809
FXUS63 KMPX 091049
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
549 AM CDT TUE SEP 9 2025
KEY MESSAGES
- SCATTERED SHOWERS AND A FEW THUNDERSTORMS ARE POSSIBLE TODAY. THE
HIGHEST CHANCES (30-50%) RESIDE ACROSS EASTERN MN/WESTERN WI.
- TEMPERATURES CONTINUE TO WARM THROUGH THE WEEK. WEEKEND HIGHS
CLIMB BACK INTO THE MID TO UPPER 80S ACROSS SOUTHERN MN.
DISCUSSION
ISSUED AT 245 AM CDT TUE SEP 9 2025
EARLY MORNING INFRARED SATELLITE DISPLAYS CONVECTION ONGOING ACROSS
THE ARROWHEAD. THIS SHOWER/STORM ACTIVITY HAS DEVELOPED ON THE NOSE
OF A ~40KT LOW-LEVEL JET, WHICH IS ORIENTED BACK TO THE SOUTHWEST
ACROSS MUCH OF MN INTO NORTHERN IA. TO THE WEST,SATELLITE IMAGERY
CAPTURES ISOLATED SHOWERS AND PERHAPS A STORM OR TWO ACROSS SD,
WHICH ARE TIED TO A WEAK ~1010 MB SURFACE LOW NEAR PIERRE. OUR
FORECAST AREA REMAINS QUIET AND DRY AT THIS HOUR, THOUGH IT IS
NOTICEABLY WARMER AS COMPARED TO RECENT MORNINGS. CONTINUED
SOUTHERLY FLOW WILL LIMIT TEMPERATURES FROM FALLING OUT OF THE
LOWER 60S THROUGH DAYBREAK (THOSE WERE OUR HIGH TEMPERATURES
JUST A FEW DAYS BACK!).
TODAY'S PRECIPITATION FORECAST FEATURES BOTH COMPLEXITY AND A DEGREE
OF UNCERTAINTY. ALOFT, A WEAK WAVE WITHIN THE UPPER-FLOW IS PROGGED
TO SLIDE SOUTHEAST OVER THE REGION, WHICH WILL PLACE THE BEST
SOURCE OF SYNOPTIC LIFT OVER EASTERN MN/WESTERN WI. IN ADDITION,
THE WARM FRONT THAT IS LOCATED ACROSS NORTHERN MN (ASSOCIATED
WITH THE ONGOING WARM ADVECTIVE PRECIPITATION) IS FORECAST TO
BECOME DIFFUSE LATER TODAY AND WILL GRADUALLY DRIFT SOUTHEAST.
THIS FEATURE WILL LIKELY NOT BE A MAJOR FORCING MECHANISM FOR
CONVECTION, HOWEVER THERE MAY VERY WELL BE ENOUGH CONVERGENCE
ALONG THE BOUNDARY TO PRODUCE ISOLATED TO SCATTERED SHOWERS AND
A FEW STORMS ACROSS WESTERN/CENTRAL MN. OVERALL, THE FORCING FOR
TODAY'S PRECIPITATION CHANCES IS ON THE WEAKER SIDE AND THAT IS
LIKELY WHY WE'VE CAN SEE A VARIETY OF SOLUTIONS DISPLAYED
ACROSS THE CAM SUITE. WE LEANED HEAVILY ON THE RRFS-A/HRRR/REFS
HANDLING OF THE SHORT TERM FORECAST IN OUR GRIDS, DUE TO THEIR
BETTER HANDLING OF THE ONGOING REGIONAL CONVECTION AT
INITIALIZATION. IN DOING THIS, THE LATEST FORECAST FEATURES
ROUGHLY THREE POP SUB-GROUPS. THE FIRST IS FROM DAYBREAK THROUGH
MIDDAY, WHERE SLIGHT CHANCE POPS ARE IN PLACE ACROSS THE ENTIRE
FORECAST AREA, LARGELY TIED TO THE POSITION OF THE LOW-LEVEL
JET AXIS OVERHEAD. IN ESSENCE, WE'RE SAYING THERE IS A CHANCE
FOR A FEW SHOWERS ANYWHERE THIS MORNING, HOWEVER COVERAGE WILL
LIKELY BE LOW. THE SECOND "SUB-GROUP" APPEARS ACROSS EASTERN
MN/WESTERN WI FROM MIDDAY THROUGH THE AFTERNOON, WHERE ~30-50%
POPS EXIST. THE PASSAGE OF THE WEAK SHORTWAVE ALOFT IS THE FOCUS
FOR THESE POPS AND IS THE DRIVING FACTOR BEHIND THE HIGHER
CONFIDENCE. WE ARE NOT EXPECTING THESE STORMS TO POSE A SEVERE
WEATHER THREAT GIVEN LIMITED INSTABILITY AND WEAK SHEAR.
