409
FXUS63 KLOT 311723
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1223 PM CDT SAT MAY 31 2025
KEY MESSAGES
- WILDFIRE SMOKE FROM CANADIAN FIRES WILL CONTINUE TO FILTER
OVER THE AREA THROUGH THE WEEKEND. MOST OF THIS SMOKE SHOULD
REMAIN ALOFT AND RESULT IN HAZY SKIES.
- ABOVE AVERAGE TEMPERATURES EXPECTED EARLY NEXT WEEK, WITH
WARMTH RIGHT UP TO THE LAKEFRONT.
- POTENTIALLY WETTER PATTERN SETTING UP MIDWEEK WITH ONE OR MORE
ROUNDS OF SHOWERS/STORMS POSSIBLE TUES NIGHT THROUGH THURSDAY.
DISCUSSION
ISSUED AT 314 AM CDT SAT MAY 31 2025
THROUGH SUNDAY:
A BACKDOOR COLD FRONT THAT SURGED ACROSS THE AREA LAST EVENING
WILL RESULT IN A SEASONABLY COOL AND DRY DAY TO THE AREA. AN
AXIS OF LOW TO MID-LEVEL CLOUDS ALONG THE STALLING FRONT MAY
PRODUCE ISOLATED SHOWERS SOUTHWEST OF THE CWA THIS AFTERNOON,
WITH PERHAPS A PERIOD OF MOSTLY CLOUDY SKIES ON THE SOUTHWEST
PERIPHERY OF THE CWA. MEANWHILE, NORTH WINDS 10-15 MPH THROUGH
THE DAY TODAY WILL GENERATE MODERATE SWIM RISK CONDITIONS WITH
WAVES IN EXCESS OF 3 FEET AND POTENTIALLY UP TO 4 FEET ALONG THE
PORTER COUNTY SHORE.
NNW FLOW ALOFT CONTINUES TO TAKE HOLD ON THE WESTERN FLANK OF A
PERSISTENT LONGWAVE TROUGH, SO WILDFIRE SMOKE ORIGINATING FROM
THE CANADIAN PRAIRIE PROVINCES WILL REMAIN A FOCUS ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA THIS WEEKEND. SMOKE
GUIDANCE FAVORS LOWER CONCENTRATIONS ALOFT WITH LITTLE SURFACE
RESPONSE TODAY, BUT AN IMPRESSIVE UPTICK IN FIRE ACTIVITY AND
ASSOCIATED INCREASE IN SMOKE WITH A FIRE COMPLEX NORTHEAST OF
WINNIPEG ON FRIDAY SHOULD FOLLOW TRAJECTORIES ALONG THE
MISSISSIPPI RIVER AND POSSIBLY NORTHERN ILLINOIS LATER TODAY.
WILL NEED TO KEEP EN EYE ON UPSTREAM SURFACE OBS, BUT HAVE YET
TO SEE ANY VISIBILITY RESTRICTIONS EARLY THIS MORNING. THAT
SAID, NUDGED SKY COVER UP AND TEMPS DOWN TO ACCOUNT FOR
POTENTIALLY HIGHER SMOKE CONCENTRATIONS ALOFT.
MOSTLY CLEAR SKIES AND LOW DEW POINTS TONIGHT AMID LIGHT WINDS
WITH A PASSING RIDGE WILL ALLOW TEMPS TO FALL INTO THE MID 40S
OUTSIDE OF THE CORE OF THE CHICAGO URBAN HEAT ISLAND.
EXPECT TEMPS TO MODERATE INTO THE MID 70S AWAY FROM THE LAKE ON
SUNDAY UNDER MOSTLY SUNNY SKIES. IN THE EVENT THAT WILDFIRE
SMOKE ALOFT REMAINS MORE PREVALENT THROUGH THE DAY, TEMPS MAY
NEED TO BE TEMPERED DOWNWARD A FEW DEGREES.
