010
FXUS63 KLOT 210530
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1230 AM CDT THU AUG 21 2025
KEY MESSAGES
- CHOPPY WAVES AND DANGEROUS RIP CURRENTS WILL CONTINUE AT LAKE
MICHIGAN BEACHES THROUGH THURSDAY MORNING.
- PATCHY DENSE FOG MAY DEVELOP OVERNIGHT.
- OTHERWISE, LITTLE TO NO IMPACTFUL WEATHER IS EXPECTED THROUGH
THE UPCOMING WEEKEND AND EARLY NEXT WEEK. AN EARLY FALL
TEMPERATURE PREVIEW REMAINS IN STORE SUNDAY-TUESDAY.
DISCUSSION
ISSUED AT 240 PM CDT WED AUG 20 2025
THE EARLY PART OF THIS AFTERNOON SEES TEMPERATURES IN THE 70S
BENEATH MOSTLY CLOUDY CONDITIONS. DENSE CUMULUS COVERAGE
OVERHEAD IS GRADUALLY BEGINNING TO THIN OUT HERE AS DRIER LOW-
MID LEVEL AIR ADVECTS IN FROM THE NORTH. MOSTLY CLEAR SKIES ARE
FORECAST OVERNIGHT WHICH WILL ALLOW TEMPERATURES TO FALL INTO
THE LOWER AND MIDDLE 60S AND SET THE STAGE FOR SOME POTENTIAL
PATCHY FOG, PRIMARILY OUTSIDE OF COOK COUNTY. FOG COULD BE DENSE
IN SPOTS AND STRETCH INTO THE MORNING COMMUTE, SO AT LEAST
ISOLATED INSTANCES OF HAZARDOUS TRAVEL WILL BE POSSIBLE THROUGH
EARLY TOMORROW.
THE HIGH SWIM RISK CONTINUES AT ALL IL AND IN LAKE MICHIGAN
BEACHES FOR THE REST OF TODAY FOR HIGH WAVES AND DANGEROUS
CURRENTS. BUOYS ARE LARGELY REPORTING 3 TO 6 FOOT WAVES AROUND
OUR SHORELINE; THE MICHIGAN CITY BUOY WAS PREVIOUSLY REPORTING
WAVES TO 7 FEET THIS MORNING. SWIMMING CONDITIONS WILL REMAIN
HAZARDOUS THROUGH TOMORROW MORNING BEFORE EASING FOR THE
AFTERNOON AND EVENING.
UPPER HIGH PRESSURE IS BROADENING OVER THE SOUTHWEST CONUS
TODAY AND WILL REMAIN INTO THE END OF THE WEEK. BENEATH ITS
LEEWARD SIDE, BROAD SURFACE HIGH PRESSURE WILL OVERSPREAD THE
GREAT LAKES REGION. THIS WILL BRING QUIET WEATHER TO TOMORROW
AND FRIDAY WITH MOSTLY SUNNY SKIES AND SEASONABLE HIGHS IN THE
UPPER 70S AND LOWER 80S. ONSHORE WINDS SHOULD KEEP AREAS AROUND
THE LAKE STUCK IN THE LOWER 70S TOMORROW.
AN UPPER TROUGH WILL OVERCOME THE HIGH LATER THIS WEEK AND
SWING ITS BASE ACROSS THE NORTHERN PLAINS AND THEN INTO THE
UPPER MIDWEST ON SATURDAY. THE SURFACE RESPONSE WILL BE A COLD
FRONT APPROACHING THE AREA FROM THE NORTHWEST LATE FRIDAY AND
MOVING ACROSS THE CWA SOMETIME DURING THE DAY ON SATURDAY.
