509
FXUS63 KMKX 180323 AAA
AFDMKX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
923 PM CST TUE DEC 17 2024
KEY MESSAGES
- A LIGHT ROUND OF SNOWFALL IS ANTICIPATED LATE TONIGHT THROUGH EARLY
WEDNESDAY MORNING. WHILE ACCUMULATIONS ARE EXPECTED TO REMAIN
BETWEEN A DUSTING AND AN INCH, MINOR IMPACTS TO THE WEDNESDAY
MORNING COMMUTE ARE POSSIBLE.
- PERIODS OF MORE SUBSTANTIAL SNOWFALL ARE FORECAST FROM
THURSDAY MORNING THROUGH THURSDAY EVENING, WITH ACCUMULATIONS
LIKELY ACROSS THE ENTIRETY OF SOUTHERN WISCONSIN. IMPACTS TO
BOTH THE THURSDAY MORNING & EVENING COMMUTE ARE POSSIBLE.
- PERIODS OF LAKE-ENHANCED SNOW WILL CONTINUE THURSDAY NIGHT
THROUGH THE FIRST HALF OF FRIDAY, PARTICULARLY ACROSS EAST-
CENTRAL AND SOUTHEASTERN WISCONSIN. ADDITIONAL TRAVEL IMPACTS
WILL BE POSSIBLE DURING THIS TIMEFRAME, WHICH WILL INCLUDE THE
FRIDAY MORNING COMMUTE.
- THE NEXT ROUND OF ARCTIC AIR SETTLES INTO SOUTHERN WISCONSIN
THIS WEEKEND, WITH TEMPERATURES MODERATING INTO EARLY NEXT
WEEK.
UPDATE
ISSUED 923 PM CST TUE DEC 17 2024
THE SNOW IS EVOLVING INTO A RELATIVELY NARROW BAND OVER CENTRAL
IA THAT EXTENDS INTO FAR SOUTHWEST WI THIS EVENING. THIS IS
ALONG THE 700MB FRONTOGENESIS AXIS, AND THAT IS FORECAST TO
SLOWLY SHIFT ESE THROUGH THE OVERNIGHT HOURS, GENERALLY ALONG
THE WI/IL BORDER. SOUTH (AHEAD) OF THIS BAND, LOW LEVEL DRY AIR
AND ALSO WEAK UPPER LEVEL FORCING ARE PREVENTING SNOW FROM
REACHING THE GROUND AT THIS TIME. BEHIND THE BAND IN NORTHEAST
IA AND SOUTHEAST MN, THE COLUMN HAS HAD TIME TO SATURATE, SO
SNOW IS REACHING THE GROUND. WE CAN EXPECT THIS LIGHTER SNOW
THAT IS ASSOCIATED WITH 600MB FRONTOGENESIS AND THE COLDER AIR
EXTENDING TO WITHIN THE DENDRITIC GROWTH ZONE TO EXPAND THROUGH
MUCH OF SOUTHERN WI OVERNIGHT.
THE ONLY CHANGE IN THE FORECAST IS TO FOCUS THE HIGHEST CHANCE
OF SNOW AND ACCUMULATIONS OF UP TO AN INCH CLOSER TO THE WI/IL
BORDER. AREAS ALONG AND NORTH OF I-94 WILL ONLY SEE A DUSTING TO
MAYBE A HALF INCH. THE SNOW WILL END FROM NORTHWEST TO
SOUTHEAST EARLY WEDNESDAY MORNING, CLEARING SOUTHEAST WI BY 6 AM
AS THE UPPER TROUGH EXITS.
CRONCE
SHORT TERM
ISSUED 335 PM CST TUE DEC 17 2024
TONIGHT THROUGH THURSDAY NIGHT:
SYNOPSIS/MESOANALYSIS: GOES WATER VAPOR IMAGERY PLACES A SHORTWAVE
TROUGH OVER CENTRAL SOUTH DAKOTA EARLY THIS AFTERNOON. SAID FEATURE
WILL PROGRESS ACROSS THE WISCONSIN-ILLINOIS STATE LINE OVERNIGHT,
BRINGING A BRIEF ROUND OF LIGHT SNOW SHOWERS TO SOUTHERN WISCONSIN.
