


Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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303 FXUS63 KMPX 281536 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1036 AM CDT Sat Jun 28 2025 .KEY MESSAGES... - A line of strong to maybe severe storms is tracking across Minnesota this morning with chances for hail and wind. - Hot and humid today with heat index values in the 90s. - Another chance for severe storms this afternoon into evening. All modes of severe are possible: tornado, wind, and hail. && .UPDATE... Issued at 1009 AM CDT Sat Jun 28 2025 Today is one of those classic summer days where you feel like you have a good conceptual model in mind for how things will go when you walk in the door to start your shift in the morning, only to see a cluster of storms develop over eastern South Dakota that throws that picture in your head into the fan... There`s literally no guidance that produced the ongoing cluster of showers and storms over southwest MN, which makes predicting how this cluster of storms will impact the expected round of convection later today difficult. The general consensus from the HREF is that we would see storms rapidly fire between 22z and 00z up in the vicinity of Little Falls, Alexandria, and Morris. However, none of these models had this mornings round of showers and storms. Looking at surface observations, there is an outflow boundary over northwest Iowa, but surface winds near the MN/SD border are already returning to their non-convection disrupted state, so it is possible this cluster of storms will have minimal impacts on the atmosphere. On satellite, there`s also a band of accas with a few storms trying to develop along eastern portions of the ND/SD border. This all makes what happens later today about as clear as mud. That band of accas across the SD/ND border will likely be the forcing that gets things going over central MN, but will those storms be able to tap into 4000+ j/kg of CAPE that was supposed to stream north out of Iowa today? We`re still in and a wait and see stance, even 8ish hours out from storms firing. The going theory though this morning is that the accas in the eastern Dakotas is the feature to key on, with storms still most likely to fire over central MN, though the ongoing activity over southern MN may delay that initiation. Once storms initiate, we`re still anticipating a high CAPE/low (but not no) shear environment. So an environment that favors multi-cell clusters with transient supercell structures, with at least an attempt at an organized forward propagating MCS. However, these weakly forced, weaker flow, high instability environments are really driven by mesoscale or smaller features that are hard to predict, so get ready for some atmospheric surprises the rest of the weekend. && .DISCUSSION... Issued at 231 AM CDT Sat Jun 28 2025 This weekend... A line of thunderstorms has developed across western Minnesota early this morning. This line is in an area of higher instability which has allowed for the rapid development of convection as the low level jet has picked up. However as these storms continue to the east the instability falls off significantly. So long lived storms will require more upscale growth into a full MCS. CAMs have not had a good show so far this morning with almost every HRRR run being wrong. The RRFS has shown some skill in determining the convective modes and overall picture even if the CI timing has been off. Overall going to have to depend more on conceptual models and observations with this poor CAM showing. Based on the trends in current observations the line continues to build itself and grow upscale. It just comes down to if it can grow enough before it outruns the best instability. How far east theses storms can get will have in influence on the environment later today. A large MCS moving across the whole state will make it hard for the environment to regenerate into a more convectively favorable one. However we still have the warm and moist air continuing to advect into the Upper Midwest. This will bring heat index values into the 90s across southern Minnesota and parts of western Wisconsin. It will not get as warm in central Minnesota, more upper 80s. Thinking back to the ingredients for thunderstorms we will have lift from the warm front moving across Minnesota, ample instability, tons of moisture with precipitable water values over 1.5", and the one parameter with some doubt is shear. This could be explosive amounts of instability like we had a week ago, the difference this time is much less CIN. This could lead to quick development of storms this afternoon. There should be an initial discrete mode with supercells possible, but it could quickly become more multicell in nature. The greatest risk will be during this chance for supercells when all severe modes will be in play. The tornado risk will be lesser in the more multicell mode. Much of the rain chances today will be convective in nature. So the temporal amount of the day impacted by rain will not be as great as the forecast makes it look. It is more a factor of uncertainty in when the rain will occur. When it does occur it will be heavier thunderstorm rain rather than what we had a few days ago with more widespread rain that laster for longer periods. Moving into Sunday a cold front will move in and bring some relief. However in the afternoon/evening time frame storms will fire along the front. Positioning of the front by this point will give most of us a chance for more rain showers or weak thunderstorms. The area that will be far enough ahead of the front for a chance a stronger storms will be parts of western Wisconsin like Eau Claire. Next week... Great summer days to start the week Monday and Tuesday with highs in the upper 70s to lower 80s and a break from the rain and storm chances. By Wednesday a frontal passage will provide the next chance for some more active weather. Still quite the spread in global ensembles so PoPs remain low. A generally more unsettled period continues into the later part of the week, but with continued spread in the ensembles. So the forecast shows low PoPs throughout this period. As we get closer the forecast envelope will shrink and these PoPs will be fine tuned to be higher for smaller periods of time. What is more certain though is no huge temperature swings expected with seasonable temperatures continuing into the mid to late week. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 622 AM CDT Sat Jun 28 2025 The main impact to aviation today will be the chance for thunderstorms. This morning`s thunderstorm chances have largely passed the terminal areas. There are still a few chance with RNH having one of the better chances. Also keeping an eye on South Dakota where some new convection could move in and impact western Minnesota terminals once again later this morning. The time with the more likely impacts for this period will be this evening. Exact timing and coverage remain uncertain, so opted to keep with more PROB30 than anything else. This can be amended in future TAFs as confidence increases and it enters the main first 6 hour window. KMSP...Morning impacts to MSP should be done with VFR now. All attention now is when storms could impact the terminal area this evening. As said in the discussion above have kept with PROB30 for now due to confidence being low in the timing. This can and will be changed as we approach the evening. /OUTLOOK FOR KMSP/ SUN...MVFR chc TSRA/IFR. Wind SW 5-10 kts. MON...VFR. Wind NW 10-15 kts. TUE...VFR. Wind NW 10-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ UPDATE...MPG DISCUSSION...NDC AVIATION...BED/NDC