079
FXUS63 KMPX 280554
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1254 AM CDT MON APR 28 2025
KEY MESSAGES
- LEVEL 4/5 (MODERATE) RISK FOR MULTIPLE ROUNDS OF SEVERE
THUNDERSTORMS LATE TONIGHT THROUGH MONDAY EVENING. PLEASE HAVE
MULTIPLE WAYS TO RECEIVE WARNINGS SO YOU CAN TAKE SHELTER IF
NEEDED.
- LATE TONIGHT INTO MONDAY MORNING THUNDERSTORMS DEVELOP, AND A
FEW MAY BE SEVERE WITH LARGE HAIL AS PRIMARY THREAT.
LOCALIZED DAMAGING WIND GUSTS ARE POSSIBLE.
- MONDAY AFTERNOON / EVENING, IS THE MOST DANGEROUS PERIOD WITH
STRONG TORNADO POTENTIAL IF STORMS DEVELOP. SCATTERED LARGE TO
VERY LARGE HAIL AND DAMAGING WINDS ARE LIKELY AS WELL.
UPDATE
ISSUED AT 749 PM CDT SUN APR 27 2025
TONIGHT INTO MONDAY MORNING...
WE'VE SEEN SOME IMPRESSIVE SUPERCELLS DEVELOP IN THE SANDHILLS
REGION OF NORTHERN NEBRASKA THIS EVENING. WE LIKE THE GENERAL
IDEA OF THE HRRR THAT THESE SUPERCELLS WILL CONGEAL INTO AN MCS
OVER SOUTH CENTRAL SODAK, THEN RIDE THE NOSE OF THE LLJ ENE
THROUGH THE NIGHT, ENDING UP IN NORTHWEST WI LATE MONDAY
MORNING. CURRENT EXPECTATIONS ARE THAT THESE STORMS WILL BE
MOVING INTO WESTERN MN AROUND 4AM, REACHING WEST CENTRAL AND
NORTHWEST WI AROUND 9 OR 10 IN THE MORNING. THIS MEANS THE
MORNING COMMUTE FOR THE TWIN CITIES WILL LIKELY FEATURE
THUNDERSTORMS TO CONTEND WITH. THESE STORMS WILL BE ELEVATED,
BUT WITH MUCAPE OF NEARLY 2000 J/KG AND 60 KTS OF DEEP SHEAR,
SOME ELEVATED SUPERCELLS ARE LIKELY WITH THIS ACTIVITY, DRIVING
A PRIMARILY HAIL THREAT LATE TONIGHT THROUGH MONDAY MORNING AS
THEY MOVE THROUGH THE AREA. AFTER THAT, IT'S A QUESTION OF WHERE
DOES ROUND TWO SETUP. EARLY ARRIVING 00Z GUIDANCE WOULD SAY
THAT THE SECOND ROUND STARTS ON THE COLD FRONT IN WESTERN MN
DURING THE EARLY AFTERNOON, WITH A QLCS SWEEPING ACROSS MN FROM
THERE. FROM THE MAIN DISCUSSION BELOW, IT LOOKS LIKE WE ARE
STARTING TO FAVOR THE SCENARIO THEY MENTIONED WHERE STORMS ARE
TIED TO WHAT DEVELOPS ALONG THE COLD FRONT, WITH A SEVERE QLCS
TO FOLLOW (SEE PARAGRAPH 4 FOR THOSE DETAILS).
