570
FXUS63 KIND 181715
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
115 PM EDT MON MAY 18 2026
KEY MESSAGES
- SEVERE STORMS POSSIBLE THIS AFTERNOON AND AGAIN TUESDAY
AFTERNOON AND EVENING WITH DAMAGING WINDS, LARGE HAIL AND
LOCALIZED FLOODING
- HIGHS IN THE 80S TODAY AND TUESDAY
- STORMS WILL END WEDNESDAY AS THE FRONT SHIFTS SOUTH, BUT UNSETTLED
WEATHER LIKELY RETURNS LATE THIS WEEK INTO THE HOLIDAY WEEKEND
FORECAST UPDATE
ISSUED AT 1014 AM EDT MON MAY 18 2026
A LINE OF THUNDERSTORMS CONTINUES TO MARCH EAST INTO CENTRAL
ILLINOIS THIS MORNING, AND SCATTERED CONVECTION IS DEVELOPING AHEAD
OF THIS LINE WITH AN AREA OF ADDITIONAL LIFT.
TEMPERATURES ACROSS CENTRAL INDIANA WERE ALREADY IN THE UPPER 70S
WITH DEWPOINTS GENERALLY IN THE LOWER TO MIDDLE 60S. UPPER 60S
DEWPOINTS WERE IN THE FAR SOUTHWEST AND FARTHER UPSTREAM TO THE
SOUTHWEST.
BASED ON LATEST RADAR TRENDS, SPED UP ARRIVAL OF POPS THIS MORNING
INTO EARLY AFTERNOON. THE NEWER CONVECTION LEADS TO SOME INCREASED
UNCERTAINTY ON HOW CONVECTION EVOLVES THIS AFTERNOON. INSTABILITY
WILL CONTINUE TO BUILD, ESPECIALLY CENTRAL AND EAST BEFORE THE
CLOUDS FROM UPSTREAM CONVECTION LIMIT HEATING. THE INITIAL
CONVECTION WILL BE ABLE TO TAP INTO THIS INSTABILITY, BUT UPSTREAM
CONVECTION MAY HAVE LESS TO WORK WITH.
EITHER WAY, STRONG TO SEVERE CONVECTION REMAINS A THREAT INTO THE
AFTERNOON SO WILL CONTINUE TO MENTION.
HIGH TEMPERATURES MAY BE OPTIMISTIC WEST BUT FOR NOW WILL MAKE NO
CHANGES AND CONTINUE TO MONITOR.
MESOSCALE UPDATE
ISSUED AT 1244 PM EDT MON MAY 18 2026
THUNDERSTORMS ARE DEVELOPING ALONG THE INDIANA ILLINOIS STATE LINE.
THESE STORMS HAVE BEEN LOOSELY ORGANIZED SO FAR, BUT AN OUTFLOW
BOUNDARY FROM CONVECTION FURTHER UPSTREAM IS IMPINGING FROM THE
WEST. THIS OUTFLOW BOUNDARY MAY ALLOW STORMS TO CONSOLIDATE INTO A
MORE COHERENT LINE AS THEY PROGRESS DEEPER INTO INDIANA.
A RECENT SOUNDING FROM PURDUE UNIVERSITY SHOWS MODEST LAPSE RATES
BETWEEN 6-7 C/KM, WITH A MOIST PROFILE TO ABOUT 500 MB.
ADDITIONALLY, MODEST SHEAR IS ALSO PRESENT (20-25 KNOTS) WITH MESSY
HODOGRAPHS CENTERED AROUND THE MEAN STORM MOTION. AS SUCH, LITTLE IN
THE WAY OF STORM RELATIVE UPPER-LEVEL OUTFLOW APPEARS
LIKELY...STORMS SHOULD BEHAVE MORE LIKE SINGLE CELLS TO MULTICELL
CLUSTERS UNTIL THEY BECOME INFLUENCED BY THE OUTFLOW BOUNDARY OR
THEIR OWN OUTFLOW.
ONCE STORMS CONSOLIDATE ON THE OUTFLOW BOUNDARY, THEY SHOULD STILL
BE RELATIVELY 'PULSEY' IN NATURE BUT MORE ORGANIZED THAN IN THE OPEN
WARM SECTOR. THE PRIMARY THREAT TODAY APPEARS TO BE STRONG WIND
GUSTS, AS ENOUGH MOISTURE LOADING WITHIN MATURE UPDRAFTS IS POSSIBLE
FOR WET MICROBURSTS. ADDITIONALLY, COLD POOL DYNAMICS SUCH AS REAR-
INFLOW JET SURGES ARE ALSO POSSIBLE WHICH MAY PRODUCE STRONG TO
DAMAGING WIND GUSTS. GIVEN A MEAN SHEAR VECTOR TOWARDS THE
NORTHEAST, COLD POOLS THAT ORIENT IN A NW TO SE DIRECTION POSE THE
GREATEST THREAT FOR SEVERE WIND GUSTS.
