758
FXUS63 KIWX 170417
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1217 AM EDT SAT OCT 17 2026
KEY MESSAGES
- PATCHY FROST EXPECTED TONIGHT FOR SOUTH CENTRAL LOWER
MICHIGAN INTO PORTIONS OF NORTHERN INDIANA. SEE THE FROST
ADVISORY FOR DETAILS.
- WIDESPREAD FROST IS EXPECTED SATURDAY NIGHT INTO SUNDAY
MORNING WITH A POTENTIAL OF TEMPERATURES DROPPING TO THE
FREEZING MARK, ESPECIALLY EAST OF INTERSTATE 69.
- AFTER THE BELOW NORMAL TEMPERATURES THIS WEEKEND, TEMPERATURES
REBOUND BACK ABOVE NORMAL FOR MUCH OF NEXT WORK WEEK WITH DRY
WEATHER EXPECTED.
DISCUSSION
ISSUED AT 324 PM EDT FRI OCT 16 2026
SHOWERS ASSOCIATED WITH SOME STRONG LOW/MID LEVEL FRONTOGENESIS
FORCING WILL CONTINUE TO EXIT NORTHWEST OHIO THE REMAINDER
AFTERNOON. THE PRIMARY FOCUS FOR ADDITIONAL RAINFALL WILL REMAIN
BACK ACROSS NORTHWEST INDIANA AND SOUTHWEST LOWER MICHIGAN WHERE
SECONDARY SURFACE TROUGH ASSOCIATED WITH STRONG POSITIVELY TILTED
UPPER TROUGH IS AUGMENTING LAKE EFFECT RAIN SHOWERS. THE FOCUS FOR
THESE LAKE EFFECT/ENHANCED RAIN SHOWERS WILL SHIFT TO NORTHWEST
INDIANA THIS EVENING AS LOW LEVEL WINDS VEER NORTHERLY BEHIND THE
SECONDARY SFC TROUGH. A WIND ADVISORY REMAINS IN EFFECT THROUGH THIS
EVENING FOR LAPORTE AND BERRIEN COUNTIES, ALTHOUGH THE WINDOW FOR 35
MPH PLUS GUSTS MAY BE CONFINED TO A 20 TO 23Z TIMEFRAME.
BOUNDARY LAYER MIXING MAY BE TEMPERED A BIT BY THE VERY MOIST
PROFILES IN PLACE, AND THUS CONFIDENCE IS BEGINNING TO DIMINISH
SOMEWHAT IN REALIZING ADVISORY LEVEL WINDS, PARTICULARLY AFTER
00Z AS A LAKE-INDUCED THERMAL TROUGH IS LIKELY TO SHARPEN AND
WEAKEN THE LOW LEVEL HEIGHT GRADIENT. AT THIS TIME WILL CONTINUE
THE WIND ADVISORY AND WILL DEFER TO NEXT SHIFT TO MONITOR FOR
POSSIBLE CANCELLATION DEPENDING ON HOW TRENDS EVOLVE. LAKE
EFFECT RAIN SHOWERS MAY PERSIST INTO THE EARLY OVERNIGHT HOURS
ACROSS NORTHWEST INDIANA AS THERMAL TROUGHING RESPONSE OVER
SOUTHERN LAKE MICHIGAN MATURES THIS EVENING.
THE POSITIVELY TILTED NATURE OF THE UPPER TROUGH SHOULD ALLOW FOR
SYNOPTIC SCALE MID LEVEL SUBSIDENCE TO BUILD IN QUICKLY LATER
THIS EVENING AND OVERNIGHT RESULTING IN EXPECTED DIMINISHING
CLOUD TREND OUTSIDE OF LINGERING LAKE EFFECT. LOW LEVELS SHOULD
REMAIN WELL MIXED INTO THE EARLY EVENING HOURS WITH SOME BETTER
POTENTIAL OF DECOUPLING OVERNIGHT. THIS INTRODUCES THE RISK OF
SOME PATCHY FROST DEVELOPMENT AND TEMPERATURES DROPPING INTO
THE LOW-MID 30S TONIGHT. THE BEST CHANCE OF FROST FORMATION
STILL APPEARS TO BE ACROSS MUCH OF SOUTHERN LOWER MICHIGAN INTO
PORTIONS OF NORTH CENTRAL INDIANA SITUATED BETWEEN MORE DELAYED
CLOUD COVER DECREASE IN THE WEST WITH LAKE EFFECT, AND SLIGHTLY
BETTER MIXING PERSISTING EAST OF I-69 INTO THE OVERNIGHT.
