715
FXUS63 KLOT 130833
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
333 AM CDT SAT SEP 13 2025
KEY MESSAGES
- SHOWERS AND STORMS ARE EXPECTED TO MOVE ACROSS THE AREA
THIS MORNING AND LINGER INTO EARLY AFTERNOON.
- THERE IS A LOW CHANCE (5% OR SO) OF FLASH FLOODING OR
SEVERE WEATHER AT ANY GIVEN LOCATION, MAINLY THIS MORNING.
- GENERALLY WARM AND DRY CONDITIONS ARE EXPECTED EARLY-TO-MID
NEXT WEEK.
- TURNING MORE SEASONABLE TOWARD THE END OF THE WEEK WITH
PERIODIC SHOWER AND STORM CHANCES RETURNING (20-40%).
DISCUSSION
ISSUED AT 333 AM CDT SAT SEP 13 2025
THROUGH SUNDAY:
A SHORTWAVE TROUGH IS PIVOTING ACROSS SOUTH-CENTRAL WI AS OF
230 AM WITH A WEAK SURFACE LOW NOTED NEAR GREEN BAY. ASSOCIATED
WITH THESE FEATURES IS A BROAD AREA OF SHOWERS AND A DEVELOPING
AXIS OF THUNDERSTORMS NEAR THE WISCONSIN DELLS. THE SHORTWAVE
WILL CONTINUE TO PIVOT ACROSS WI AND INTO NORTHERN IL THIS
MORNING AS A WARM FRONT NEAR THE MISSISSIPPI RIVER LIFTS INTO
THE AREA WHICH WILL ALLOW THE ATMOSPHERE TO MOISTEN AND
DESTABILIZE. THEREFORE, THE AREA OF SHOWERS AND THUNDERSTORMS IS
EXPECTED TO REMAIN INTACT AS THEY MOVE THROUGH NORTHERN IL AND
EVENTUALLY NORTHWEST IN BETWEEN 5 AM AND MIDDAY (EARLIEST NEAR
THE IL-WI LINE, LATEST NW IN). GIVEN THAT THE SHOWERS AND STORMS
WILL BE MOVING PARALLEL TO THE AFOREMENTIONED WARM FRONT,
CONDITIONS REMAIN FAVORABLE FOR TRAINING CONVECTION TO ESTABLISH
ACROSS THE AREA PARTICULARLY EAST OF A BELVIDERE TO VALPARAISO
LINE. WITH PWATS EXPECTED TO PEAK AROUND 1.5-1.7 INCHES, THESE
SHOWERS AND STORMS WILL BE EFFICIENT RAINFALL PRODUCERS (RAIN
RATES ON THE ORDER OF 1-2 IN/HR) WHICH COULD LEAD TO LOCALIZED
INSTANCES OF FLOODING ESPECIALLY IN URBAN AREAS. FURTHERMORE,
THERE IS ALSO 25-30 KTS OF EFFECTIVE SHEAR ASSOCIATED WITH THESE
SHOWERS AND STORMS WHICH COULD SUPPORT A STRONGER STORM OR TWO
AS INSTABILITY TRIES TO BUILD AFTER DAYBREAK. IF A STRONGER
STORM DOES MATERIALIZE THE MAIN THREAT WILL BE LOCALLY GUSTY
WINDS AND HAIL.
HEADING INTO THIS AFTERNOON, THE SHORTWAVE IS EXPECTED TO BE
PIVOTING INTO EASTERN IN AND WESTERN OH WHICH SHOULD ALLOW THE
COVERAGE OF SHOWERS AND THUNDERSTORMS TO DIMINISH AS FORCING
WANES. HOWEVER, THE WARM FRONT IS STILL EXPECTED TO BE LIFTING
ACROSS NORTHEAST IL AND NORTHWEST IN WHICH MAY ALLOW SCATTERED
SHOWERS AND STORMS TO LINGER THROUGH EARLY TO MID-AFTERNOON IF
SUFFICIENT INSTABILITY REMAINS IN PLACE. FORECAST SOUNDINGS THIS
AFTERNOON DON'T LOOK OVERLY IMPRESSIVE FROM AN INSTABILITY
STANDPOINT SO CONFIDENCE ON THE COVERAGE OF SHOWERS AND STORMS
REMAINS LOW (SAY A 20-30% CHANCE AT THIS TIME). THAT SAID, ANY
SHOWER/STORMS THAT DO DEVELOP WILL STILL BE CAPABLE OF HEAVY
RAINFALL AND POSSIBLY GUSTY WINDS AND/OR HAIL GIVEN THE HUMID
AIRMASS AND 35 KTS OF SHEAR PRESENT. DESPITE THE RAIN,
TEMPERATURES ARE STILL EXPECTED TO BE ON THE SEASONABLY WARM
SIDE TODAY WITH HIGHS IN THE LOW TO MID-80S INLAND AND MID TO
UPPER 70S NEAR THE LAKE.
