000
FXUS63 KIWX 131718
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
118 PM EDT MON APR 13 2026
KEY MESSAGES
- UNSEASONABLY WARM TEMPERATURES EXPECTED THROUGH THE WORK WEEK WITH
HIGHS IN THE 70S AND EVEN SOME 80S AT TIMES.
- THERE IS A SLIGHT RISK OF SEVERE STORMS TODAY FROM MID
AFTERNOON THROUGH THIS EVENING. ISOLATED LARGE HAIL AND
ISOLATED DAMAGING WIND GUSTS WOULD BE THE MAIN THREATS.
- THE ACTIVE PERIOD OF WEATHER CONTINUES TUESDAY THROUGH
THURSDAY WITH CONTINUED PERIODIC HIGHER CHANCES OF SHOWERS AND
STORMS. THERE IS A SLIGHT RISK OF SEVERE STORMS TUESDAY LATE
AFTERNOON THROUGH THE EARLY OVERNIGHT HOURS WHICH REPRESENTS
THE PERIOD OF GREATEST SEVERE WEATHER POTENTIAL. ALL SEVERE
HAZARDS ARE POSSIBLE INCLUDING THE POTENTIAL OF SOME LOCALLY
HEAVY RAINFALL. CONFIDENCE IN SEVERE WEATHER IS LOWER FOR
WEDNESDAY.
UPDATE
ISSUED AT 935 AM EDT MON APR 13 2026
WHILE THE OVERALL FORECAST REMAINS UNCHANGED AT THE MOMENT, WE
WILL BE CLOSELY MONITORING A MID LEVEL WAVE CURRENTLY MOVING NE
THROUGH MISSOURI WITH A SMALL AREA OF SHOWERS AND STORMS.
SEVERAL MODELS ARE HINTING AT DEVELOPMENT LATER THIS AFTERNOON
(AFTER 21Z) OF AT LEAST ISOLATED STORMS IN ASSOCIATION WITH THIS
FEATURE AND AN ASSOCIATED EML AND STEEP LAPSE RATES. DEGREE OF
DESTABILIZATION IS STILL IN QUESTION WITH POCKETS OF CLEARING
AHEAD OF THE WAVE POSSIBLY LIMITING THE THREAT. BASED ON THE
THREAT, SPC HAS EXPANDED THE SLIGHT RISK FOR TODAY INTO OUR AREA
(WEST OF I-69 AND NORTH OF US-24) FOR A HAIL/WIND THREAT. THIS
IS BY NO MEANS A SLAM DUNK, BUT WILL NEED TO WATCH TRENDS INTO
THIS AFTERNOON.
DISCUSSION
ISSUED AT 330 AM EDT MON APR 13 2026
THE COMBINATION OF A MID LEVEL SHORT WAVE AND BROAD ADVECTIVE
FORCING HAS SUSTAINED RAIN SHOWERS FROM WEST TO EAST ACROSS THE
AREA THIS MORNING. DESPITE THE DECENT MOISTURE TRANSPORT THIS
MORNING, THE STRENGTH OF THE LOW LEVEL THERMAL RIDGE HAS ALLOWED
FOR LARGE ENOUGH LOW LEVEL DEW POINT DEPRESSIONS TO PROVIDE
SOME ENHANCEMENT TO SURFACE WIND GUSTS IN ASSOCIATION WITH
THESE SHOWERS. FAIRLY STRONG BACKGROUND FLOW (~40 KNOTS IN
LOWEST GATE OF KIWX VWP DATA) HAS ALSO MIXED DOWN FAIRLY
EFFICIENTLY WITH THESE SHOWERS WITH SOME INSTANCES OF 40-50 MPH
WIND GUSTS. THIS POTENTIAL SHOULD GRADUALLY WANE OVER NEXT FEW
HOURS. HIGHER RES GUIDANCE DOES INDICATE SOME RENEWED CONVECTIVE
DEVELOPMENT ON SOUTHERN PERIPHERY OF DEPARTING MID LEVEL WAVE,
AND WHERE SECONDARY LOW LEVEL THETA-E RIDGE STARTS TO NOSE INTO
NORTH CENTRAL IN NEXT FEW HOURS. THIS COULD YIELD A CLUSTER OF
SHOWERS WITH PERHAPS EMBEDDED THUNDERSTORMS ACROSS NORTHERN
IN/NORTHWEST OH EARLY THIS MORNING THROUGH DAYBREAK.