DISCUSSION
ISSUED AT 300 PM CDT SUN APR 27 2025
GENERAL DISCUSSION...WE'RE EXPECTING THUNDERSTORMS TO DEVELOP
LATE TONIGHT ACROSS THE EASTERN DAKOTAS INTO WESTERN MINNESOTA,
AND SPREAD ACROSS CENTRAL MINNESOTA INTO NORTHERN WISCONSIN
EARLY MONDAY MORNING. THE MAIN THREAT WITH THIS MORNING
CONVECTION IS LARGE HAIL, WITH DAMAGING WIND AS AS SECONDARY
THREAT. THEN WE EXPECT A BREAK FROM LATE MORNING INTO EARLY
AFTERNOON. THIS SHOULD ALLOW THE ATMOSPHERE TO RECHARGE DURING
THIS TIME AS STRONG SOUTHERLY WINDS BRING WARM AND MOIST AIR
ACROSS THE REGION. BY MONDAY AFTERNOON, ANOTHER ROUND OF STORMS
ARE EXPECTED TO DEVELOP. THIS SECOND ROUND IS THE MOST DANGEROUS
WITH STRONG TORNADO POTENTIAL IF STORMS DEVELOP. THE
INGREDIENTS WILL BE IN PLACE FOR ROTATING STORMS, AND IN
ADDITION TO TORNADOES, VERY LARGE HAIL AND DAMAGING WIND WILL BE
POSSIBLE. THERE IS SOME UNCERTAINTY ON TIMING AND LOCATION OF
THIS SECOND ROUND OF STORMS, BUT WE ASK THAT FOLKS REMAIN
VIGILANT AND TAKE ANY WARNINGS THAT ARE ISSUED SERIOUSLY. FOR
MONDAY AFTERNOON/EVENING, THE MODERATE RISK ISN'T THAT EVERYONE
WILL SEE STORMS, RATHER IT'S THAT IF STORMS FORM, THEY COULD BE
BAD.
TECHNICAL DISCUSSION...THE FIRST ROUND OF STORMS IS INTERESTING
IN THE FACT THAT WE HAVE A VERY IMPRESSIVE ELEVATED MIXED LAYER
MOVING OVER THE REGION, AND CONFIDENCE IS QUITE HIGH THAT STORMS
WILL DEVELOP ON THE LEADING EDGE OF THIS EML. THE WIND SHEAR IN
THESE ELEVATED STORMS IS QUITE UNIDIRECTIONAL, BUT THE SPEED
SHEAR SHOULD BE SUFFICIENT FOR SUPERCELLS CAPABLE OF PRODUCING
LARGE HAIL. THE LOW LEVEL JET WILL ALSO BE STRENGTHENING WITH
SPEEDS OF 40 TO 45 KTS DEVELOPING WITHIN THE 900-800MB LAYER.
GIVEN THESE STRONG WINDS JUST OFF THE DECK, DAMAGING WIND IS
ALSO A SECONDARY THREAT FOR LATE TONIGHT INTO EARLY MONDAY
MORNING.
THERE IS SOME UNCERTAINTY IN THE EXACT TIMING OF WHEN THESE
STORMS CLEAR OUT MONDAY MORNING, BUT WE DO EXPECT THEM TO EXIT
TO THE NORTHEAST. MEANWHILE BOUNDARY LAYER SOUTHERLY WINDS WILL
ADVECT WARM AND MOIST AIR ACROSS THE REGION BENEATH THIS
ELEVATED MIXED LAYER. THIS SHOULD ALLOW THE ATMOSPHERE TO
DESTABILIZE DESPITE LITTLE IF ANY SOLAR INSULATION. IN FACT, LOW
LEVEL STRATUS FROM THE MORNING CONVECTION COULD ENHANCE THE
TORNADO THREAT FOR LATER IN THE DAY BY ALLOWING THE STRONG
INVERSION TO REMAIN IN PLACE, WHICH WOULD CAUSE THE SURFACE
WINDS TO RESPOND MORE TO THE SYNOPTIC PRESSURE GRADIENT AND TAKE
ON A SOUTHEASTERLY COMPONENT. IN THIS TYPE OF SETUP, YOU CAN
GET HODOGRAPHS THAT RESEMBLE A SICKLE, WHICH HAVE BEEN NOTED ON
SIGNIFICANT SEVERE WEATHER DAYS. IF THIS SCENARIO PLAYS OUT,
EXPECT LOW STRATUS TO EVENTUALLY TRANSITION TO BOUNDARY LAYER
CONVECTIVE ROLLS, OR CLOUD STREETS, SIMILAR TO WHAT TO WHAT WE
SEE TODAY. THESE CLOUD STREETS ARE A VISUAL REPRESENTATION OF
STREAMWISE HELICITY, AND CAN BE A MORNING PRECURSOR TO AN
ENVIRONMENT FAVORABLE FOR TORNADOES (JULY 19, 2018 IN IOWA, AND
MAY 17, 2016 IN WESTERN WISCONSIN). THE CLOUD STREETS WILL
EVENTUALLY MIX OUT INTO CUMULUS, FOLLOWED BY CONVECTIVE
INITIATION.
