE NOSE OF
THE LLJ. OVERNIGHT LOWS ARE EXPECTED TO DIP TO THE LOWER 70S AREA-
WIDE.
HEAT AND HUMIDITY ARE EXPECTED TO INCREASE FURTHER ON MONDAY AS THE
HEAT DOME BUILDS NORTHWARD. THE LREF ENSEMBLE CLUSTER ANALYSIS
REMAINS IN VERY GOOD AGREEMENT ON THIS OCCURRING, WITH 500 MB
HEIGHTS OF 594 DECAMETERS OVER THE SOUTHERN PLAINS/SOUTHERN MS RIVER
VALLEY REGIONS. HIGH TEMPERATURES ON MONDAY ARE EXPECTED TO WARM TO
THE UPPER 80S OVER NORTHWEST ILLINOIS/NORTHEAST IOWA TO THE
LOWER/MIDDLE 90S OVER SOUTHEAST IOWA/NORTHEAST MISSOURI/WEST-CENTRAL
ILLINOIS. HEAT INDICES ARE FORECAST TO EXCEED 100 DEGREES FOR AREAS
ALONG AND SOUTH OF I-80, AND INDEED THE 30.12Z HREF EXCEEDANCE
PROBABILITIES OF 100 DEGREES FOR HEAT INDICES ARE 60-90% OVER THESE
AREAS. THIS HAS PROMPTED THE ISSUANCE OF A HEAT ADVISORY FOR THESE
AREAS. THERE ARE SOME SIGNALS IN THE GLOBAL MODELS FOR A MID-LEVEL
SHORTWAVE TO SWEEP THROUGH THE AREA MONDAY AFTERNOON THAT COULD
SUPPORT ANOTHER ROUND OF SHOWERS AND STORMS, WHICH COULD TAMPER DOWN
THE HEAT FARTHER NORTH.
LONG TERM /MONDAY NIGHT THROUGH SUNDAY/
ISSUED AT 219 PM CDT SUN AUG 30 2026
MONDAY NIGHT THROUGH TUESDAY WILL NEED TO BE WATCHED FOR THE
POTENTIAL OF ISOLATED STRONG TO SEVERE STORMS OVER THE NORTHERN
PORTIONS OF OUR REGION AS ADDITIONAL SHORTWAVE IMPULSES RIDE THE TOP
OF THE HEAT DOME. THIS SEVERE STORMS RISK APPEARS TO BE CONDITIONAL,
AND THUS, CONFIDENCE IS LOW FOR STORMS TO BECOME SEVERE. HOWEVER,
GIVEN SUFFICIENT MUCAPE VALUES AROUND 2000-3000 J/KG, COMBINED WITH
25 TO 35 KNOTS OF 0-6 KM SHEAR, THE CONVECTIVE PARAMETER SPACE WOULD
BE SUPPORTIVE OF STRONG/SEVERE STORMS LATE MONDAY NIGHT AND AGAIN
TUESDAY AFTERNOON IF ANYTHING DEVELOPS. OVERALL, THE LARGE SCALE
FORCING FROM THESE SHORTWAVES REMAINS PRETTY WEAK, SO SPC CONTINUES
TO HAVE ONLY A MARGINAL RISK (LEVEL 1 OF 5) FOR SEVERE STORMS FOR
THESE TIME FRAMES. THE TUESDAY AFTERNOON STORM POTENTIAL WILL HAVE
THE POTENTIAL TO LIMIT DAYTIME HEATING, AND THUS, LIMITING THE HEAT
INDICES. STORMS WILL BE MOST LIKELY NORTH OF I-80 FOR EACH TIME
FRAME.
OUTSIDE OF THE STORM THREAT, WE WILL CONTINUE TO HAVE HOT AND HUMID
CONDITIONS OVER AT LEAST THE SOUTHERN PORTIONS OF THE AREA WHERE
STORM CHANCES ARE MUCH MORE LIMITED THROUGH MUCH OF THE WEEK.