HAIL IS POSSIBLE BUT GIVEN ONLY MODEST LAPSE RATES, HIGH MOISTURE
CONTENT, AND THE LACK OF LONG STRAIGHT HODOGRAPHS IT DOES NOT APPEAR
TO BE ALL THAT LIKELY. TORNADO POTENTIAL ALSO APPEARS LOW, GIVEN THE
OUTFLOW DOMINANT NATURE OF STORMS TODAY. A BRIEF QLCS SPIN UP CANNOT
BE RULED OUT, HOWEVER.
ANOTHER THREAT, LIKELY REPLACING WIND AS THE PRIMARY HAZARD LATER
THIS EVENING, IS THE POTENTIAL FOR FLOODING AND FLASH FLOODING. HIGH-
RESOLUTION GUIDANCE SHOWS THE COLD POOL SETTLING IN A SW TO NE
FASHION ACROSS CENTRAL INDIANA. THIS MAY ALLOW FOR REPEATED ROUNDS
OF STORMS INTO TONIGHT. AS MENTIONED ABOVE, MOISTURE CONTENT IN THE
PROFILE IS HIGH AND FREEZING LEVELS ARE NEAR 15,000 FEET. WITH A
WARM CLOUD LAYER OVER 10,000 FEET IN THICKNESS, WARM RAIN PROCESSES
SHOULD LEAD TO EFFICIENT RAINFALL PRODUCTION TODAY. AS SUCH, VARIOUS
CAMS ARE SHOWING POCKETS OF VERY HEAVY RAINFALL TOTALS BETWEEN 3 TO
5 INCHES. HREF ENSEMBLE MEAN SHOWS A LARGE AREA OF 1 TO 2 INCHES.
BECAUSE OF THIS POTENTIAL, A FLOOD WATCH HAS BEEN ISSUED FOR FOR
WESTERN PORTIONS OF THE AREA. AS COLD POOLS BECOME MORE DEFINED,
THIS MAY NEED TO BE TRIMMED OR EXPANDED.
DISCUSSION (TODAY THROUGH SUNDAY)
ISSUED AT 258 AM EDT MON MAY 18 2026
AN AMPLIFIED UPPER LEVEL PATTERN FOR EARLY THIS WEEK ANCHORED BY A
DEEP TROUGH OVER THE NORTHERN ROCKIES AND STRONG RIDGING OVER THE
EASTERN PART OF THE COUNTRY. THE RIDGE WILL GRADUALLY FLATTEN AS THE
TROUGH SHIFTS EAST ENABLING A STRONG COLD FRONT TO TRACK INTO THE
REGION BY LATE TUESDAY. WITH A WARM AND UNSTABLE AIRMASS AHEAD OF
THE FRONT...MULTIPLE OPPORTUNITIES FOR THUNDERSTORMS WILL EXIST
THROUGH TUESDAY NIGHT WITH SEVERE WEATHER POSSIBLE THIS AFTERNOON
AND POTENTIALLY AGAIN TUESDAY AFTERNOON AND EVENING AS THE COLD
FRONT MOVES THROUGH. HIGH PRESSURE WILL BRING A BRIEFLY DRIER PERIOD
MIDWEEK BEFORE UNSETTLED CONDITIONS RETURN LATE WEEK IN RESPONSE TO
THE FRONT LIFTING BACK NORTH INTO THE REGION.
TODAY THROUGH TUESDAY NIGHT
QUIET EARLY MORNING ACROSS CENTRAL INDIANA WITH CLEAR SKIES. 06Z
TEMPERATURES REMAINED WARM IN THE UPPER 60S AND LOWER 70S IN MANY
LOCATIONS.
AN ACTIVE 48 HOURS IS ANTICIPATED THROUGH TUESDAY NIGHT WITH
MULTIPLE OPPORTUNITIES FOR RAIN AND THUNDERSTORMS AND THE POTENTIAL
FOR SEVERE WEATHER IN ADVANCE OF A COLD FRONT CURRENTLY OVER THE
PLAINS AND POISED TO MOVE ACROSS THE AREA BY TUESDAY EVENING.
