063
FXUS63 KIWX 201143
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
643 AM EST THU FEB 20 2025
KEY MESSAGES
- THE WINTER WEATHER ADVISORY HAS BEEN EXTENDED UNTIL 1 AM EST
FRIDAY FOR BERRIEN, CASS, ST JOSEPH (IN), AND NORTHERN LA
PORTE COUNTIES. ADDITIONAL LAKE EFFECT SNOW ACCUMULATIONS
BETWEEN 2 TO 6 INCHES POSSIBLE, WITH THE HIGHEST TOTALS IN
BERRIEN COUNTY. DIFFICULT TRAVEL IS LIKELY THROUGHOUT THE DAY
WITH AREAS OF BLOWING SNOW EXPECTED.
- A DRY STRETCH ENSUES FOR THE WEEKEND, WITH TEMPERATURES
FINALLY CLIMBING BACK ABOVE FREEZING BY SUNDAY.
- MILD WITH HIGHS IN THE 40S NEXT WEEK WITH CHANCES FOR RAIN AND
SNOW MIDWEEK.
DISCUSSION
ISSUED AT 230 AM EST THU FEB 20 2025
LIGHT SYSTEM SNOW IS MAKING ITS WAY OUT OF THE AREA EARLY THIS
MORNING, WITH OBSERVED AMOUNTS BETWEEN 0.5" TO 1". THIS HAS ALLOWED
FOR ROADS, BRIDGES, AND OVERPASSES TO BECOME SNOW-COVERED AND SLICK
SO TAKE IT SLOW FOR THE MORNING COMMUTE! SECONDARY AND UNTREATED
ROADS WILL BE ESPECIALLY SLICK THIS MORNING WITH POTENTIAL FOR BLACK
ICE TO DEVELOP WHERE CARS HAVE DRIVEN OVER THE SNOW AND COMPACTED IT.
WE CONTINUE TO MONITOR LAKE EFFECT SNOW ALONG AND DOWNWIND OF LAKE
MICHIGAN. CURRENT RADAR IMAGERY SHOWS TWO ONGOING LAKE EFFECT SNOW
BANDS ACROSS BERRIEN COUNTY AND INTO CASS AND ST JOSEPH (IN)
COUNTIES. A MESOLOW CAN ALSO BE SEEN ON RADAR OVER LAKE MICHIGAN
OFFSHORE OF LUDINGTON, WHICH WILL CONTINUE TO MOVE SOUTHWARD AND
POTENTIALLY IMPACT OUR FORECAST AREA LATER THIS MORNING INTO EARLY
AFTERNOON. WE'VE HAD A FEW LAKE EFFECT SNOW BANDS VISIBLE ON RADAR
OVERNIGHT, BUT WE ARE STILL EXPECTING A DOMINANT SINGLE BAND OF LAKE
EFFECT SNOW TO SET UP LATER THIS MORNING (WITH POTENTIAL ENHANCEMENT
FROM THE AFOREMENTIONED MESOLOW). FAVORABLE PARAMETERS INCLUDE
PRONOUNCED LOW LEVEL CONVERGENCE, A LAKE MICHIGAN TO LAKE
SUPERIOR CONNECTION GIVEN THE LONG NORTHERLY FETCH, INVERSION
HEIGHTS AROUND 6-8 KFT, DELTA-TS OF -15C, AND NEGATIVE THETA E
LAPSE RATES. FORECAST SOUNDINGS DEPICT INCREASING LIFT AND
SATURATION AS INVERSION HEIGHTS RISE THIS MORNING. LATEST HI RES
MODEL GUIDANCE, PARTICULARLY THE HRRR, SUGGESTS SW BERRIEN, NW
ST JOSEPH (IN), AND NE LA PORTE COUNTIES WILL BE THE BULLSEYE
FOR THIS SINGLE BAND OF LAKE EFFECT. HOWEVER, FORECASTING A
SINGLE, STRONG LAKE EFFECT SNOW BAND CAN BE QUITE TRICKY AS
SMALL WOBBLES IN ITS TRACK CAN HAVE IMPLICATIONS ON SNOW
AMOUNTS. THE LAKE EFFECT SNOW BAND IS LIKELY TO ONLY BE 20 TO 30
MILES WIDE, WITH A SHARP GRADIENT IN SNOW AMOUNTS ON EITHER
SIDE. ADDITIONAL SNOW ACCUMULATIONS FROM NOW INTO FRIDAY MORNING
ARE HIGHEST IN BERRIEN COUNTY WITH UP TO 6", WITH THE REST OF
THE ADVISORY AREA EXPECTED TO SEE ANYWHERE BETWEEN 2-5" WITH A
SHARP CUTOFF IN TOTALS. HIGHER AMOUNTS ARE DEFINITELY POSSIBLE,
ESPECIALLY GIVEN THE HIGHLY VARIABLE NATURE OF LAKE EFFECT SNOW.
