246
FXUS63 KARX 211908
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
210 PM CDT SAT SEP 21 2019
SHORT TERM
(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 210 PM CDT SAT SEP 21 2019
WET, CLOUDY WEEKEND FOR THE AREA AS UPPER LEVEL TROUGH AND SFC COLD
FRONT MAKE SLOW PROGRESS EAST.
FIRST, IN THE IMMEDIATE TERM, CLEAR SLOT AHEAD OF COLD FRONT OVER
WESTERN MN COUPLED WITH MLCAPES AROUND 2500 J/KG HAS RESULTED IN
THIN BANDS OF STORMS FROM NW IA INTO NW WI. SHEAR MOSTLY LAGS WEST
OF THE INSTABILITY AXIS, WITH THE INSTABILITY GENERALLY ELEVATED
THANKS TO WARMING IN THE 850-700 MB LAYER. COULD SEE SOME STRONGER
STORMS (SEVERE?) WITH THIS ACTIVITY WITH HAIL AND HEAVY RAIN BEING
THE MAIN THREATS. A THIS TIME, THINK ANY SEVERE POTENTIAL WILL HOLD
WEST/NORTHWEST OF THE LOCAL AREA.
UPPER LEVEL TROUGH CURRENTLY ACROSS THE ROCKIES, PER LATEST
WATERVAPOR IMAGERY, WITH THE VARIETY OF MODELS SLIDING THE TROUGH
AXIS ACROSS THE LOCAL AREA LATER SUNDAY NIGHT. RIPPLES IN THE UPPER
LEVEL FLOW WILL LEAD THE MEAN THROUGH INTO THE REGION WHILE
ASSOCIATED SFC COLD FRONT TREKS ACROSS THE LOCAL FORECAST AREA
OVERNIGHT-SUNDAY MORNING. IN ADDITION, COUPLED 300 MB JET PROMISES
TO ENHANCE ALL THIS AVAILABLE LIFT ON AN OFF INTO SUNDAY EVENING.
AMPLE LIFTING MECHANISMS FOR SHOWER/STORM PRODUCTION.
MEANWHILE, SOME INSTABILITY ALONG/AHEAD OF THE SFC BOUNDARY INTO
TONIGHT, ROUGHLY 1500-2500 J/KG AND GENERALLY ELEVATED. DEEPER SHEAR
LAGS WEST OF THE INSTABILITY AXIS. LITTLE/IF ANY INSTABILITY TO WORK
WITH AFTER THAT. MORE IMPORTANTLY IS THE MOIST/HEAVY RAIN CONDUCIVE
AIRMASS THE LINGERS ACROSS EASTERN IA INTO SOUTHEAST WI TONIGHT-SUN.
WARM CLOUD DEPTHS HOVER AROUND 4 KFT WITH PWS AROUND 2 INCHES. THE
LOW LEVEL MOISTURE TRANSPORT STRETCHES AHEAD OF THE SFC FRONT,
FOCUSING MORE INTO IL COME SUN. ALL IN ALL, HEAVY RAIN REMAINS A
POSSIBILITY (IF NOT LIKELIHOOD) TONIGHT INTO SUN EVENING WITH ANY
STORM (OR SHOWER FOR THAT MATTER). THE HIGHER THREAT WILL LIE ACROSS
FAR NORTHEAST IA INTO SOUTHWEST WI.
EXPANDED A FLASH FLOOD WATCH FOR THAT AREA INTO SUNDAY EVENING AND
INCLUDED A FEW COUNTIES IN NE IA. THE HIGHER THREAT TIMES FOR
HEAVIER RAIN IN THESE AREAS CURRENTLY SHAPING UP TO BE OVERNIGHT
INTO EARLY SUN MORNING AND FROM MID AFTERNOON SUN INTO THE EVENING.
LONG TERM
(MONDAY THROUGH SATURDAY)
ISSUED AT 210 PM CDT SAT SEP 21 2019
SHORTWAVE RIDGING A LOFT COUPLED WITH A HIGH AT THE SFC WILL KICK
THE NEW WORK WEEK OFF ON A VERY WELCOME DRY NOTE. AFTER THE COOL
WEEKEND, SHOULD ALSO SEE A SLIGHT BUMP UPWARDS IN TEMPS TOO.
COME TUE NIGHT, UPPER LEVEL SHORTWAVE TROUGH/SFC COLD FRONT LOOKS TO
TRACK IN FROM THE WEST, BRINGING A GOOD SHOT FOR SHOWERS AND STORMS.
SHOWERS LOOK TO LINGER (PERHAPS MORESO IN THE NORTH) WED IN THE COLD
AIR/CYCLONIC FLOW A LOFT, POST THE DEPARTING TROUGH.
THURSDAY CURRENTLY SHAPING UP DRY BEFORE ANOTHER SHORTWAVE TROUGH
SLIDES IN FROM THE EAST, BRINGING MORE RAIN CHANCES FOR THU
NIGHT/FRI. ON AND OFF RAIN CHANCES LOOK TO LINGER INTO THE WEEKEND,
ALTHOUGH PLENTY OF UNCERTAINTY WITH TIMING/COVERAGE.
THE THREAT FOR ORGANIZED SEVERE WEATHER LOOKS LOW NEXT WEEK WITH
ONLY MARGINAL INSTABILITY/SHEAR CURRENTLY PROGGED. THE HEAVY RAIN
THREAT ALSO LOOKS TO BE LESSENING WITH THE JUICIER AIR HOLDING
FARTHER TO THE SOUTH.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1216 PM CDT SAT SEP 21 2019
IFR/MVFR CLOUD DECKS WILL PERSIST THROUGH THE AFTERNOON AT RST/LSE,
RESPECTIVELY, ALONG WITH GUSTY SOUTHERLY WINDS. IN ADDITION, EXPECT
LIGHT SHOWERS TO MOVE THROUGH THE AREA, THOUGH GIVEN THE SPOTTY
NATURE OF THEM, LEAVING VCSH MENTION GOING. CEILINGS EXPECTED TO
RISE INTO VFR BY THIS EVENING, THOUGH GREATER THUNDERSTORM CHANCES
WILL ALSO BE MOVING IN. HOWEVER, STORM DEVELOPMENT WILL REMAIN
SPOTTY, SO KEPT VCTS MENTION FOR NOW. ANY STORM THAT MOVES OVER A
TAF SITE COULD LEAD TO MVFR OR IFR CONDITIONS FOR A BRIEF TIME. RAIN
CHANCES WILL END AS A COLD FRONT MOVES THROUGH OVERNIGHT, WITH WINDS
BECOMING NORTHWESTERLY BEHIND THE FRONT. SOME HINTS AT MORE SHOWERS
MOVING IN TOWARD THE END OF THE TAF PERIOD, BUT OVERALL MODEL
CONSENSUS IS TO HOLD OFF UNTIL AFTER 18Z.
ARX WATCHES/WARNINGS/ADVISORIES
WI...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH LATE
SUNDAY NIGHT FOR WIZ061.
MN...NONE.
IA...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH LATE
SUNDAY NIGHT FOR IAZ029-030.
SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...CA
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