564
FXUS63 KIWX 151737
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
137 PM EDT THU MAY 15 2025
KEY MESSAGES
- INCREASING CONFIDENCE IN SEVERE THUNDERSTORMS THIS EVENING.
ALL HAZARDS ARE POSSIBLE, BUT LARGE HAIL FROM DISCRETE
SUPERCELLS FOLLOWED BY DAMAGING WIND GUSTS FROM LINEAR
SEGMENTS ARE THE PRIMARY HAZARDS.
- VERY WARM TODAY WITH NEAR RECORD HIGH TEMPERATURES
APPROACHING 90 DEGREES.
- ON FRIDAY EVENING, ANOTHER ROUND OF SEVERE THUNDERSTORMS ARE
POSSIBLE.
DISCUSSION
ISSUED AT 305 AM EDT THU MAY 15 2025
DRY WEATHER IS EXPECTED DURING THE DAY DESPITE AN ADVANCING
WARM FRONT MIDDAY. FORECAST SOUNDINGS DEPICT A STOUT DRY LAYER
STOP A CAPPING INVERSION. THIS CAP DOES PERMIT STEEP LOW-LEVEL
LAPSE RATES, BUT AN ABSENCE OF UPPER-LEVEL SUPPORT AND A DEEP
MOISTURE COLUMN PRECLUDE DAYTIME POP-UP STORMS. INSTEAD, THE
PRIMARY DRIVER OF STORMS THIS EVENING WILL BE AN APPROACHING
COLD FRONT / DRYLINE FROM ILLINOIS. CAMS HAVE COME INTO FAIRLY
STRONG AGREEMENT THAT STORMS WILL OVERCOME THE CAP AND ERUPT
OVER EASTERN IL AND TRACK EAST- NORTHEAST. THIS CAP IS THE ONLY
REMAINING PIECE OF UNCERTAINTY AND THERE ARE STILL A COUPLE OF
MODELS THAT STEER CONVECTION ELSEWHERE, BUT THESE SOLUTIONS SEEM
TO BE OUTLIERS. THE BEST 500-MB JET DYNAMICS ARE FOCUSED ACROSS
NORTHERN IL AND MUCH OF WI WHICH DOES RAISE SOME QUESTIONS AS
TO HOW FAR EAST STORMS CAN SUSTAIN THEMSELVES, BUT CAMS SUGGEST
DISCRETE IL STORMS AND NORTHWEST IN STORMS WILL CONGEAL INTO A
LINE WITHIN OUR FORECAST AREA. ALL HAZARDS REMAIN POSSIBLE,
THROUGH IT SHOULD BE NOTED THAT LOW-LEVEL HODOGRAPHS ARE
SOMEWHAT FLAT, AND THAT LCLS NEAR 1000M AREA COULD BE A TOUCH
ELEVATED FOR A TRUE TORNADO RISK.
OTHERWISE, VERY WARM THIS AFTERNOON WITH HEAT INDICES IN THE LOW-90S
AND AIR TEMPERATURES APPROACHING 90, ESPECIALLY ALONG AND WEST OF US
31.
ON THE HEELS OF THIS EVENING'S SEVERE WEATHER RISK IS INCREASING
CONCERN FOR SEVERE STORMS FRIDAY EVENING. A STOUT 500-MB JET RACES
IN ACROSS IL AND IN AHEAD OF AN ADVANCING UPPER-LEVEL TROUGH AND
COLD FRONT. OUR ATMOSPHERE WILL HAVE TO RECOVER FROM THRUSDAY'S
STORMS IN ORDER TO ACCOMMODATE THE FRIDAY RISK. ADDITIONALLY, DEW
POINTS ARE FORECAST TO BE HIGHLY VARIABLE NORTH TO SOUTH WHICH WILL
LIMIT THE SEVERE RISK ACCORDINGLY. MANY DETAILS TO SORT OUT OVER THE
NEXT 24 HOURS, BUT, DAMAGING WIND APPEARS TO BE THE PRIMARY RISK.
YET, ALL HAZARDS REMAIN ON THE TABLE.
NOTABLY COOLER AND DRYING OUT FOR THE WEEKEND BEFORE A SERIES OF
SYSTEMS NEXT WEEK BRING RENEWED SHOWER AND STORM CHANCES.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 126 PM EDT THU MAY 15 2025
A STRONG UPPER LEVEL JET STREAK WILL NOISE INTO THE SOUTHERN
GREAT LAKES REGION TONIGHT. THE PRIMARY UPPER LEVEL LOW LINGERS
WELL BACK TO THE WEST ACROSS THE NORTHERN PLAINS, BUT INCREASING
LARGE SCALE LIFT AT THOSE NOSE OF THIS JET COUPLED WITH MODERATE
TO STRONG SURFACE BASED INSTABILITY SHOULD LEAD TO CONVECTIVE
INITIATION ACROSS NORTHEAST ILLINOIS LATE THIS AFTERNOON,
EVENTUALLY SHIFTING INTO NORTHWEST INDIANA AFTER 00Z. HAVE
GENERALLY MAINTAINED IDEA OF PREVIOUS TAF TIMING OF BETTER
CONVECTIVE TRENDS AT KFWA AND KSBN WITH A 3 TO 4 HOUR WINDOW OF
PREVAILING THUNDER. GIVEN MODERATE TO STRONG INSTABILITY AND
AMPLE SHEAR, THESE STORMS MAY BE STRONG TO SEVERE WITH A
POTENTIAL OF SOME LARGE HAIL AND THUNDERSTORM WIND GUSTS IN
EXCESS OF 50 KNOTS. PRE-FRONTAL FORCING FEATURE WILL SHIFT EAST
OF THE TERMINALS DURING THE EARLY OVERNIGHT HOURS. BETTER LOW
LEVEL MOISTURE WILL GET SHUNTED SOUTHEAST AND EAST OF TERMINALS
LATE TONIGHT, BUT THIS MOISTURE GRADIENT IS EXPECTED TO RETURN
NORTHWARD LATER FRIDAY. THE COMBINATION OF THIS RETURN MOISTURE
ADVECTION FORCING AND APPROACH OF PRIMARY UPPER LEVEL TROUGH
WILL RESULT IN RENEWED SHOWER AND STORM POTENTIAL OUTSIDE OF
THIS FORECAST VALID PERIOD LATE FRIDAY AFTERNOON/EVENING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...BROWN
AVIATION...MARSILI
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