494
FXUS63 KMPX 281125
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
625 AM CDT MON APR 28 2025
KEY MESSAGES
- ROUND 1 OF THUNDERSTORMS WILL ENTER WESTERN MINNESOTA AROUND
4-5AM. PRIMARY THREAT WITH THIS ROUND WILL BE LARGE HAIL,
WHICH COULD BE IMPACTFUL TO THE MORNING COMMUTE.
- ROUND 2 OF THUNDERSTORMS IS DRIVING FORCE BEHIND THE MODERATE
RISK (4 OF 5) LATER TODAY INTO THIS EVENING. ALL HAZARDS ARE
POSSIBLE, WITH AN EMPHASIS ON THE TORNADO POTENTIAL IF STORMS
COME TO FRUITION.
- THE MOST IMPORTANT THING TO DO TODAY IS TO NOT LET YOUR GUARD
DOWN. WITH CONDITIONAL THREATS, STORMS CAN INTENSIFY QUICKLY,
HIGHLIGHTING THE NEED FOR HAVING MULTIPLE WAYS TO RECEIVE
WARNINGS AT A MOMENT'S NOTICE.
DISCUSSION
ISSUED AT 303 AM CDT MON APR 28 2025
AS THE 50-55KT LOW-LEVEL JET ADVANCES EAST/NORTHEAST ACROSS NEBRASKA
AND SOUTH DAKOTA, FORMERLY SEVERE STORMS HAVE LESSENED IN INTENSITY
FOR THE TIME BEING. THIS LINE WILL MOVE INTO SOUTHERN AND WESTERN
MINNESOTA WITHIN A FEW HOURS, AROUND 4 TO 5AM. THIS TIMING PLACES
CONVECTION NEAR THE TWIN CITIES METRO RIGHT AROUND THE MORNING RUSH
(7 TO 8AM) AND WESTERN WISCONSIN BY 9 TO 10AM. IN TERMS OF WHAT TO
EXPECT FROM THIS ROUND, NOTHING TOO IMPRESSIVE. MOST UNSTABLE CAPE
AROUND 1000J/KG, 0-6KM SHEAR OF 40-50KTS, AND ELEVATED LAPSE RATES
AROUND 8 C/KM COULD CREATE SOME STRONGER STORMS, BUT THE MAIN THREAT
REMAINS WITH ROUND 2 THIS AFTERNOON. NONETHELESS, A FEW STRONG AND
POTENTIALLY SEVERE STORMS COULD RESULT IN THOSE ATMOSPHERIC
CONDITIONS, AND IT DOESN'T TAKE MUCH TO CREATE CHAOS DURING AN
ALREADY BUSY TIME ON THE ROAD.
AFTER THE MORNING CONVECTION DIES OFF AND MOVES OUT, THERE WILL BE A
FEW HOURS OF TRANQUILITY AT THE SURFACE, THE CALM BEFORE THE STORM,
IF YOU WILL. HOWEVER, THE ATMOSPHERE WILL BE DOING ALL BUT REMAINING
CALM IN PREPARATION FOR ROUND 2. IN SOME SCENARIOS, MORNING
CONVECTION CAN DAMPEN THE POTENTIAL FOR REDEVELOPMENT LATER IN THE
DAY. IN TODAY'S SCENARIO, MORNING CONVECTION MAY ACTUALLY AID IN
CREATING A BETTER ENVIRONMENT FOR ROUND 2. HOW IS THAT SO? THE
MORNING STORMS WILL ALLOW THE STRONG INVERSION TO REMAIN IN PLACE.
