624
FXUS63 KIWX 191036
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
636 AM EDT MON MAY 19 2025
KEY MESSAGES
- DRY TODAY WITH HIGHS AROUND 70.
- WIDESPREAD RAIN WITH A FEW EMBEDDED THUNDERSTORMS IS EXPECTED
ON TUESDAY. SEVERE WEATHER IS NOT ANTICIPATED.
- COOL WEATHER WITH PERIODIC CHANCES FOR RAIN CONTINUES DURING
THE SECOND HALF OF THE WEEK.
DISCUSSION
ISSUED AT 252 AM EDT MON MAY 19 2025
ONE MORE DRY DAY TODAY AS HIGH AMPLITUDE MID/UPPER LEVEL RIDGE
REMAINS LOCKED OVER THE GREAT LAKES WITH UPPER LOW REMAINING WELL TO
OUR WEST. LOW LEVEL WINDS VEER TO A MORE EASTERLY DIRECTION TODAY,
MAINTAINING A FEED OF COOL/DRY/STABLE AIR. SOME GUIDANCE SUGGESTS
REMNANTS OF NE/IA NOCTURNAL CONVECTION WILL SURVIVE LONG ENOUGH TO
SUPPORT SOME SPRINKLES IN OUR WESTERN ZONES BUT THIS APPEARS
UNLIKELY BASED ON DEGREE OF DRY/STABLE AIR IN PLACE. EXPECT JUST AN
INCREASE IN HIGH CLOUDS WITH AFTERNOON TEMPS AROUND 70F. BULK OF
TONIGHT WILL REMAIN DRY AS WELL WITH ELEVATED WARM FRONT AND
THETA-E SURGE NOT ARRIVING UNTIL RIGHT AROUND 12Z TUE AM.
TUE STILL LOOKS WET, ESPECIALLY FOR AREAS SOUTH OF US-30.
INITIAL WING OF 295-300K ISENTROPIC UPGLIDE LIFTS THROUGH THE
AREA TUE AM. CROSS-ISOBAR FLOW IS DECENT BUT NOTHING SPECTACULAR
AND LAPSE RATES ABOVE THE FRONTAL ZONE REMAIN MEAGER (MOIST
ADIABATIC AT BEST). HI-RES CAM'S SUGGEST A MARKED WEAKENING
TREND AS THIS INITIAL PRECIP LIFTS NORTH AND DISLODGES VERY
DRY/STABLE ENVIRONMENT. BEST CHANCES FOR HEAVIER PRECIP LOOK TO
BE LATER IN THE DAY AS PRIMARY VORTICITY LOBE SWINGS INTO THE
AREA (AGAIN, BEST CHANCES SOUTH). INSTABILITY PROFILES TUE
EVENING STILL AREN'T GREAT BUT ARE BETTER AND SUPPORT AT LEAST A
THUNDER MENTION. STRENGTH AND DEPTH OF STABLE LAYER BELOW 850MB
WILL PREVENT ANY SURFACE-BASED CONVECTION AND PREVENT ANY
STRONG WIND THREAT. SOME SMALL HAIL MIGHT NOT BE OUT OF THE
QUESTION IN OUR FAR S/SW ZONES BUT INSTABILITY APPEARS TOO
MEAGER TO SUPPORT A LARGE HAIL THREAT. POCKETS OF HEAVY RAIN ARE
ALSO POSSIBLE IN OUR SOUTH GIVEN PW VALUES AROUND 1.5 INCHES
BUT QUICK STORM MOTIONS AND DRY ANTECEDENT CONDITIONS WILL LIMIT
THE FLOODING THREAT. OVERALL EXPECT BASIN-AVERAGE RAIN AMOUNTS
ROUGHLY 0.5-0.75 INCHES ON TUE WITH THE HIGHEST AMOUNTS SOUTH OF
US-30.
CENTRAL CONUS UPPER LOW THEN MERGES WITH A DEVELOPING QUEBEC UPPER
LOW ON WED. UPPER LEVEL PATTERN ACTUALLY GETS VERY MESSY DURING THE
SECOND HALF OF THE WEEK AS THESE TWO UPPER LOWS MERGE INTO ONE LARGE
UPPER LOW OVER THE GREAT LAKES/NEW ENGLAND WITH MULTIPLE EMBEDDED
SHORTWAVES ROTATING THROUGH THE REGION. LIGHT RAIN IS EXPECTED TO
CONTINUE ON WED AS THIS PROCESS UNFOLDS BUT CONFIDENCE IN PRECIP
CHANCES THU AND BEYOND DROPS SIGNIFICANTLY. HELD CLOSE TO NBM POP'S
DURING THIS PERIOD. MUCH HIGHER CONFIDENCE IN TEMPS REMAINING BELOW
NORMAL THROUGH THE END OF THE WEEK. WARM WEATHER IS NOT LIKELY TO
RETURN UNTIL AT LEAST MEMORIAL DAY (POSSIBLY NOT EVEN BY THEN).
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 636 AM EDT MON MAY 19 2025
A LOW PRESSURE SYSTEM SLOWLY APPROACHES THE AREA THROUGH THE
FORECAST PERIOD. ITS FRONTAL SYSTEM RUNS INTO DRY AIR AND THERE'S
EVIDENCE THAT A BACKDOOR COLD FRONT DIVES SOUTHWARD OUT OF MI AND
THIS LIKELY HELPS STALL THE ADVANCE OF THE WARM FRONT FROM THAT
ARRIVING LOW PRESSURE SYSTEM. WITH THIS IN MIND, WILL LEAN DRY ON
THE FORECAST AND CONTINUE VFR CONDITIONS THROUGH THE FORECAST PERIOD
WITH PLENTY OF LOW LEVEL MOISTURE RESIDING IN TIME SECTION MODEL
OUTPUT. RAIN LIKELY DOESN'T ARRIVE UNTIL THE LAST FEW HOURS OF THE
NEXT TAF PERIOD. WIND-WISE, EXPECT NORTH WINDS TO CONTINUE TO VEER
MORE EASTERLY BY THE END OF THE PERIOD. WINDS DON'T QUITE GO CALM
THROUGH THE PERIOD, BUT EXPECT WEAK TO NO WIND GUSTS UNTIL WE GET TO
AT LEAST 6Z MONDAY NIGHT WHEN THE LOW LEVEL JET ARRIVES.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 2 AM EDT
WEDNESDAY FOR LMZ043-046.
DISCUSSION...AGD
AVIATION...ROLLER
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