310 FXUS63 KMPX 262024 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 324 PM CDT Sat Apr 26 2025 .KEY MESSAGES... - Showers and a few thunderstorms late tonight and early Sunday. - Thunderstorms redevelop Sunday night into Monday morning. Some storms may be severe with large hail as the primary hazard. - An outbreak of severe weather possible across southern/eastern MN and WI Monday afternoon and early evening. A level 4 out of 5 severe risk remains in place across this portion of the region. All severe hazards are possible, including strong tornadoes. && .DISCUSSION... Issued at 324 PM CDT Sat Apr 26 2025 SHORT TERM (THROUGH SUNDAY AFTERNOON)... Our beautiful Saturday weather continues this afternoon, with temperatures warming into the low to mid 60s for highs. Satellite reveals increasing cloud cover moving east out of the Dakotas, which is in response to increasing moisture return behind the departing area of surface high pressure over the Great Lakes. Moisture advection will continue to increase tonight by way of a 40+ knot low-level jet forecast to tilt from southwest to northeast across the Dakotas into northwest Minnesota. Hi-res guidance continues to depict the development of a band of showers and a few thunderstorms ahead of the low- level jet, which will move from west to east overnight. No severe weather is expected through tomorrow morning. Following the conclusion of the morning activity, the forecast will trend on the drier side tomorrow. We cannot rule out a few showers or thunderstorms within the southwesterly mid-level flow, though coverage would appear to be relatively limited. Temperatures climb into the mid to upper 60s, with breezy southeasterly surface winds gusting between 20-30 mph. **HISTORICAL NOTE -- THE STORM PREDICTION CENTER INTRODUCED A DAY 3 MODERATE RISK ACROSS SOUTHEAST MINNESOTA, WESTERN WISCONSIN, AND NORTHEAST IOWA EARLIER TODAY. THIS IS THE FIRST SUCH OCCURRENCE ACROSS THE NWS TWIN CITIES FORECAST AREA SINCE APRIL 8, 2011** SUNDAY PM/MONDAY AM: ROUND #1 OF POTENTIAL SEVERE WEATHER... Water vapor imagery captures an upper-low coming ashore over the California coast this afternoon. By tomorrow evening, the upper-level low is forecast to have moved east and be located over Four Corners region of the southwest CONUS. The upper-level low is then forecast to eject northeast across the northern Plains, becoming a positively tilted elongated trough will be the main driver of our expected severe weather episode on Monday. Surface low pressure is forecast to develop across the Dakotas ahead of the advance of the upper-low. A strong 50+ knot low-level jet will expand northeast out the central Plains tomorrow evening and will be the focus for the first round of potential severe weather. Capping evident on forecast soundings should limit convective development through much of Sunday evening. Later on (or early depending on how you look at it), convection is forecast to blossom on the nose of the low-level jet. We`re just starting to enter the window where a of the longer range CAMs are able to resolve and simulate this convective mode, which should take the look of an line of convection developing across southern Minnesota, set to lift from southwest to northeast through daybreak. While this isn`t going to be the "main show" we encourage folks not to sleep on this round of convection. Steep lapse rates and sufficient shear will combine to support strong elevated convection capable of producing large hail. Damaging wind gusts are also possible. Convection may maintain intensity heading into the morning commute, before departing to the north/northeast. SPC has expanded the Day 2 (Thru 12z Monday) Risk area east to reflect this potential. MONDAY PM: ROUND #2 - POTENTIAL SEVERE WEATHER OUTBREAK... A stout EML (characterized by ~9.0C/km lapse rates) will overspread much of the region following the morning round of convection. This will act as a cap, allowing strong instability to build within a broad warm sector rich with high theta-e air. The expected quick translation of strong (70-80 kt) 500mb jet streak and associated 850mb flow will push a warm front across the area by Monday afternoon. Boundary layer recovery and quick destabilization is expected following the morning round of convection, given the potent dynamics in play. Guidance places the position of the surface low across west-central Minnesota by early afternoon, with a trailing cold front near the MN/SD border. Ahead of the front, guidance illustrates an environment