THE LAKE EFFECT SNOW IN NORTHWEST INDIANA AND SOUTHWEST LOWER
MICHIGAN WILL RESULT IN DIFFICULT TRAVEL CONDITIONS THIS MORNING AND
AFTERNOON, ESPECIALLY ALONG THE I-94 AND PARTS OF THE TOLL ROAD (I-
80/I-90). BE PREPARED FOR IMPACTS TO THE THURSDAY MORNING AND
EVENING COMMUTES. RAPID CHANGES IN THE VISIBILITY OVER A FEW MILES
ARE POSSIBLE WITHIN THE SINGLE DOMINANT LAKE EFFECT SNOW BAND.
NORTHWESTERLY WIND GUSTS WILL INCREASE THIS AFTERNOON TO 20-25
MPH, WHICH WILL YIELD AREAS OF BLOWING SNOW IN THE NW FLOW LAKE
EFFECT ZONES. N-S ROADS AND RURAL, OPEN AREAS WILL BE THE MOST
IMPACTED. TO ACCOUNT FOR THESE IMPACTS (AND THE LIKELIHOOD THAT
THE LAKE EFFECT SNOW PERSISTS INTO EARLY FRIDAY MORNING), HAVE
OPTED TO EXTEND THE WINTER WEATHER ADVISORY UNTIL 1 AM EST
FRIDAY.
LAKE EFFECT ENDS AND A DRY STRETCH ENSUES FOR FRIDAY AND INTO THE
WEEKEND AS HIGH PRESSURE BUILDS ACROSS THE EASTERN CONUS.
TEMPERATURES FINALLY CLIMB ABOVE FREEZING BY THE END OF THE
WEEKEND AND INTO THE 40S BY THE MIDDLE OF NEXT WEEK. AN ACTIVE
PATTERN RETURNS NEXT WEEK WITH CHANCES FOR RAIN AND SNOW.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 643 AM EST THU FEB 20 2025
AN UPPER LEVEL LOW HAS PUSHED INTO CENTRAL OHIO THIS MORNING,
WITH AN ACCOMPANYING DECREASE IN THE SYNOPTIC SNOW. LAKE EFFECT
SNOW IS BECOMING MORE ORGANIZED ACROSS SOUTHWEST AND WEST
CENTRAL LOWER MICHIGAN WHERE MESOLOW TYPE FEATURE TRACKING SOUTH
ACROSS THE LACK APPEARS TO BE ENHANCING DOMINANT SINGLE BAND.
THE HEAVIEST SNOW SHOWERS WITH THIS FEATURE MAY BYPASS KSBN JUST
TO NORTH/NORTHEAST, BUT A PERIOD OF LIFR VSBYS APPEARS TO BE A
POSSIBILITY AT KSBN FROM MID MORNING INTO EARLY AFTERNOON. SOME
DIRECTIONAL SHEAR HAS LIMITED LAKE EFFECT BAND ORGANIZATION TO
THIS POINT, BUT WITH UPPER LEVEL SYSTEM EXITING THE AREA, SHEAR
PROFILES SHOULD BECOME MORE FAVORABLE FOR LAKE EFFECT BANDING
HEADING INTO THIS AFTERNOON. WILL ALSO MAINTAIN PERIODS OF IFR
VSBYS AT KFWA THIS AFTERNOON AS STRENGTHENING LOW LEVEL FLOW
ALLOWS THESE SNOW SHOWERS TO PUSH INLAND. A GRADUAL DIMINISHMENT
IN LAKE INDUCED INSTABILITY IS EXPECTED THIS EVENING WITH LAKE
EFFECT SNOW SHOWERS EXPECTED TO TAPER DURING THE MID-LATE
EVENING HOURS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER WEATHER ADVISORY UNTIL 1 AM EST /MIDNIGHT CST/ FRIDAY
FOR INZ005-103-104-204.
OH...NONE.
MI...WINTER WEATHER ADVISORY UNTIL 1 AM EST FRIDAY FOR MIZ078-177-
277.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR LMZ043-046.
DISCUSSION...JOHNSON
AVIATION...MARSILI
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