358
FXUS63 KARX 231117
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
617 AM CDT SAT OCT 23 2021
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 244 AM CDT SAT OCT 23 2021
A DEEP UPPER LOW RETROGRADING FROM JAMES BAY TODAY IS KEEPING CHILLY
CYCLONIC FLOW OVER THE REGION. EARLY MORNING WATER VAPOR IMAGERY
REVEALS A SHORTWAVE DROPPING THROUGH THE UPPER MISSISSIPPI VALLEY,
SUPPORTING VARIABLE CLOUDINESS OVER PORTIONS OF WISCONSIN. THESE
CLOUDS HAVE INTRODUCED SOME TEMPERATURE FORECAST COMPLEXITIES, WITH
TEMPS UNDERNEATH HOLDING A BIT WARMER. TEMPS OUTSIDE THE CLOUD COVER
STILL LOOK ON TRACK FOR DIPPING INTO THE UPPER 20S BY DAYBREAK. ALSO
SOME VALLEY FOG/STRATUS SHOWING UP ON SATELLITE IN THE MAIN
MISSISSIPPI CHANNEL SOUTH OF LA CROSSE AS WELL AS THE WISCONSIN.
CLOUDS ARE EXPECTED TO LINGER OVER AREAS NEAR AND NORTH OF I-94 INTO
THIS AFTERNOON, WITH CIRRUS ALSO INCREASING FROM THE WEST. QUIET
OVERALL AS SURFACE RIDGE AND BAGGY PRESSURE GRADIENT DRIFT OVER THE
AREA, RESULTING IN LIGHT NORTH TO NORTHEAST WINDS AND HIGHS IN THE
UPPER 40S TO MID 50S.
WILL BE WATCHING A DEVELOPING SYSTEM OVER THE CENTRAL PLAINS HEADING
INTO TONIGHT AS A PRONOUNCED UPPER TROUGH CROSSES THE FOUR CORNERS
REGION. THE RESULTANT DEEPENING SURFACE LOW WILL SET UP A TIGHT
BAROCLINIC ZONE TO OUR SOUTH HEADING INTO SUNDAY. DEVELOPING
ISENTROPIC ASCENT NORTH OF A WARM FRONT FROM EASTERN KS TO
SOUTHERN OH WILL BEGIN TO SPREAD NORTHWARD INTO OUR AREA LATE
TONIGHT. EXPECT THICKENING CLOUD COVER AS A RESULT, THOUGH RAIN
CHANCES SHOULD LARGELY HOLD OFF UNTIL DAYTIME.
LONG TERM
(SUNDAY THROUGH FRIDAY)
ISSUED AT 244 AM CDT SAT OCT 23 2021
THE NEGATIVELY TILTED, STRENGTHENING SYSTEM WILL CREEP INTO WESTERN
IOWA ON SUNDAY. MEANWHILE THERE WILL BE A PRETTY STRONG HIGH
PRESSURE SYSTEM AND ASSOCIATED DRY AIRMASS ANCHORED OVER HUDSON BAY
INTO MONDAY. THIS WILL AID IN KEEPING THE SYSTEM'S MOST SUBSTANTIAL
RAINFALL JUST SOUTH OF OUR AREA. IN FACT, THE BIGGEST FORECAST
QUESTION REMAINS JUST HOW FAR NORTH RAIN CHANCES WILL EXTEND. IT
DOES LOOK LIKE SOME BANDS OF FRONTOGENESIS WILL LIFT AS FAR
NORTHWARD AS I-94 SUNDAY INTO MONDAY MORNING, WITH PWATS INCREASING
TO 0.75 TO 1+ INCHES -- A FAVORABLE SETUP FOR SOME NEEDED RAINFALL
FOR MUCH OF THE AREA. PRETTY STRONG MODEL CONSENSUS FOR I-90 BEING
THE GENERAL NORTHWARD EXTENT OF THE RAIN SHIELD. EPS CONTINUES TO
SHOW GOOD RUN-TO-RUN CONSISTENCY WITH I-90 AS THE NORTHWARD EXTENT
(AND CAMS SEEM TO BE INDICATING THE SAME). ON THE OTHER HAND, GEFS
HAS BEEN MORE ERRATIC BUT STILL THE FURTHEST NORTH SOLUTION WITH
RAIN NOW WELL INTO NORTH-CENTRAL WI. REGARDLESS, CONSENSUS FAVORS
AROUND 0.5 TO JUST SHY OF 1" OF RAINFALL SOUTH OF I-90 BEFORE RAIN
QUICKLY EXITS MONDAY MORNING. COULD BE A FEW RUMBLES OF THUNDER IN
OUR FAR SOUTHERN COUNTIES. THE OTHER THING OF NOTE WILL BE AN
INCREASE IN WINDS SUNDAY AFTERNOON INTO THE OVERNIGHT AS THE
INTENSIFYING SURFACE LOW PASSES BY TO OUR SOUTH. 925MB WINDS WILL BE
STRONGEST SOUTH OF I-90, INCREASING TO 35-40 KNOTS. THUS, EXPECT
GUSTS OF 25-35 MPH AREA WIDE, STRONGEST SOUTH OF I-90 WHERE A FEW
GUSTS COULD APPROACH 40 MPH. FORECAST SOUNDINGS SHOW BOUNDARY LAYER
MIXING CONTINUING AFTER DARK, SO WINDY CONDITIONS ARE EXPECTED TO
PERSIST OVERNIGHT.
