026
FXUS63 KIWX 201120
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
620 AM EST WED NOV 20 2024
KEY MESSAGES
- BRIEF PERIOD OF LIGHT RAIN THIS MORNING WILL SIGNAL THE START
OF A MORE LATE FALL/EARLY WINTER SETUP.
- RAIN AND SNOW WILL BE POSSIBLE MAINLY NEAR LAKE MICHIGAN
TONIGHT, WITH EVERYONE SEEING AT LEAST SOME SNOWFLAKES ON
THURSDAY AS COLDER AIR RUSHES ON ON STRONG WEST TO NORTHWEST
WINDS.
- CONFIDENCE REMAINS ON THE LOWER SIDE ON ACCUMULATION POTENTIAL
THURSDAY GIVEN AIR TEMPERATURES NEAR OR ABOVE FREEZING, WARM
GROUND TEMPS AND WET NATURE OF THE SNOW. HEAVIER BANDS COULD
BRING A QUICK INCH OR SO TO SOME AREAS.
- TRAVEL IMPACTS, IF ANY, SHOULD BE LIMITED TO THE THURSDAY
AFTERNOON COMMUTE FOR AREAS THAT SEE THE SNOW STICK TO ROADS
OR ELEVATED SURFACES.
DISCUSSION
ISSUED AT 442 AM EST WED NOV 20 2024
A COLD FRONT WAS MAKING STEADY PROGRESS EAST ACROSS IL EARLY
THIS MORNING, SIGNALING THE START OF AN INCREASINGLY ACTIVE
PERIOD. THE DEEP UPPER LOW, CENTERED OVER NW MINNESOTA WILL
BEGIN ITS DIVE SOUTH OVER THE NEXT 24 HOURS, REACHING LOWER
MICHIGAN BY 12Z THU. A SERIES OF RATHER STOUT SHORTWAVES WILL
IMPACT THE AREA, WITH THE FIRST ALREADY MAKING ITS PRESENCE
KNOWN BY FORCING A SLOWLY EXPANDING AREA OF SHOWERS ALONG THE
COLD FRONT, FURTHER AIDED BY A 120+ KT JET STREAK. AS THE WAVE
WORKS EAST, THE BAND OF SHOWERS SHOULD EXPAND AND INTENSIFY
SOMEWHAT, REACHING WESTERN AREAS NEAR/JUST AFTER 12Z WED AND
THEN QUICKLY EXITING BY 18Z OR SO. OVERALL QPF WILL BE LIGHT, ON
THE ORDER OF A TENTH OF AN INCH OR SO AND WILL BE IN THE FORM
OF RAIN DESPITE CAA ALREADY UNDERWAY (0 DEGREE 850 MB TEMPS
RIGHT AT THE LEADING EDGE OF THE FRONT). MANY AREAS WILL SEE A
LULL IN PRECIP THIS AFTERNOON WITH FOCUS SHIFTING TO ALONG/N OF
THE TOLL ROAD NEAR/AFTER 00Z THU AS THE DEEP UPPER LOW DRAWS
CLOSER AND RAPID DEVELOPMENT AND DEEPENING OF A SURFACE LOW OVER
LOWER MI DRAWS IN THE START OF THE COLDEST AIR SO FAR THIS FALL
(850 MB TEMPS OF -5 TO
-10 C). THIS WILL START THE LAKE EFFECT PROCESS WITH BANDS OF
RAIN/SNOW SHOWERS FROM WEST TO EAST, LESSENING WITH SOUTHWARD EXTENT
AND INLAND.
