657
FXUS63 KIWX 161736
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
136 PM EDT FRI MAY 16 2025
KEY MESSAGES
- SEVERE THUNDERSTORMS ARE POSSIBLE FROM 6-11PM EDT THIS
EVENING. THE GREATEST RISK WILL BE IN THE SOUTHERN HALF OF OUR
AREA.
- DAMAGING STRAIGHT-LINE WINDS WILL BE THE PRIMARY THREAT BUT
HAIL AND TORNADOES CANNOT BE RULED OUT.
- DRY WEATHER RETURNS FOR THE WEEKEND WITH HIGHS IN THE 60S TO
LOW 70S.
DISCUSSION
ISSUED AT 352 AM EDT FRI MAY 16 2025
ROUND 1 OF SEVERE WX HAS ENDED AND WE NOW PREPARE FOR A POTENTIAL
ROUND 2 LATER TODAY. DEEP UPPER LOW WILL CONTINUE TO PINWHEEL OVER
THE UPPER MIDWEST WITH A SECOND EMBEDDED SHORTWAVE SWINGING THROUGH
OUR AREA LATER TODAY, PULLING THE UPPER LOW FURTHER ESE AND PUSHING
A SURFACE OCCLUDED/COLD FRONT THROUGH THE AREA. THIS FRONT PASSES
DURING THE FAVORABLE TIME FOR SEVERE WEATHER (EARLY EVENING) BUT THE
INSTABILITY PICTURE IS MUCH MORE MUDDLED TODAY. COLD MIDLEVEL TEMPS
WILL SUPPORT DECENT MIDLEVEL LAPSE RATES BUT SURFACE DEWPOINTS WILL
ONLY BE AROUND 60F AT BEST. THIS KEEPS SBCAPE VALUES GENERALLY AT OR
BELOW 2000 J/KG. THERE WILL BE A STOUT CAPPING INVERSION FOR MUCH OF
THE DAY BUT THAT DOES LOOK TO BREAK WITH THE PASSING FRONT ROUGHLY
23-03Z. WIND/SHEAR PROFILES ARE OBVIOUSLY HIGHLY FAVORABLE FOR
ORGANIZED STORMS IF SUSTAINED UPDRAFTS MANAGE TO DEVELOP. WITH THE
PASSING FRONT AND AT LEAST MODERATE INSTABILITY THERE SEEMS LIKE A
DECENT CHANCE FOR THAT TO HAPPEN. MULTICELL LINES/CLUSTERS WILL
LIKELY BE THE PRIMARY MODE GIVEN LINEAR FORCING WITH DAMAGING
STRAIGHT-LINE WINDS THE PRIMARY HAZARD GIVEN 50+ KTS OF FLOW NOT TOO
FAR FROM THE SURFACE. THERE IS ALSO A SECONDARY HAIL AND TORNADO
RISK THOUGH. HAIL WILL BE SOMEWHAT LIMITED BY MORE MODEST
INSTABILITY BUT THERE IS LIKELY ENOUGH FOR SOME 1"+ HAIL GIVEN COLD
MIDLEVEL TEMPS. AND WHILE SURFACE WINDS ARE NOT AS BACKED AS ONE
WOULD LIKE TO SEE FOR A TORNADO RISK, THE DEGREE OF 0-1KM SHEAR
CAN'T BE IGNORED. 0-3KM LINE-NORMAL SHEAR VECTORS SHOULD ALSO EASILY
EXCEED 30 KTS AND WILL PRESENT A QLCS TORNADO RISK (IF OTHER STORM-
SCALE CRITERIA ARE MET). OUR ENTIRE CWA WILL HAVE SOME CHANCE
OF SEVERE WEATHER THIS EVENING BUT THE BEST CHANCES APPEAR IN OUR
SOUTHERN HALF. POTENTIAL FAILURE POINTS INCLUDE MORE LIMITED
INSTABILITY AND LATER/WEAKER FORCING WHICH WOULD LIKELY LEAD TO A
MORE ISOLATED THREAT GIVEN THE LACK OF A SOLID/ORGANIZED CONVECTIVE
LINE. MORE ORGANIZED ACTIVITY SOUTH OF OUR AREA MAY ALSO LIMIT THE
THREAT THIS FAR NORTH.
GIVEN HIGHLY ACTIVE SHORT-TERM AND RELATIVELY QUIET WEATHER OVER THE
WEEKEND INTO EARLY NEXT WEEK, DID NOT MAKE ANY CHANGES TO THE NBM
INITIALIZATION. UPPER LOW CONTINUES TO PINWHEEL EAST ON SAT WITH JUST
A LOW CHANCE OF A FEW SPRINKLES IN OUR N/NE ZONES. SUNDAY WILL
BE DRY AND PLEASANT WITH COOL TEMPS, MOSTLY SUNNY SKIES, AND LOW
HUMIDITY. PRECIP CHANCES DO RETURN TO THE AREA LATE MON INTO
WED AS ANOTHER UPPER LOW APPROACHES THE REGION. STILL SOME
UNCERTAINTY WITH THE TRACK OF THIS LOW BUT MOST GUIDANCE KEEPS
US ON THE COOLER/MORE STABLE SIDE WITH DECENT RAIN CHANCES BUT A
LOW SEVERE RISK AT THIS TIME.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 127 PM EDT FRI MAY 16 2025
AN UPPER LEVEL SPEED MAX LIFTING ACROSS DOWNSTREAM PORTION OF
UPPER TROUGH AND AN ACCOMPANYING UPPER LEVEL SHORT WAVE WILL
HELP TO ADVECT SOME INCREASED LOW LEVEL MOISTURE NORTHWARD LATE
THIS AFTERNOON/EARLY THIS EVENING. SFC DEW POINTS HAVE MIXED OUT
NICELY EARLY THIS AFTERNOON INTO THE UPPER 40S TO LOWER 50S. THE
CHALLENGING PART OF THIS CONVECTIVE FORECAST IS TRYING TO ASSESS
EXTENT OF MOISTURE RETURN IN ADVANCE OF THIS SHORT WAVE TONIGHT
AND HOW MUCH DESTABILIZATION CAN OCCUR. STRENGTHENING LOW/MID
LEVEL WIND FIELDS AND INITIAL DRY PROFILES DO SUGGEST POTENTIAL
OF SOME STRONG WINDS WITH ANY STORMS (OR SHOWERS). HAVE NOT MADE
SUBSTANTIAL CHANGES TO PREVIOUS TIMING OF MAIN POTENTIAL THREAT
IN THE 00Z-03Z WINDOW FOR THUNDER. OTHERWISE, SOUTHERLY GUSTS
TO 20 TO 25 KNOTS WILL BE MAINTAINED IN ADVANCE OF THE
ASSOCIATED COLD FRONT THIS EVENING, WITH POST-FRONTAL WEST WINDS
GUSTING TO 30 TO 35 KNOTS BY SATURDAY AFTERNOON. CONDITIONS
SHOULD REMAIN PRIMARILY VFR THIS PERIOD WITH THE EXCEPTION OF
ANY STRONGER SHOWERS AND STORMS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 5 PM EDT
SATURDAY FOR LMZ043-046.
DISCUSSION...AGD
AVIATION...MARSILI
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