109
FXUS63 KMPX 171758
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1258 PM CDT SUN AUG 17 2025
KEY MESSAGES
- ONGOING LINE OF THUNDERSTORMS WILL LEAD TO LOCALIZED AND/OR FLASH
FLOODING THROUGH SUNRISE.
- SHOWERS AND THUNDERSTORMS POSSIBLE THIS AFTERNOON AND EVENING,
WITH STRONG WIND GUSTS THE PRIMARY CONCERN.
- QUIET WEATHER RETURNS AFTER MONDAY.
DISCUSSION
ISSUED AT 239 AM CDT SUN AUG 17 2025
AN ONGOING LINE OF SHOWERS AND THUNDERSTORMS OVER PORTIONS OF
SOUTHERN MINNESOTA HAS ALREADY LED TO A FEW FLASH FLOOD WARNINGS,
WITH RAINFALL RATES EXCEEDING 1 INCH PER HOUR IN SPOTS WITH UP TO 3
INCHES ALREADY ON THE GROUND AND ANOTHER 1 TO 3 INCHES POSSIBLE
THROUGH THE NEXT 4 TO 5 HOURS. HIGH RESOLUTION GUIDANCE THIS MORNING
FAVORS VERY SLOW NORTHWARDS MOVEMENT OF THE LINE OF SHOWERS AND
STORMS WHICH IS MOST EVIDENT IN THE WESTERN CLUSTER, WITH SHOWERS
AND STORMS WEAKENING AS THE THERMAL GRADIENT LOOSENS BY SUNRISE.
PWATS PER RAP/SPC MESOANALYSIS AROUND 2 INCHES ARE PRESENT WHICH
WILL CONTINUE TO FUEL THE ONGOING ACTIVITY AND ALSO KEEP ANY SEVERE
WEATHER CONCERNS SUCH AS HAIL ON THE LOWER END OF PROBABILITY.
MUCAPE CONTINUES TO SIT AROUND 2000-2500 J/KG WITH WEAK DEEP LAYER
SHEAR, POINTING TOWARDS CONTINUED SLOW MOVING STORMS WITH A
RELATIVELY LOW RISK OF SEVERE LEVEL THREATS. OTHER THAN A FEW STRONG
WIND GUSTS, LOCALIZED AND FLASH FLOODING ARE THE MOST LIKELY
OUTCOMES FROM THIS LINE OF STORMS ALONGSIDE THE FREQUENT LIGHTNING.
REDEVELOPMENT OF SHOWERS AND STORMS IS POSSIBLE BY MIDDAY AS DAYTIME
HEATING REPLENISHES INSTABILITY AND SHEAR INCREASES DUE TO THE
POSITIONING OF THE SURFACE FRONTAL BOUNDARIES AHEAD OF THE SURFACE
LOW WHICH LOOKS TO MOVE THROUGH OVERNIGHT INTO MONDAY. FORCING LOOKS
TO BE RELATIVELY WEAK DESPITE THE PRESENT OF A FRONTAL BOUNDARY,
MAINLY DUE TO THE DE-COUPLING OF THE SHORTWAVE TROUGH WITH THE UPPER
LEVEL JET, WITH A STRENGTHENING LOW LEVEL JET BEING THE PRIMARY
FORCING MECHANISM OVERNIGHT.
THE WARM FRONT IS EXPECTED TO LIFT NORTHWARDS AS THE SURFACE LOW
TRACKS NORTHEAST TOWARDS CENTRAL TO NORTHERN MINNESOTA BY MONDAY
MORNING, WITH THE COLD FRONT STALLING OVER WESTERN MINNESOTA AROUND
12Z MONDAY BEFORE MOVING THROUGH DURING THE DAY. THE COLD FRONT WILL
PRESENT THE FINAL CHANCE FOR SHOWERS AND STORMS FOR THE PERIOD WITH
BETTER SHEAR ALLOWING FOR THE POTENTIAL FOR ROTATING UPDRAFTS UNLIKE
THE WEAKER SHEARED ENVIRONMENT THAT PRECEDED IT. BY MONDAY EVENING,
THE COLD FRONT WILL BE PUSHING THROUGH SOUTHEASTERN MINNESOTA WITH
THE SURFACE LOW OVER WESTERN WI, ENDING OUR SHOWER AND STORM CHANCES
BY THAT POINT. TUESDAY AND THE DAYS THAT FOLLOW WILL SEE
NORTHWESTERLY FLOW ALOFT ALONGSIDE SURFACE HIGH PRESSURE AND
SUBSIDENCE, WHICH SHOULD KEEP CONDITIONS MUCH QUIETER COMPARED TO
THE PREVIOUS FEW DAYS. TEMPERATURES WILL REMAIN SEASONAL IN THE
UPPER 70S TO LOW 80S WITH SUNSHINE RETURNING, WITH THE TRAJECTORY OF
UPPER LEVEL WINDS LOOKING TO AVOID THE WORST OF THE CANADIAN
WILDFIRES WHICH HAVE TARNISHED SOME OF THE POTENTIAL BETTER WEATHER
DAYS OVER THE LAST MONTH.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1250 PM CDT SUN AUG 17 2025
LATEST RADAR TRENDS SHOW MORE NOTABLE DECAYING OF SHOWERS ACROSS
WESTERN MN. STATIONARY BOUNDARY DRAPED ACROSS SOUTH CENTRAL
MN IS THE DIVIDING LINE BETWEEN VFR CONDITIONS ACROSS FAR
SOUTHERN MN AND MVFR OR LOWER CIGS ACROSS CENTRAL MN/WESTERN
WI. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS IS FORECAST TO
DEVELOP LATE THIS AFTERNOON ACROSS SD AND MOVE ACROSS THE
REGION OVERNIGHT. HAVE INCLUDED TEMPOS TO TRY AND ISOLATE
WINDOWS WHERE THUNDER IS MOST LIKELY. UNCERTAINTY EXISTS IN HOW
PROGRESSIVE CONVECTION WILL BE AT ANY SINGLE TERMINAL AND GIVEN
THE GOING PATTERN OPTED TO LEAN ON THE PESSIMISTIC SIDE AND
PROCEED WITH LARGE PRECIPITATION WINDOWS. SIGNIFICANT
IMPROVEMENTS TO THE FORECAST ARRIVE MONDAY MORNING AND WINDS
TURN NORTHWESTERLY.
KMSP...LATEST FORECAST DATA KEEPS THUNDER/PRECIPITATION IMPACTS
AWAY FROM THE TERMINAL UNTIL AFTER ~2Z. HAVE MAINTAINED THE
TEMPO FOR -TSRA, WHICH IS MOST LIKELY EARLY IN THE PRECIPITATION
WINDOW. OPTED TO KEEP VISIBILITY REDUCTIONS FROM RAIN IN THE
TAF THROUGH 12Z DUE TO UNCERTAINTY IN HOW QUICKLY RAIN CHANCES
WILL END.
/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...NONE.
WI...NONE.
DISCUSSION...TDH
AVIATION...STRUS
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