195
FXUS63 KLOT 051151
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
651 AM CDT FRI JUN 5 2026
KEY MESSAGES
- WAVES OF SHOWERS AND STORMS ARE EXPECTED STARTING TODAY AND
LASTING THROUGH SUNDAY. MANY HOURS WILL BE DRY.
- A FEW STORMS THIS AFTERNOON AND TONIGHT MAY BE SEVERE AND
PRODUCE TORRENTIAL DOWNPOURS.
- TEMPERATURES WILL BE FAIRLY SEASONABLE TO SLIGHTLY ABOVE
AVERAGE THIS WEEK BEFORE TRENDING WARMER NEXT WEEK.
DISCUSSION
ISSUED AT 240 AM CDT FRI JUN 5 2026
A RECENT HAND SURFACE ANALYSIS AUGMENTED BY REGIONAL 00Z RAOBS
PLACES AN EXPANSIVE RESERVOIR OF HIGHER-QUALITY LOW-LEVEL
MOISTURE CHARACTERIZED BY DEW POINTS IN UPPER 60S TO AROUND 70
AND MEAN LOW-LEVEL MIXING RATIOS AT OR ABOVE 12 G/KG WEST OF
THE MISSISSIPPI RIVER. SEVERAL BANDS OF SHOWERS AND
THUNDERSTORMS EXTEND FROM NORTHERN MISSOURI TO CENTRAL WISCONSIN
ALONG THE EASTERN FRINGE OF THE LOW-LEVEL MOISTURE AXIS TIED TO
LOW-LEVEL ISENTROPIC ASCENT AHEAD OF AN UPPER-LEVEL SHORTWAVE
LIFTING INTO CENTRAL IOWA. MEANWHILE, A SECONDARY UPPER-LEVEL
SHORTWAVE IS READILY EVIDENT IN OVERNIGHT GOES-19 WATER VAPOR
IMAGERY MOVING ACROSS THE DAKOTAS, AND IS SUPPORTING A
CONVECTIVE SYSTEM MOVING INTO WESTERN MINNESOTA. FINALLY A
LARGER AND MUCH SLOWER-MOVING UPPER-LEVEL LOW IS CURRENTLY
MEANDERING ALONG THE US/MEXICO BORDER. THE OVERARCHING WEATHER
PATTERN IS CERTAINLY FOREBODING OF A MORE ENERGETIC PERIOD
HEADING OUR WAY.
TODAY:
AS THE MORNING PROGRESSES, THE SHOWERS AND STORMS NEAR THE
MISSISSIPPI RIVER ARE EXPECTED TO SLIDE NORTHEASTWARD GENERALLY
ALONG AND NORTHWEST OF A LINE FROM MENDOTA TO EVANSTON, IL.
COVERAGE OF THUNDER MAY BE ISOLATED THROUGH THE MORNING HOURS AS
THE MAIN INSTABILITY AXIS LAGS TO THE WEST. WITH THAT SAID, THE
EXPECTATION IS FOR EPISODIC DOWNPOURS AMIDST A BROADER RAIN
SHIELD ACROSS NORTHWESTERN ILLINOIS THIS MORNING. MEANWHILE,
SOUTHEAST OF THE AFOREMENTIONED LINE, RESIDUAL DRY LOW-LEVEL AIR
SHOULD LIMIT COVERAGE OF RAIN SHOWERS THIS MORNING.
AN ENSEMBLE OF CAM-BASED GUIDANCE SUGGESTS THAT AN ORGANIZED
MCV WILL EMERGE ACROSS SOUTHERN IOWA LATER THIS MORNING, WHICH
SEEMS REASONABLE GIVEN THE ONGOING BROAD ZONE OF ACTIVE
CONVECTION STRETCHING ACROSS NORTHERN MISSOURI AND THE
NORTHEASTERLY TRAJECTORY OF THE PARENT SHORTWAVE. SOUTHWESTERLY
FLOW WILL BE POISED TO GUIDE THE MCV TOWARD THE SOUTHERN
WISCONSIN/NORTHERN ILLINOIS REGION BY LATE MORNING TO EARLY
AFTERNOON ALONG THE EASTERN EDGE OF THE INSTABILITY AXIS. AS A
RESULT, DO HAVE GROWING CONFIDENCE IN A PERIOD OF THUNDERSTORMS
THIS AFTERNOON, FAVORING AREAS GENERALLY NORTH OF INTERSTATE 80.