MEDIUM-RANGE GUIDANCE CONTINUES TO BE PESSIMISTIC WITH PRECIP
CHANCES AROUND THE FRONT. IT APPEARS THAT THE MUCH BETTER LAYER
MOISTURE WILL BE POOLED JUST AHEAD OF THE FRONT WHILE THE MORE
APPRECIABLE FORCING AND COOLER MID-LEVEL AIR (STEEPER LAPSE
RATES) WILL LAG BEHIND WITH PROFILES QUICKLY DRYING OUT
IMMEDIATELY BEHIND THE BOUNDARY. THERE IS ALSO UNCERTAINTY WITH
THE TIMING OF THE FRONTAL PASSAGE, WHICH LOOKS TO PLAY A BIG
ROLE. IN EARLIER SOLUTIONS LIKE THE EURO, THERE ISN'T MUCH
OPPORTUNITY TO DESTABILIZE AHEAD OF THE FRONT AND PRECIP
COVERAGE MAY BE TIGHTLY CONFINED TO THE BOUNDARY. BUT IF THE
FRONT CAN HOLD OFF UNTIL LATER IN THE AFTERNOON TO PUSH ACROSS,
BOUNDARY LAYER DESTABILIZATION SHOULD INTERACT WITH THE HIGHER
MOISTURE AHEAD OF THE FRONT AND PRESENT A BETTER OPPORTUNITY FOR
SCATTERED CONVECTION. THE NBM CONTINUES TO RESOLVE ONLY SLIGHT
CHANCE OR DRY POPS DURING THE DAYTIME, BUT JUST ABOUT EVERY
PIECE OF DETERMINISTIC GUIDANCE THAT LOOKS BEYOND SATURDAY
RESOLVES MEASURABLE QPF AROUND THE CWA BY THE END OF THE DAY,
AND A BIG MAJORITY OF ENSEMBLE MEMBERS FROM THE EPS AND GEFS
RESOLVE PRECIP AS WELL. SO WHILE COVERAGE AND INTENSITY REMAIN
RATHER UNCERTAIN, AT LEAST SOME PRECIP IS LOOKING LIKELY AROUND
MOST OF THE AREA ON SATURDAY. ACCORDINGLY, COORDINATED WITH
NEIGHBORING OFFICES TO BOOST POPS SLIGHTLY FROM THE NBMS
SOLUTION TO INCLUDE CHANCES FOR RAIN AND STORMS DURING THE DAY.
THE BASE OF THE UPPER TROUGH WILL DIP SOUTH INTO OUR GENERAL
REGION AND REMAIN THERE FOR A FEW DAYS NEXT WEEK. DEEP COLD
ADVECTION WILL RESULT AND BRING AN EARLY FALL-LIKE FEEL TO THE
EARLY PART OF NEXT WEEK. HIGHS SUNDAY THROUGH TUESDAY ARE
FORECAST IN THE UPPER 60S AND LOWER 70S WITH TEMPERATURES
LOOKING TO MODERATE CLOSER TO NORMAL TOWARD THE END OF THE WEEK.
DOOM
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1230 AM CDT THU AUG 21 2025
NO SIGNIFICANT CONCERNS THROUGH THE CURRENT TAF PERIOD.
ASIDE FROM A CHANCE RFD AND DPA OCCASIONALLY DIP TO MVFR VSBY
EARLY THIS MORNING AND PATCHY BRIEF MVFR CIGS NEAR THE LAKE,
PRIMARILY VFR CONDITIONS ARE EXPECTED. LIGHT NORTHERLY TO
CALM/VRB WINDS IN THE PRE-DAWN HOURS OF THIS MORNING WILL
INCREASE TO AROUND 10 KT FROM THE NORTHEAST AFTER SUNRISE THIS
MORNING AND THEN SPEEDS WILL DIMINISH AGAIN WITH SUNSET.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...BEACH HAZARDS STATEMENT UNTIL 10 AM CDT THIS MORNING FOR
ILZ006-ILZ103-ILZ104.
IN...BEACH HAZARDS STATEMENT UNTIL 10 AM CDT THIS MORNING FOR
INZ001-INZ002.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM CDT EARLY THIS MORNING FOR THE
IL AND IN NEARSHORE WATERS.
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