448
FXUS63 KDVN 170807
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
307 AM CDT WED SEP 17 2025
KEY MESSAGES
- BESIDES THE CHANCE FOR AN ISOLATED SHOWER OR STORM IN THE LATE AFTERNOON
AND EVENING IN THE FAR WESTERN DVN CWA, MAINLY DRY AND ABOVE
NORMAL WARMTH TO CONTINUE THROUGH AT LEAST THURSDAY.
- BETTER INCOMING RAIN CHANCES CONTINUE TO SLOW UP IN A BLOCKED
PATTERN AND NOW MAY BE MORE LATER FRIDAY INTO SATURDAY.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 305 AM CDT WED SEP 17 2025
TODAY...MORE OF THE SAME AS THE PAST FEW DAYS AS THE AREA REMAINS
UNDER AN UPPER LEVEL RIDGE LOBE IN ONGOING BLOCKED PATTERN ACRS THE
CONUS. WILL AGAIN HAVE TO PUT LOW CHC POPS IN THE FAR WEST CENTRAL
AND NORTHWESTERN CWA THIS AFTERNOON AND INTO MID EVENING WITH THE
WESTERN HALF OF IA UNDER THE INFLUENCE OF DIFFLUENT CYCLONIC FLOW
ALOFT OFF PERSISTENT PLAINS UPPER TROF COMPLEX. AGAIN ANOTHER DAY
OF HIGH WEST-TO-EAST GRADIENT OF SEVERAL PARAMETERS, AND CENTRAL IA
IN A LOW SHEAR-HIGH CAPE SCENARIO. IF A FEW STORMS ARE ABLE TO MAKE
THEIR WAY INTO OUR WEST, SLOW MOVEMENT WITH 1.2 TO 1.4 PWAT'S WOULD
MEAN LOCALLY HEAVY RAINFALL. ALSO SOME PRECIP LOADED DOWN DRAFTS
FROM A CELL COULD MEAN UP TO 50 MPH RADIAL OUTFLOW AT THE SFC. AND
THE STORMS WOULD BE PROFICIENT LIGHTNING/CG PRODUCERS IN THESE
CONDITIONS. BUT AGAIN, A MINIMAL PART OF THE AREA TO HAVE A CHANCE
TO EXPERIENCE ANY OF THIS ACTIVITY AND MOST AREAS WILL HAVE ANOTHER
VERY WARM AND DRY DAY WITH LIGHT SFC WINDS. MOST AREAS TO HAVE HIGHS
IN THE UPPER 80S WITH A FEW SPOTS REACHING THE LOW 90S, AND SFC DPTS
CONTINUE TO RANGE LOWER TO THE EAST AND HIGHER AS YOU TREK WEST.
TONIGHT...ISOLATED TO WDLY SCTRD SHOWERS AND STORMS CONTINUE TO BE
POSSIBLE WEST OF THE MS RVR, BUT MORE AREAS REMAINING DRY THAN THOSE
THAT MAY GET A DROP. LOW TEMP GRADIENT FROM THE UPPER 50S IN THE
EAST, TO THE LOWER 60S IN THE WEST.
LONG TERM /THURSDAY THROUGH TUESDAY/
ISSUED AT 305 AM CDT WED SEP 17 2025
THURSDAY...LATEST RUN MEAN PATTERN ENSEMBLES CONTINUE TO SLOW THE
ARRIVAL OF THE UPSTREAM PLAINS UPPER TROF. THIS IDEA WITH CONTINUED
LOWER LEVEL DRY EASTERLY FETCH BACK INTO THE LOCAL AREA MAY KEEP
MUCH OF THE LOCAL FCST AREA DRY THIS DAY, WITH PRECIP CHANCES THEN
INCREASING FROM THE WEST AND SOUTHWEST BY LATE AFTERNOON AND INTO
THU NIGHT. BUT THE TREND WILL LOOK TO CONTINUE OF MOST OF THE PRECIP
HOLDING OFF TO THE WEST OF THE MS RVR INTO FRIDAY. VERTICAL THERMAL
PROFILES INCH UP SOME AN LACK OF RAIN OR DEBRIS CLOUDS MAY ALLOW FOR
A WARMER DAY WITH MORE AREAS PUSHING OR SURPASSING THE 90 DEGREE
MARK. OR JUST COULD SAY UPPER 80S TO LOW 90S, COOLER IN THE
NORTHWEST ACRS PORTIONS OF NORTHEAST IA.
FRIDAY ON...IT'S THIS PERIOD WHERE WE'LL HAVE THE BEST DYNAMIC
SUPPORT FOR SYNOPTIC SCALE LIFT IN OUR AREA AS THE UPPER TROF
FINALLY MAKES SOME HEADWAY EAST, AND THUS OUR BEST RAIN CHANCES
LATER FRIDAY AND SATURDAY. AT THE SURFACE WE CONTINUE TO HAVE A WARM
AND MODERATELY MOIST AIR MASS IN PLACE, SO THE ARRIVAL OF THE COOL
CORE TROUGH ALOFT WILL GENERATE INSTABILITY FOR THE PRODUCTION OF
SHOWERS AND THUNDERSTORMS, POSSIBLY IN MULTIPLE ROUNDS. WHILE THE
OVERALL SEVERE WEATHER THREAT LOOKS LOW AT THIS POINT, IT IS WORTH
NOTING THAT THE TROUGH'S PRESENCE ALOFT WILL GIVE US ACCESS TO
GREATER WIND SHEAR THAN WE'VE SEEN IN A WHILE, AND THERE SHOULD BE
AT LEAST SOME INSTABILITY AROUND AS WELL. SO CAN'T RULE OUT A PERIOD
OF MORE ORGANIZED THUNDERSTORMS AT SOME POINT, BUT THE LACK OF A CAP
WILL LIKELY PREVENT MORE EXTREME INSTABILITY FROM BUILDING UP. WE'LL
ALSO SEE COOLER DAYTIME TEMPERATURES, MAINLY IN THE 70S AND 80S, AS
CLOUDS AND COOLER AIR ALOFT KEEP US FROM GETTING AS HOT. BUT WE
DON'T GET A THOROUGH CHANGE IN AIR MASS, THOUGH, AS THE LOW LEVEL
MOISTURE LINGERS. DEWPOINTS PERSISTING IN THE 60S WILL BUOY
NIGHTTIME TEMPERATURES ENSURING WE STAY ABOVE NORMAL EVEN ON OUR
COOLER DAYS.