SNOW WILL DEPART THE REGION BY SUNRISE WEDNESDAY, WITH PASSING HIGH
PRESSURE ALLOWING FOR PARTLY CLOUDY SKIES BY THE AFTERNOON HOURS.
DESPITE THE SUNNIER CONDITIONS, NORTHWEST SURFACE WINDS WILL KEEP
HIGH TEMPERATURES A TOUCH COOLER RELATIVE TO TODAY. A SECOND, MORE
DYNAMIC UPPER DISTURBANCE IS FORECAST TO CROSS SOUTHERN WISCONSIN
DURING THE DAY ON THURSDAY, WITH STACKED ASCENT SUPPORTING PERIODS
OF MORE SUBSTANTIAL SNOWFALL. PERIODS OF SNOW WILL CARRY THROUGH THE
ENTIRETY OF THE DAY ON THURSDAY, POTENTIALLY BRINGING MESSY TRAVEL
CONDITIONS TO THE AREA. CONSIDERABLE UNCERTAINTY REMAINS REGARDING
THE PRECISE PLACEMENT, AND THUS ACCUMULATION OF SNOWFALL ON
THURSDAY, SO COMMUTERS AND EARLY HOLIDAY TRAVELERS ARE ENCOURAGED
TO KEEP UP WITH THE FORECAST. LAKE-ENHANCED SNOW IS FORECAST TO
CONTINUE INTO THURSDAY NIGHT & PREDAWN FRIDAY AS SURFACE LOW
PRESSURE MIGRATES FROM ILLINOIS INTO THE OHIO RIVER VALLEY.
TONIGHT: EXPECT A LIGHT ROUND OF SNOWFALL AS AN UPPER SHORTWAVE &
ACCOMPANYING MID-LEVEL LIFT CROSSES THE REGION. LIGHT ACCUMULATIONS
GENERALLY BETWEEN A DUSTING AND 1 INCH ARE ANTICIPATED, GIVEN WHAT'S
EXPECTED TO BE A BRIEF RESIDENCE TIME OF SYNOPTIC ASCENT, AS WELL AS
DRYING CONDITIONS WITHIN THE DGZ APPROACHING SUNRISE WEDNESDAY.
DESPITE THE LIGHT ACCUMULATION FORECAST, SOME MINOR IMPACTS TO THE
MORNING COMMUTE ARE POSSIBLE, PARTICULARLY WHERE ANY LIGHT SNOW
BUILD-UP OCCURS ON ROADS OVERNIGHT. BUDGET EXTRA TRAVEL TIME IF
COMMUTING EARLY WEDNESDAY MORNING.
THURSDAY: A SECOND ROUND OF SNOWFALL IS ANTICIPATED AS THE SECOND
DISTURBANCE OF THE PERIOD PASSES OVER SOUTHERN WISCONSIN. SAID
SNOWFALL IS EXPECTED TO BE MORE SIGNIFICANT RELATIVE TO TONIGHT'S
ROUND, GIVEN A STACKING OF SYNOPTIC-SCALE ASCENT FROM 850 MB UP TO
THE TROPOPAUSE. INITIAL EXPECTATION IS THAT THE THURSDAY ROUND OF
SNOW WILL OCCUR IN TWO DIFFERENT ROUNDS, WITH THE FIRST MOVING
ACROSS THE AREA DURING THE MORNING HOURS AND THE SECOND PASSING
THROUGH DURING THE LATE AFTERNOON AND EARLY EVENING HOURS. BETWEEN
THE TWO, SNOWFALL RATES ARE EXPECTED TO BE THE HEAVIEST DURING THE
FIRST/MORNING ROUND, WHEN A COMBINATION OF 850-700 MB FRONTOGENESIS,
WARM ADVECTION, AND 300 MB LEFT EXIT REGION DYNAMICS WILL ALL BE
POSITIONED OVER THE AREA. ADDITIONAL MORE LIGHT TO MODERATE SNOW
WILL THEN PROGRESS ACROSS THE REGION DURING THE AFTERNOON AND EARLY
EVENING AS THE CORE OF THE MID-LEVEL SHORTWAVE & ATTENDANT MID-LEVEL
