937
FXUS63 KLOT 220527
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1227 AM CDT THU MAY 22 2025
KEY MESSAGES
- PERIODS OF SHOWERS AND DRIZZLE TO PERSIST THROUGH THURSDAY AFTERNOON.
- INCREASING WINDS AND WAVES TONIGHT THROUGH THURSDAY WILL MAKE
FOR HAZARDOUS CONDITIONS AT COOK COUNTY AND INDIANA LAKE
MICHIGAN BEACHES.
- BELOW TO WELL BELOW NORMAL TEMPERATURES ARE FAVORED THROUGH
THE MEMORIAL DAY HOLIDAY WEEKEND.
DISCUSSION
ISSUED AT 239 PM CDT WED MAY 21 2025
THROUGH THURSDAY NIGHT:
A VERTICALLY STACKED LOW PRESSURE SYSTEM CONTINUES TO SLOWLY
PROPAGATE EASTWARD ACROSS THE GREAT LAKES THIS AFTERNOON
RESULTING IN AREAS OF SHOWERS AND DRIZZLE ACROSS LOWER MI, WI,
NORTHEAST IL AND NORTHWEST IN. WHILE THE DRIZZLE THREAT SHOULD
DIMINISH THIS EVENING AS MOISTURE DEPTHS INCREASE, PERIODS OF
OFF AND ON SHOWERS ARE EXPECTED TO PERSIST THROUGH TONIGHT AS
SHORTWAVES PIVOT OVERHEAD. OTHERWISE, EXPECT TEMPERATURES TO
HOLD NEARLY STEADY IN THE LOW TO MID-50S THIS AFTERNOON UNDER
CLOUDY SKIES BEFORE TEMPERATURES GRADUALLY COOL INTO THE MID TO
UPPER 40S OVERNIGHT.
HEADING INTO THURSDAY, THE STACKED LOWS WILL BE MOVING INTO THE
NORTHEAST CONUS ALLOWING SHOWERS TO GRADUALLY TAPER THROUGH THE
MORNING. HOWEVER, FORECAST SOUNDINGS DO SHOW AT LEAST SOME
MODEST LOW-LEVEL MOISTURE LINGERING THROUGH THURSDAY AFTERNOON.
THEREFORE, AN ADDITIONAL PERIOD OF SCATTERED SHOWERS (20-30%
CHANCE) LOOKS LIKELY DURING THE AFTERNOON HOURS AS ANOTHER
SHORTWAVE DIVES THROUGH THE REGION AND INTERACTS WITH A LAKE
BREEZE. GIVEN THE SCATTERED NATURE, MANY HOURS WILL SHOULD
REMAIN DRY ESPECIALLY THOSE IN NORTHWEST IL AND BEHIND THE LAKE
BREEZE (FAR NORTHEAST IL). ON THE BRIGHT SIDE, TEMPERATURES ARE
EXPECTED TO BE WARMER THAN TODAY WITH HIGHS IN THE LOWER 60S
INLAND AND MID TO UPPER 50S NEAR THE LAKE.
OUTSIDE OF THE SHOWERS, NORTH-NORTHEAST WINDS WILL ALSO BE
INCREASING (ESPECIALLY OVER THE LAKE) ON THURSDAY WHICH WILL
LEAD TO INCREASING WAVES AT COOK COUNTY AND INDIANA LAKE
MICHIGAN BEACHES. WHILE THE WEATHER IS NOT HIGHLY CONDUCIVE FOR
BEACH ACTIVITIES, STILL FELT THAT MAINTAINING THE BEACH HAZARD
STATEMENTS THROUGH THURSDAY NIGHT FOR COOK, LAKE IN, AND PORTER
COUNTIES WAS WARRANTED DUE TO THE HIGH WAVES AND CURRENTS. WINDS
AND WAVES WILL GRADUALLY SUBSIDE THURSDAY NIGHT WITH OTHERWISE
CLEAR SKIES AND COOL TEMPERATURES IN THE LOWER TO MID-40S.
YACK
FRIDAY THROUGH WEDNESDAY:
THE MAIN WEATHER MESSAGE FOR THE EXTENDED PART OF THE FORECAST
IS THAT MEMORIAL DAY WEEKEND WILL (UNFORTUNATELY) NOT LIVE UP TO
ITS NICKNAME (UNOFFICIAL START OF SUMMER) TEMPERATURE-WISE THIS
YEAR. EXPECT SOLIDLY BELOW NORMAL TEMPS ALL THE WAY THROUGH
WEDNESDAY, ALTHOUGH THE STRONG LATE MAY SUN CERTAINLY WILL MAKE
IT FEEL WARMER WHEN ITS NOT OBSCURED BY CLOUDS. MID AND UPPER
TROUGHING OVER NORTHEASTERN NORTH AMERICA WILL KEEP US IN
NORTHWEST FLOW ALOFT THROUGH SUNDAY, FOLLOWED BY A TRANSITION TO
A SOMEWHAT BLOCKY PATTERN BY MONDAY AND TUESDAY. IN THIS BLOCKY
REGIME, YET ANOTHER UPPER LEVEL LOW MAY AFFECT OUR WEATHER IN
THE TUESDAY-WEDNESDAY PERIOD.
