288
FXUS63 KMPX 180534
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1234 AM CDT MON AUG 18 2025
KEY MESSAGES
- ANOTHER ROUND OF THUNDERSTORMS AND HEAVY RAIN TONIGHT INTO
MONDAY MORNING. UNCERTAINTY STILL EXISTS ON THE EXACT
PLACEMENT OF THE HEAVIEST RAIN.
- A FEW SEVERE THUNDERSTORMS ALSO POSSIBLE THIS EVENING, WITH
DAMAGING WIND GUSTS THE PRIMARY THREAT FOLLOWED BY HAIL.
- SEASONABLY COOL & DRY THROUGH THE REST OF THE WEEK.
DISCUSSION
ISSUED AT 244 PM CDT SUN AUG 17 2025
ONE MORE ROUND OF HEAVY RAIN & POTENTIAL FLOODING IS EXPECTED
TONIGHT INTO TOMORROW MORNING, BUT UNFORTUNATELY WE'RE STILL
DEALING WITH UNCERTAINTY ON WHERE EXACTLY THAT CHANCE WILL BE
GREATEST. IN THE LARGE SCALE, WE HAVE A VERY FAVORABLE PATTERN
FOR WIDESPREAD THUNDERSTORMS TONIGHT, WITH A STATIONARY FRONT
ACROSS SOUTHERN MINNESOTA SLOWLY LIFTING NORTHWARDS OVERNIGHT AS
A WARM FRONT & ACTING AS THE MAIN FORCING MECHANISM FOR STORMS
TONIGHT. A LOBE OF VORTICITY PASSING OVER THE CENTRAL HALF OF
MINNESOTA WILL PROVIDE THE UPPER LEVEL FORCING, BUT THE EXACT
LOCATION OF THE HEAVIEST RAINFALL TONIGHT WILL DEPEND ON TWO
SEPARATE MESOSCALE FORCING MECHANISMS. THE FIRST IS THE REMNANTS
OF A THUNDERSTORM COMPLEX OVER NORTHEAST SOUTH DAKOTA, WHICH IS
FORECAST TO TRACK ACROSS CENTRAL MINNESOTA THIS EVENING &
TONIGHT. MANY OF THE GLOBAL ENSEMBLES & AI ENSEMBLES FAVOR THIS
PLACEMENT OVER CENTRAL MINNESOTA & WESTERN WISCONSIN, WHERE THE
UPPER LEVEL FORCING IS STRONGER & THE MESOSCALE FORCING FROM THE
MCV PROVIDES PLENTY OF FORCING ALONG THE SURFACE FRONT.
HOWEVER, A SECOND GROUP OF HIGH-RESOLUTION MODELS FAVORS A MORE
SOUTHERLY FOCUS AREA, ACROSS SOUTHERN MINNESOTA & SOUTHWEST
WISCONSIN, WHERE THE LOW-LEVEL JET BECOMES THE MAIN MODE OF
FORCING & INTERACTS WITH THE SURFACE FRONT & OUTFLOW FROM THIS
MORNIGN'S STORMS. UNFORTUNATELY IT IS STILL NOT CLEAR WHICH OF
THESE FORCING MECHANISMS WILL WIN OUT, BUT THE TRENDS OF ONGOING
CONVECTION ALONG THE SOUTH DAKOTA/MINNESOTA BORDER SHOULD GIVE
US OUR ANSWER BY EARLY EVENING.
THUNDERSTORMS ARE EXPECTED TO BECOME MORE WIDESPREAD ACROSS
WESTERN MINNESOTA THIS EVENING (5-7 PM), CONGEALING INTO A
CLUSTER OF STORMS THROUGH THE EVENING & NIGHT ACROSS MINNESOTA &
EVENTUALLY WANING OVER WESTERN WISCONSIN EARLY TOMORROW
MORNING. THESE STORMS WILL BE SLOW- MOVING WITH STORM MOTIONS
LIKELY 20 KTS OR LESS, WHICH ALONG WITH RAINFALL RATES NEAR 2"
PER HOUR WILL RESULT IN OUR FLOODING THREAT TONIGHT. AS
MENTIONED EARLIER, CONFIDENCE IS LOW ON WHERE EXACTLY THE MOST
WIDESPREAD THUNDERSTORMS & HEAVIEST RAIN WILL OCCUR, BUT NEARLY
ALL HIGH-RESOLUTION MODELS DEPICT LOCALIZED AMOUNTS OF 4+ WHERE
THEY HAVE THE HEAVIEST THUNDERSTORMS. THIS LEADS TO HIGHER
CONFIDENCE IN THE POTENTIAL FOR HEAVY RAIN & FLOODING TONIGHT,
EVEN IF WE WONT KNOW EXACTLY WHERE UNTIL STORMS FIRE THIS
EVENING. SO IN GENERAL, MOST OF THE AREA CAN EXPECT
THUNDERSTORMS AND AMOUNTS OF 1-2" THROUGH TOMORROW MORNING, WITH
HIGHER CHANCES FOR 3-4" OR MORE WHEREVER THAT MAIN AXIS OF
THUNDERSTORMS SETS UP TONIGHT. GIVEN HOW NEARLY THE ENTIRE AREA
HAS SEEN 2-3" OF RAIN SINCE FRIDAY & SOILS ARE NEARLY SATURATED
ALREADY, OPT TO ISSUE AN AREA-WIDE FLASH FLOOD WATCH TONIGHT AS
ANYWHERE THAT SEES THUNDERSTORMS TONIGHT COULD HAVE THE
POTENTIAL FOR RAPID RUNOFF LEADING TO FLOODING.