ADDITIONAL SHOWERS AND STORMS ARE POSSIBLE TODAY, AND THE STORM
PREDICTION CENTER HAS CONTINUED A MARGINAL RISK OF SEVERE STORMS FOR
MOST OF THE FORECAST AREA. SOME LULL IN SCATTERED/SHOWERS STORMS IS
EXPECTED BY MID MORNING, BUT WILL NEED TO WATCH FOR POSSIBILITY OF
WEAK MID LEVEL WAVE ACROSS KANSAS AS IT REACHES THE WESTERN GREAT
LAKES THIS EVENING. A RENEWED SURGE OF STRONGER LOW LEVEL THETA-E
ADVECTION IS EXPECTED TO ACCOMPANY THIS SHORT WAVE WITH
STRONGEST ADVECTIVE FORCING EXPECTED ACROSS NORTHEAST IL. THE
APPROACH OF THIS CENTRAL PLAINS WAVE WILL ALSO MARK THE LEADING
EDGE OF STRONGER MID LEVEL LAPSE RATES. WHILE SYNOPTIC FORCING
DOES NOT APPEAR STRONG TODAY, DESTABILIZING TRENDS IN
THERMODYNAMIC ENVIRONMENT WITH THE STEEPER MID LEVEL LAPSE RATES
AND THE PRESENCE OF THE MORE DISTINCT LOW/MID LEVEL THETA-E
BOUNDARY COULD PROVIDE A FOCUS FOR AT LEAST AN ISOLATED SEVERE
THREAT LATE THIS AFTERNOON INTO THIS EVENING. WHILE GREATEST
THREAT FOR ISOLATED SEVERE TODAY MAY BE NORTH OF US 30 AS MID
LEVEL SPEED MAX SHIFTS ACROSS SOUTHERN GREAT LAKES, HARD TO
DISCOUNT ANY LOCATION ACROSS FORECAST AREA GIVEN THETA-E
BOUNDARY WILL LIKELY BE HANGING BACK A BIT MORE TO THE SOUTH
FROM NORTHEAST ILLINOIS INTO THE LOCAL AREA. MLCAPES ON THE
ORDER OF 1500-2000 J/KG, MODEST DEEP LAYER SHEAR OF 30 TO 40
KNOTS, AND STEEP LOW LEVEL LAPSE RATES COULD POSE SOME THREAT OF
ISOLATED DAMAGING WIND GUSTS IN ADDITION TO LARGE HAIL THREAT
WITH STEEP MID LEVEL LAPSE RATES. SOME LULL IN THUNDER CHANCES
IS EXPECTED EARLY OVERNIGHT, BUT MAY NEED TO WATCH FOR
POSSIBILITY OF REMNANTS OF STRONGER GREAT LAKES CONVECTION TO
PROPAGATE SOUTHWARD TO THE SOUTHERN GREAT LAKES TOWARD DAYBREAK
TUESDAY. THESE STORMS COULD HAVE SOME STRONG WIND GUSTS
PERSISTING EARLY TUESDAY MORNING BUT CONFIDENCE IN THIS
EVOLUTION IS LOW.
TUESDAY/TUESDAY NIGHT STILL APPEARS TO BE THE PERIOD OF GREATEST
CONCERN FOR SCATTERED SEVERE STORMS AND MOST OF THE FORECAST
AREA REMAINS IN AN SPC DAY 2 SLIGHT RISK FOR SEVERE STORMS. THE
FORECAST CHALLENGE FOR THIS EVENT REMAINS ON CONVECTIVE
INITIATION PORTION OF THE EVENT. STRONGER MID/UPPER LEVEL
FORCING WILL LIKELY BE HANGING BACK TO THE WEST ACROSS THE
ROCKIES AS PRIMARY UPPER LEVEL WAVE BEGINS TO SHEAR EASTWARD.
BEST FORCING MECHANISMS FOR CONVECTIVE INITIATION WILL BE AT
NOSE OF STRONGER LOW LEVEL FLOW AND STRONG LOW LEVEL MOISTURE
CONVERGENCE ACROSS NW IL/SW WI/NE IA. WILL NEED TO SEE IF THERE
IS ANY REMNANT LEFTOVER BOUNDARY FROM EARLY TUESDAY GREAT LAKES
CONVECTION THAT HELP OVERCOME SOME SURFACE BASED CIN FOR MORE OF
AN ISOLATED STORM DEVELOPMENT LOCALLY DURING THE EARLY/MID
AFTERNOON HOURS. THE EXPECTATION IS STILL THAT DISCRETE STORM
DEVELOPMENT ACROSS MID MS RVR VALLEY SHOULD TEND TO CONGEAL
ACROSS WESTERN/SOUTHERN GREAT LAKES LATER EVENING TUESDAY WITH
STRONG COMPONENT OF SHEAR PARALLEL TO THE BOUNDARY. GREATEST
POTENTIAL SEVERE RISKS STILL APPEAR TO BE LARGE HAIL 1-2" IN
DIAMETER GIVEN VERY STEEP MID LEVEL LAPSE RATES AND DAMAGING
WIND GUSTS, WITH GREATEST POTENTIAL OF HAIL ACROSS THE NORTHWEST
WHICH COULD BE INVOLVED IN THE EARLIER STAGES OF THE EVENT MID-
LATE EVENING. SOME POTENTIAL OF HEAVY RAINFALL WILL ALSO HAVE
TO BE MONITORED AS OUTFLOW EMANATING FROM THIS CONVECTION MAY
BECOME PARALLEL TO ENVIRONMENTAL SHEAR. A STRENGTHENING
SOUTHWEST LLJ SOUTH FEEDING INTO THESE POTENTIAL STORMS/OUTFLOW
SHOULD ALSO WEAKEN UPWIND PROPAGATION VECTORS YIELDING POTENTIAL
OF TRAINING CONVECTION.
