764
FXUS63 KARX 241112
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
612 AM CDT SUN OCT 24 2021
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 254 AM CDT SUN OCT 24 2021
MID TO HIGH CLOUDS HAVE OVERSPREAD THE AREA AHEAD OF A DEVELOPING
SYSTEM OVER THE CENTRAL PLAINS. UPPER TROUGHING CROSSING THE ROCKIES
CONTINUES TO SUPPORT A ~997MB SURFACE LOW PRESENTLY OVER CENTRAL
KANSAS. A WARM FRONT EXTENDS EASTWARD FROM THIS SYSTEM, MARKING A
TIGHT BAROCLINIC ZONE FROM MISSOURI INTO SOUTHERN OHIO. AS THIS
SYSTEM MAKES HEADWAY TOWARD THE LOCAL AREA LATER TODAY INTO TONIGHT,
THE MAIN FORECAST CONCERNS WILL BE RAINFALL AMOUNTS AND NORTHERN
EXTENT, AS WELL AS INCREASINGLY GUSTY WINDS HEADING INTO TONIGHT.
ENSEMBLE AND DETERMINISTIC (INCLUDING HI-RES) GUIDANCE HAS GENERALLY
LOCKED ONTO THE RAIN SHIELD REACHING ROUGHLY AS FAR NORTH AS THE I-
90 CORRIDOR LATER TODAY. THERE'S STILL SOME SLIGHT NORTH OR SOUTH
VARIANCE, BUT THIS I-90 TREND HAS REMAINED FAIRLY CONSISTENT OVER
THE LAST 24 HOURS. THAT'S THANKS TO A STRONG SURFACE HIGH SITTING
OVER ONTARIO KEEPING DRIER MID-LEVEL AIR IN PLACE NORTH OF I-90.
SYNOPTIC LIFT WILL BEGIN TO SPREAD RAIN NORTHWARD INTO OUR AREA
TOWARDS MID-MORNING AS THE LOW LEVELS MOISTEN UP. RAINFALL WILL PICK
UP MORESO THIS AFTERNOON AND EVENING AS FORCING IS ENHANCED BY MID-
LEVEL FRONTOGENESIS LIFTING JUST NORTH IF I-90. RAIN CONTINUES INTO
THE OVERNIGHT AS THE SURFACE LOW CUTS EAST ACROSS CENTRAL ILLINOIS,
AND THEN THE PRECIP QUICKLY PEELS EAST LATE TONIGHT AS THE SYSTEM
DEPARTS. RAIN SHOULD BE COMPLETELY OUT OF OUR AREA BY DAYBREAK
MONDAY. LOOKS LIKE AROUND 0.5 TO 1.25" ACROSS NORTHEAST IA AND
SOUTHWEST WI, WITH LESSER AMOUNTS NORTHWARD TO I-90.
THE OTHER CONCERN WITH THIS SYSTEM WILL BE AN INCREASE IN WINDS THIS
AFTERNOON AND EVENING. THE PRESSURE GRADIENT WILL BEGIN TO TIGHTEN
ACROSS OUR SOUTH THIS AFTERNOON AS THE SURFACE LOW REACHES THE IA/MO
BORDER. WHILE THE LOW DOESN'T LOOK TO BE DEEPENING MUCH BY THAT TIME
ANYMORE, AS IT CROSSES THE MISSISSIPPI RIVER THIS EVENING HIGH
PRESSURE TO THE NORTH WILL BUILD SOUTHWARD AROUND THE BACK SIDE OF
IT, FURTHER TIGHTENING THE GRADIENT. 0-1KM LAPSE RATES LOOK TO BE
SUPPORTIVE FOR SOME CONTINUED LOW LEVEL MIXING EVEN INTO THE
OVERNIGHT, AS WINDS IN THE 925-900MB LAYER INCREASE TO 40-45 KNOTS
ACROSS OUR SOUTH. EXPECTING GUSTINESS THIS EVENING WILL BE MORE TIED
TO GRADIENT WINDS, BUT EVEN LIMITED MIXING WILL LIKELY SUPPORT
ENOUGH DOWNWARD MOMENTUM FOR A FEW GUSTS JUST OVER 40 MPH IN OUR FAR
SOUTH. SEVERAL EPS MEMBERS SUPPORT GUSTS OF THIS MAGNITUDE, BUT
CERTAINLY 30 TO 40 MPH WILL BE MORE COMMON. SIDE NOTE: FV3 IS AN
OUTLIER WITH ITS GUSTS OF 45-50 MPH IN OUR SOUTH, WHICH RESULTED
IN 24.00Z HREF MEAN/MAX GUSTS LOOKING OVERDONE. THUS, NOT
ANTICIPATING NEED FOR A WIND ADVISORY AT THIS TIME. PRESSURE
GRADIENT AND WINDS LOOK TO GRADUALLY RELAX AFTER MIDNIGHT.