SHOWERS AND STORMS WILL FINALLY BEGIN TO TAPER BY THIS EVENING
AS THE FRONT PUSHES EAST AND MID-LEVEL RIDGING BEGINS TO BUILD
INTO THE AREA. WITH SKIES EXPECTED TO CLEAR OUT THROUGH THE
NIGHT AND THE LINGERING HUMIDITY FROM TODAY'S RAIN, CONDITIONS
WILL BECOME FAVORABLE FOR FOG TO DEVELOP AREAWIDE OVERNIGHT.
WHILE INTENSITY OF FOG REMAINS UNCERTAIN, POCKETS OF DENSE FOG
CANNOT BE RULED OUT ESPECIALLY LATE TONIGHT INTO EARLY SUNDAY
MORNING. ANY FOG THAT DOES DEVELOP TONIGHT WILL ERODE BY MID-
MORNING ON SUNDAY LEAVING US WITH ANOTHER MOSTLY SUNNY AND
SEASONABLY WARM AFTERNOON. THAT SAID, PERSISTENT EASTERLY WINDS
ON SUNDAY WILL KEEP HIGH TEMPERATURES IN THE MID-70S TO LOWER
80S NEAR THE LAKE WITH MID-80S FORECAST INLAND DESPITE THE
CONTINUED WARM ADVECTION. THOUGH, LOCALIZED UPPER 80 TO NEAR 90
DEGREE READINGS MAY BE SEEN NEAR AND WEST OF I-39 CLOSER TO THE
RIDGE AXIS.
YACK
SUNDAY NIGHT THROUGH FRIDAY:
THE UPPER LEVEL PATTERN NEXT WEEK WILL FEATURE HIGH AMPLITUDE
RIDGING ACROSS THE GREAT LAKES PAIRED WITH A CLOSED UPPER LOW
IN THE SOUTHEAST SETTING UP A PSEUDO-REX BLOCK PATTERN ACROSS
THE EASTERN CONUS. THIS SHOULD KEEP THE VARIOUS WESTERN CONUS
SHORTWAVE TROUGHS AND ASSOCIATED SHOWERS AND STORMS MAINLY WEST
OF THE REGION THROUGH THE FIRST HALF OF THE UPCOMING WEEK. LONG-
RANGE GUIDANCE CONTINUES TO DIVERGE SLIGHTLY ON THE POSITION AND
STRENGTH OF THE UPPER LOW WHICH HAS SOME IMPLICATIONS FOR THE
DEGREE OF WARMING EACH DAY AND ONSET OF MORE UNSETTLED WEATHER
LATER IN THE WEEK. THE GEFS HAS THIS FEATURE CLOSER TO THE COAST
ALLOWING MUCH WARMER AIR TO LIFT INTO THE REGION PAIRED WITH AN
EARLIER BREAKDOWN OF THE RIDGE BY MIDWEEK AND RETURN TO SHOWER
CHANCES. MEANWHILE, THE EPS MAINTAINS A FURTHER WEST POSITION
OF THE UPPER LOW (CLOSER TO THE MORE CLASSIC REX BLOCK PATTERN)
WHICH SLOWS THE BREAKDOWN OF THE RIDGE AND ARRIVAL OF
PRECIPITATION CHANCES TO LATER IN THE WEEK. THIS STILL FAVORS
WARMER (ALBEIT COOLER THAN THE GEFS) AND DRY CONDITIONS
PREVAILING IN THE LOCAL AREA FOR THE MAJORITY OF THE WORKWEEK.
