Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 121959
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
259 PM CDT Tue Mar 12 2024

.KEY MESSAGES...

- DOUBLE DIGIT ANOMALOUS WARMTH CONTINUES THROUGH WEDNESDAY,
  DECREASING NEAR 10 DEGREES ABOVE NORMAL THURSDAY, 5 DEGREES
  THROUGH FRIDAY, & 5 DEGREES BELOW NORMAL INTO NEXT WEEK

- TIGHT MOISTURE GRADIENT PARKS ITSELF FROM NORTHERN IOWA INTO
  SOUTHERN WISCONSIN THROUGH THURSDAY, PROVIDING STRONG GRADIENT
  IN RHS & TEMPERATURES

- MULTI-PRECIPITATION TYPES REACH THE FORECAST AREA WEDNESDAY
  NIGHT INTO THURSDAY MORNING, HIGHEST CONFIDENCE FOR SNOW IN
  CENTRAL WISCONSIN AND THUNDER IN NORTHEAST IOWA.

&&

.DISCUSSION...
ISSUED AT 213 PM CDT TUE MAR 12 2024

ONGOING OBSERVATIONS & NOW TO NEAR TERM IMPACTS:

MORNING OBSERVATIONS FROM METARS, SATELLITE IMAGERY, AND DERIVED
SATELLITE PRODUCTS HAVE EXHIBITED A FEW NOTEWORTHY CHARACTERS
WITHIN THE PROGRESSIVE PATTERN. UTILIZING A SYNOPTIC "TOP-
DOWN" APPROACH, UPPER LEVEL WATER VAPOR (GOES IMAGERY) LOOPS
SHOW TWO PERTURBATIONS, OVER SOUTHERN CANADA AND OVER THE
CENTRAL PLAINS, PASSING THROUGH THE MISSISSIPPI RIVER VALLEY.
THIS NORTHERN PERTURBATION HAS BEEN PUSHING THE LOCALLY HIGHER
HEIGHTS SOUTH, ADVECTING THE DRIER LOW LEVEL AIR MASS SOUTH THROUGH
THE UPPER MISSISSIPPI RIVER VALLEY EARLY THIS AFTERNOON. THE
UPPER LEVEL WINDS (GOES DERIVED) RESPONSIBLE FOR ADVECTING THIS
PERTURBATION EAST-SOUTHEASTERLY EARLY THIS AFTERNOON IS ALSO
LIFTING AND WEAKENING THE SOUTHERLY STREAM. AN UPSTREAM PV
ANOMALY (RAP ANALYSIS/GOES IMAGERY) ALONG THE 1.5 PV SURFACE HAS
SHOWN THE CONTINUAL SEPARATION AND WEAKENING OF THIS "S"-SHAPED
ANOMALY FROM SOUTHERN CANADA THROUGH THE SOUTH-CENTRAL PLAINS.
GOES-DERIVED WINDS AND RAP POTENTIAL TEMPERATURES SHOW A
WEAKENING AND FILLING THIS FOLD THROUGH THE NORTHERN PLAINS,
LIFTING RAP DERIVED PRESSURE VALUES BACK INTO THE UPPER-MOST
LEVELS. COMPARING ALL OF THESE UPPER LEVEL OBSERVATIONS TO
SURFACE OBSERVATIONS, THE SURFACE LOW TRUDGING THROUGH KANSAS IS
BECOMING MORE STACKED, WEAKENING AND LOSING ITS OVERALL PIZAZZ.
LOCAL IMPACTS STEM FROM THE ATTACHED MOISTURE BOUNDARY
EXTENDING THROUGH IOWA INTO THE UPPER MISSISSIPPI RIVER VALLEY.
CONFLUENCE WITH THE WESTERN PERIPHERY OF THE SOUTHEAST CONUS
ANTICYCLONE HAS ADVECTED THE 40 DEGREE ISODROSOTHERM INTO
EASTERN WISCONSIN, COMPARED TO THE 20 DEGREE ISODROSOTHERM IN
WESTERN WISCONSIN.

SURFACE FRONT, TEMPERATURES, & MOISTURE THROUGH WEDNESDAY:

THE WEAKENING OF THE SYNOPTIC FORCING AND ASSOCIATED FILLING OF THE
SURFACE LOW WILL LEAVE THE AFOREMENTIONED LOW LEVEL FRONTAL BOUNDARY
STRANDED FROM NORTHERN IOWA INTO FAR SOUTHERN WISCONSIN INTO
THURSDAY. AS A RESULT THERE`S QUITE A VARIATION IN RHS FROM
SOUTH TO NORTH TODAY, LOW TEENS IN MINNESOTA TO 30S IN FAR
SOUTHWEST WISCONSIN.