FINALLY, THE THIRD "SUB-GROUP" IS ALSO THE LOWEST CONFIDENCE
PORTION OF TODAY'S FORECAST. WE HAVE OPTED TO MAINTAIN SLIGHT-
CHANCE POPS THROUGH THE AFTERNOON AND INTO THE EVENING ACROSS
SOUTH CENTRAL MN, TIED TO THE APPROACH OF THE AFOREMENTIONED
DIFFUSE BOUNDARY THAT WILL ACT AS A WIND SHIFT/FOCUS FOR
SURFACE CONVERGENCE. GUIDANCE VARIES GREATLY IN THE WHAT THE
ENVIRONMENT MAY LOOK LIKE ACROSS WESTERN/SOUTHERN MN DURING THIS
TIME PERIOD, HOWEVER THE GENERAL CONSENSUS IS AN ATMOSPHERE
CHARACTERIZED BY SLIGHTLY HIGHER DEW POINTS AND AS A RESULT
GREATER INSTABILITY. PERHAPS THIS SCENARIO WILL ALLOW FOR SOME
AIRMASS TYPE SHOWERS/STORMS (THOUGH THIS IS POORLY REPRESENTED
ACROSS MOST OF THE HI-RES GUIDANCE SUITE).
TO SUM IT ALL UP, IT'S LIKELY THAT THERE WILL BE PLENTY OF DRY
TIME TODAY. HOWEVER, VARIOUS WEAK FORCING MECHANISMS WILL
SUPPORT ISOLATED TO SCATTERED CONVECTION THROUGHOUT THE DAY.
DESPITE THE LOW CONFIDENCE IN SPECIFIC'S REGARDING POINT-BASED
TIMING, THERE IS FAIRLY HIGH CONFIDENCE THAT ANY CONVECTION THAT
DEVELOPS WILL REMAIN SUB-SEVERE DUE TO LIMITED INSTABILITY AND
WEAK SHEAR. RAINFALL AMOUNTS ARE GENERALLY EXPECTED TO REMAIN
BELOW A QUARTER OF AN INCH.