LONG TERM
(MONDAY THROUGH SATURDAY)
ISSUED AT 254 AM CDT SUN OCT 24 2021
EXPECT A RETURN TO SUNSHINE MONDAY AND TUESDAY AS AMPLIFYING RIDGING
ALOFT CROSSES THE REGION. FOCUS WILL BE ON A DEEP LONGWAVE TROUGH
MAKING ITS WAY THROUGH WESTERN CONUS. A SPLIT FLOW PATTERN WILL
DEVELOP ONCE IT CROSSES THE ROCKIES, WITH A NORTHERN STREAM
SHORTWAVE CROSSING THE DAKOTAS BY WEDNESDAY AND A SOUTHERN STREAM
WAVE MORPHING INTO A CLOSED LOW OVER THE SOUTHERN PLAINS. MAIN
FORECAST CONCERN IS HOW THESE FEATURES EVENTUALLY INTERACT WITH EACH
OTHER TOWARDS THE END OF THE WEEK. GUIDANCE SEEMS TO BE COMING INTO
BETTER AGREEMENT FOR THE CUTOFF LOW TO DEEPEN/EXPAND AS IT CROSSES
THE MISSISSIPPI RIVER BY FRIDAY. OUR AREA IS PROGGED TO BE ON THE
NORTHERN/NORTHWESTERN PERIPHERY OF THIS SYSTEM AS IT WOBBLES OVER
THE MIDDLE MISSISSIPPI VALLEY INTO APPALACHIA. A FAVORABLE PLUME
OF MOISTURE WILL GRADUALLY WORK INTO THE AREA ON WEDNESDAY. LOOKS
LIKE WE WILL BE IN FOR AN UNSETTLED PERIOD LATE IN THE WEEK AS
PERSISTENT SYNOPTIC FORCING INTERACTS WITH THIS MOISTURE, BUT
CONFIDENCE IN SPECIFIC DETAILS REMAINS LOW. WEDNESDAY NIGHT
THROUGH FRIDAY IN PARTICULAR LOOKS LIKE THE WETTEST PERIOD AT THIS
TIME. TEMPERATURES WILL REMAIN NEAR OR JUST BELOW SEASONAL
NORMALS WITH HIGHS IN THE 50S.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 612 AM CDT SUN OCT 24 2021
MAIN TAF CONCERNS ARE THE POSSIBILITY OF MVFR CONDITIONS AT BOTH
RST/LSE TAF SITES THIS AFTERNOON INTO TONIGHT. SURFACE LOW WILL MOVE
INTO THE CENTRAL PLAINS STATES TODAY INTO TONIGHT AND SPREAD
RAIN/STRATUS DECK OF CLOUDS INTO THE AREA. WITH A DRY AIRMASS ALONG
AND NORTH OF INTERSTATE 90...THIS WILL INHIBIT ANY RAIN AND STRATUS
DECK NORTH OF INTERSTATE 90. AT THIS TIME...VFR CONDITIONS WILL
PREVAIL AT BOTH RST/LSE TAF SITES THROUGH THE PERIOD. HOWEVER...IF
SURFACE LOW TRACKS SLIGHTLY FURTHER NORTH THAN WHAT IS
FORECAST...THEN LOWER CEILINGS WILL MOVE OVER THE TAF SITES THIS
AFTERNOON INTO TONIGHT AND POSSIBLY BE MVFR TO IFR. AS SURFACE LOW
DEEPENS OVER THE CENTRAL PLAINS STATES...WINDS WILL INCREASE AND
POTENTIALLY GUSTS UP 25 KNOTS AT TAF SITES THIS AFTERNOON INTO
TONIGHT.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
SHORT TERM...KURZ
LONG TERM...KURZ
AVIATION...DTJ
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