AN ONGOING AREA OF CONVECTION CONTINUES EARLY THIS MORNING FROM THE
UPPER MIDWEST SOUTHWEST INTO CENTRAL KANSAS. MUCH OF THE LINE HAS
WEAKENED FROM SUNDAY EVENING WITH THE EXCEPTION OF THE SOUTHERN PART
OF THE LINE OVER THE MISSOURI VALLEY WHERE INSTABILITY AND BL SHEAR
REMAIN MORE THAN SUFFICIENT TO MAINTAIN CONVECTIVE INTENSITY. THIS
PORTION OF THE LINE IS LIKELY TO REMAIN STRONG FOR THE REMAINDER OF
THE NIGHT WITH AN IN CREASING FLOOD RISK AS IT SAGS INTO SOUTH
CENTRAL MISSOURI AND BECOMES INCREASINGLY PARALLEL TO THE MEAN FLOW.
THE WEAKER PORTION OF THE LINE OVER IOWA IS OF GREATER INTEREST TO
THE FORECAST AREA AS ITS REMNANTS WILL ENABLE THE OLD OUTFLOW
BOUNDARY TO DRIFT INTO CENTRAL ILLINOIS BY MID TO LATE MORNING WITH
CONVECTION BECOMING REINVIGORATED AS THE OUTFLOW INTERACTS WITH A
RAPIDLY DESTABILIZING AIRMASS OVER THE REGION.
CONVECTION WILL CONTINUE TO GROW UPSCALE AS IT TRACKS INTO THE
WABASH VALLEY EARLY THIS AFTERNOON THEN PRESSES SOUTHEAST ACROSS THE
FORECAST AREA. MODEL SOUNDINGS SHOW STEEPENING MID LEVEL LAPSE RATES
WITH SBCAPES 2000-2500 J/KG AND SUFFICIENT SHEAR THAT WOULD SUPPORT
DAMAGING WINDS...ESPECIALLY IF THE COLD POOL CAN MATURE.
FURTHERMORE...DCAPE VALUES APPROACH 1000 J/KG IMMEDIATELY AHEAD OF
THE CONVECTIVE LINE WHICH ALSO LENDS CREDENCE TO THE DAMAGING WIND
RISK. ABUNDANT CAPE IS PRESENT WITHIN THE HAIL GROWTH ZONE AS WELL
AND STRONGER CELLS WILL CARRY A LARGE HAIL THREAT AS WELL. TIMING OF
THE GREATEST RISK FOR SEVERE WEATHER WILL BE BETWEEN 17Z AND 22Z.
STORMS WILL WEAKEN AS THEY TRACK TOWARDS THE INDIANA-OHIO BORDER BY
EARLY EVENING AS IT MOVES AWAY FROM THE DEEPER INSTABILITY AND
STRONGER LOW LEVEL WINDS. AN AXIS OF PWATS BETWEEN 1.75 AND 2 INCHES
WILL SUPPORT TORRENTIAL RAINFALL AND FLOODING. THE GREATEST CONCERN
WILL BE ACROSS THE SOUTHWEST HALF OF THE FORECAST AREA AS TRAINING
CELLS BECOME A FACTOR WITH THE LINE CURVING BACK TO THE WEST ALONG
THE INSTABILITY AXIS. SHOWERS AND EMBEDDED STORMS WILL CONTINUE INTO
THE EVENING BUT WITH THE AIRMASS WORKED OVER FROM THE AFTERNOON
CONVECTION...THE GENERAL TREND WILL BE TOWARDS RAIN DIMINISHING AS
WEAK RIDGING ALOFT REESTABLISHES FOR THE OVERNIGHT.
TUESDAY HAS BECOME A BIT MORE UNCERTAIN WITH RESPECT TO CONVECTIVE
EVOLUTION AND THE POTENTIAL FOR ANOTHER ROUND OF SEVERE WEATHER AS
THE MODEL SUITE HAS SPED UP THE ARRIVAL OF THE FRONT INTO THE
FORECAST AREA IN THE AFTERNOON. MORE IMPACTFUL THOUGH WILL BE THE
POSSIBILITY OF CONVECTIVE CLOUD DEBRIS BY TUESDAY MORNING FROM AN
MCS OVER THE MISSOURI VALLEY MONDAY NIGHT. THAT WILL STUNT DIURNAL
HEATING AND AVAILABLE INSTABILITY AND THE EARLIER ARRIVAL OF THE
FRONT DURING THE AFTERNOON PRESENTS THE POSSIBILITY THAT THE GREATER
RISK FOR MORE ROBUST CONVECTION WILL FOCUS ACROSS THE SOUTHEAST HALF
OF THE FORECAST AREA AND POINTS EAST LATE AFTERNOON INTO THE
EVENING. THAT BEING SAID...MODEL SOUNDINGS DO CONTINUE TO HIGHLIGHT
MID LEVEL LAPSE RATES UP TO 7.5C/KM WITH A DEEP LAYER OF DRY
ADIABATIC FLOW ACROSS THE REGION COMBINED WITH SUFFICIENT LEVELS OF
BL SHEAR TO SUPPORT SCATTERED STRONGER CONVECTION AT A MINIMUM WITH
THE AVAILABLE INSTABILITY. DAMAGING WINDS WILL AGAIN BE THE PRIMARY
RISK FROM THESE STORMS WITH LARGE HAIL SERVING AS A SECONDARY
THREAT.