THROUGH WEDNESDAY, THE RECENT TREND OF 20+ DEGREES ABOVE NORMAL
TEMPERATURES CONTINUES THROUGH WEDNESDAY (100% CONFIDENCE --
GEFS/EPS). GIVEN THE PERSISTENT OVERACHIEVEMENT, HAVE SLIGHTLY
UPPED DAYTIME HIGHS FOR WEDNESDAY, PROVIDING THE 70 DEGREE
ISOTHERM GRAZING OUR SOUTHERN MOST COUNTIES AND THE 60 DEGREE
ISOTHERM IN CENTRAL WISCONSIN.

INITIAL PRECIPITATION CHANCES RETURN WEDNESDAY NIGHT:

SUBSEQUENT IMPACTFUL WEATHER (I.E., PRECIPITATION CHANCES) ORIGINATE
FROM THE RETURN OF UPPER LEVEL FORCING DRIVING A SURFACE LOW
ALONG THE AFOREMENTIONED BAROCLINIC ZONE. LOCAL FORECAST
CHALLENGE WILL BE THE EXACT LOCATION OF THIS BOUNDARY AS THE
NORTHERN DRY AIR WILL GREATLY INHIBIT INITIAL ONSET AS WELL AS
NORTHERLY EXTENT. UNFORTUNATELY, PRECISE LOCATION OF THIS
SURFACE LOW HAS DECREASED IN BOTH THE EPS & GEFS OVER RECENT
RUNS. MOST RECENT RUN (12.12Z) FORMS THE SURFACE LOW WEDNESDAY
MORNING OVER THE SOUTHERN PLAINS, LIFTING NORTHEAST THROUGH
THURSDAY. LOCATION OF SURFACE LOW SPREAD INCREASES THROUGH
WEDNESDAY NIGHT, FROM EASTERN IOWA TO NORTHERN TEXAS. I
REPEATEDLY MENTION IT BECAUSE THE BOUNDARY AND SUBSEQUENT LOW
LOCATION WILL ALSO RESULT IN A SPREAD OF PRECIPITATION TYPE. AN
EXTRA FORECAST DETAIL WILL BE A ZONAL AXIS OF DILATATION THAT
WILL FURTHER ENFORCE THE MERIDIONAL TEMPERATURE GRADIENT AHEAD
OF THE LOW. FINE DETAIL TO PAY ATTENTION AS FORECAST HOUR
DECREASES.

THE FASTER SOLUTION IN THE GEFS INTRODUCES 100% CONFIDENCE FOR
0.01"+ OF QPF LATE WEDNESDAY INTO THE OVERNIGHT WHILE THE EPS DELAYS
TILL THURSDAY MORNING. THE AFOREMENTIONED SHRINKING ZONE
REINFORCES THE SURFACE BOUNDARY, CREATING INCREASED FORECAST
DIFFICULTY WITH NORTHERLY ADVECTION OF PRECIPITATION (I.E.,
ONSET) INTO THE STOUT DRY AIR MASS. SIMILAR TO PREVIOUS
FORECASTS AND MODEL TRENDS, HAVE SLIGHTLY SLOWED HIGHER POPS
UNTIL THE OVERNIGHT HOURS INTO THURSDAY MORNING. HIGHEST
CONFIDENCE FOR A TIGHT GRADIENT OF HIGHER STORM TOTAL RAINFALL
AMOUNTS OF 0.75" TO 1" WHERE THE MORE MOIST AIRMASS CAN
PENETRATE LOCALLY, FROM SOUTHEAST MINNESOTA INTO WEST-CENTRAL
WISCONSIN.

EXPECTED PRECIPITATION TYPES:

ALSO SIMILAR TO PREVIOUS FORECASTS, HAVE INCREASED SNOW MENTION
THURSDAY NIGHT INTO FRIDAY MORNING WHEN TEMPERATURES ARE MOST
CONDUCIVE FOR FROZEN PRECIPITATION. LONG TERM GLOBAL ENSEMBLE
CONFIDENCE HAS REMAINED CONSISTENT OVER PREVIOUS RUNS WITH A
PRIMARY AXIS OF A FEW INCHES ALONG THE DEFORMATION BAND IN
CENTRAL WISCONSIN. EXPECT A TIGHT SNOWFALL GRADIENT, ESPECIALLY
GIVEN THE ENHANCED TEMPERATURE GRADIENT. IRREGARDLESS, THE
HIGHER CONFIDENCE FOR SATURATION AND INCREASING LOBES OF
HEIGHTENED FRONTOGENESIS TIED TO THE MAIN BOWLING BALL OF THE
LOW WILL PROVIDE THUNDER CHANCES ALONG OUR SOUTHERN PERIPHERY
INTO THURSDAY MORNING. AGAIN, THE SHUNT AND ONGOING COMBAT
BETWEEN THE NORTHERN DRY AIR AND SOUTHERN MOIST AIR LIMITS
CONFIDENCE AND EXPECTED NORTHERN EXTENT.