DPVA MOVE OVERHEAD. GIVEN ANTICIPATED SNOWFALL DURING BOTH THE
MORNING AND EVENING COMMUTES, THOSE DRIVING TO/FROM WORK, IN
ADDITION TO THOSE WITH EARLY HOLIDAY TRAVEL PLANS ARE ENCOURAGED TO
BUDGET EXTRA TIME ON THURSDAY. THE CURRENT EXPECTATION IS THAT
THURSDAY'S SNOW WILL BRING APPRECIABLE ACCUMULATIONS TO ALL OF
SOUTHERN WISCONSIN, THOUGH THE QUESTION OF HOW MUCH, AS WELL AS THE
PLACEMENT OF HEAVIEST TOTALS, REMAINS UNCERTAIN GIVEN MODEL
DISAGREEMENTS REGARDING THE PLACEMENT OF LIFTING MECHANISMS, IN
ADDITION TO POSSIBLE DRY AIR INTRUSIONS DURING THE AFTERNOON HOURS.
INITIAL ACCUMULATION FORECASTS POINT TOWARD EAST-CENTRAL WISCONSIN
BEING FAVORED FOR THE HIGHEST TOTALS, GIVEN A COMBINATION OF THE TWO
ROUNDS OF SYNOPTICALLY-FORCED SNOWS, IN ADDITION TO POSSIBLE LAKE
ENHANCEMENTS WITH NORTHEAST WINDS BLOWING OFF OF LAKE MICHIGAN. WILL
CONTINUE TO CLOSELY MONITOR TRENDS TONIGHT AND TOMORROW, AS WINTER
HEADLINES MAY BECOME NECESSARY IF INITIAL ACCUMULATION FORECASTS
HOLD.
THURSDAY NIGHT: LAKE-ENHANCED SNOWFALL WILL CONTINUE OVER EAST-
CENTRAL AND SOUTHEASTERN WISCONSIN GIVEN PERSISTENT ONSHORE FLOW
FROM LAKE MICHIGAN. SAID SNOWS COULD CONTINUE INTO THE PREDAWN HOURS
FRIDAY AND THE MORNING COMMUTE.
QUIGLEY
LONG TERM
ISSUED 335 PM CST TUE DEC 17 2024
FRIDAY THROUGH TUESDAY:
BY FRIDAY MORNING, THE SURFACE LOW WILL HAVE TRANSLATED SOUTHEAST
INTO THE FAR EASTERN REACHES OF THE CORN BELT AND OHIO RIVER
VALLEY. HOWEVER, MODELS DEPICT A SURFACE TROUGH EXTENDING
NORTHWEST FROM THE SFC LOW OVER LAKE MICHIGAN. THIS TROUGH WILL
DRIVE NORTHEASTERLY SFC FETCH OVER THE 6 TO 8C SFC WATERS OF LAKE
MICHIGAN. MODELS DEPICT -18 TO -19C AIR INTRUDING ALOFT AT 700MB
OVER THE LAKE FRIDAY MORNING, WHICH SHOULD RESULT IN VERY STEEP
LAPSE RATES AND LAKE-INDUCED INSTABILITY AMID UNIDIRECTIONAL FLOW
FROM THE LAKE SFC TO THE EQUILIBRIUM LVL AT 3KM (700MB). GFS AND
NAM SFC WIND FIELDS SHOW CONVERGENCE AND A WIND MAX POINTING
TOWARD THE LAKESHORE AT 12Z FRIDAY, HIGHLIGHTING THE POTENTIAL
FOR A STRONG LAKE EFFECT SNOW BAND TO MAKE A SWIPE DOWN THE
SHORELINE AS WINDS COME AROUND FROM NORTHEASTERLY TO NORTHERLY
BEHIND THE TROUGH. THIS MAY CAUSE LINGERING SNOW IMPACTS FOR THE
FRIDAY MORNING COMMUTE AND POTENTIALLY BEYOND, AS THE NAM DEPICTS
LAKE EFFECT SNOW LINGERING INTO FRIDAY EVENING IN OUR SOUTHEAST,
ALBEIT IN A SOMEWHAT WEAKER CAPACITY. MORE DETAILS WILL COME INTO
FOCUS ONCE CAMS COME INTO RANGE FOR THIS TIME PERIOD.
