580
FXUS63 KLOT 102040
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
340 PM CDT SAT MAY 10 2025
KEY MESSAGES
- GENERALLY WELL ABOVE NORMAL TEMPERATURES ARE EXPECTED THROUGH
THE UPCOMING WORK WEEK, WITH HIGHS POTENTIALLY APPROACHING 90F
ON THURSDAY IN SOME LOCATIONS.
- PERIODIC SHOWERS AND THUNDERSTORMS ARE EXPECTED DURING THE
MONDAY THROUGH THURSDAY TIME FRAME, THOUGH MANY HOURS WILL
ALSO BE DRY.
DISCUSSION
ISSUED AT 340 PM CDT SAT MAY 10 2025
THROUGH SUNDAY NIGHT:
A LAKE-ENHANCED COLD FRONT CONTINUES TO PRESS INLAND THIS
AFTERNOON, WITH WINDS TURNING NORTHEASTERLY AND BECOMING GUSTY
IN ITS WAKE. AFTER AN INITIAL SHARP DROP IN TEMPERATURES
IMMEDIATELY BEHIND THE FRONT, THE FULL SUNSHINE BEING OBSERVED
ACROSS THE AREA HAS HELPED OFFSET SOME OF THE TEMPERATURE
FALLOFF AND ALLOWED FOR TEMPERATURES TO STABILIZE A BIT IN SOME
LOCATIONS, BUT TEMPERATURES SHOULD START TO FALL STEADILY ONCE
AGAIN LATER THIS AFTERNOON INTO THIS EVENING AS SOLAR INSOLATION
DIMINISHES BUT POST-FRONTAL COLD AIR ADVECTION CONTINUES.
TEMPERATURES LOOK TO BOTTOM OUT IN THE UPPER 30S TO MID 40S
TONIGHT/EARLY TOMORROW MORNING. PATCHY FROST DEVELOPMENT COULD
OCCUR WHERE THE COLDEST (SUB-40 DEGREE) TEMPERATURES END UP
BEING OBSERVED (LIKELY IN PORTIONS OF FAR NORTHERN ILLINOIS,
ESPECIALLY NEAR THE WISCONSIN STATE LINE), BUT CERTAINLY NOT
EXPECTING FROST TO BE AS WIDESPREAD AS IT WAS THURSDAY
NIGHT/YESTERDAY MORNING.
ON SUNDAY/MOTHER'S DAY, OUR FORECAST AREA WILL REMAIN TUCKED
BETWEEN A CUT-OFF UPPER-LEVEL LOW NEAR THE GULF COAST AND AN
AMPLIFIED NORTHERN STREAM JET. SURFACE HIGH PRESSURE WILL THUS
PRESIDE OVER THE GREAT LAKES ONCE AGAIN, MAINTAINING QUIET
WEATHER CONDITIONS ACROSS THE REGION. OUTSIDE OF SOME TUFTS OF
CIRRUS THAT MAY BE VOLLEYED OUR WAY FROM DOWN SOUTH, SKIES
SHOULD OTHERWISE REMAIN CLEAR, FACILITATING RELATIVELY EFFICIENT
WARMING OF THE DRY AIR MASS THAT WILL BE IN PLACE IN SPITE OF
THE CONTINUED ONSHORE FLOW. MOST INLAND LOCATIONS SHOULD END UP
WARMING INTO THE 70S, WITH SOME LOCATIONS IN OUR SOUTHERN AND
WESTERN COUNTIES POSSIBLY TAGGING 80 DEGREES AGAIN IN THE
AFTERNOON. LOCATIONS WITHIN A FEW MILES OF LAKE MICHIGAN,
HOWEVER, LIKELY WILL NOT MAKE IT OUT OF THE 60S DUE TO THE
AFOREMENTIONED ONSHORE FLOW.
MONDAY THROUGH SATURDAY:
A CHANGE IN THE SYNOPTIC WEATHER PATTERN IS EXPECTED THIS
UPCOMING WORK WEEK AS AN UPPER-LEVEL TROUGH INITIALLY DIGS INTO
THE WESTERN CONUS, PRODDING THE GULF COAST UPPER LOW
NORTHEASTWARD TOWARDS THE GREAT LAKES. RICHER GULF MOISTURE
CHARACTERIZED BY 60+ DEGREE SURFACE DEW POINTS WILL COMMENSURATELY
BE USHERED INTO THE REGION AND STICK AROUND FOR MUCH OF THE WEEK.
AMIDST THE CONTINUED SUMMER-LIKE TEMPERATURES, THIS MORE HUMID
AIR WILL ALLOW FOR DAILY PERIODIC SHOWER AND THUNDERSTORM
CHANCES TO BE REALIZED MONDAY THROUGH THURSDAY.
