887
FXUS63 KLOT 040812
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
312 AM CDT SAT JUL 4 2026
KEY MESSAGES
- PERIODS OF SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH
SUNDAY. A FEW STORMS COULD BE STRONG TO SEVERE WITH A THREAT
FOR DAMAGING WINDS ESPECIALLY TODAY NEAR AND SOUTH OF I-80.
- LOCALLY HEAVY RAINFALL WILL ALSO ACCOMPANY ANY THUNDERSTORMS
AND MAY RESULT IN FLASH FLOODING ESPECIALLY IF STORMS DEVELOP
OVER AREAS THAT RECEIVED HEAVY RAIN THE PAST COUPLE DAYS.
- DRIER AND MORE SEASONABLE CONDITIONS EXPECTED TO START THE
WEEK BEFORE STORMIER WEATHER RETURNS LATE WEEK.
DISCUSSION
ISSUED AT 312 AM CDT SAT JUL 4 2026
A DECAYING LINE OF SHOWERS AND THUNDERSTORMS CONTINUES TO DRIFT
ACROSS NORTH-CENTRAL IL AND NORTHWEST IN EARLY THIS MORNING.
THESE SHOWERS/STORMS ARE EXPECTED TO CONTINUE TO WANE FROM NORTH
TO SOUTH BY DAYBREAK LEAVING THE AREA WITH DRY CONDITIONS TO
START THE DAY. HOWEVER, THERE IS A CLUSTER OF THUNDERSTORMS IN
CENTRAL IA THAT, IF IT HOLDS TOGETHER, WOULD MOVE INTO THE
WESTERN PORTIONS OF THE FORECAST AREA BY MID-MORNING. WHILE
LATEST FORECAST GUIDANCE CONTINUE TO SHOW THIS CLUSTER
WEAKENING AND DISSIPATING PRIOR TO ARRIVING, THE DECENT
ORGANIZATION NOTED ON RADAR AND THE FACT THAT INSTABILITY SHOULD
BE INCREASING AS THIS CLUSTER MOVES EAST SUPPORTS THE IDEA THAT
THE STORMS MAY SURVIVE INTO PORTIONS OF NORTHERN IL. DESPITE
THE LOWER CONFIDENCE ON THE STORM'S EVOLUTION, HAVE OPTED TO
INTRODUCE SOME 20-40% POPS FOR AREAS NEAR AND NORTH OF I-80
THROUGH THE MORNING TO TEASE THE POTENTIAL FOR THIS CLUSTER TO
MAKE IT INTO THE AREA. IF THE STORMS DO SURVIVE THE MAIN THREAT
WITH THEM WILL BE LIGHTNING STRIKES AND LOCALLY HEAVY DOWNPOURS,
BUT SOME LOCALLY GUSTY WINDS CANNOT BE RULED OUT EITHER.
REGARDLESS OF HOW THE MORNING STORMS PAN OUT, THE SHORTWAVE
TROUGH IN NE AND ITS ASSOCIATED CLUSTER OF STORMS IS EXPECTED TO
MOVE INTO NORTHERN IL AND EVENTUALLY NORTHWEST IN THIS
AFTERNOON AND LINGER THROUGH THE EARLY EVENING HOURS. GIVEN THE
MUCH BETTER ENVIRONMENT FORECAST FOR THIS AFTERNOON THIS SECOND
CLUSTER WILL HAVE NO PROBLEMS MAKING IT INTO THE AREA. THE ONLY
QUESTION WITH IT IS HOW COULD THE MORNING STORMS ALTER THE
ENVIRONMENT IN OUR NORTHERN CWA TO PERHAPS MAKE STORM COVERAGE
OR INTENSITY SLIGHTLY LOWER THERE. AT THIS TIME THE THINKING IS
THAT A LINE OF SCATTERED THUNDERSTORMS WILL MOVE ACROSS THE
ENTIRE AREA BETWEEN THE HOURS OF 1-8 PM (PLUS OR MINUS AN HOUR)
AND LAST ABOUT 2-3 HOURS AT ANY ONE LOCATION. WHILE WIND SHEAR
TODAY IS NOT AS GOOD AS YESTERDAY (ONLY AROUND 20- 25 KTS) THE
DECENT INSTABILITY AND FORCING FROM THE SHORTWAVE MAY SUPPORT A
FEW STRONG TO SEVERE STORMS CAPABLE OF PRODUCING DAMAGING WINDS
ESPECIALLY NEAR AND SOUTH OF I-80 WHERE SPC HAS THEIR LEVEL 1 OF
5 SEVERE RISK. IN ADDITION TO THE GUSTY WIND THREAT, THESE
STORMS WILL BE CAPABLE OF HEAVY DOWNPOURS THAT MAY RESULT IN
MORE FLASH FLOOD, PARTICULARLY IN AREAS THAT HAVE SEEN HEAVY
RAIN OVER THE PAST COUPLE OF DAYS.
