767
FXUS63 KIWX 210149
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
949 PM EDT MON JUL 20 2026
KEY MESSAGES
- THERE IS A 30-50% CHANCE OF THUNDERSTORMS OVERNIGHT.
CONFIDENCE IN SEVERE WEATHER OCCURRING IS LOW, BUT CANNOT
COMPLETELY RULE OUT INSTANCES OF ISOLATED DAMAGING WIND GUSTS
OR HEAVY RAIN.
- HIGH WAVES AND STRONG CURRENTS ARE EXPECTED AT SOUTHEAST LAKE
MICHIGAN BEACHES ON TUESDAY. STAY DRY WHEN WAVES ARE HIGH.
- DRY, COOLER AND LESS HUMID CONDITIONS ARRIVE LATE TUESDAY AND
PERSIST THROUGH THE REMAINDER OF THE WEEK.
UPDATE
ISSUED AT 937 PM EDT MON JUL 20 2026
PREVIOUS THINKING REMAINS LARGELY INTACT WITH RADAR, SATELLITE
AND MODEL TRENDS ALL CONTINUING TO AT A MINIMUM DELAY THE
ARRIVAL OF ANY PRECIP UNTIL AFTER 6Z WITH THE MORE FAVORABLE
WINDOW SEEMING TO MY BETWEEN 8 AND 12Z AS THE WEAK COOL FRONT
MOVES IN. A VERY BROKEN LINE OF SHOWERS AND STORMS ALONG THE
COLD FRONT BACK ACROSS CENTRAL WI HAVE ATTEMPTED TO ORGANIZE
WITH CELLS FROM WISCONSIN RIVER NE TO THE U.P EXHIBITING
ROTATION AND A FEW BRIEF TORNADOES WHERE THE BEST SHEAR AND
DYNAMICS STILL EXIST. IN OUR AREA SPC MESO ANALYSIS DEPICTS A
HOSTILE ENVIRONMENT RIGHT NOW WITH VERY LIMITED CAPE OR SHEAR.
HRRR HAS BEEN PICKING UP ON NEW DEVELOPMENT OCCURRING SOMEWHERE
IN THE FORECAST AREA AFTER 9Z WITH PREVIOUS RUNS VARYING IN
STRENGTH, COVERAGE AND LOCATION. HAVE REMOVED ALL LIKELY POPS
AND ATTEMPTED TO ALIGN TIMING AND POPS IN BETTER AGREEMENT WITH
TRENDS. THE STORMS IN WI WILL MOST LIKELY CONTINUE ESE INTO
PORTIONS OF CENTRAL LOWER MI WITH LOCATIONS SW OF THE ABOVE AREA
SHOWING LITTLE DEVELOPMENT RIGHT NOW. SPC DID MAINTAIN THE
SLIGHT RISK IN OUR FAR NW OVERNIGHT, BUT GIVEN THE TRENDS
SUSPECT MORE OF A MARGINAL RISK AT WORST WITH MAYBE SOME LOCALLY
GUSTY WINDS OR A BIT OF HAIL LATER TONIGHT ALONG THE FRONT.
TRENDS WILL BE MONITORED INTO THE OVERNIGHT HOURS.
DISCUSSION
ISSUED AT 150 PM EDT MON JUL 20 2026
PRIMARY ITEM OF INTEREST CONTINUES TO BE THE (MURKY) RISK OF SEVERE
STORMS TONIGHT AND AGAIN ON TUESDAY. WATER VAPOR, AS OF THIS MIDDAY
WRITING, DEPICTS A SHARP TROUGH DIGGING PAST THE ARROWHEAD OF
MINNESOTA. WELL SOUTH OF THIS, PERHAPS ON THE FAR LEADING EDGE OF
THE RIGHT-FRONT EXIT REGION OF A 50-70 KNOT 500MB JET, LIES A
CLUSTER OF THUNDERSTORMS THAT HAS PERSISTED TO SOME CAPACITY
THROUGHOUT THE MORNING HOURS. THE HEALTHIEST PART OF THE LINE IS
DIVING SOUTH OF THE QUAD CITIES POSING NO SEVERE RISK TO OUR
LOCAL AREA. HOWEVER, LINGERING OUTFLOW BOUNDARIES OR TRAILING
MCVS APPEAR TO THE FOCUS FOR RENEWED, UPSTREAM CONVECTION EARLY
THIS EVENING ACROSS WISCONSIN AND IOWA.