LARGE SCALE RIDGING WILL BUILD EAST OVER THE UPPER MIDWEST FOR THE
REMAINDER OF THE WORK WEEK. THE LARGE SCALE SUBSIDENCE WILL
YIELD DRY WEATHER AND WARMING TEMPERATURES. AFTERNOON HIGHS ARE
FORECAST TO TOP OUT IN THE MID 70S WEDNESDAY, THE UPPER 70S/LOW
80S THURSDAY, AND CONTINUE TO WARM INTO THE LOW TO MID 80S FOR
FRIDAY. IT'S DOESN'T LOOK LIKE THE WARMING TREND STOPS FOR THE
FIRST HALF OF THE WEEKEND, AS THE RIDGE AXIS REMAINS POSITIONED
DIRECTLY OVER THE REGION. NBM'S LATEST RUN ADVERTISES HIGHS IN
THE MID TO UPPER 80S, PERHAPS NEAR 90 DEGREES ACROSS SOUTHERN MN
ON SATURDAY. THE NBM TAKES A STEP BACK INTO THE LOW 80S SUNDAY
AND THEN INTO THE UPPER 70S EARLY NEXT WEEK. AT THIS TIME, I'D
SAY CONFIDENCE IN SURFACE TEMPERATURES DROPS QUITE A BIT FROM
SUNDAY ONWARD GIVEN DIVERGING SOLUTIONS IN THE GLOBAL GUIDANCE
WITH RESPECT TO THE STRENGTH/DURATION/AND POSITION OF THE LARGE
SCALE RIDGING. GLOBAL GUIDANCE ILLUSTRATES AN OMEGA BLOCK
SETTING UP ON SUNDAY, HOWEVER THE DEGREE OF "BLOCKING" VS. A
MORE PROGRESSIVE TRANSITION OF THE UPPER FEATURES IS A
QUESTION AT THIS DISTANCE. SHOULD THE UPPER MIDWEST REMAIN
BENEATH THE RIDGE AXIS, TEMPERATURES MAY REMAIN WELL ABOVE
NORMAL INTO NEXT WEEK. CONVERSELY, A MORE ACTIVE UPPER PATTERN
AND QUICKER BREAKDOWN OF THE RIDGE SHOULD PROMOTE COOL, BUT
STILL MILD TEMPERATURES AND THE RETURN OF PRECIPITATION CHANCES.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 549 AM CDT TUE SEP 9 2025
INITIAL FOCUS TO OPEN THE 12Z TAF PERIOD IS THE EXPECTED
LOWERING OF CIGS TO MVFR AND POTENTIAL ARRIVAL OF PRECIPITATION.
SHOWERS MOVING EAST OUT OF SD MAY HOLD TOGETHER LONG ENOUGH TO
APPROACH AXN/RWF/MKT/STC, HOWEVER CONFIDENCE IN IMPACTS FROM
THESE SHOWERS IS LOW SO HAVE OPTED TO KEEP THESE TERMINALS DRY.
THE BETTER CHANCE FOR IMPACTFUL PRECIPITATION (INCLUDING THUNDER)
ARRIVES THIS AFTERNOON, AS A WEAK UPPER WAVE MOVES OVER THE
REGION. WHILE HI-RES GUIDANCE CONTINUES TO ADVERTISE CONVECTION
ACROSS EASTERN MN/WESTERN WI THIS AFTERNOON, CONFIDENCE REMAINS
TOO LOW TO UPGRADE THE PROB30S THAT ARE IN THE TAFS. MADE MINOR
TWEAKS TO THE PROB30 TIMING BASED ON THE LATEST HI-RES OUTPUT.
SKIES CLEAR AND WINDS BECOME LIGHT TONIGHT, WHICH WILL PROMOTE
FOG DEVELOPMENT. HAVE INCLUDED VISIBILITY REDUCTIONS AT THE END
OF THE 12Z TAFS.
KMSP...CAN'T RULE OUT A FEW SHOWERS IN THE VICINITY LATER THIS
MORNING, HOWEVER THE BEST CHANCE FOR -TS CONTINUES TO BE LATER
THIS AFTERNOON THROUGH EARLY EVENING. CONTINUED WITH THE PROB30
FROM 20-24Z. PRETTY GOOD SIGNAL IN THE GUIDANCE FOR FOG TONIGHT
INTO EARLY WEDNESDAY, SO HAVE INTRODUCED A VISIBILITY REDUCTION
AT THE END OF THE NEW TAF.
/OUTLOOK FOR KMSP/
THU...VFR. WIND SE 5-10 KTS.
FRI...VFR. WIND SE 10-15 KTS.
SAT...VFR. WIND SE 5-10 KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
DISCUSSION...STRUS
AVIATION...STRUS
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