ONCE THE LINE OF STORMS MOVES THROUGH THIS EVENING THERE IS A
DECENT SIGNAL FOR A PERIOD OF TRANQUIL WEATHER FOR THE LATER
PORTION OF THE EVENING. SHOULD THIS HOLD TRUE IT LOOKS AS IF WE
MAY GET A BREAK JUST IN TIME FOR JULY 4TH FIREWORKS. WITH THE
SHORTWAVE STILL EXPECTED TO BE PIVOTING OVERHEAD SOME ISOLATED
TO WIDELY SCATTERED SHOWERS/STORMS CANNOT BE RULED OUT AT TIMES
OVERNIGHT, BUT MOST AREAS SHOULD BE DRY. HOWEVER, THE
COMBINATION OF LIGHT WINDS AND AMPLE LOW-LEVEL MOISTURE DOES
LOOK TO SUPPORT A PERIOD OF PATCHY FOG TONIGHT INTO SUNDAY
MORNING. SINCE CONFIDENCE ON FOG COVERAGE AND LOCATION IS RATHER
LOW AND WILL BE DEPENDENT ON STORM TRENDS THIS AFTERNOON (WHERE
THE BEST MOISTURE RESIDES FROM THE RAIN) AND INLAND PROGRESS
FROM LAKE MICHIGAN, HAVE OPTED TO FOREGO A FORMAL FOG MENTION
IN THE FORECAST FOR NOW.
HEADING INTO SUNDAY, ANOTHER SHORTWAVE TROUGH IS PROGGED TO DIG
OUT OF THE NORTHERN PLAINS AND PHASE WITH THE AFOREMENTIONED
SHORTWAVE THAT IS EXPECTED TO STILL BE LINGERING OVER THE GREAT
LAKES. THE PHASING OF THESE TROUGHS SHOULD ALLOW UPPER-LEVEL
HEIGHTS TO DEEPEN AND GIVE WAY TO MORE SCATTERED SHOWERS AND
THUNDERSTORMS SUNDAY AFTERNOON. RECENT CAM GUIDANCE TRENDS HAVE
STARTED TO INDICATE THAT THE DEEPENING TROUGH OVERHEAD SHOULD
ALLOW A WEAK SURFACE LOW TO DEVELOP IN CENTRAL IL AND TRAVERSE
TOWARDS CENTRAL IN SUNDAY AFTERNOON. IF THIS DOES OCCUR THEN IT
SEEMS THAT THE BETTER INSTABILITY SHOULD STAY MORE INTO THE
SOUTHERN PORTIONS OF OUR AREA (IF NOT FULLY SOUTH OF US) AND
THEREFORE LIMIT SHOWER/STORM COVERAGE WITH NORTHWARD EXTENT.
THOUGH, IF THE LOW DEVELOPS FURTHER NORTH THEN MORE OF THE AREA
COULD SEE SHOWERS AND STORMS ONCE AGAIN. FOR NOW HAVE OPTED TO
KEEP SOME 30-50% POPS AREAWIDE (HIGHEST VALUES SOUTH OF I-80)
FOR THIS POTENTIAL BUT SUSPECT THESE WILL BE ABLE TO GET REFINED
IN FUTURE FORECASTS. OUTSIDE OF THE RAIN CHANCES, TEMPERATURES
ON SUNDAY WILL BE A TAD COOLER (HIGHS IN THE LOWER TO MID-80S)
DUE TO EAST-NORTHEAST WINDS. IN FACT HIGHS NEAR THE LAKE ON
SUNDAY MAY STRUGGLE TO GET OUT OF THE 70S.
BY MONDAY THE UPPER TROUGH WILL BE EJECTING EASTWARD AND TAKING
WITH IT THE CHANCES FOR SHOWERS AND THUNDERSTORMS AS A SURFACE
HIGH SETTLES INTO THE WESTERN GREAT LAKES. IT SHOULD BE NOTED
THAT OUR OFFICIAL FORECAST DOES HAVE SOME 20-30% POPS IN OUR FAR
SOUTHERN CWA MONDAY AFTERNOON WHERE SOME SLOWER GUIDANCE HAS A
STRAY SHOWER/STORMS TRYING TO DEVELOP, BUT THE OVERALL
ENVIRONMENT LOCALLY SHOULD SUPPORT DRY CONDITIONS AREAWIDE SO
SUSPECT THESE POPS WILL GET REMOVED IN FUTURE UPDATES.
NEVERTHELESS, TEMPERATURES ON MONDAY WILL BE ON THE SEASONABLE
SIDE WITH HIGHS ONCE AGAIN IN THE LOWER TO MID-80S INLAND WITH
70S EXPECTED NEAR THE LAKE DUE TO ONSHORE WINDS. TUESDAY WILL
FEATURE SIMILARLY DRY CONDITIONS, BUT WITH SLIGHTLY WARMER
CONDITIONS (HIGHS IN THE MID TO UPPER 80S) AS WINDS TURN BACK
SOUTHERLY.