MAINTAINING THIS INVERSION CAUSES SURFACE WINDS TO RESPOND MORE TO
THE DEEPENING PRESSURE GRADIENT. ADDITIONALLY, A ROARING LOW-LEVEL
JET WILL HAVE NO ISSUE RE-ENERGIZING THE ATMOSPHERE AFTER MORNING
STORMS ROLL THROUGH. SOUTHERLY WINDS WILL ADVECT WARM AND MOIST AIR
AIR INTO SOUTHERN MINNESOTA BENEATH THE ELEVATED MIXED LAYER. THIS
DIFFERENCE IN CONDITIONS (DRY AIR IN THE EML AND MOIST AIR AT THE
SURFACE) CREATES THE INSTABILITY NEEDED FOR STORMS. THE HREF IS
FORECASTING MUCAPE VALUES OF 2000-2500 J/KG, DEWPOINTS IN THE MID
60S, MEAN DEEP LAYER SHEAR AROUND 50KTS, AND BREAKABLE CIN (-30 J/KG
OR LESS) THROUGH AROUND 6PM. WITH THIS IN MIND, MOST OF THE
CONDITIONS NEEDED FOR SEVERE STORMS WILL BE PRESENT, BUT IT'S THE
INITIAL TRIGGER MECHANISMS THAT ARE NEEDED TO ACTUALLY GET STORMS TO
INITIATE. THIS IS WHERE THE CONDITIONAL THREAT COMES IN. IF THAT
TRIGGER OCCURS (BREAKING ANY POTENTIAL CAP) AHEAD OF THE SQUALL LINE
ANTICIPATED TO RIDE THE COLD FRONT LATER IN THE EVENING, THEN STRONG
TORNADOES ARE POSSIBLE WITH DISCRETE SUPERCELLS. THIS POTENTIAL FOR
STRONG TORNADOES IS WHAT IS DRIVING THE MODERATE RISK (4/5). IT IS
ENTIRELY POSSIBLE THE TRIGGER NEVER HAPPENS AND THE ONLY CONVECTION
WE SEE IN ROUND 2 IS WITH THE PASSAGE OF THE COLD FRONT THIS
EVENING. TORNADOES WOULD STILL BE POSSIBLE WITH THIS SCENARIO, BUT
THE STORM MODE WOULD BE LINEAR (QLCS) VERSUS DISCRETE (SUPERCELLS).
THIS TYPICALLY TRANSLATES TO BRIEF SPIN-UPS AND THE THE PRIMARY
THREAT TRANSITIONS TO DAMAGING WIND ALONG THE LINE OF STORMS.
THE TAKEAWAY FROM TODAY'S SEVERE STORM POTENTIAL IS TO REMAIN
VIGILANT OF THE POTENTIAL FOR STORMS TO GO UP QUICKLY. THIS MAY
MEAN CHECKING YOUR PHONE MORE OFTEN OR KEEPING AN EYE TO THE
SKY, BUT DON'T LET YOUR GUARD DOWN IN THIS ENVIRONMENT.
STORM CHANCES ASIDE, IT WILL BE WINDY TODAY THANKS TO THE LLJ.
SUSTAINED SOUTHERLY WINDS OF 20-25MPH FOR MOST OF SOUTHERN
MINNESOTA WITH GUSTS TO 35-40MPH. COMBINE THESE WINDS WITH ANY
STORM AND IT WON'T BE HARD TO GET A SEVERE LEVEL GUST (50KTS OR
GREATER).
AFTER TODAY, HIGH PRESSURE WILL BUILD INTO THE UPPER MIDWEST. DRY
CONDITIONS WILL RESULT AT LEAST THROUGH WEDNESDAY BEFORE A
RELATIVELY WEAK DISTURBANCE BRINGS THE RETURN OF THE CHANCE FOR RAIN
SHOWERS. TEMPERATURES SHOULD REMAIN MILD IN THE 60S AND 70S
WEDNESDAY THROUGH FRIDAY BEFORE EVEN WARMER TEMPERATURES (UPPER
70S) ARE POSSIBLE FOR THE WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 625 AM CDT MON APR 28 2025
WELL-DEVELOPED SQUALL LINE WILL PROGRESS EASTWARD ACROSS MOST OR
ALL OF THE TAF SITES THIS MORNING. HEAVY RAIN AND LIFR
CONDITIONS ARE EXPECTED, BUT SO FAR NO SIGNS OF HAIL OR STRONGER
WINDS THAN WHAT IS OCCURRING CURRENTLY. A BREAK WILL FOLLOW INTO
EARLY AFTERNOON, THEN ANOTHER LINE OF THUNDERSTORMS SHOULD
DEVELOP MID AFTERNOON AND TRACK EAST AGAIN LATER THIS AFTERNOON
AND EVENING. MVFR/IFR CONDITIONS WILL IMPROVE MODESTLY THIS
AFTERNOON. GUSTY SOUTH SOUTHEAST WINDS WILL TURN WEST OR
NORTHWEST THIS EVENING BEHIND THE FRONT.
KMSP...TS EXPECTED TO ARRIVE AROUND 14Z, GIVE OR TAKE A BIT.
THE LINE SHOULDN'T LAST LONG, BUT WILL NEED TO WATCH ADDITIONAL
TS FARTHER SOUTHWEST IN SOUTHEASTERN SD WHICH MAY EXTEND TS
CHANCES LONGER THAN 15Z.
/OUTLOOK FOR KMSP/
TUE...MVFR/-SHRA LIKELY IN MRNG. WIND NW 10-20 KTS.
WED...VFR, CHC MVFR/-SHRA LATE. WIND SSE 10-15 KTS.
THU...MVFR, CHC -SHRA. WIND NW 10-20 KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
DISCUSSION...PV
AVIATION...BORGHOFF
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