IN ADDITION TO THE HEAVY RAIN THREAT, A FEW SEVERE STORMS ARE
ALSO POSSIBLE THIS EVENING. WE'VE SEEN MORE CLEARING THAN
EXPECTED THIS AFTERNOON, WHICH WILL ALLOW FOR SURFACE-BASED CAPE
VALUES OF 2000 J/KG TO DEVELOP SOUTH OF THE SURFACE FRONT ALONG
SOUTHERN MINNESOTA. THE MID-LEVEL LAPSE RATES ARE NOT GREAT AND
WILL PROBABLY LIMIT THE THREAT FOR WIDESPREAD SEVERE WEATHER,
BUT IT'S LIKELY THAT AT LEAST A FEW STORMS WILL BE ABLE TO TAP
INTO THIS HIGHER CAPE AND DEVELOP INTO MORE ORGANIZED CLUSTERS
OR LINES AS THE EVENING PROGRESSES. DAMAGING WIND GUSTS WOULD BE
THE PRIMARY HAZARDS WITH THESE STORMS, BUT HAIL IS ALSO
POSSIBLE EARLIER THIS EVENING IF ANY DEEPER UPDRAFTS ARE ABLE TO
TAP INTO THE INCREASING WIND SHEAR & BECOME SUPERCELLULAR.
THE HEAVIEST RAIN WILL END FROM WEST TO EAST DURING THE EARLY
MORNING HOURS, WITH LINGERING LIGHTER RAINFALL CONTINUING ACROSS
SOUTHEAST MINNESOTA & WESTERN WISCONSIN INTO EARLY AFTERNOON.
BEYOND THAT, WE'LL BE ABLE TO DRY OUT WITH COOLER AND DRIER
WEATHER EXPECTED THROUGH THE REST OF THE WEEK.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1227 AM CDT MON AUG 18 2025
RA/TSRA CONTINUES AT INITIALIZATION, PARTICULARLY IN SOUTHERN MN
INTO WESTERN WI, WHILE ADDITIONAL ROUNDS OF CONVECTION ARE
LIKELY TO DEVELOP IN EASTERN SD OVERNIGHT WHICH WILL DRIFT
ACROSS MN THROUGH SUNRISE. HAVE TAKEN A HRRR LOOK TO THINGS
WHICH SHIFTS THE ONGOING LARGE SHIELD OF RAIN EAST INTO WI WHILE
SCATTERED CONVECTION WILL RE-DEVELOP IN SW MN OVERNIGHT AND
BECOME SOMEWHAT MORE ORGANIZED TO MOVE ACROSS MOST TERMINALS
NEAR AND AFTER SUNRISE. PLENTY OF MVFR CEILINGS WITH THE
ADDITIONAL ROUNDS OF PRECIPITATION, WITH IFR POSSIBLE FROM TIME
TO TIME. HEAVIER RAIN BURSTS MAY AGAIN PRODUCE SHORT-DURATION
IFR WITH THE BULK OF THE VISIBILITY BETWEEN VFR AND MVFR. AS THE
PRECIPITATION FROM LATE MORNING DIMINISHES WITH THE PASSAGE OF A
COLD FRONT, CONDITIONS WILL STEADILY IMPROVE MONDAY AFTERNOON
INTO MONDAY EVENING, WITH LIFTING CEILINGS AND NO VISIBILITY
RESTRICTIONS THROUGH MONDAY EVENING (ALTHOUGH PATCHY FOG IS
POSSIBLE GOING INTO TUESDAY MORNING).
KMSP...ONLY A FEW WEAK RAIN SHOWERS AT THE START OF THIS TAF
PERIOD BUT ANOTHER ROUND OF CONVECTION IS LOOKING LIKELY CLOSE
TO AND SHORTLY AFTER THE MONDAY MORNING PUSH. HAVE HELD CEILINGS
ABOVE 1700FT AT THIS POINT BUT SUB-1700FT CEILINGS ARE CERTAINLY
POSSIBLE. ONCE THE NEXT ROUND OF CONVECTION SHIFTS EAST LATE
MONDAY MORNING, CONDITIONS WILL STEADILY IMPROVE THROUGH THE DAY
WITH WINDS 10-15KT SHIFTING FROM S TO W MONDAY AFTERNOON THEN NW
GOING INTO MONDAY EVENING WITH MUCH MORE TRANQUIL CONDITIONS BY
THEN.
/OUTLOOK FOR KMSP/
TUE...VFR. WIND NE 5-10KTS.
WED...VFR. WIND NE 5KTS.
THU...VFR. WIND S 5-10KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...FLOOD WATCH UNTIL 7 AM CDT THIS MORNING FOR BLUE EARTH-BROWN-
CHIPPEWA-DOUGLAS-FARIBAULT-KANDIYOHI-LAC QUI PARLE-MARTIN-
MCLEOD-MEEKER-NICOLLET-POPE-REDWOOD-RENVILLE-SIBLEY-
STEARNS-STEVENS-SWIFT-TODD-WATONWAN-YELLOW MEDICINE.
FLOOD WATCH UNTIL 10 AM CDT THIS MORNING FOR ANOKA-BENTON-
CARVER-CHISAGO-DAKOTA-FREEBORN-GOODHUE-HENNEPIN-ISANTI-
KANABEC-LE SUEUR-MILLE LACS-MORRISON-RAMSEY-RICE-SCOTT-
SHERBURNE-STEELE-WASECA-WASHINGTON-WRIGHT.
WI...FLOOD WATCH UNTIL 10 AM CDT THIS MORNING FOR BARRON-CHIPPEWA-
DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX.
DISCUSSION...ETA
AVIATION...JPC
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