LOCALLY AUGMENTED AND VEERING LOW-LEVEL FLOW ALONG THE SOUTHERN
SIDE OF THE CIRCULATION (AS STRONG AS 40KT FROM 925 TO 700MB
PER LATEST RAP GUIDANCE) DOES RAISE CONCERN FOR SUPERCELL
STRUCTURES IN THE MOST PERSISTENT CONVECTIVE CELLS SHOULD THE
MCV REMAIN ON THE EASTERN FRINGE OF THE INSTABILITY AXIS. FOR
THIS REASON, CANNOT RULE OUT A FEW FUNNEL CLOUDS OR EVEN A BRIEF
TORNADO EARLY THIS AFTERNOON TIED TO THE MCV, WHICH AGAIN WILL
FAVOR AREAS NORTH OF I-80 AND PERHAPS EVEN EAST OF I-39. WITH
THAT SAID, DO SUSPECT THAT CONVECTION MAY STRUGGLE TO BECOME
ROOTED TO THE INSTABILITY AXIS GIVEN THE PREDOMINANT CONVECTIVE-
SCALE INFLOW WILL BE FROM THE RELATIVELY MORE STABLE AIR TO THE
EAST (THOUGH SUCH A LIMITING FACTOR WILL NOT BE AS MUCH OF AN
ISSUE BY LATE AFTERNOON, SHOULD CONVECTION STILL BE ONGOING).
FOR AREAS SOUTH OF INTERSTATE 80, TODAY IS SHAPING UP TO BE A
WARM AND BREEZY DAY. AT LEAST FILTERED SUNSHINE SHOULD ALLOW FOR
HIGHS TO RISE INTO THE LOW TO MID 80S. MIXING INTO THE SOUTHERN
SIDE OF THE WIND FIELD TIED TO THE MCV WILL ALLOW FOR PERIODIC
WIND GUSTS OF 25 TO 30 MPH. HUMIDITY LEVELS WILL INCREASE
THROUGHOUT THE DAY, WITH DEW POINTS POISED TO RISE TOWARD 70
DEGREES BY THIS EVENING. THE AIR WILL FEEL QUITE A BIT HEAVIER
THAN THE PAST WEEK! LINGERING ISENTROPIC ASCENT IN THE WAKE OF
THE MCV MAY ALLOW FOR ISOLATED TO SCATTERED STORMS TO DEVELOP
TOWARD AND EVENTUALLY SOUTH OF I-80 THIS EVENING, THOUGH
COVERAGE SHOULD NOT BE NEARLY AS HIGH AS POINTS TO THE NORTH.
TONIGHT:
FORECAST CONFIDENCE LOWERS AFTER SUNSET OWING TO A SOMEWHAT
COMPLEX REGIME. LATER TODAY, AN EPISODE OF CONVECTION IS
EXPECTED ACROSS MINNESOTA AND CENTRAL WISCONSIN TIED TO THE
AFOREMENTIONED DAKOTAS SHORTWAVE. INCREASING ISENTROPIC ASCENT
AHEAD OF AND BENEATH THE LEFT ENTRANCE REGION OF A JET MAX
ASSOCIATED WITH THE WAVE INTO THE MIDWEST REGION, AS WELL AS AN
APPROACHING SUBTLE 700MB SPEED MAX ITSELF ADVECTING A REMNANT
EML PLUME EASTWARD FROM THE PLAINS, SHOULD EXCITE A SEPARATE
REGION OR TWO OF THUNDERSTORMS AFTER DARK FROM CENTRAL IOWA
TOWARD NORTHERN ILLINOIS. WHILE PIN-POINTING EXACTLY WHERE
THUNDERSTORMS WILL ERUPT IN THIS KIND OF NOCTURNAL REGIME CAN BE
DIFFICULT, THE LATEST CAM GUIDANCE SEEMS TO FAVOR AN AXIS NEAR
AND SOUTH OF INTERSTATE 80 BETWEEN 9 PM AND MIDNIGHT, ESPECIALLY
ACROSS IOWA.