ATTENTION THEN TURNS TO ANOTHER SYSTEM TOWARDS MID-WEEK AS DEEP
TROUGHING CROSSES THE WESTERN CONUS. CONSIDERABLE FORECAST
UNCERTAINTY AS MODELS CONTINUE TO SHOW VARIOUS OUTCOMES ONCE THIS
TROUGH CROSSES THE ROCKIES. ECMWF AND CMC DEVELOP SPLIT UPPER FLOW
WITH A SOUTHERN-STREAM CUTOFF LOW AND NORTHERN STREAM SHORTWAVE THAT
EVENTUALLY PHASE EAST OF THE MISSISSIPPI RIVER THURSDAY INTO FRIDAY.
MEANWHILE GFS DEVELOPS A DEEP CUTOFF LOW OVER THE MID-MISSISSIPPI
VALLEY BY THURSDAY. WILL ALSO HAVE SOME DRY AIR TO CONTEND WITH
LOCALLY AS THIS SYSTEM APPROACHES, SO CONFIDENCE IN PRECIP CHANCES
IS LOW TO MEDIUM FROM TUESDAY NIGHT AND BEYOND. STILL LOOKS LIKE A
DECENT SETUP FOR RAIN, BUT AMOUNTS AND COVERAGE ARE STILL VERY MUCH
UNCERTAIN. TEMPERATURE-WISE, NO SIGNIFICANT WARM UPS ARE EXPECTED
OVER THE UPCOMING WEEK.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 617 AM CDT SAT OCT 23 2021
LATEST NIGHTTIME SATELLITE IMAGERY SHOWS FOG/LOW STRATUS FORMATION
IN THE MISSISSIPPI RIVER VALLEY THIS MORNING. AT THIS TIME...THE
FOG/LOW STRATUS REMAINS SOUTH/NORTH OF THE KLSE TAF SITE AND IFR
CEILINGS/VISIBILITY CONDITIONS WOULD BE VERY BRIEF AT THE KLSE TAF
SITE EARLY IN THE TAF PERIOD. HAVE INTRODUCED BCFG AT KLSE TAF
SITE FOR A COUPLE OF HOURS EARLY IN THE TAF PERIOD. VFR
CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD WITH SURFACE RIDGE
IN CONTROL OVER THE UPPER GREAT LAKES REGION TODAY AND INTO
TONIGHT. A STORM SYSTEM WILL MOVE INTO THE CENTRAL PLAINS STATES
AFTER 06Z SUNDAY AND SPREAD SOME MID TO HIGH CLOUDS LATE IN THE
TAF PERIOD. CEILINGS SHOULD REMAIN IN VFR.
ARX WATCHES/WARNINGS/ADVISORIES
WI...FREEZE WARNING UNTIL 9 AM CDT THIS MORNING FOR WIZ041-053>055-
061.
MN...FREEZE WARNING UNTIL 9 AM CDT THIS MORNING FOR MNZ087-088-
094>096.
IA...FREEZE WARNING UNTIL 9 AM CDT THIS MORNING FOR IAZ008>011-018-
019-029-030.
SHORT TERM...KURZ
LONG TERM...KURZ
AVIATION...DTJ
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