FIRST, ON MONDAY, SCATTERED, PULSE-TYPE CONVECTION (PERHAPS
CONSOLIDATING INTO LOOSELY-ORGANIZED CLUSTERS WITH TIME) SHOULD
SLOWLY TRICKLE INTO OUR FORECAST AREA FROM THE SOUTH DURING THE
AFTERNOON IN CONCERT WITH THE ARRIVAL OF THE NORTHERN EDGE OF
THE RICHER MOISTURE AND THE NORTHERN PERIPHERY OF THE GULF COAST
UPPER LOW. SHOWER/THUNDERSTORM COVERAGE SHOULD LARGELY REMAIN
CONFINED TO AREAS SOUTH OF I-80 THROUGH THE DAYTIME HOURS BEFORE
THE LOSS OF DIURNAL HEATING CAUSES THE COVERAGE OF THIS DIURNAL
CONVECTION TO DIMINISH AFTER SUNSET. THE MEAGER DEGREE OF
INSTABILITY AND OVERALL DEARTH OF FLOW THROUGH THE TROPOSPHERIC
COLUMN SHOULD KEEP HAZARDS WITH ANY STORMS LIMITED TO LIGHTNING,
RELATIVELY BRIEF DOWNPOURS, AND GUSTY WINDS. A SIMILAR STORY
WILL LIKELY PLAY OUT ON TUESDAY, THOUGH CONVECTION SHOULD TEND
TO BE EVEN MORE TRULY PULSE-LIKE AS THERE WILL PRACTICALLY BE NO
DEEP-LAYER SHEAR WHATSOEVER TO DISPLACE CONVECTIVE UPDRAFTS
FROM WHERE THEY INITIALLY GO UP. OUR WHOLE FORECAST AREA WILL
ALSO BE SUBJECT TO THE SCATTERED DIURNAL CONVECTION THIS TIME
AROUND WITH THE GULF AIR MASS LIKELY TO HAVE FULLY ENVELOPED
NORTHERN ILLINOIS AND NORTHWEST INDIANA PRIOR TO TUESDAY
AFTERNOON.
BY WEDNESDAY, THE UPPER LOW IS EXPECTED TO HAVE DEFORMED
SOMEWHAT AND DRIFTED EASTWARD IN RESPONSE TO THE EASTWARD
PROGRESSION OF THE WESTERN CONUS TROUGH. ACCORDINGLY, THE
COVERAGE OF THE NEXT ROUND OF DIURNAL CONVECTION IN OUR FORECAST
AREA ON WEDNESDAY SHOULD BE LOWER COMPARED TO MONDAY AND
TUESDAY AND APPEARS TO BE BEST HANDLED BY AREA-WIDE SLIGHT
CHANCE AND LOW-END CHANCE POPS (UP TO 30%) AT THIS TIME. THE
LESSER DEGREE OF CONVECTIVE COVERAGE SHOULD MEAN THAT MORE
SUNSHINE SHOULD BE SEEN, AND THAT SHOULD TRANSLATE TO MORE
WIDESPREAD LOW-MID 80 DEGREE READINGS BEING OBSERVED ACROSS
LOCATIONS AWAY FROM LAKE MICHIGAN'S INFLUENCE. THE SUMMER-LIKE
WARMTH AND HUMIDITY WILL THEN LIKELY CONTINUE INTO THURSDAY,
WITH TEMPERATURES EVEN WARMER THAN WEDNESDAY'S APPEARING TO BE
ACHIEVABLE. FOR ONCE, THESE WARMER TEMPERATURES MAY ALSO APPLY
TO OUR LAKESIDE LOCALES AS WINDS ON THURSDAY SHOULD BE BREEZY
AND FROM THE SOUTH. WILL NOTE THAT THE NBM'S FORECAST HIGH
TEMPERATURES FOR BOTH WEDNESDAY AND THURSDAY ARE ONCE AGAIN
TOWARDS THE UPPER ECHELON OF THE LATEST DETERMINISTIC AND
ENSEMBLE GUIDANCE. PONDERED BRINGING THEM DOWN A SMIDGE, BUT
OPTED TO LEAVE THEM BE FOR NOW GIVEN THAT THIS WAS THE CASE A
FEW DAYS AGO FOR TODAY AND SUNDAY, WHICH THE NBM HAS SEEMINGLY
FARED WELL FOR.
LATE WEDNESDAY INTO THURSDAY, THE WESTERN CONUS TROUGH IS
EXPECTED TO EJECT INTO THE NORTHERN PLAINS AND UPPER MIDWEST.
