399
FXUS63 KMKX 181606
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1006 AM CST WED DEC 18 2024
KEY MESSAGES
- ACCUMULATING SNOW REMAINS LIKELY THURSDAY MORNING THROUGH
THURSDAY EVENING ACROSS THE ENTIRETY OF SOUTHERN WISCONSIN.
INCREASING POTENTIAL FOR 2+ OF SNOW OVER THE MAJORITY OF
SOUTHERN WI. LIGHT SNOW STARTS BY THE MORNING COMMUTE, WITH
THE HIGHEST RATES EXPECTED FOR THE AFTERNOON/EVENING COMMUTE.
- PERIODS OF LAKE-ENHANCED SNOW SHOWERS CONTINUE THURSDAY NIGHT
THROUGH THE FIRST HALF OF FRIDAY ACROSS FAR EASTERN WISCONSIN,
PARTICULARLY EAST-CENTRAL WISCONSIN. INCREASING POTENTIAL FOR
6+ INCHES STORM-TOTAL SNOW IN FOND DU LAC AND SHEBOYGAN
COUNTIES, AND A WINTER STORM WATCH HAS BEEN ISSUED FOR THIS
REGION. FRIDAY MORNING COMMUTES MAY BE IMPACTED ALONG LAKE
MICHIGAN CITIES.
- THE NEXT ROUND OF ARCTIC AIR SETTLES INTO SOUTHERN WISCONSIN
THIS WEEKEND, WITH TEMPERATURES SETTLING BACK TOWARD NORMAL
INTO EARLY NEXT WEEK.
UPDATE
ISSUED 1007 AM CST WED DEC 18 2024
MOSTLY CLOUDY SKIES WITH A FEW BREAKS IN THE CLOUD DECK WILL
CONTINUE THROUGH THE DAY, WITH NORTHWESTERLY BREEZES. A FEW
FLURRIES ARE POSSIBLE THIS AFTERNOON AS THE BASE OF 500 MB
TROUGHING PROVIDES JUST ENOUGH LIT ACROSS CENTRAL WISCONSIN.
EXPECT HIGHS IN THE UPPER 20S TO LOWER 30S, WITH THE WARMEST
TEMPERATURES NEAR LAKE MICHIGAN. OVERNIGHT, LOWS IN THE UPPER
TEENS TO LOW 20S ARE EXPECTED, WITH LIGHT WINDS SLOWLY SHIFTING
SOUTHERLY BY THE MORNING HOURS THURSDAY.
MH
SHORT TERM
ISSUED 410 AM CST WED DEC 18 2024
TODAY AND TONIGHT:
700MB FGEN AND ASSOCIATED LIGHT SNOW HAVE NEARLY EXITED THE
SOUTHEASTERN CWA BY NOW. SOME SLICK SPOTS POSSIBLE FOR THE AM
COMMUTE TODAY, BUT NO FURTHER ACCUMULATING SNOW EXPECTED TODAY
(FLURRIES CAN'T BE COMPLETELY RULED OUT WITH LINGERING LOW
STRATUS THIS MORNING, BUT ARE NOT LIKELY). NORTHWEST WINDS TODAY
WILL USHER IN A COOLER AIRMASS, WITH OVERNIGHT LOWS IN THE
TEENS TO AROUND 20. NEXT CHANCE FOR SNOW ARRIVES THURSDAY
MORNING.
SHEPPARD
LONG TERM
ISSUED 410 AM CST WED DEC 18 2024
THURSDAY THROUGH TUESDAY:
THE TRACK FOR THURSDAY'S CLIPPER SYSTEM REMAINS WIDELY DISPUTED
BETWEEN MODELS (EVEN AT SUCH A SHORT RANGE). THAT SAID, A
PATTERN IS BEGINNING TO EMERGE... COARSER-RESOLUTION LONGER-
RANGED MODELS (ECMWF, GFS, CANADIAN) HAVE CONVERGED ON A TRACK
THAT TAKES THE CENTER OF THE LOW PRESSURE THROUGH NORTHERN
ILLINOIS, WHILE HIGHER RESOLUTION CAMS (RAP / HRRR) PREFER A
NORTHERN WISCONSIN / MICHIGAN-UP TRACK. IT IS TOO EARLY TO SAY
WHICH OF THESE WILL PAN OUT, BUT THE CONVERGENCE OF ECMWF, GFS,
AND CANADIAN MODEL GUIDANCE ON THE ILLINOIS TRACK HAS LEAD TO AN
INCREASE IN SNOW PROBS ACROSS OUR CWA COMPARED TO THE PRIOR
FORECAST ITERATION.
