586
FXUS63 KIWX 171819
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
219 PM EDT SAT MAY 17 2025
KEY MESSAGES
- WINDY THIS AFTERNOON WITH WEST WINDS GUSTING NEAR 35 MPH AT
TIMES.
- REMAINING COOL THROUGH NEXT WEEK.
- PERIODS OF RAIN EXPECTED TUESDAY INTO WEDNESDAY.
DISCUSSION
ISSUED AT 219 PM EDT SAT MAY 17 2025
RAW CONDITIONS WILL PERSIST THIS AFTERNOON THANKS TO GUSTY WEST
WINDS, MOSTLY CLOUDY SKIES AND STEADY TEMPS IN THE MID 50S TO MID
60S. THIS IS OCCURRING UNDER COOL/CYCLONIC NORTHWEST FLOW ON THE
SOUTHWEST FRINGE OF AN EXITING LOW PRESSURE SYSTEM. THIS SYSTEM
WILL GRADUALLY BEGIN TO LOSE ITS INFLUENCE LOCALLY TONIGHT INTO
SUNDAY WHILE TRACKING TRACKING TOWARD NEW ENGLAND AND FAR SOUTHERN
QUEBEC. THE RESULT WILL BE A LESS WINDY SUNDAY AND A TREND TOWARD
MOSTLY SUNNY SKIES FROM SW TO NE BY THE AFTERNOON HOURS AS LARGE
SCALE SUBSIDENCE AND DRYING OVERSPREADS.
MODELS CONTINUE TO COME INTO BETTER AGREEMENT WITH A LARGE LOW
PRESSURE SYSTEM EMERGING OVER THE CENTRAL PLAINS MONDAY, THEN SLOWLY
TRACKING EAST INTO THE MID MS/NORTHERN OH VALLEYS TUESDAY INTO
WEDNESDAY. MONDAY SHOULD BE MAINLY DRY THANKS TO DRY LOW LEVEL ENE
FLOW ON THE SOUTHERN FRINGE OF HIGH PRESSURE. RAIN IS THEN
EXPECTED TO OVERSPREAD THE AREA FROM SW TO NE LATE MONDAY
NIGHT INTO TUESDAY AS DEEPER MOISTURE ADVECTS INTO A TIGHTENING
FRONTAL SLOPE. INSTABILITY APPEARS LIMITED DUE TO NEARLY MOIST
ADIABATIC LAPSE RATES NORTH OF THE SFC BOUNDARY IN CENTRAL
IL/IN. HOWEVER, COULD SEE LOCALLY HEAVY RAIN AND EMBEDDED
THUNDER GIVEN THE FORCING AND MOISTURE QUALITY (PRECIPITABLE
WATER VALUES NEAR 1.25 INCHES). COVERAGE AND INTENSITY OF THE
RAIN SHOWER ACTIVITY MAY TREND TO DIMINISH NEAR THE LOW PRESSURE
CENTER A BIT THEN INTO WEDNESDAY AS DEEPER MOISTURE EXITS EAST.
DRIER AIR DOES EVENTUALLY FILTER IN TOWARD THE END OF THE WEEK
IN WAKE OF THIS SYSTEM WITH BELOW NORMAL TEMPERATURES HOLDING IN
RESPONSE TO NEGATIVE HEIGHT ANOMALIES MERGING OVER THE NORTHEAST
AND SOUTHEAST CANADA.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 140 PM EDT SAT MAY 17 2025
COLD ADVECTION VFR STRATOCU WILL LINGER AT TERMINALS THIS
EVENING, WITH SOME POTENTIAL SCATTERING AT KFWA LATER THIS
EVENING. POST-FRONTAL INVERSION/SUBSIDENCE AND SHALLOW LOW
LEVEL MOISTURE MAY ALLOW THESE LOW CLOUDS TO LINGER THROUGH MUCH
OF THE PERIOD, ALTHOUGH SOME SUBTLE MID LEVEL HEIGHT RISES ON
SUNDAY MAY RESULT IN MORE OF SCATTERED TO BROKEN NATURE OF THESE
LOW CLOUDS. MIXING TODAY HAS BEEN ENHANCED BY THIS COLD
ADVECTION WITH GUSTS AS HIGH AS 35 KNOTS REPORTED. THESE GUSTS
SHOULD DIMINISH EARLY EVENING, ALTHOUGH SOME GUSTS TO 15 TO 20
KNOTS MAY PERSIST THROUGH THE EARLY EVENING HOURS AS LAPSE
RATES ARE SLOW TO WEAKEN. INCOMING LOW LEVEL RIDGE AXIS TONIGHT
INTO SUNDAY WILL RESULT IN WEAKER WEST-NORTHWEST WINDS FOR
SUNDAY, GENERALLY 10-15G15-20KT RANGE.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR LMZ043-
046.
DISCUSSION...STEINWEDEL
AVIATION...MARSILI
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