057
FXUS63 KARX 190502
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1102 PM CST MON NOV 18 2024
KEY MESSAGES
- WIDESPREAD RAIN THROUGH TONIGHT WILL BRING A GENERAL 1-1.5
INCHES, WITH LOCALLY HIGHER AMOUNTS. IT WILL TURN WINDY AS
WELL WITH PEAK GUSTS IN THE 40 TO 45 MPH RANGE POSSIBLE..
- SNOW CHANCES ON WEDNESDAY INTO WEDNESDAY NIGHT, WITH A 50 TO
80% CHANCE OF 0.1 INCHES OR MORE TO OCCUR, WILL BE
ACCOMPANIED BY BREEZY WESTERLY WINDS.
- COOLER TEMPERATURES FROM WEDNESDAY THROUGH THE WEEKEND WITH
HIGHS IN THE MID 30S TO LOW 40S.
DISCUSSION
ISSUED AT 208 PM CST MON NOV 18 2024
WELL ADVERTISED AND DYNAMIC WAVE CONTINUES TO APPROACH THIS
AFTERNOON AS STRONG FORCING AND ANOMALOUSLY STRONG MOISTURE
ADVECTION HAVE LED TO A LARGE PRECIPITATION SWATH. MOST UNSTABLE
CAPE VALUES VIA ENSEMBLE MEANS REALLY GET PINCHED OFF THE FURTHER
NORTH YOU GO SO JUST NOT SEEING MUCH SIGNAL FOR THUNDER.
FORECAST DETAILS APPEAR ON TRACK WITH THIS WARM SECTOR SCENARIO AND
EXPECTED RAINFALL TOTALS HAVE REMAINED SURPRISINGLY CONSISTENT,
GENERALLY IN THE 1 TO 1.5" RANGE. ENSEMBLE PROBABILITIES DROP OFF
OVER THIS RANGE BUT AN OUTLIER SCENARIO /10-20%/ COULD LEAD TO
ISOLATED AMOUNTS CLOSER TO 2 INCHES ACROSS PARTS OF NORTHEAST IOWA
INTO SOUTHERN WISCONSIN. FORWARD PROGRESSION OF PRECIPITATION SHOULD
KEEP IMPACTS TO A MINIMUM, EVEN WITH A FEW RIVER FORECAST MODELS
BRINGING TRIBUTARIES SOUTH OF INTERSTATE 90 INTO ACTION STAGE.
ANOTHER ITEM TO WATCH TONIGHT WILL BE INCREASE IN WIND FIELD AS
PREVIOUSLY MENTIONED WAVE BECOMES MORE NEGATIVELY TILTED. ALREADY
NOTING IMPRESSIVE INCREASES IN LOW LEVEL VAD WIND FIELDS ON WSR88DS
TO THE SOUTH BUT UNSURE HOW MUCH TRUE MIXING WILL ACCOMPANY THIS LOW
LEVEL JET, EVEN WITH IMPRESSIVE WIND SPEEDS /40-60KTS/ A FEW
THOUSAND FEET OFF THE SURFACE. SOME ENSEMBLE MEMBERS HIGHLIGHT THESE
STRONGER WINDS BUT CONFIDENCE IS NOT STRONG ENOUGH FOR WIND RELATED
HEADLINES. COULD CERTAINLY SEE SOME GUSTS IN EXCESS OF 40 MPH SO
WILL HAVE TO BE WATCH THIS TREND AND MIGHT NEED SOME ADDITIONAL
MESSAGING TO CONVEY A POTENTIAL THREAT.
BY TUESDAY MORNING, WAVE WILL BE PASSING BUT ALSO BECOME PHASED WITH
ANOTHER SHORT WAVE DROPPING INTO THE NORTHERN PLAINS FROM SOUTHERN
CANADA. AREA WILL LIKELY BE MORE INTO THE DRY SECTOR WITH CHANCE FOR
SOME DRY TIME AND LIGHTER WINDS. FRONT WILL ALSO BE APPROACHING FROM
THE WEST AND PROVIDE A WIND SHIFT AND CHANGE TO A COLD AIR ADVECTION
REGIME BY LATE DAY.
WEDNESDAY - THURSDAY: NEXT PRECIPITATION CHANCE, SNOW?