WITH ALL OF THAT SAID, THERE ARE NO MAJOR CHANGES IN
EXPECTATIONS THROUGH THE UPCOMING WORK WEEK WITH THE GOING
FORECAST FAVORING THE EPS SOLUTIONS WITH DRY AND GENERALLY WARM
CONDITIONS EXPECTED WELL INLAND OF LAKE MICHIGAN THROUGH
MIDWEEK. EXPECT HIGHS IN THE 80S TO POTENTIALLY NEAR 90 TOWARD
WESTERN AND CENTRAL ILLINOIS. LIGHT SURFACE FLOW WILL ALLOW
DAILY LAKE BREEZES TO SURGE WELL INLAND EACH AFTERNOON WHICH
SHOULD HOLD HIGHS IN THE 70S ALONG THE LAKESHORE WITH FALLING
TEMPERATURES IN THE AFTERNOON EXPECTED FOR INLAND AREAS IN ITS
WAKE.
THE UPPER RIDGE/BLOCKING PATTERN BEGINS TO BREAKS DOWN TOWARD
THE END OF THE WEEK WITH THE WESTERN TROUGH AXIS GRADUALLY
SHIFTING TOWARD AND OVER THE AREA INTO NEXT WEEKEND. THIS WILL
LEAD TO INCREASING SHOWER AND THUNDERSTORM CHANCES THURSDAY
NIGHT ONWARD; HOWEVER, THERE IS NOT A STRONG SIGNAL FOR MORE
ORGANIZED CONVECTION OR HEAVY RAIN AT THIS TIME. IN TANDEM,
TEMPERATURES WILL TREND COOLER AND MORE AUTUMN-ESQUE WITH HIGHS
IN THE 70S AND LOWS IN THE 50S.
PETR
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1250 AM CDT SAT SEP 13 2025
- A PERIOD OF SHRA/TSRA EXPECTED THIS MORNING
SHOWERS AND THUNDERSTORMS HAVE REDEVELOPED ACROSS PORTIONS OF
WEST CENTRAL WISCONSIN AND CONTINUE TO BACK BUILD ALONG A
NORTHWEST TO SOUTHEAST ORIENTED AXIS. THIS ACTIVITY IS EXPECTED
TO GRADUALLY EXPAND AND SHIFT SOUTHEASTWARD EARLY THIS MORNING,
EVENTUALLY BRINGING A PERIOD OF SHOWERS AND THUNDERSTORMS TO THE
TERMINALS THROUGH THE MORNING HOURS.
CURRENT SHOWERS/STORMS ARE NOT MAKING A LOT OF FORWARD PROGRESS
JUST YET SO IT IS STILL DIFFICULT TO TRACK WHEN THEY MAY REACH
THE LOCAL AREA. AS A RESULT, OPTED TO NOT MAKE TOO MANY CHANGES
TO THE INHERITED TAFS (WHICH WERE BASED ON MODEL DATA AND
TIMING OF LARGER SCALE FEATURES) AND WILL PLAN TO HANDLE
ADDITIONAL UPDATES TACTICALLY. IN ADDITION TO LIGHTNING AND
GUSTY WINDS, HEAVY RAIN WILL LEAD TO VSBY REDUCTIONS TO LOW-END
IFR TO POTENTIALLY LIFR UNDER ANY OF THE STRONGER STORMS. IN THE
WAKE OF THE MORNING STORMS THERE REMAINS A 20% CHANCE FOR
ISOLATED THUNDERSTORMS TO LINGER LATER INTO THE AFTERNOON, STILL
TOO LOW FOR A FORMAL TAF MENTION FOR NOW.
WINDS OVERNIGHT WILL BE GENERALLY LIGHT OUT OF THE SOUTHEAST
BETWEEN 5-10 KT. CONFIDENCE IN DIRECTIONS THROUGH THE DAYTIME
HOURS REMAINS LOW DUE TO POTENTIAL INFLUENCE FROM THE MORNING
CONVECTION AND POSITION OF ANY REMNANT OUTFLOW BOUNDARIES. THERE
IS THE POSSIBILITY THAT WINDS RETURN TO A SSW DIRECTION BRIEFLY
DURING THE AFTERNOON BEFORE RETURNING TO A SOUTHEAST DIRECTION
TOWARD SUNSET. WINDS THEN TURN LIGHT AND VARIABLE AFTER SUNSET
THROUGH EARLY SUNDAY MORNING.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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