THE LOW PRESSURE SYSTEM THAT DEVELOPS IN RESPONSE WILL HELP
ADVECT A MORE PRONOUNCED EML INTO THE MIDWEST AND WILL ALSO
CAUSE KINEMATIC FIELDS ACROSS THE REGION TO STRENGTHEN. THIS
WILL AUGMENT THE PRE-EXISTING WARMTH AND MOISTURE TO FOSTER A
POTENTIAL THREAT FOR SEVERE WEATHER ACROSS THE REGION LATE
THURSDAY INTO EARLY FRIDAY. IT IS THUS NOT SURPRISING THAT AI,
MACHINE LEARNING, AND ANALOG GUIDANCE ALL CONTINUES TO HIGHLIGHT
OUR FORECAST AREA AS BEING UNDER THE GUN FOR POTENTIAL SEVERE
WEATHER DURING THIS TIME. HOWEVER, THIS GUIDANCE ISN'T ALWAYS
PARTICULARLY SKILLFUL IN IDENTIFYING AND ACCOUNTING FOR
POTENTIAL FAILURE MODES SUCH AS CAPPING, SUB-OPTIMAL FORCING,
ETC., AND AT FIRST GLANCE, IT APPEARS THERE COULD BE SOME
FAILURE MODES TO CONTEND WITH ON THURSDAY. THUS, WHILE
CONFIDENCE IS RELATIVELY HIGH AT THIS POINT IN TIME THAT THE
PARAMETER SPACE THAT WILL BE IN PLACE OVER THE REGION LATE
THURSDAY WILL LARGELY BE FAVORABLE FOR SEVERE THUNDERSTORMS,
CONFIDENCE IS STILL FAIRLY LOW IN WHETHER EVERYTHING WILL COME
TOGETHER JUST RIGHT FOR THIS PARAMETER SPACE TO BE FULLY
UTILIZED, OR WHETHER WE'LL EVEN SEE STORMS AT ALL. IT WILL STILL
LIKELY BE A FEW MORE DAYS BEFORE WE'LL BE ABLE TO MORE CLOSELY
ASSESS THE FINER SCALE DETAILS OF THIS SEVERE WEATHER POTENTIAL,
SO STAY TUNED FOR ADDITIONAL UPDATES.
OUR WEATHER FOR FRIDAY WILL LARGELY DEPEND ON HOW THE THURSDAY
LOW PRESSURE SYSTEM PLAYS OUT. A STRONG COLD FRONTAL PASSAGE
THURSDAY NIGHT/FRIDAY MORNING COULD FAVOR DRY AND BREEZY
CONDITIONS ACROSS THE AREA ON FRIDAY, BUT ON THE OTHER HAND, THE
NEARBY PRESENCE OF THE AFOREMENTIONED UPPER-LEVEL TROUGH COULD
STILL SUPPORT SHOWER AND THUNDERSTORMS CHANCES HERE IF THE COLD
FRONT ARRIVES TOO EARLY OR TOO LATE AND/OR ISN'T ROBUST ENOUGH
TO SCOUR OUT THE WARMTH AND MOISTURE IN THE AREA. BEYOND FRIDAY,
THE OVERALL WEATHER PATTERN ACROSS THE CENTRAL CONUS IS
EXPECTED TO REMAIN FAIRLY ACTIVE. THIS COULD RESULT IN
ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS IN OUR AREA
GOING INTO NEXT WEEK.
OGOREK
AVIATION /18Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 1216 PM CDT SAT MAY 10 2025
FORECAST CONCERN FOR THE TERMINALS...
- BREEZY (20-25 KT) NORTHEAST WINDS THIS AFTERNOON.
A LAKE ENHANCED COLD FRONT CONTINUES TO SURGE ACROSS NORTHEAST
IL AND NORTHWEST IN RESULTING A SHARP NORTHEAST WIND SHIFT AND
INCREASE IN WINDS IN THE FRONT'S WAKE. WHILE THERE HAVE BEEN
PERIODS OF 30 KT GUSTS IMMEDIATELY BEHIND THE FRONT, MOST GUSTS
HAVE GENERALLY BEEN IN THE 20-25 KT AND THEY SHOULD REMAIN AS
SUCH THROUGH THE AFTERNOON. GUSTS WILL GRADUALLY TAPER THIS
EVENING BEFORE FULLY SUBSIDING BETWEEN 03Z AND 05Z TONIGHT, THUS
WINDS IN THE 8-12 KT RANGE CAN BE EXPECTED OVERNIGHT THROUGH
SATURDAY WITH DIRECTIONS BECOMING MORE EASTERLY SATURDAY
MORNING. OTHERWISE, EXPECT MOSTLY CLEAR SKIES TO PREVAIL THROUGH
THE PERIOD.
YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM CDT SUNDAY FOR THE IL AND IN
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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