COOLING TREND INTO & THROUGH THE WEEKEND:

AS SNOW CHANCES INCREASE OVERNIGHT THURSDAY INTO FRIDAY, THE
UPPER LEVEL TROUGH SAGS SOUTHEAST, DRAGGING A COLDER AIRMASS
THROUGH THE UPPER MISSISSIPPI RIVER VALLEY FRIDAY THROUGH THE
WEEKEND. TEMPERATURE ANOMALIES REDUCE TO 5 TO 10 DEGREES ABOVE
NORMAL FOR THE WEEKEND BEFORE DIPPING THE OPPOSITE DIRECTION IN
LONG TERM GLOBAL ENSEMBLE 100% CONFIDENCE (EPS/GEFS).


&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
ISSUED AT 1114 AM CDT TUE MAR 12 2024

CIGS: A FEW HIGH CLOUDS HERE AND THERE INTO WED MORNING. CLOUDS THEN
ON THE INCREASE WITH LOWERING AS WE MOVE INTO WED NIGHT WITH MODEL
TRENDS FAVORING DROPPING INTO MVFR/IFR OVERNIGHT.

WX/VSBY: NO IMPACTS EXPECTED THROUGH THE DAY WED. RAIN CHANCES COULD
START TO CREEP IN FROM THE SOUTH LATER WED NIGHT, ALTHOUGH THE
HIGHER CHANCES (60-80%) FAVORED DURING THE DAY THU. ANY THUNDER
CHANCES LOOK MOSTLY SOUTH OF I-90 AT THIS TIME. SOME VSBY
RESTRICTIONS WITH THE RAIN (MVFR...BUT A 30-40% SHOT FOR IFR).

WINDS: NORTHWEST WINDS WILL SWING NORTH AND NORTHEAST OVERNIGHT,
BECOMING LIGHT WITH THE LOSS OF DAYTIME HEATING. SOME UPTICK WED,
BUT MOSTLY 10 KTS OR LESS.

&&

.FIRE WEATHER...
ISSUED AT 213 PM CDT TUE MAR 12 2024

SURFACE FRONTAL BOUNDARY SEEN SAGGING SOUTHEAST THIS AFTERNOON
IS CAUSING RAPID DRYING WITH RHS DECREASING INTO THE LOW TEENS TO
LOW 20S FROM SOUTHEAST MINNESOTA INTO CENTRAL WISCONSIN.
SLIGHTLY INCREASED WINDS BEHIND THE FRONT REMAIN NEAR AND UNDER
20 MPH. OTHERWISE, THIS MOISTURE BOUNDARY IS EXPECTED TO REMAIN
RELATIVELY STAGNANT LOCALLY WITH INCREASED MOISTURE FROM
NORTHEAST IOWA INTO FAR SOUTHERN WISCONSIN. AS A RESULT, A
INCREASED GRADIENT IN RHS EXPECTED FOR WEDNESDAY. NORTH OF WHERE
THIS BOUNDARY LIES, RHS EXPECTED TO DROP INTO THE LOW 20S.
HIGHEST CONFIDENCE FOR THIS DRIER AREA TO BE FROM SOUTHEAST
MINNESOTA INTO WEST-CENTRAL WISCONSIN. FARTHER SOUTH, FROM
NORTHEAST IOWA INTO FAR SOUTHWEST WISCONSIN, THE MORE MOIST AIR
WILL RESULT IN MINIMUM RHS BOTTOMING OUT NEAR 30%.

&&

.CLIMATE...
ISSUED AT 213 PM CDT TUE MAR 12 2024

MODERATE MIXING EARLY THIS AFTERNOON AS THE DRY FRONTAL BOUNDARY
PASSES FROM NORTHWEST TO SOUTHEAST HAS SLIGHTLY TEMPERED
TEMPERATURES FROM INCREASED MIXING. TEMPERATURES STILL EXPECTED
TO INCREASE A COUPLE OF DEGREES INTO THIS EVENING, POTENTIALLY
TIEING BOTH DAYTIME HIGH RECORDS AT LA CROSSE AND ROCHESTER.
PROBABILITY FOR RECORD BREAKING TEMPERATURES DECREASES BELOW
10% ON WEDNESDAY OWING TO INCREASED CLOUD COVER.

                    TODAY                WEDNESDAY
LOCATION       FORECAST / RECORD      FORECAST / RECORD
-----------------------------------------------------------


LA CROSSE            72 / 74 (1990)         68 / 71 (2015)
ROCHESTER            67 / 67 (1990)         65 / 66 (2012)

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

DISCUSSION...JAR
AVIATION...RIECK
FIRE WEATHER...JAR
CLIMATE...JAR


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