998
FXUS63 KIWX 120819
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
419 AM EDT THU JUN 12 2025
KEY MESSAGES
- PARTLY TO MOSTLY CLOUDY SKIES TODAY WITH HIGHS IN THE 80S.
THERE ARE LOW CHANCES FOR SHOWERS AND THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING, MAINLY IN MICHIGAN AND NEAR LAKE
MICHIGAN IN NORTHWEST INDIANA. LOWS TONIGHT WILL FALL INTO THE
60S.
- CHANCES FOR SHOWERS AND THUNDERSTORMS PERSIST ON AND OFF
THROUGH NEXT WEEK, WITH THE BEST CHANCES LATE FRIDAY NIGHT
INTO SATURDAY. HIGHS WILL BE IN THE UPPER 70S AND 80S.
DISCUSSION
ISSUED AT 417 AM EDT THU JUN 12 2025
TRICKY FORECAST FOR LATE THIS AFTERNOON INTO FRIDAY, WITH MODELS ALL
OVER THE PLACE IN TERMS OF WHERE/WHEN/HOW MUCH PRECIPITATION WE GET
THANKS TO FAIRLY ZONAL FLOW ALOFT. AT THE MOMENT WE HAVE A WEAK
SURFACE LOW OVER SOUTHERN LAKE MICHIGAN WITH A STATIONARY BOUNDARY
DRAPED FROM DAVENPORT, IA THROUGH SOUTH HAVEN, MI AND INTO DETROIT,
MI. ALL OVERNIGHT CONVECTION HAS STAYED WELL NORTH OF THE AREA,
DESPITE SOME CLOUD DEBRIS (MAINLY HIGH CLOUDS, SOME MID LEVEL). ALL
MODELS ARE IN AGREEMENT AS TO THE INITIALLY DRY CONDITIONS
(THROUGH ABOUT 21Z) GIVEN THE SLIGHT RIDGING ALOFT AND FAIRLY
DRY AIR IN PLACE. HOWEVER, DISCREPANCIES ARISE IN THE 21-03Z
TIME FRAME, WITH THE HRRR AND SOME OF THE CAMS GENERATING
SHOWERS/STORMS AS A SHORTWAVE APPROACHES ALOFT. AS THE
STATIONARY BOUNDARY SHIFTS SLIGHTLY SOUTHWARD THIS AFTERNOON
(MODELS DISAGREE ON IF AND HOW MUCH IT SHIFTS), WINDS BECOME
MORE N-NW NEAR THE LAKESHORE AND MORE E-NE GENERALLY NORTH OF US
30. FLOW SOUTH OF THE BOUNDARY REMAINS SOUTHERLY. I SUSPECT
THAT AS THIS OCCURS, WE'LL SEE SOME ENHANCEMENT TO THE
CONVERGENCE WITH FLOW OF LAKES MICHIGAN AND ERIE, WHICH SEEMS TO
BE WHERE THE SHOWERS/STORMS ARE GENERATED AROUND THE 21-00Z
TIME FRAME, LINGERING THROUGH ABOUT 3Z. IT'S DIFFICULT TO SAY IF
THIS WILL OCCUR GIVEN DRY AIR AROUND AND THE POTENTIALLY STRONG
CAP IN PLACE INITIALLY (NAM HAS NOTHING)-BUT FELT 20-25 PERCENT
CHANCES WERE REASONABLE DURING THIS TIME FRAME. DEPENDING ON
HOW MUCH OF THIS CLOUD COVER STICKS AROUND, WE'LL PROBABLY SEE
HIGHS CLIMB INTO THE MID-UPPER 80S FOR SOME LOCATIONS (WARMEST
ALONG AND SOUTH OF US 30 AND WEST OF US 31). THE LAKE MICHIGAN
SHORELINE, HILLSDALE CO, MI AND FULTON CO, OH MAY ONLY SEE HIGHS
IN THE LOW TO MID 80S.