SURFACE HIGH PRESSURE WILL BUILD IN OVER THE WESTERN AND
CENTRAL GREAT LAKES THROUGH THE WEEKEND. THIS WILL KEEP THE
BAROCLINIC ZONE MOSTLY SHUNTED TO OUR SOUTH AND LIMIT CHANCES
FOR ANY MEANINGFUL RAINFALL. A STRONGER SHORT-WAVE MAY TAKE A
CLOSE ENOUGH APPROACH TO OUR SOUTHWEST ON SATURDAY NIGHT INTO
SUNDAY WHEN SOME SHOWERS ARE POSSIBLE PRIMARILY OVER THE
SOUTHWEST 1/3 OR SO OF THE CWA (20-30% POPS). THEN ON MEMORIAL
DAY, RAIN CHANCES WITH THE NEXT POSSIBLE SYSTEM SHOULD BE
CONFINED TO PRIMARILY SOUTH OF I-80 WITH HIGH PRESSURE STILL
ANCHORED OVER THE GREAT LAKES. WHILE SOME SPOTTY SHOWERS MAY
RETURN TUESDAY-WEDNESDAY IF UPPER LEVEL LOW PRESSURE SETS UP
OVERHEAD, THE PROSPECTS FOR ANY WIDESPREAD SOAKING RAIN APPEAR
LOW. THE 12Z EPS (ECMWF ENSEMBLE) IN FACT KEEPS PROBABILITIES OF
24 HOUR QPF >=0.5" AT 10-20% OR LESS THROUGH NEXT WEEK AND INTO
THE FIRST WEEKEND OF JUNE.
HIGH TEMPERATURES INLAND WILL ONLY BE IN THE 60S (PRIMARILY
MID-UPPER 60S) FRIDAY THROUGH WEDNESDAY. MEANWHILE, PERSISTENT
ONSHORE WINDS WILL KEEP THE LAKESHORE SEVERAL DEGREES COOLER.
KEEP THAT IN MIND IF YOU HAVE ANY TENTATIVE PLANS TO HEAD TO THE
SHORE FOR THE HOLIDAY WEEKEND. OVERNIGHT LOWS WILL BE PRIMARILY
IN THE 40S TO AROUND 50F, THOUGH SOME SPOTTY UPPER 30S ARE
POSSIBLE ACROSS PORTIONS OF FAR NORTHERN ILLINOIS EARLY
SATURDAY.
CASTRO
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1227 AM CDT THU MAY 22 2025
FORECAST CONCERNS INCLUDE...
MVFR, POSSIBLY IFR, CIGS EARLY THIS MORNING.
WIND SHIFT TO NORTHEAST THIS AFTERNOON.
CHANCE OF SHOWERS EARLY THIS MORNING AND AGAIN THIS AFTERNOON.
PREVAILING LOW MVFR CIGS CONTINUE ACROSS MUCH OF NORTHERN IL
EARLY THIS MORNING ALONG WITH SOME AREAS OF IFR CIGS. THESE WILL
CONTINUE THROUGH THE PREDAWN HOURS AND THEN BEGIN TO LIFT.
GUIDANCE HAS BEEN IN VERY GOOD AGREEMENT WITH THE IMPROVING
TREND AROUND/JUST AFTER DAYBREAK, WITH CIGS EVENTUALLY BECOMING
LOW VFR. GIVEN CIG TRENDS ACROSS WI AND NORTHERN LOWER MI, THESE
SEEM ON TRACK.
NORTHWEST WINDS AROUND 10KT OVERNIGHT WILL BECOME NORTH/
NORTHWEST LATER THIS MORNING WITH GUSTS INTO THE 15-20KT RANGE
POSSIBLE. WINDS WILL SHIFT TO THE NORTHEAST FOR THE CHICAGO AREA
TERMINALS THIS AFTERNOON AS A LAKE BREEZE/COLD FRONT MOVES
INLAND. WINDS ARE EXPECTED TO TURN BACK TO LIGHT WESTERLY LATER
THIS EVENING.
SCATTERED SHOWERS WILL CONTINUE THROUGH DAYBREAK THIS MORNING
AND THEN THERE WILL BE ANOTHER CHANCE OF SHOWERS THIS AFTERNOON.
THE SHOWERS FOR THIS AFTERNOON MAY REMAIN FAR ENOUGH INLAND
THAT THE CHICAGO TERMINALS STAY DRY. COVERAGE MAY ALSO REMAIN
ISOLATED AND MAINTAINED A DRY FORECAST. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...BEACH HAZARDS STATEMENT FROM 9 AM CDT THIS MORNING THROUGH
THIS EVENING FOR ILZ103-ILZ104.
IN...BEACH HAZARDS STATEMENT THROUGH LATE TONIGHT FOR INZ001-INZ002.
LM...SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 10 PM CDT THIS
EVENING FOR WILMETTE HARBOR TO CALUMET HARBOR IL.
SMALL CRAFT ADVISORY FROM 4 AM EARLY THIS MORNING TO 1 AM CDT
FRIDAY FOR THE IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page