UNFORTUNATELY THE TRANQUIL WEATHER IS NOT FORECAST TO LAST LONG
AS GUIDANCE CONTINUES TO SHOW THE RETURN OF WEST-SOUTHWEST FLOW
ALOFT FOR THE MIDDLE AND LATTER HALF OF NEXT WEEK. WHILE
TEMPERATURES LOOK TO REMAIN SEASONABLE, HUMIDITY WILL BE ON THE
INCREASE WHICH WILL ALSO BRING THE RETURN OF SHOWER AND
THUNDERSTORM CHANCES.
YACK
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 105 AM CDT SAT JUL 4 2026
KEY AVIATION MESSAGES:
- A PERIOD OF SHRA/TSRA POSSIBLE IN THE AM, MAINLY TOWARD RFD
(30% CHANCE)
- GREATER COVERAGE OF STORMS FAVORED DURING THE AFTERNOON AT ALL
SITES (18-01Z TIMEFRAME MOVING FROM WEST TO EAST).
- LOW CONFIDENCE IN WIND DIRECTION TRENDS THROUGH THE AFTERNOON
- POTENTIAL FOR FOG/LOW STRATUS OFF THE LAKE LATE TONIGHT INTO
EARLY SUNDAY AM
STORMS CONTINUE TO WEAKEN AND SHIFT SOUTHEAST OF THE TERMINALS
WITH LINGERING RAIN ENDING OVER THE NEXT 30-60 MINUTES.
ATTENTION TURNS TO CONVECTION CURRENTLY OVER CENTRAL IOWA THAT
WILL BE MOVING EAST TOWARD THE AREA OVERNIGHT THROUGH DAYBREAK.
CONFIDENCE IN CONVECTIVE TRENDS REMAINS LOW YET AGAIN WITH THE
MAJORITY OF GUIDANCE WEAKENING THESE STORMS WITH EASTWARD
EXTENT. WHILE IT WILL BE ENCOUNTERING A LESS FAVORABLE
ENVIRONMENT, DO HAVE CONCERNS THAT IT WILL AT LEAST HOLD
TOGETHER INTO PART OF NW IL. HAVE ACCORDINGLY INTRODUCED
PROB30S FOR TSRA AT RFD FROM 13-15Z TO ACCOUNT FOR THIS.
CONFIDENCE REMAINS TOO LOW FOR A FORMAL INTRODUCTION AT THE
CHICAGO TERMINALS OF AN EARLIER ROUND OF STORMS.
A REMNANT MCV FEATURE EXPECTED TO DRIFT EAST NORTHEAST TOWARD
THE REGION ASSOCIATED WITH A SEPARATE AREA OF CONVECTION OVER
EASTERN NEBRASKA MAY SERVE AS THE FOCUS FOR RENEWED TSRA
DEVELOPMENT ACROSS THE AREA THIS AFTERNOON. HAVE CONVERTED THE
INHERITED PROB30 GROUPS TO TEMPOS WITH THIS UPDATE. THE STRENGTH
OF THE STORMS REMAINS LOWER CONFIDENCE OWING TO A LAKE BREEZE
EXPECTED TO PUSH INLAND EARLY IN THE AFTERNOON WHICH MAY HELP
FOCUS THE THREAT FOR SEVERE WEATHER MAINLY SOUTH OF THE
TERMINALS.
WIND DIRECTIONS ARE EXPECTED TO REMAIN HIGHLY VARIABLE THROUGH
MIDDAY BEFORE A LAKE BREEZE MOVES INLAND IN THE AFTERNOON
TURNING WINDS MORE SOLIDLY NORTHEAST. ANY CONVECTION THAT
DEVELOPS WILL ALSO LEAD TO VARIED WIND DIRECTIONS AT TIMES
DURING THE AFTERNOON INTO EARLY EVENING BEFORE SETTLING BACK
INTO A NORTHEAST DIRECTION THROUGH EARLY SUNDAY MORNING.
LASTLY THERE IS A SIGNAL FOR FOG (POTENTIALLY DENSE) AND/OR LOW
STRATUS (LIFR/VLIFR) OVER LAKE MICHIGAN THAT MAY TRY TO OOZE
INLAND LATE THIS EVENING THROUGH EARLY SUNDAY MORNING.
CONFIDENCE IS TOO LOW TO INCLUDE WITH THIS UPDATE BUT WILL BE
MONITORED CLOSELY GIVEN IT MAY HAVE SOME DEPENDENCE IN HOW
CONVECTIVE TRENDS ALSO EVOLVE LATER TODAY.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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