AS FAR AS TONIGHT GOES, LOWS WILL BE IN THE 60S WITH INCREASING
CLOUDS. POPS LATE TONIGHT INTO FRIDAY ARE STILL LOW TO MEDIUM
CONFIDENCE. MODELS ARE ALL OVER THE PLACE IN TERMS OF LOCATION AND
TIMING, AND THE EXTENT OF COVERAGE. HAVE GENERALLY 30 TO 60 PERCENT
CHANCES MAX ON FRIDAY, WITH THE HIGHER CHANCES IN THE SOUTHWEST
[GENERALLY SOUTH OF US 30 AND WEST OF I 69]. DELAYED START TIME
TONIGHT IN THIS AREA UNTIL 9-12Z, THEN HAVE CHANCES INCREASING
THROUGH THE AFTERNOON AS MOISTURE TRANSPORT INCREASES (PARTICULARLY
ALONG THE STATIONARY FRONT WHICH IS THEORETICALLY DRAPED FROM STARK
CO, IN TO ALLEN CO, OH AT THAT POINT). HIGHS FRIDAY WILL BE IN THE
70S AND LOW 80S.
MEANWHILE, A CUT OFF LOW OVER THE CENTRAL PLAINS MOVES INTO MO BY
00Z SAT-THEN SHIFTS EASTWARD THROUGH SATURDAY NIGHT, WHICH WILL
INCREASE OUR POTENTIAL FOR SHOWERS AND A FEW STORMS LATE FRIDAY
NIGHT INTO SATURDAY. HAVE THE HIGHEST POPS (30-84%, HIGHEST ALONG
AND SOUTH OF US 24-PARTICULARLY EAST OF IN SR-15) DURING THIS PERIOD-
SHIFTING EASTWARD THROUGH SUNDAY MORNING. THE UPPER LEVEL LOW BEGINS
TO WASH OUT BY SUNDAY INTO SUNDAY NIGHT, SO CONFIDENCE DECREASES
AFTER THAT IN REGARDS TO HOW MUCH FORCING WE'LL HAVE AROUND. KEPT 20-
50 PERCENT CHANCES SUNDAY, BUT SUSPECT WE MAY BE ABLE TO LOWER THOSE
IF THE SYSTEM DRIFTS SOUTHEASTWARD FASTER THAN WHAT IS CURRENTLY
FORECASTED. HIGHS SATURDAY INTO SUNDAY WILL BE IN THE 70S AND LOW
80S.
A LULL IN CHANCES IS EXPECTED SUNDAY NIGHT INTO MONDAY, WITH ANOTHER
SHORTWAVE MOVING IN FROM THE WEST THAT CROSSES THROUGH THE AREA BY
ABOUT TUESDAY EVENING. CONFIDENCE IS LOWER IN THIS PERIOD GIVEN SO
MUCH INITIAL UNCERTAINTY-BUT HAVE 20-40 PERCENT POPS FOR NOW-WHICH
IS REASONABLE. HIGHS WILL MAKE THEIR WAY INTO THE MID 80S ONCE AGAIN
BY TUESDAY. ANOTHER MORE POTENT WAVE BUILDS THROUGH AT SOME POINT
WED-THUR, BUT MODELS DISAGREE ON THE EXACT TIMING. FOR EXAMPLE-THE
ECMWF IS MORE PROGRESSIVE AND BRINGING A BROADER TROUGH IN WED-THU;
AND THE GFS BY COMPARISON KEEPS A STRONGER RIDGE INITIALLY IN PLACE
AND THEN BRINGS A WEAKER TROUGH THROUGH BY THU-FRI. FOR NOW KEPT
CONSENSUS POPS OF 30-60 PERCENT IN (HIGHEST WED AFTERNOON), WITH
HIGHS IN THE MID TO UPPER 80S.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1228 AM EDT THU JUN 12 2025
THE BOTTOM LINE AS FAR AS STORMS - IT WILL BE VERY DIFFICULT TO
OVERCOME THE COMBINATION OF DRY AIR ENTRAINMENT, STABLE MID
LEVEL LAPSE RATES AND A CAPPING INVERSION AT THE BASE OF THE
SUBSIDENCE. THE DYNAMICS WITH A VERY WEAK FRONT SHOULD NOT BE
ENOUGH TO TRIGGER STORMS. HAVE KEPT STORMS OUT OF TAFS GIVEN
THESE PARAMETERS. WINDS SHOULD STAY SOUTH TO SOUTHWEST AT 3-8
KNOTS WITH VERY WEAK SYNOPTIC FLOW. SOME HAZE OR SMOKE MAY BE
PRESENT, BUT AT THIS TIME THE CONCENTRATION APPEARS LOW AND DOES
NOT APPEAR TO BE OPERATIONALLY SIGNIFICANT.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...MCD
AVIATION...SKIPPER
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