FOLLOWING THE LAKE EFFECT POTENTIAL FRIDAY, MODELS BEGIN TO
DIVERGE IN THEIR SOLUTIONS GOING INTO THE WEEKEND. FRIDAY NIGHT,
HIGH PRESSURE BUILDS INTO THE REGION AHEAD OF ANOTHER CLIPPER
SYSTEM. THE ECMWF FEATURES A MUCH STRONGER SFC HIGH PRESSURE,
CAUSING THE CLIPPER TO DRY OUT AS IT APPROACHES SOUTHERN WI, WHILE
THE GFS FAVORS A WEAKER SFC HIGH AND ALLOWS THE CLIPPER TO COME
THROUGH MAINLY WEST OF MADISON SATURDAY MORNING. FOR NOW THE NBM
ONLY MAINTAINS 15% POPS FOR THIS TIME PERIOD. IN EITHER CASE, COLD
AIR LINGERS THROUGH THE WEEKEND, WITH HIGHS IN THE LOW 20S.
BEYOND, WARM ADVECTION RETURNS OVER THE UPPER GREAT LAKES ON
SOUTHERLY WINDS. TEMPERATURES RISE TO NEAR FREEZING ON THE 23RD,
WITH UPPER 30S POSSIBLE BY CHRISTMAS EVE.
CMILLER
AVIATION
ISSUED 923 PM CST TUE DEC 17 2024
THE MAIN BAND OF SNOW WILL BE FOCUSED ALONG AN AXIS OF 700MB
FRONTOGENESIS TONIGHT, WHICH WILL TRACK ALONG THE WI/IL BORDER.
LOWEST CEILINGS (DOWN TO 1500 FT AT TIMES) AND STEADIER SNOW
WILL BE HERE, WITH LIGHTER SNOW AND HIGHER CEILINGS (2500 TO
4000 FT) NORTH OF THIS AXIS. MVFR CEILINGS WILL DEVELOP ACROSS
SOUTHERN WI LATE THIS EVENING LOW LEVEL MOISTURE MOVES IN. THE
LIGHT SNOW WILL END FROM NORTHWEST TO SOUTHEAST THROUGH 6 AM/12Z,
GIVING WAY TO VFR CONDITIONS BY MID-MORNING.
CRONCE
MARINE
ISSUED 335 PM CST TUE DEC 17 2024
BRISK NORTHWEST WINDS WILL BECOME ESTABLISHED ACROSS THE OPEN WATERS
ON WEDNESDAY AS 1032 MB HIGH PRESSURE MIGRATES FROM THE NORTHERN
GREAT PLAINS INTO THE MISSISSIPPI RIVER VALLEY.
WINDS WILL TAPER WEDNESDAY NIGHT 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 1016 MB LOW PRESSURE APPROACHES LAKE MICHIGAN
FROM THE UPPER MISSISSIPPI VALLEY. THE APPROACH OF THE SURFACE LOW
WILL BE ACCOMPANIED BY PERIODS OF RAIN AND SNOW 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.
DESPITE ANTICIPATED BREEZY NORTHWEST WINDS ON WEDNESDAY AFTERNOON,
GUSTS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS
IN NEARSHORE ZONES. A COMBINATION OF GUSTY NORTHWEST WINDS AND
ELEVATED WAVE HEIGHTS WILL RESULT IN POTENTIAL SMALL CRAFT ADVISORY
CONDITIONS ON FRIDAY. TRENDS WILL BE MONITORED OVER COMING SHIFTS
FOR ANY POTENTIAL HEADLINES.
QUIGLEY
MKX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
LM...NONE.
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