THIS CONVECTIVE INITIATION IS PROBABLY THE BIGGEST WILDCARD FOR
THE AFTERNOON/EVENING STORMS. IF STORMS MANAGE TO FORM AHEAD OF
AN APPROACHING COLD FRONT IN THE WARM SECTOR, THEN STRONG
TORNADOES ARE POSSIBLE FOR THE REASONS OUTLINED ABOVE. THESE
STORMS POSE THE RISK FOR PRODUCING STRONG TORNADOES. HOWEVER,
THERE IS A CHANCE THAT STORMS ONLY FIRE ALONG THE COLD FRONT. IN
THAT SCENARIO, TORNADOES ARE STILL POSSIBLE, BUT STORMS WOULD
MORE LIKELY QUICKLY GROW UPSCALE INTO A LINE, AND THE MAIN
THREAT WOULD BE DAMAGING WIND WITH SHORTER-LIVED (AND USUALLY
WEAKER) QLCS TORNADOES. AN ALTERNATE SCENARIO IS THAT GIVEN THE
POSITIVE TILT OF THE UPPER LEVEL WAVE, STORMS STRUGGLE TO FORM
ALONG THE COLD FRONT, AND THIS ENDS UP BEING A LOWER IMPACT
EVENT.
TUESDAY THROUGH SATURDAY...SKIES WILL CLEAR AS THIS PARENT STORM
SYSTEM RACES QUICKLY OFF TO THE NORTHEAST, AND HIGH PRESSURE
WILL BUILD IN LEADING TO DRY CONDITIONS THROUGH WEDNESDAY.
ANOTHER WEAK SYSTEM WILL BRING A CHANCE FOR SHOWERS AND
THUNDERSTORMS LATE WEDNESDAY INTO THURSDAY, BUT THE THREAT FOR
SEVERE WEATHER IS VERY LOW. THEN CONDITIONS DRY OUT AGAIN FOR
THE WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1254 AM CDT MON APR 28 2025
SCATTERED SHOWERS ARE BEGINNING TO DEVELOP ACROSS SOUTHERN MN,
WITH A FEW TS ALSO BEGINNING TO POP UP SOUTHEAST OF MSP.
COVERAGE AND INTENSITY WILL CONTINUE TO INCREASE AS THE NIGHT
WEARS ON UNTIL THE FINAL ROUND OVER SOUTH DAKOTA PASSES THROUGH
BY MID TO LATE MORNING. CONDITIONS WILL DETERIORATE AND SHOULD
BECOME IFR IN MOST LOCATIONS LATE TONIGHT AND MONDAY MORNING. A
BREAK IN TSRA FOR THE REST OF THE MORNING AND INTO THE EARLY
AFTERNOON, THEN ADDITIONAL TS SHOULD FORM IN THE MID TO LATE
AFTERNOON AND LAST INTO THE EARLY TO MID EVENING.
KMSP...SOME TS TO THE SOUTHEAST SHOULD REMAIN FAR ENOUGH FOR NOW
TO INCLUDE ANY MENTION UNTIL LATER TONIGHT WHEN THE MAIN ROUND
DEVELOPS/APPROACHES. THERE MAY BE TS BEFORE 11Z, BUT THE TAF IS
HIGHLIGHTING THE BEST WINDOW UNTIL RADAR TRENDS CAN BE BETTER
ESTABLISHED DURING THE NEXT FEW HOURS.
/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.
UPDATE...MPG
DISCUSSION...JRB
AVIATION...BORGHOFF
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