WEDNESDAY'S SEVERE POTENTIAL WILL BE CONDITIONAL ON CONVECTIVE
EVOLUTION TUESDAY NIGHT, AND IF MORE MATURE CONVECTIVE SYSTEM CAN
DEVELOP TUESDAY NIGHT AN EFFECTIVE BOUNDARY MAY GET PUSHED ACROSS
SOUTHERN HALF OF THE FORECAST AREA DURING THE DAY. INSTABILITY
MAGNITUDES SHOULD BE MORE QUESTIONABLE ON WEDNESDAY AND STRONGER
SYNOPTIC FORCING WILL STILL LIKELY BE LAGGING BACK TO THE WEST. SOME
ISOLATED SEVERE POTENTIAL MAY EVOLVE (MAINLY WIND), BUT CONFIDENCE
IS LOWER IN COMPARISON TO LATE TUESDAY.
THE PRIMARY UPPER LEVEL WAVE WILL FINALLY TOP THE RIDGE ACROSS THE
GREAT LAKES ON THURSDAY, BUT SLOW EVOLUTION OF THIS FEATURE WILL
KEEP THUNDER CHANCES GOING INTO THURSDAY. SOME INDICATIONS IN
GUIDANCE THAT BETTER KINEMATIC FIELDS ON THURSDAY COULD BE EASTWARD
DISPLACED FROM BETTER INSTABILITY HANGING BACK TO THE
WEST/SOUTHWEST, SO ANY ORGANIZED SEVERE THREAT APPEARS TO BE LOW AT
THIS TIME.
108
AFTER BRIEF LOW LEVEL CAA LATE THURSDAY, QUICK REBOUND OF MID LEVEL
HEIGHTS AND RAPID ONSET OF LOW LEVEL WAA WILL KEEP THE MUCH ABOVE
NORMAL TEMPS GOING THROUGH FRIDAY (HIGHS POSSIBLY BACK NEAR 80 BY
FRIDAY). NO SIGNIFICANT CHANGES MADE TO TEMP FORECAST THROUGH
FRIDAY, WITH CONFIDENCE IN CONTINUED MUCH ABOVE NORMAL TEMPERATURES
AND DAILY HIGHS IN THE 70S. MEDIUM RANGE GUIDANCE CONTINUES TO
STRUGGLE WITH ENSEMBLE/DETERMINISTIC CONSENSUS ON TIMING
FRONTAL PASSAGE WITH NEXT STRONGER LONGWAVE TROUGH NEXT WEEKEND,
BUT AN OVERALL TREND TO LEAST A BRIEF SHOT OF COOLER
TEMPERATURES STILL APPEARS ON TRACK FOR LATE WEEKEND/EARLY NEXT
WEEK, ALONG WITH A POTENTIAL OF MORE SHOWERS/STORMS FIRST HALF
OF WEEKEND WITH COLD FRONTAL PASSAGE.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 118 PM EDT MON APR 13 2026
A GENERAL TREND TO VFR CEILINGS IS ANTICIPATED FOR THE
AFTERNOON, BUT CANNOT COMPLETELY DISCOUNT A ROGUE BKN MVFR
CEILING AMID FAIR-WEATHER CUMULUS. THE MAIN QUESTION OF THIS
TAF PERIOD IS HOW DO ANY THUNDERSTORMS EVOLVE THIS AFTERNOON AND
WHAT IMPACT DOES THAT HAVE FOR THE REST OF THE TAF PERIOD.
GIVEN THE VERY HIGH PWATS, HAVE OPTED TO BRING THE VISIBILITY
DOWN TO IFR FOR TSRA. STORMS ARE TRYING TO REMAIN ORGANIZED
ACROSS ILLINOIS. OUR LOCAL ENVIRONMENT APPEARS WELCOMING TO
THESE STORMS. AT THIS STAGE, KSBN APPEARS THE BEST CANDIDATE TO
SEE TSRA, WHILE KFWA WOULD WAIT UNTIL TONIGHT. CONFIDENCE IS
UNUSUALLY LOW FOR THESE NEXT 24 HOURS GIVEN A LACK OF MODEL
CONSISTENCY AND MURKY MESOSCALE FACTORS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
UPDATE...FISHER
DISCUSSION...MARSILI
AVIATION...BROWN
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