SNOW IS UNLIKELY TO BEGIN UNTIL ROUGHLY 5 AM THURSDAY OR LATER
(REGARDLESS OF TRACK), BUT ALL AREAS ARE LIKELY TO RECEIVE THE
FIRST DOSE OF SNOWFALL BEFORE LATE THURSDAY MORNING (AM COMMUTE
IMPACTS MAY OCCUR). THE NORTHERN WI SYSTEM TRACK WOULD PREFER A
MID-DAY LULL IN SNOWFALL FOLLOWED BY MODERATE TO HEAVY SNOW
SHOWERS ALONG THE COLD FRONT IN THE LATE AFTERNOON / EVENING,
WHILE THE ILLINOIS TRACK WOULD ALLOW FOR A MORE PERSISTENT
SNOWFALL THROUGHOUT THURSDAY. EITHER WAY, THURSDAY PM COMMUTE
IMPACTS ARE LIKELY. AS THE LOW DEPARTS TO THE EAST, LAKE-
ENHANCEMENT IS LIKELY TO ALLOW FOR CONTINUED SNOW SHOWERS FOR
THE EASTERN CWA INTO THURSDAY NIGHT AND FRIDAY MORNING. JUDGING
BY THE MODELED WIND FIELD (ILLINOIS SYSTEM TRACK), THE BEST
COMBINATION OF SHORELINE CONVERGENCE AND LAKE ENHANCEMENT WOULD
BE OVER EAST-CENTRAL WI, HENCE A WINTER STORM WATCH HAS BEEN
ISSUED FOR FOND DU LAC AND SHEBOYGAN COUNTIES, DUE TO INCREASING
POTENTIAL OF 6+ INCHES OF STORM- TOTAL SNOWFALL. THE REMAINDER
OF THE CWA HAS WIDESPREAD POTENTIAL FOR 2-4 INCHES OF SNOW,
PERHAPS A BIT LOWER POTENTIAL FAR SOUTHWESTERN WI. NO FURTHER
HEADLINES HAVE BEEN ISSUED AT THIS TIME, BUT A WINTER WEATHER
ADVISORY COULD EASILY BE ISSUED FOR THE MAJORITY OF THE CWA
ON THE NEXT FORECAST ITERATION (IF CONFIDENCE IN THE IL TRACK
INCREASES).
MOSTLY DRY WEATHER EXPECTED FRIDAY AFTERNOON AND ONWARD (ASIDE
FROM SLIGHT CHANCES OF LIGHT LAKE EFFECT SNOW SHOWERS IN LAKE
MICHIGAN COUNTIES). SIMILAR STORY FOR THE REMAINDER OF THE
WEEKEND AS THE ARCTIC HIGH PRESSURE PASSES BY. COOL WEATHER THIS
WEEKEND, BUT WITH RELATIVELY LIGHT WINDS.
SHEPPARD
AVIATION
ISSUED 1007 AM CST WED DEC 18 2024
MVFR CEILINGS EXPECTED TO RISE TO VFR BY THIS AFTERNOON, WITH
SOME BREAKS IN CLOUD COVER POSSIBLE. HOWEVER, MID-LEVEL MOISTURE
CONTINUES THROUGHOUT THE DAY, SO GENERALLY EXPECTING A BROKEN TO
OVERCAST CLOUD DECK. A FEW FLURRIES ARE POSSIBLE, ESPECIALLY
FROM MSN THROUGH MKE NORTHWARD. NORTHWESTERLY WINDS DIMINISH AND
SKIES CLEAR INTO TONIGHT AS HIGH PRESSURE DOMINATES. WINDS SHIFT
SOUTHERLY AND INCREASE AS CLOUD COVER BUILDS BACK IN LATE
TONIGHT INTO THURSDAY MORNING. MID-MORNING THURSDAY, CEILINGS
LOWER INTO THE 1000-2000 FT RANGE AS SNOWFALL SPREADS ACROSS THE
REGION. SNOW CONTINUES THROUGH THURSDAY EVENING, WITH CEILINGS
CONTINUING TO LOWER THROUGH THE AFTERNOON AND EVENING. IFR
CONDITIONS ARE POSSIBLE BY THE EVENING HOURS.
MH
MARINE
ISSUED 410 AM CST WED DEC 18 2024
BRISK NORTHWEST WINDS WILL BECOME ESTABLISHED ACROSS THE OPEN
WATERS TODAY AS 30.5 INCH HIGH PRESSURE MIGRATES FROM THE
NORTHERN GREAT PLAINS INTO THE MISSISSIPPI RIVER VALLEY. WINDS
WILL TAPER TONIGHT INTO EARLY THURSDAY MORNING AS THE
AFOREMENTIONED AREA OF HIGH PRESSURE MOVES ACROSS LAKE MICHIGAN.
WINDS WILL SHIFT PREDOMINANTLY OUT OF THE SOUTH DURING THE DAY
TIME HOURS ON THURSDAY AS 29.9 INCH LOW PRESSURE APPROACHES LAKE
MICHIGAN FROM THE UPPER MISSISSIPPI VALLEY. THE APPROACH OF THE
SURFACE LOW WILL BE ACCOMPANIED BY PERIODS OF SNOW AND RAIN
SHOWERS. THE LOW WILL MOVE OVER AND EAST OF THE OPEN WATERS
THURSDAY EVENING INTO FRIDAY MORNING, RESULTING IN GUSTY NORTH
WINDS ACROSS THE LAKE FRIDAY AFTERNOON.
SHEPPARD
MKX WATCHES/WARNINGS/ADVISORIES
WI...WINTER STORM WATCH...WIZ051-WIZ052...6 AM THURSDAY TO NOON
FRIDAY.
LM...NONE.
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