SUNDAY NIGHT THROUGH FRIDAY:
MID AND UPPER LEVEL RIDGE IS PROGGED TO BUILD EASTWARD ACROSS
THE MISSISSIPPI VALLEY AND GREAT LAKES REGION MONDAY INTO
TUESDAY. SOUTHERLY WINDS AND WARM AIR ADVECTION SHOULD SET THE
STAGE FOR A COUPLE OF DAYS WITH VERY WARM TEMPERATURES. WHILE IT
LOOKS LIKE MONDAY SHOULD BE LARGELY CLOUD-FREE, THERE IS A
GREAT DEAL OF UNCERTAINTY REGARDING HOW MUCH RECYCLED UPPER
LEVEL SMOKE COULD BE AROUND MONDAY. IF THERE IS AN UPPER LEVEL
LAYER OF SMOKE IT WOULD LIKELY TEMPER INSOLATION SOME AND RESULT
IN TEMPS A BIT COOLER THAN CURRENTLY FORECAST. BY TUESDAY, ANY
SMOKE SHOULD BE SAFELY BLOWN WELL TO OUR NORTH AND EAST, BUT
CLOUDINESS WILL PROBABLY BE ON THE INCREASE IN ADVANCE OF THE
NEXT SYSTEM. DESPITE SOME INCREASE IN CLOUD COVER, STRONG
SOUTHERLY WINDS SHOULD STILL ALLOW FOR HIGHS TO CLIMB WELL INTO
THE 80S TO PERHAPS SOME LOW 90S IF CLOUDS ARE A BIT SLOWER TO
ARRIVE.
UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT ARE PROGGED TO
MOVE ACROSS THE ARE TUESDAY NIGHT INTO EARLY WEDNESDAY WITH
CHANCES FOR SHOWERS AND THUNDERSTORMS. MOISTURE RETURN FROM THE
GULF WILL BE SOMEWHAT STUNTED BY SFC RIDGING BEING SLOW TO MOVE
OFF TO THE EAST AND ALLOW FOR BETTER MOISTURE RETURN. THIS COULD
TEMPER THE SEVERE THREAT SOME, BUT AT THIS DISTANCE CAN'T ARGUE
WITH LIKELY POPS OFFERED UP BY THE NBM GIVEN THE RESPECTABLE
FORCING.
THERE IS SPREAD IN MEDIUM RANGE GUIDANCE LATER WEDNESDAY THROUGH
THURSDAY REGARDING HOW FAR SOUTH THIS BOUNDARY SETTLES. THE 00Z
OPERATIONAL RUNS OF THE GFS AND ECMWF BOTH EJECT OUT AN UPPER
LOW FROM THE SOUTHWEST WITH THIS SHEARING OUT SHORTWAVE RIDING
THE WEST-SOUTHWESTERLY FLOW INTO THE MIDWEST. THERE IS
SIGNIFICANT SPREAD IN BOTH MODELS' ENSEMBLE SUITES IN HOW THIS
UPPER LOW EJECTION IS HANDLED, SO CONFIDENCE IS STILL PRETTY
LOW. IF THIS SHEARING OUT UPPER LOW WERE TO EJECT OUT IN AND
DRAG THAT BOUNDARY BACK NORTH, THERE WOULD LIKELY BE ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS IN THE LATER WED NIGHT OR
THURSDAY TIME FRAME. GIVEN THE LARGE SPREAD IN THE ENSEMBLES,
DIDN'T SEE ANY COMPELLING REASONS TO STRAY FROM NBM POPS WHICH
DO HAVE HIGH END CHANCE/LOW END LIKELY POPS LATE WED NIGHT OR
THURSDAY.
A TREND TOWARD COOLER, MORE SEASONABLE TEMPERATURES IS EXPECTED
DURING THE SECOND HALF OF THE UPCOMING WORK WEEK.
- IZZI
AVIATION /18Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 1223 PM CDT SAT MAY 31 2025
THERE ARE NO AVIATION WEATHER CONCERNS FOR THE 18Z TAF PERIOD.
HAZE ORIGINATING FROM CANADIAN WILDFIRES IS OBSTRUCTING
OTHERWISE CLEAR SKIES. THE HAZY CONDITIONS WILL CONTINUE INTO
SUNDAY BUT SHOULD REMAIN ALOFT AND ARE NOT EXPECTED TO IMPACT
VSBYS NEAR THE SFC AT THIS TIME. MEANWHILE, NE WINDS NEAR 10 KT
WILL CONTINUE GUSTING INTO THE TEENS KTS BEFORE SUBSIDING TO
LIGHT AND VARIABLE THIS EVENING. WINDS WILL THEN REMAIN LIGHT
THROUGH SUNDAY MORNING BEFORE A LAKE BREEZE BRINGS EASTERLY
WINDS BELOW 10 KT EARLY IN THE AFTERNOON.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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