IN SPITE OF SOMEWHAT MARGINAL DEEP-LAYER SHEAR (AS THE UPPER-
LEVEL JET MAX WILL BE DISPLACED ACROSS CENTRAL WISCONSIN AND
MICHIGAN), MOISTURE-LADEN INSTABILITY PROFILES AIDED BY MID-
LEVEL LAPSE RATES NEAR 7 TO 7.5 K/KM WILL SUPPORT MUCAPE OF 2000
TO LOCALLY 3000 J/KG. TAKEN TOGETHER, THE MOST VIGOROUS
CONVECTION MAY BE ABLE TO SUPPORT SCATTERED DAMAGING HAIL AND
WINDS (A HIGHER COVERAGE BEING LIMITED BY A LACK OF MORE
APPRECIABLE DEEP-LAYER SHEAR). PERHAPS MORE PERVASIVE WILL BE
TORRENTIAL DOWNPOURS MOVING OVER THE SAME GENERAL AREA, GIVEN MODEST
BACKWARD CORFIDI VECTOR MAGNITUDES (A CONSEQUENCE OF A SOMEWHAT
WEAK LOW-LEVEL JET MAGNITUDE). ACCORDINGLY, DO BELIEVE THERE IS
A THREAT FOR LOCALIZED FLASH FLOODING IN THE GENERAL REGION
TONIGHT IN SPITE OF THE RECENT DRY STRETCH. NOTE THAT SOME
AREAS, AND PERHAPS EVEN A LARGE PORTION OF OUR AREA, WILL
REMAIN COMPLETELY DRY TONIGHT.
SATURDAY:
COVERAGE OF OVERNIGHT SHOWERS AND STORMS SHOULD WANE TOWARD
DAYBREAK OWING TO THE DIURNAL WEAKENING OF THE LOW-LEVEL JET AND
SUBSIDENCE IN THE WAKE OF THE OVERNIGHT SHORTWAVE. CURRENTLY DO
ANTICIPATE A FAIR AMOUNT OF SUNSHINE BY EARLY AFTERNOON, WHICH
SHOULD ALLOW FOR TEMPERATURES TO WARM TO THE MID TO LOCALLY
UPPER 80S. THE GENERALLY WEAK LOW-LEVEL PRESSURE GRADIENT AND
CONTINUED COOL LAKE MICHIGAN TEMPERATURES (IN THE UPPER 50S TO
LOWER 60S PER THE RECENT OMRLOT PRODUCT) SHOULD ALLOW FOR A LAKE
BREEZE TO DEVELOP AND PUSH INLAND DURING THE AFTERNOON HOURS.
THE CONTINUED HUMID CONDITIONS (DEW POINTS IN THE UPPER 60S TO
LOWER 70S) WILL SUPPORT CONVECTIVE TEMPERATURES SOMEWHERE IN THE
UPPER 80S, SETTING THE STAGE FOR ISOLATED TO PERHAPS SCATTERED
"POP-UP" DIURNAL THUNDERSTORMS BY MID AFTERNOON. COVERAGE MAY BE
LOCALLY HIGHER NEAR THE LAKE BREEZE GIVEN LOCALLY STRONGER LOW-
LEVEL CONVERGENCE. MOST AREAS SHOULD BE DRY.
SUNDAY INTO MONDAY:
TOWARD THE START OF NEXT WEEK, THE UPPER-LEVEL LOW CURRENTLY
TRAVERSING THE US/MEXICAN BORDER WILL FINALLY BEGIN LIFTING
NORTHEASTWARD TOWARD THE MISSISSIPPI RIVER VALLEY. THE (BY THIS
POINT SOMEWHAT STAGNANT) HUMID AIRMASS WILL HENCE BE POISED TO
SUPPORT EPISODES OF SHOWERS AND STORMS AS THE UPPER-LEVEL LOW
APPROACHES AND EVENTUALLY MOVES OVERHEAD. PERIODS OF CLOUD
COVER, AS WELL AS ONSHORE FLOW FORCED BY A SURFACE HIGH PRESSURE
SYSTEM MOVING ACROSS EASTERN CANADA, WILL LEAD TO SEASONABLE
TEMPERATURES GENERALLY CLOSE TO 80 DEGREES BOTH DAYS.
TUESDAY ONWARD:
IN THE WAKE OF THE UPPER-LEVEL LOW, ENSEMBLE MODEL GUIDANCE
APPEARS STEADFAST IN DEPICTING THE DEVELOPMENT OF PERSISTENT
TROUGHING ACROSS THE PACIFIC COAST AND UPPER-LEVEL RIDGING
ACROSS THE MIDWEST AND GREAT LAKES REGION. AS A RESULT,
TEMPERATURES SHOULD WARM THROUGHOUT NEXT WEEK WITH HIGHS
CLIMBING INTO UPPER 80S TO PERHAPS LOWER 90S BY THE WEEKEND.