THE COLDEST AIR WILL CLIP SW AREAS NEAR 12Z AND THEN TRANSLATE SE
INTO CENTRAL IN AS THE STRONG SFC LOW OVER LK HURON QUICKLY SHIFTS W
THEN SW, EVENTUALLY REACHING THE IN/MI STATE LINE BY 00Z FRI. MODELS
HAVE BEEN CONSISTENT ON A LARGE AREA OF LIGHT TO MODERATE
PRECIPITATION OVERSPREADING THE FORECAST AREA STARTING AROUND 18Z
THU AND THEN PROGRESSING RAPIDLY SOUTH. WHILE CONFIDENCE IS HIGH ON
THE PRECIP, FINER DETAILS ON PTYPE AND MORE SPECIFICALLY SNOW
ACCUMULATION POTENTIAL, REMAIN A BIT MORE DICEY AS AIR TEMPERATURES
WILL BE NEAR OR JUST ABOVE FREEZING, WARM GROUND CONDITIONS LINGER
AND OVERALL PRECIP RATES WILL VARY AT ANY GIVEN LOCATION. STEEPENING
LAPSE RATES SHOULD AID IN SOME EFFECTIVE COOLING OF THE COLUMN IN
THE HEAVIER PRECIP, LEADING TO INCREASE CONCERNS VS THE PAST COUPLE
OF DAYS FOR POSSIBLY ACCUMULATIONS. IF THE DYNAMIC PROCESSES
WIN, SOME AREAS IN THE SW PART OF THE CWA COULD SEE 1 TO 2
INCHES OF SLOPPY SNOWFALL. WHILE THE CURRENT FORECAST REFLECTS
AMOUNTS IN THIS RANGE, MUCH REMAINS TO BE SORTED OUT OVER THE
NEXT 24 HOURS. DAYTIME OCCURRENCE OF THE PRECIP WILL HELP
SOMEWHAT ON LIMITING ROAD IMPACTS, BUT HEAVIER SNOW RATES AND
TEMPERATURES NEAR FREEZING COULD STILL BRING SOME SLICK SPOTS.
PTYPE ISSUES AREN'T THE ONLY THING TO MONITOR AS THE DEEPENING LOW
WILL CREATE A DECENT PRESSURE GRADIENT WITH WINDS OF 15 TO 25 MPH
AND GUSTS OF 30 MPH OR HIGHER. NOT ONLY COULD THIS IMPACT
VISIBILITIES WITH ANY SNOW, IT WILL MAKE IT FEEL DOWNRIGHT RAW
(WIND CHILLS IN THE 20S) COMPARED TO THE WEEKS OF WARMER WEATHER
WE ENJOYED.
FEW CHANGES MADE BEYOND THURSDAY NIGHT AS THE REGION REMAINS UNDER
THE INFLUENCE OF THE MAIN UPPER LOW STILL SITTING THE NE US THROUGH
SATURDAY. ONE MORE ROUND OF MAINLY LAKE ENHANCED PRECIP APPEARS
LIKELY FRI INTO FRI EVENING, BUT BY THIS POINT THERMAL PROFILES
SHOULD BE SUFFICIENTLY WARM ENOUGH TO SUPPORT ALL RAIN.
ADDITIONAL MODERATION IN TEMPERATURES AND AT LEAST A TEMPORARY
REPRIEVE TO THE WET CONDITIONS ARRIVES FOR THE WEEKEND BEFORE
PIECES OF ENERGY FROM THE MONSTER LOW OFF THE PACIFIC COAST MOVE
EAST.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 620 AM EST WED NOV 20 2024
STRONG MIDLEVEL SHORTWAVE WILL SEND A LINE OF RAIN THROUGH THE
AREA IN THE 14-17Z WINDOW TODAY. CEILINGS WILL DROP TO AROUND 1
KFT WITH BETTER CHANCES FOR IFR CONDITIONS AT KFWA. CLEARING
EXPECTED BEHIND THE WAVE BUT ANOTHER SYSTEM WILL APPROACH
TONIGHT AND BRING ANOTHER ROUND OF LIGHT PRECIP AND LOWER
CEILINGS. INITIAL RAIN WILL CHANGEOVER TO SNOW JUST BEFORE 06Z
TONIGHT BUT LITTLE/NO ACCUMULATION IS EXPECTED PRIOR TO 12Z. THE
BEST CHANCES FOR HEAVIER, ACCUMULATING SNOW WILL BE DURING THE
DAY THURSDAY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 11 AM EST
THURSDAY FOR LMZ043-046.
GALE WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY NIGHT
FOR LMZ043-046.
DISCUSSION...FISHER
AVIATION...AGD
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