QUIET WEATHER IS EXPECTED ON SUNDAY AS THE SOUTHERN GREAT LAKES AND
OHIO VALLEY WILL BE POSITIONED DOWNSTREAM OF BROAD LONGWAVE RIDGE
AXIS ACROSS CENTRAL CONUS ALLOWING FOR EXTENDED SYNOPTIC SCALE
SUBSIDENCE. SFC ANTICYCLONE WILL OVERSPREAD THE REGION LATE
SATURDAY AFTERNOON INTO SATURDAY EVENING WITH SOME LIGHTER
SOUTHWEST RETURN FLOW SETTING UP ACROSS THE WESTERN GREAT LAKES
BY SUNDAY MORNING. FROST/FREEZE POTENTIAL WILL NEED TO BE
CONSIDERED AGAIN FOR THIS PERIOD. SOME MINOR MODIFICATION OF LOW
LEVEL THERMAL TROUGH IS EXPECTED SATURDAY BUT MAINLY CLEAR
SKIES AND LIGHT WINDS SHOULD ALLOW FOR GOOD RADIATIONAL COOLING
SATURDAY NIGHT AND A POTENTIAL OF TEMPERATURES DROPPING TO THE
FREEZING MARK. BEST CHANCES BASED ON TIMING OF THE HIGH PRESSURE
STILL APPEAR TO BE EAST OF I-69 WHERE A FREEZE WATCH HAS BEEN
ISSUED. SOME COMBINATION OF FROST ADVISORIES AND/OR FREEZE
WARNINGS WILL LIKELY BE NEEDED SATURDAY NIGHT.
UPPER FLOW PATTERN WILL BECOME MORE STAGNANT AND BLOCKED IN
NATURE FOR MUCH OF NEXT WEEK WITH LITTLE OVERALL PROGRESSION IN
MEAN POSITIONING OF CENTRAL CONUS RIDGE. GRADUAL DAY TO DAY
MODERATION AND MAX TEMPERATURES IN UPPER 60S TO LOWER 70S AND
DRY CONDITIONS WILL PREVAIL FOR MUCH OF NEXT WEEK. CANNOT
COMPLETELY RULE OUT SOME PATCHY FROST CONCERNS SUNDAY AND MONDAY
NIGHTS, BUT THIS IS A LOW CONFIDENCE ITEM AT THIS TIME.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1217 AM EDT SAT OCT 17 2026
NORTHERLY WINDS GUSTING TO AROUND 20 KNOTS WILL DIMINISH TO LESS
THAN 10 KNOTS BY DAYBREAK AS HIGH PRESSURE BUILDS IN. VFR WITH
LIGHT WINDS AND LITTLE IN THE WAY OF CLOUD COVER OTHERWISE THIS
WEEKEND INTO MUCH OF NEXT WEEK.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FROST ADVISORY FROM 4 AM TO 9 AM EDT THIS MORNING FOR
INZ005>009-014-017-104-116-204-216.
FREEZE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
INZ006>009-017-018-023>027-032>034-116-216.
OH...FREEZE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
OHZ001-002-004-005-015-016-024-025.
MI...FROST ADVISORY FROM 4 AM TO 9 AM EDT THIS MORNING FOR
MIZ078>081.
MARINE...GALE WARNING UNTIL 2 AM EDT EARLY THIS MORNING FOR LMZ043-046.
SMALL CRAFT ADVISORY UNTIL 11 AM EDT SUNDAY FOR LMZ043-046.
DISCUSSION...MARSILI
AVIATION...STEINWEDEL
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