GUIDANCE THIS MORNING HAS BEEN IN FAIR AGREEMENT THAT SHOWERS
OR STORMS, LIKELY SUB- SEVERE, MOVE THROUGH AFTER 11PM. FORECAST
SOUNDINGS DEPICT RATHER DRY, STABLE AIR BELOW 600MB, AS HIGH
PRESSURE OVER NYC CONTINUES TO EXERT PERHAPS A HINT OF
INFLUENCE LOCALLY. SINCE YESTERDAY, FORECAST BULK SHEAR VALUES
NEAR 30 KNOTS ARE FAVORABLE OVER PREVIOUS, LESSER VALUES. FADING
INSTABILITY REMAINS TROUBLESOME, THOUGH MID-LEVEL LAPSE RATES
NEAR 7 C/KM CONTINUE TO OFFER A GLIMMER OF HOPE THAT SOME
CONVECTION COULD SUSTAIN ITSELF. LIKE YESTERDAY, WE OVERALL
REMAIN DOUBTFUL OF ANY SIGNIFICANT CONVECTION THIS EVENING BUT
CANNOT COMPLETELY RULE OUT ROGUE INSTANCES OF DAMAGING WIND
GUSTS OR HEAVY RAIN.
WITH ANTICIPATED MINIMAL SEVERE WEATHER CONCERNS DURING THE
OVERNIGHT HOURS, ATTENTION THEN TURNS TO THE ADVERTISED COLD FRONT
NOW SOUTH OF US 24 LATER TUESDAY MORNING. THIS APPEARS TO BE FOCUS
FOR AN ISOLATED SEVERE STORM, BUT THE UPPER-LEVEL SUPPORT IS
LACKLUSTER AS THE TROUGH HAS BECOME POSITIVELY TILTED. SHEAR IS
NOTABLY IMPROVED TOWARD 40 KNOTS BUT INSTABILITY REMAINS
PROBLEMATIC, ESPECIALLY CONSIDERING ANY CLOUD DEBRIS FROM EARLY-
MORNING SHOWERS/STORMS. HERE TOO, NOT OVERLY CONCERNED ABOUT
THE SEVERE WEATHER CHANCES ON TUESDAY.
BEHIND THIS COLD FRONT AND PERIOD OF SHOWERS AND STORMS, A
REINFORCING DOSE OF COOL AIR DESCENDS ALONG A TRAILING SECONDARY
UPPER-LEVEL VORTICITY MAXIMUM. THIS RESULTS IN A 20-30% CHANCE OF
SHOWERS TUESDAY NIGHT THROUGH WEDNESDAY MORNING DOWNWIND OF LAKE
MICHIGAN AMID 10C DELTA-TS AND CLOUD TOPS NEAR 10,000 FT. OTHERWISE,
A PERIOD OF COOLER AND RATHER TRANQUIL CONDITIONS LIE AHEAD. HIGHS
IN THE LOW-70S ARE ABOUT 10 DEGREES BELOW NORMAL, WHILE THURSDAY
MORNING LOWS NEAR 50 WILL BE FALL-LIKE. TEMPERATURES TREND BACK INTO
THE 80S BY THE WEEKEND AND HIGH PRESSURE SHIFTS EAST AND WARM
SOUTHERLY FLOW RESUMES. WE'LL KEEP AN EYE ON AN AREA OF LOW PRESSURE
MOVING THROUGH THE CENTRAL PLAINS LATER FRIDAY, BUT FOR NOW, THIS
FEATURE CONTINUES TO BE ADVERTISED AS PASSING TO OUR WEST. ANOTHER
TROUGH DROPS IN FROM CANADA LATER SUNDAY, REPRESENTING THE NEXT BEST
CHANCE FOR RAIN.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 722 PM EDT MON JUL 20 2026
CONFIDENCE REMAINS QUITE LOW ON POSSIBLE CONVECTIVE IMPACTS
OVERNIGHT AND INTO TUESDAY (AT KFWA) AS UPSTREAM STORMS HAVE
BEEN LIMITED TO 2 CAMPS, ONE DIVING SOUTH ACROSS IA INTO WESTERN
IL ALONG AN OUTFLOW BOUNDARY AND THE OTHER MOVING ACROSS THE U.P
OF MI. IN BETWEEN THESE AREA, WEAK SHOWERS AND STORMS ARE TRYING
TO GET GOING ALONG THE FRONT BUT WILL RUN INTO DECREASING
INSTABILITY AS THEY COME SE. AS A RESULT, HAVE REMOVED ANY
THUNDER MENTION FROM THE TAFS AND WENT WITH A TEMPO FOR SHOWERS.
IF TRENDS BEGIN TO POINT TOWARDS SOMETHING MORE SIGNIFICANT,
WILL ADJUST. OTHERWISE COLD FRONT WILL ARRIVE LATE TONIGHT INTO
TUESDAY MORNING WITH WINDS SHIFTING AND INCREASING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...AIR QUALITY ALERT UNTIL MIDNIGHT EDT /11 PM CDT/ TONIGHT FOR
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
OH...NONE.
MI...AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR MIZ078>081-
177-277.
BEACH HAZARDS STATEMENT FROM 2 AM EDT TUESDAY THROUGH LATE
WEDNESDAY NIGHT FOR MIZ177-277.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TUESDAY TO 1 AM EDT THURSDAY
FOR LMZ043.
UPDATE...FISHER
DISCUSSION...BROWN
AVIATION...FISHER
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