THE TROF SLOWLY MIGRATES EAST OVER THE COURSE OF SEVERAL DAYS, WITH
MULTIPLE EMBEDDED WAVES MOVING THROUGH OUR AREA OVER THE WEEKEND.
MODEL GUIDANCE IS CONSIDERABLY MORE VARIABLE ON EACH SUBSEQUENT WAVE
AFTER THE FIRST ONE, SO THERE'S LESS CONFIDENCE IN TIMING AND
LOCATIONS IMPACTED WITH RAIN FROM EACH OF THEM. HOWEVER, THERE IS
CONFIDENCE OVERALL THAT PERIODS OF SHOWERS AND THUNDERSTORMS WILL
EVENTUALLY AFFECT JUST ABOUT EVERYONE. AMONG THE 00Z GUIDANCE,
NEARLY 100 PERCENT OF MEMBERS PRODUCE MEASURABLE RAIN ACROSS THE
ENTIRE FORECAST AREA IN THE 48 HOURS ENDING SUNDAY NIGHT. SO
CONFIDENCE IS HIGH THAT IT WILL RAIN THIS WEEKEND, EVEN IF THE POP
EACH PERIOD IS CONSIDERABLY LOWER DUE TO THE UNCERTAINTY ON TIMING
OF EACH OF THOSE EMBEDDED WAVES. THIS IS WHY WE FEEL THE MESSAGE
THROUGH THE WEEKEND IS ABOUT PERIODS OF SHOWERS AND THUNDERSTORMS,
SOMETHING WE HAVEN'T SEEN THAT MUCH OF IN RECENT WEEKS.
WHILE GUIDANCE CONTINUES TO DIVERGE SOMEWHAT ON THE HANDLING OF THIS
WEEKEND'S UPPER TROF, EVEN MORE VARIANCE IS NOTED FOR NEXT WEEK.
WHILE ALL GUIDANCE DOES MOVE THE TROF OUT OF OUR AREA BY MONDAY
EVENING, THE 00Z ECMWF CONTINUES ITS TREND OF DIGGING ANOTHER UPPER
TROF SOUTHWARD THROUGH THE PLAINS, CUTTING OFF AND SETTLING ACRS THE
SOUTHEASTERN PLAINS FOR MIDWEEK. THIS KEEPS NORTHEASTERLY SFC WINDS,
COOLER TEMPERATURES AND SOME RAIN CHANCES AROUND EVEN IN OUR AREA.
OTHER GUIDANCE, NOTABLY THE GFS AND CMC, TRACK THIS WAVE MORE
CLEARLY TO THE EAST, LEAVING SOME DEGREE OF RIDGING IN ITS WAKE WITH
THE POTENTIAL FOR A RETURN TO HOT TEMPERATURES. THE SPREAD IN THE
PROBABILISTIC NBM ALSO REFLECTS THIS GREATER UNCERTAINTY, WITH THE
IQR FOR HIGH TEMPS RISING TO 7 TO 10 DEGREES OR MORE THIS WEEKEND
AND THRU NEXT WEEK. SO WHILE THE DETERMINISTIC FORECAST DOES SHOW A
RATHER CONSISTENT FORECAST OF HIGHS IN THE LOW 80S, THERE'S MORE TO
THAT STORY. IF RIDGING TAKES HOLD WE'LL START TO WARM UP AGAIN, TO
THE UPPER 80S OR EVEN 90 AGAIN. IF THE ECMWF SOLUTION TROF COMES
MORE INTO PLAY THEN WE'LL BE COOLER, IN THE 70S, WITH BETTER RAIN
CHANCES.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1238 AM CDT WED SEP 17 2025
WILL KEEP THE SIMPLE ONGOING VFR TAF CYCLE GOING ON MORE DAY.
LIGHT EAST TO SOUTHEAST SFC WINDS AND PASSING HIGHER LEVEL
CLOUDS THROUGH WED EVENING. AGAIN JUST A LOW CHANCE FOR SOME
MVFR FOG AT A FEW OF THE TAF SITES BEFORE DAWN, AND WILL BANK ON
THE SCTRD AFTERNOON THUNDERSTORMS POPPING UP STAYING WEST OF ALL
THE TAF SITES. CID WILL HAVE THE BEST CHANCE FOR A ROGUE SHOWER
OR STORM GETTING INTO THE VCNTY BY LATE AFTERNOON, BUT WILL NOT
MENTION IT AT THIS TIME.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...12
LONG TERM...12/KIMBLE
AVIATION...12
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