CONFIDENCE IN THE HOT CONDITIONS TUESDAY THROUGH THURSDAY REMAIN
HIGH, GIVEN THE LATEST ECMWF EFI/SHIFT OF TAILS VALUES FOR HIGH
TEMPERATURES TUESDAY THROUGH THURSDAY ARE IN EXCESS OF 0.8 TO 0.9
(EVEN SOME VALUES OVER 0.95 IN ISOLATED SPOTS), ALONG WITH SHIFT OF
TAILS VALUES AROUND 1. THIS SUGGESTS HIGH CONFIDENCE IN ANOMALOUSLY
WARM HIGH TEMPERATURES, ALTHOUGH NOT EXTREME VALUES BASED ON THE
LOWER SHIFT OF TAILS. WITH THE POTENTIAL FOR THESE ANOMALOUSLY HOT
CONDITIONS TO LAST THIS WEEK, WE'VE DECIDED TO HAVE THE HEAT
ADVISORY GO THROUGH THE DAYLIGHT HOURS WEDNESDAY. IT'S ENTIRELY
POSSIBLE FOR THE ADVISORY TO BE EXTENDED INTO THURSDAY, GIVEN LREF
ENSEMBLE EXCEEDANCE PROBABILITIES OF 100 DEGREE HEAT INDICES
APPROACHING 50% ACROSS OUR SOUTHERN TWO TIERS OF COUNTIES.
ADDITIONALLY, OVERNIGHT LOWS MIGHT NOT DIP BELOW 75 DEGREES MONDAY
NIGHT THROUGH WEDNESDAY NIGHT, SO THIS WOULD COMPOUND THE HEAT
STRESS - EVEN AT NIGHT. THERE IS POTENTIAL FOR SOME RECORD WARM LOW
TEMPERATURES DURING THIS PERIOD. SEE THE CLIMATE SECTION BELOW FOR
THE CURRENT RECORDS.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 552 PM CDT SUN AUG 30 2026
SCATTERED SHOWERS AND ISOLATED STORMS TO PUSH EAST INTO NORTHERN
IL OVER THE NEXT HOUR. SOME LIGHT RETURNS MAY BRING SOME
SPRINKLES THROUGH 04Z AT DBQ, OTHERWISE VFR CONDITIONS WILL
PREVAIL. A STRENGTHENING LLJ LATE TONIGHT/EARLY MONDAY TO BRING
A RISK OF LLWS TO THE TERMINALS ONCE AGAIN UNTIL 14Z. SOME
SHOWERS MAY DEVELOP NEAR BRL AROUND SUNRISE AND HAVE INCLUDED
PROB30 WORDING FOR THIS OCCURRENCE.
ANOTHER WEAK SHORTWAVE TO ROUND THE TOP OF THE RIDGE MONDAY
AFTERNOON BRINGING SCATTERED SHOWERS AND ISOLATED STORMS TO
AREAS ACROSS NORTHERN AND NORTHEAST IA, SIMILAR TO WHAT OCCURRED
TODAY. SOME HI-RES ENSEMBLE GUIDANCE WOULD PLACE SOME OF THIS
ACTIVITY NEAR DBQ AND HAVE ADDED A PROB30 GROUP FOR THIS
POTENTIAL. WINDS TO REMAIN SOUTHERLY THROUGH THE PERIOD UNDER
15KTS.
CLIMATE
ISSUED AT 222 PM CDT SUN AUG 30 2026
RECORD WARM LOW TEMPERATURES:
AUGUST 30:
KMLI: 75/1947
AUGUST 31:
KDBQ: 74/2000
KMLI: 75/2000
SEPTEMBER 1:
KDBQ: 73/1937
KMLI: 75/1913
SEPTEMBER 2:
KDBQ: 74/2011
KMLI: 77/1913
SEPTEMBER 3:
KDBQ: 73/1939
KMLI: 76/1939
SEPTEMBER 4:
KDBQ: 71/1912
KMLI: 74/2018
DVN WATCHES/WARNINGS/ADVISORIES
IA...HEAT ADVISORY FROM 1 PM MONDAY TO 7 PM CDT WEDNESDAY FOR
IAZ063>065-067-068-076>078-087>089-098-099.
IL...HEAT ADVISORY FROM 1 PM MONDAY TO 7 PM CDT WEDNESDAY FOR
ILZ015-016-024>026-034-035.
MO...HEAT ADVISORY FROM 1 PM MONDAY TO 7 PM CDT WEDNESDAY FOR
MOZ009-010.
SHORT TERM...SCHULTZ
LONG TERM...SCHULTZ
AVIATION...GROSS
CLIMATE...GROSS
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