THE COLD FRONT WILL BECOME MORE PARALLEL TO THE FLOW ALOFT ON
TUESDAY NIGHT WHICH WILL KEEP SHOWERS AND THUNDERSTORMS ACROSS MUCH
OF THE FORECAST AREA INTO TUESDAY NIGHT...GRADUALLY ENDING FROM THE
NORTH OVERNIGHT AS DRIER AIR ADVECTS INTO THE REGION.
HIGHS WILL BE TRICKY BOTH TODAY AND TUESDAY...DEPENDENT ON
CONVECTIVE TIMING THIS AFTERNOON AND CLOUD DEBRIS TUESDAY. NUDGED
HIGHS BOTH DAYS DOWN FROM THE MODEL BLEND WITH LOW TO MID 80S FOR
MUCH OF THE FORECAST AREA.
WEDNESDAY THROUGH SUNDAY
CONVECTION MAY STILL BE ONGOING ACROSS THE SOUTHEAST HALF OF THE
FORECAST AREA WEDNESDAY MORNING BUT WILL GRADUALLY END THROUGH THE
MORNING AS THE FRONT SHIFTS SOUTH OF THE REGION AND HIGH PRESSURE
BUILDS INTO THE GREAT LAKES. CONFIDENCE CONTINUES TO GROW ON THE
BOUNDARY BECOMES QUASI STATIONARY ACROSS THE TENNESSEE VALLEY INTO
THURSDAY BEFORE LIFTING BACK NORTH INTO THE OHIO VALLEY FRIDAY AS
THE HIGH PASSING TO THE NORTH MOVES EAST INTO NEW ENGLAND. THE
ENSEMBLE GUIDANCE HAS GOTTEN MORE AGGRESSIVE IN THIS SOLUTION WITH
SCATTERED TO NUMEROUS SHOWERS AND STORMS FRIDAY AND FRIDAY NIGHT AS
THE FRONT LIFTS NORTH THROUGH THE FORECAST AREA.
LOWER CONFIDENCE REMAINS FOR THE WEEKEND AS THE RETURN OF A WARMER
AND MORE UNSTABLE AIRMASS SOUTH OF THE FRONT WILL SUPPORT AT LEAST A
DAILY THREAT FOR SCATTERED CONVECTION BUT THE LACK OF MUCH AGREEMENT
IN THE MODEL ENSEMBLE MAKES EMPLOYING DETAIL IN THE TIMING AND
COVERAGE OF RAINFALL DIFFICULT THROUGH MUCH OF THE HOLIDAY WEEKEND.
AFTER TEMPERATURES MAINLY IN THE UPPER 60S AND LOW 70S WEDNESDAY AND
THURSDAY...HIGHS WILL CLIMB BACK INTO THE UPPER 70S AND LOWER 80S
SATURDAY AND SUNDAY.
AVIATION (18Z TAF ISSUANCE)
ISSUED AT 114 PM EDT MON MAY 18 2026
IMPACTS:
- SHOWERS AND STORMS AT TIMES INTO THIS EVENING
- PEAK WIND GUSTS THIS AFTERNOON AT 25 TO 30KTS
DISCUSSION:
INITIAL AREA OF CONVECTION IMPACTING THE WESTERN SITES AT THE MOMENT
WILL CONTINUE TO MOVE EAST AND WILL IMPACT THE OTHER SITES EARLY IN
THE PERIOD. ADDITIONAL DEVELOPMENT WILL CONTINUE INTO THE EVENING,
SO THERE WILL BE PERIODS OF SHOWERS AND STORMS THROUGH ABOUT 03Z.
IFR AND WORSE ARE POSSIBLE IN CONVECTION.
WHILE ADDITIONAL CONVECTION MAY POP UP OVERNIGHT, BETTER CHANCES FOR
CONVECTION RETURN CLOSER TO 18Z TUESDAY.
GUSTY WINDS WILL CONTINUE THIS AFTERNOON, AND NEAR LLWS CONDITIONS
ARE POSSIBLE TONIGHT.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...50
AVIATION...50
DISCUSSION...RYAN
MESOSCALE...ECKHOFF
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