WHEN COMBINED WITH THE CONTINUED HUMIDITY, IT'LL START TO FEEL
MORE LIKE SUMMER NEXT WEEK. WILL NOTE THAT THERE ARE DIFFERENCES
IN THE PLACEMENT OF THE RIDGE NEXT WEEK, SUGGESTING THAT THERE
MAY BE OPPORTUNITIES FOR STORMS (AND ASSOCIATED LOCALIZED
NATURAL AIR CONDITIONING) IN THE GENERAL REGION AS WELL.
(NOTE THAT THE HIGH TEMPERATURES IN THE MID TO UPPER 90S AND
ASSOCIATED MUCH HIGHER HEAT INDICES BEING ADVERTISED BY THE NBM
TOWARD THE END OF NEXT WEEK ARE NOT CURRENTLY SUPPORTED BY INPUT
ENSEMBLE DATA).
BORCHARDT
AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 651 AM CDT FRI JUN 5 2026
MAIN CONCERNS:
- OCCASIONAL SHRA/TS WITH ASSOCIATED VSBY REDUCTIONS TODAY AND
POSSIBLY AGAIN LATE THIS EVENING-OVERNIGHT
- LOWER CIG TRENDS THROUGH EARLY THIS EVENING
- CHANCE FOR A NORTH-NORTHEASTERLY WIND SHIFT ASSOCIATED WITH
THE SHRA/TS THREAT LATE THIS EVENING-OVERNIGHT, THOUGH
CONFIDENCE IS LOW
THE TRAJECTORY OF CURRENT TS (IN 11-12Z HOUR) THAT HAVE BEEN
AFFECTING RFD AREA WILL LIKELY KEEP THEM NORTH OF DPA AND ORD,
BUT WILL NEED TO MONITOR RADAR AND LIGHTNING TRENDS OVER THE
NEXT FEW HOURS. CURRENT ON STATION TS AT RFD HAS LOWERED
CONFIDENCE SOME IN ADDITIONAL TS BEING OBSERVED THERE DURING
DAYLIGHT HOURS TODAY. FOR THE CHICAGO AREA TERMINALS, HAVE
MAINTAINED SIMILAR TIMING FOR SHRA AND MOST FAVORED WINDOW FOR
TEMPO TS (17-20Z AT DPA, ORD, MDW, AND 19-22Z AT GYY). FORECAST
SOUNDINGS SUGGEST THAT ANY ACTIVITY LINGERING BEYOND CURRENT
TEMPOS COULD STILL HAVE LIGHTNING, THOUGH THE MAIN DISTURBANCE
WILL BE SHIFTING EAST.
FOLLOWING A PROBABLE LULL INTO/DURING THE EARLY EVENING TODAY,
ADDITIONAL SHOWERS AND STORMS COULD DEVELOP OVER/MOVE INTO THE
REGION. ANY TS PUSHING IN FROM THE NORTH MAY HAVE A BRIEF NORTH
OR NORTHEAST WIND SHIFT. ALL IN ALL, CONFIDENCE IS LOW AND THUS
MAINTAINED PROB30 MENTION. IT APPEARS THAT CONDITIONS WILL BE
PRIMARILY DRY TOWARDS AND AFTER SUNRISE ON SATURDAY.
SOUTHWEST WINDS SHOULD GUST UP TO 20-25 KT FROM THE LATE MORNING
THROUGH EARLY EVENING, WITH SOME POTENTIAL FOR GUSTS AS HIGH AS
25-30 KT IN THE EARLY TO MID AFTERNOON AT THE CHICAGO METRO
TERMINALS. LOWEST CIGS (LOWER MVFR TO TEMPORARY IFR) DURING
DAYLIGHT HOURS TODAY SHOULD FOCUS INTO RFD AREA, THOUGH 2-3KFT
AGL CIGS APPEAR PROBABLE AT TIMES AT THE CHICAGO METRO
TERMINALS, WITH THE LIKELY EXCEPTION OF GYY.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
EVENING FOR WILMETTE HARBOR IL TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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