THE STORM SYSTEM THAT IS CURRENTLY PRODUCING RAIN AND WIND WILL
WEAKEN AND GET ABSORBED BY THE BIGGER LONGWAVE TROUGH. AS THIS
LONGWAVE TROUGH SHIFTS EASTWARD, IT WILL DEEPEN OVER THE UPPER
MIDWEST. THIS WILL BRING COOLER TEMPERATURES AND GUSTY WEST TO
NORTHWEST WINDS ON WEDNESDAY. WIND GUSTS ON WEDNESDAY ARE FORECASTED
TO BE 20 TO 30 MPH. TEMPERATURES WILL BE COLD ENOUGH THAT ANY
PRECIPITATION THAT DOES FALL WOULD BE SNOW. ACCUMULATIONS WILL BE
POSSIBLE ON GRASSY SURFACES AND HIGHER ELEVATION. WHEN LOOKING AT
HOW MUCH SNOW WE WILL GET, THERE CONTINUES TO BE A GOOD SIGNAL (50
TO 80%) THAT MEASURABLE SNOW (>0.1") WILL BE POSSIBLE ACROSS THE
FORECAST AREA. TOTAL ACCUMULATIONS LOOK TO BE BETWEEN A TRACE TO
AROUND 0.5", HOWEVER THERE IS A LOW CHANCE (10 TO 30%) THAT OVER AN
INCH WILL BE POSSIBLE, MAINLY FOR AREAS NORTH OF I-90. COMPARED TO
THE PREVIOUS FORECAST, THE SNOW SQUALL PARAMETER FROM THE NAM STILL
SHOWS VALUES BETWEEN 1 AND 4 WEDNESDAY AFTERNOON AND EVENING. THERE
CONTINUES TO BE SOME INSTABILITY, UP TO 100 J/KG OF SBCAPE, STEEP
LAPSE RATES, AND GUSTY WINDS. EVEN WITH THE LIGHT SNOW SHOWERS THAT
ARE EXPECTED, THERE REMAINS A GOOD CHANCE THAT REDUCED VISIBILITIES
COULD OCCUR GIVEN THESE CONDITIONS.
FRIDAY - THE WEEKEND: NEAR NORMAL TEMPERATURES, DRIER
AFTER THIS SYSTEM EXITS, RIDGING BUILDS IN, HOWEVER OUR AREA IS
FORECASTED TO BE ON THE EDGE OF THE RIDGE AND MAINTAIN A NORTHWEST
FLOW. WITH THIS FLOW PATTERN, HIGH TEMPERATURES WILL BE IN THE MID
30S TO LOW 40S. HEADING INTO SUNDAY, ENSEMBLE AND DETERMINISTIC
GUIDANCE BEGINS TO SPLIT ON WHAT WILL HAPPEN. THE GEFS FAVORS A
BREAKDOWN OF THE RIDGE AND HAS A SHORTWAVE TROUGH PASS THROUGH THE
AREA. ABOUT 70% OF GEFS MEMBERS FAVOR THIS SOLUTION. OF THOSE 70%,
ABOUT HALF SHOW MEASURABLE PRECIPITATION. THE EPS REMAINS MOSTLY DRY
FOR SUNDAY. BOTH GEFS AND EPS SHOW POTENTIAL FOR AN UNSETTLED
PATTERN NEXT WEEK WITH SCATTERED PRECIPITATION CHANCES.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1100 PM CST MON NOV 18 2024
THE MAIN TAF CONCERNS CONTINUE TO BE CEILINGS AND VISIBILITIES
AS RAIN MOVES THROUGH THE REGION. VISIBILITIES ASSOCIATED WITH
THE RAIN HAVE GENERALLY REMAINED MVFR TO VFR OVER THE LAST
SEVERAL HOURS WITH SOME BOUTS OF IFR AT TIMES. EXPECT THIS TREND
TO CONTINUE THROUGH THE OVERNIGHT HOURS WITH THE LOWER
VISIBILITIES IN HEAVIER RAINFALL. RAINFALL IS EXPECTED TO END
TUESDAY MORNING. IFR TO LIFR CEILINGS WILL CONTINUE THROUGH THE
OVERNIGHT HOURS, ESPECIALLY AT KRST. THE NBM PROBABILITIES
REMAIN 40-50% FOR IFR CEILINGS OVER THE NEXT FEW HOURS AS DRIER
AIR MOVES INTO THE REGION. STILL THINKING THAT THERE SHOULD BE
SOME IMPROVEMENT TO THE 1-2KFT RANGE DURING THIS TIME WITH A
SCATTERED DECK POSSIBLE BELOW 1KFT GIVEN THE PROBABILITIES FOR
IFR CEILINGS. CEILINGS SHOULD DETERIORATE AGAIN ON THE BACKSIDE
OF THE LOW. THIS THINKING IS SUPPORTED BY OBSERVATIONS ACROSS
NORTHERN IOWA SUGGESTING IMPROVEMENT AND LOWER CEILINGS FURTHER
WEST ON THE BACKSIDE OF THE LOW. GUSTY WINDS ARE STILL EXPECTED
THROUGHOUT THE TAF PERIOD, SHIFTING FROM A SOUTHEAST DIRECTION
CURRENTLY TO THE SOUTH AND THEN WEST THROUGHOUT THE DAY.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...CECAVA/SHEA
AVIATION...FALKINHAM
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