985
FXUS63 KIWX 191938
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
238 PM EST WED FEB 19 2025
KEY MESSAGES
- A PERIOD OF LIGHT SNOW EXPECTED THIS EVENING INTO EARLY
THURSDAY. LIGHT ACCUMULATIONS UP TO 1" EXPECTED.
- WIND CHILLS AS LOW AS -10 THURSDAY MORNING, COLDEST ALONG AND
SOUTH OF US 30 IN INDIANA.
- PERIODS OF HEAVY LAKE EFFECT SNOW LATE TONIGHT INTO THURSDAY
IN NORTHWEST FLOW PRONE AREAS DOWNWIND OF LAKE MICHIGAN.
REDUCED VISIBILITIES AND DIFFICULT TRAVEL EXPECTED, MAINLY IN
AREAS UNDER A WINTER WEATHER ADVISORY.
DISCUSSION
ISSUED AT 238 PM EST WED FEB 19 2025
MAIN FOCUS REMAINS ON LIGHT SYSTEM SNOW THIS EVENING INTO THE EARLY
OVERNIGHT, TRANSITIONING TO PURE LAKE EFFECT SNOW FOR OUR NW FLOW
SNOW BELTS LATER TONIGHT THROUGH THURSDAY EVENING.
SHORTWAVE AND DEEPER MOISTURE, CURRENTLY OVER EASTERN IA, WILL
TRANSLATE EAST THROUGH THE AREA TONIGHT AS A WEAK CLOSED LOW.
ASSOCIATED MODEST DEEP LAYER ASCENT OVER STEEPENING LOW LEVEL
LAPSE RATES (WITHIN A PORTION OF THE DGZ) TO PROMOTE THIS LIGHT
SNOW, PARTICULARLY ALONG AND SOUTHEAST OF US 24 NEAR THE NOSE OF
A 70 KT MID LEVEL JET. LIGHT SNOW ACCUMS OF A HALF INCH TO INCH
SHOULD TEND TO STICK ON UNTREATED ROADS GIVEN LINGERING COLD
SFC TEMPS.
ATTENTION THEN TURNS TO LAKE EFFECT/ENHANCED SNOW, MOST ORGANIZED IN
THE 06-18Z WINDOW ON THURSDAY WHEN 0-2KM THETA-E LAPSE RATE VALUES
TREND NEGATIVE WITHIN A DEVELOPING LONG LAKE AXIS THERMAL TROUGH.
MODEL SOUNDINGS/X-SECTIONS ALSO CONTINUE TO SUGGEST OMEGA AND
SATURATION WITH RESPECT TO ICE MAXIMIZED WITHIN A PORTION OF THE DGZ
WITH SIGNS OF SEEDING ON THE BACKSIDE OF THE EXITING UPPER WAVE.
THIS LONG AXIS FETCH, AND SUPPORTIVE THERMODYNAMIC PARAMETERS,
SUGGEST A DECENT POTENTIAL FOR 1"/HR RATES (12Z HREF 10-30%
PROBS) AND LOCALLY HEAVY SNOW TOTALS (HREF MAX TOTALS EXCEED 8"
IN BERRIEN CT) WITHIN ANY BANDED ELEMENTS. POTENTIAL FAILURE
POINTS COULD BE EMBEDDED DISRUPTING MESOLOWS AND/OR AN EARLIER
BREAKDOWN OF THE LAKE AGGREGATE TROUGH.
THERE SHOULD BE A TREND TOWARD LESS ORGANIZED, CELLULAR, MULTIBANDS
THURSDAY AFTERNOON INTO THURSDAY EVENING AS TRAJECTORIES SLIGHTLY
BACK WITH THE CONVERGENT LAKE PLUME EVENTUALLY RELEASING FROM THE
EASTERN LAKE MI SHORELINE. THE ONLY CHANGE IN HEADLINES FOR THIS
PACKAGE WAS TO ADD ELKHART CT INTO THE WINTER WEATHER ADVISORY.
CONSIDERED UPGRADING BERRIEN CT TO A WINTER STORM WARNING
(CRITERIA IS >8"), BUT OPTED TO HOLD OFF FOR NOW WITH PROBABILISTIC
DATA FAVORING TOTALS MORE IN THE 4-6" RANGE OVERALL IN THE
COUNTY. DID ISSUE A SPS FOR THE REST OF AREA TO COVER MORE OF A
NUISANCE IMPACT TO TRAVEL AND WIND CHILLS AS COLD AS -10 BY
DAYBREAK THURSDAY.
FRIDAY THROUGH EARLY NEXT WEEK WILL FEATURE A MODERATING TREND AS
RETURN WSW FLOW SETS UP UNDER A LOWER AMPLITUDE FLOW REGIME ALOFT. A
FEW MID LEVEL SHORTWAVES WILL TAKE AIM ON THE GREAT LAKES NEXT WEEK
WITH LOW PERIODIC CHANCES FOR PRECIPITATION. AS EXPECTED, THERE ARE
SIZABLE DIFFERENCES WITHIN THE ENSEMBLE GLOBAL SYSTEMS REGARDING
TRACK AND TIMING OF THESE MID LEVEL FEATURES RESULTING IN LOW
PREDICTABILITY IN DAILY RAIN/SNOW CHANCES.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1235 PM EST WED FEB 19 2025
AS AN UPPER LOW PRESSURE SYSTEM MOVES THROUGH DURING THIS TAF
PERIOD, SYSTEM AND LAKE EFFECT SNOW ACROSS THE AREA WILL KEEP
FLIGHT CONDITIONS IN MVFR FOR A GOOD PORTION OF THE TIME WITH
SNOW FALLING AND FROM CIGS. AFTER AN INITIAL TROUGH MOVED
THROUGH THE AREA THIS MORNING AND INVIGORATED LAKE EFFECT SNOW
WITH SMALL FLAKES BRINGING VISBYS DOWN TO AROUND 2 MILES, A
WEAKENING IN LAKE EFFECT SNOW BECOMES POSSIBLE AFTER AROUND 21Z.
IT IS THEN EXPECTED TO RETURN AROUND 6Z WITH MORE MVFR FLIGHT
CONDITIONS POSSIBLE. SBN COULD ALSO DROP INTO IFR VISBY DURING
THAT TIME FRAME. EXPECT WINDS TO BE OUT OF THE WEST NORTHWEST
AND GUSTS MAY APPROACH 20 KTS DURING THE MIDDAY AND AFTERNOON
THURSDAY, BUT THAT IS JUST AT THE TAIL END OF THIS TAF PERIOD SO
WILL WAIT FOR THE NEXT ISSUANCE TO INCLUDE IT. THIS APPEARS TO
BE CAUSED BY A TROUGH THAT MOVES DOWN THE LAKE AND MAY ENHANCE
SNOW AND BRING LOWER FLIGHT CONDITIONS AS A RESULT.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER WEATHER ADVISORY UNTIL 7 PM EST /6 PM CST/ THURSDAY FOR
INZ005-103-104-204.
OH...NONE.
MI...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR MIZ078-177-
277.
MARINE...NONE.
DISCUSSION...STEINWEDEL
AVIATION...ROLLER
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