that is very favorable for severe weather: 1500+ J/kg of MLCAPE, steep lapse rates in excess of 7.5C/km), deep layer shear in excess of 60+ knots, low-level curvature to the hodographs, surface temperatures in the mid 70s to low 80s, and dew points between 60-65F. Forecast guidance displays the classic severe weather "loaded gun" soundings (moist layer up to about ~5k feet just below a strong capping inversion). When paired with strong shear, as is forecast Monday, this environment is primed for robust convection. As for the convective evolution, there are a few regimes in play: 1) The translation of the jet streak may produce several semi- discrete supercells (capable of all severe weather hazards, including strong tornadoes) across the warm sector Monday afternoon. The early read within the extended CAM guidance is that coverage may remain somewhat muted owing to the capping inversion referenced above, however this seems a bit underdone given the strong upper-level forcing that is in play (particularly the deep elongated trough/forcing). The current forecast features the expected development of scattered semi- discrete supercells across the open warm sector capable of producing strong tornadoes. Confidence is highest in this development (and associated threats) across SE MN/western WI and has prompted the Moderate Risk. 2) The trailing cold front will slide from west to east across the region Monday evening. Convection should begin to develop across western MN ahead of the front Monday afternoon and increase in coverage with eastward extend. Several clusters or segments of storms will likely grow upscale into a QLCS as the event unfolds. All hazards will still be possible, including brief tornadoes, as the line of convection moves through. In other words, some communities across the warm sector may be in for multiple rounds of severe weather within the Monday afternoon/evening timeframe. As with any forecast, there are areas of uncertainty that remain ~48 hours out from a convective event. However, the pros for an outbreak of severe weather significantly outweigh the cons with this particular setup. There has been a strong signal across ML guidance since early this week and the signal has only grown more concerning with time. In fact, the CSU/NCAR ML tools have continued to trend upwards, which leads to increasing confidence in a significant severe weather event across the Upper Midwest Monday. The issuance of the Day 3 Moderate (Level 4/5) Risk across SE MN/western WI captures the rare and dangerous nature of the expected setup for severe thunderstorms capable of producing all hazards. Now is the time to review severe weather safety plans and know what to do if/when severe weather watches and warnings are issued. EXTENDED PERIOD... High pressure returns Tuesday, which will signal dry weather and cooler temperatures (50s) behind the passage of the potent storm system. However, the unsettled northern stream aims to send the next shortwave across the north central CONUS during the Wednesday/Thursday timeframe. Temperatures will rebound into the upper 60s/low 70s ahead of this feature. The passage of a cold front will bring the chance for scattered showers and perhaps a few thunderstorms through late Wednesday into Thursday, which is reflected by 30-40% PoPs in the latest NBM. High pressure returns to close the work week, prior the expansion of a ~570dm ridge over the central CONUS late next weekend and beyond. Global guidance depicts the evolution of the upper-air pattern into a classic omega block, which should yield much warmer into the first portion of May. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1249 PM CDT Sat Apr 26 2025 The forecast still looks on track for increasing mid level clouds later this afternoon/evening and then showers likely late tonight. VFR expected through the period, except there may be some MVFR that develops with any heavier showers in parts of southern and central MN. ESE winds at midday will become more southeast and increase tomorrow, with some gusts over 20 kts. There is a small chance of thunder late tonight, but it did not look to be enough to include it in the forecast. KMSP...No additional concerns. /OUTLOOK FOR KMSP/ SUN AFTN/NIGHT...TSRA likely Sunday night. Wind SE 10-20G25kts. MON...TSRA with IFR/MVFR cigs early, then VFR. TSRA redeveloping in the afternoon. Wind S 15-20G30kts. TUE...Chc MVFR cigs in the morning. Wind NW 10-20kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Strus AVIATION...TDK