FXUS63 KDLH 281755 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 1255 PM CDT Wed Jul 28 2021 .UPDATE... Issued at 1255 PM CDT Wed Jul 28 2021 We believe our main show of storms are now developing in our far northwest around International Falls and back up into Ontario and North Dakota, and we are seeing additional enhancements beginning to show up along the MN/ND border on Satellite. This should continue to grow upscale where there is better low level convergence, and the stronger winds in the upper levels should produce both better shear and support for stronger storms. Instability ther is also getting up over 3000 j/Kg. The convection now farther southeast mostly over NW WI should continue to fester and slide to the southeast, but we do not expect any more than isolated severe reports out of these storms. UPDATE Issued at 1044 AM CDT Wed Jul 28 2021 Storms are beginning to get more energetic out there, and we may have a few of the strongest getting strong enough to need a warning, but we are expecting a few more hours of this more intermittent convection before consistently stronger cells begin developing over far northwestern Minnesota where instability is building and capping is weakening. These to then slide southeast across the forecast area during the afternoon, where long hodographs with plenty of shear in the lowest layers means we will be getting all the severe weather threats this afternoon. UPDATE Issued at 717 AM CDT Wed Jul 28 2021 Areas of dense fog have developed this morning. High stratus from storms over central Minnesota may inhibit the dissipation of fog this morning. Have issued Dense Fog Advisories for the land and marine areas which have the lowest visibility. Updated POPs and storm timing this morning through this afternoon to better reflect current trends and an expected westward shift of the storm threat this afternoon. && .DISCUSSION...(Today through Tuesday) Issued at 442 AM CDT Wed Jul 28 2021 Summary: Thunderstorms are expected this morning and again this afternoon and evening. Some storms may be severe from late morning through this evening. Hot today with highs in the low 80s to low 90s. Heat indices of 95 to 100 degrees for portions of central Minnesota and the I-35 corridor from Moose Lake south. A little cooler and drier Thursday. Chance of showers and storms returns Friday through Saturday. At 09Z a warm front stretched from near Devils Lake to near Fargo, ND to near Saint Cloud, MN to around Albert Lea. The latter location more of a composite front and outflow boundary. South of the front dewpoints were in the low to upper 70s, impressive moisture for this time of night even in July. A southwesterly nocturnal low-level jet was indicated both by the RAP analysis and regional VAD profiles, the leading edge of which was providing convergence for elevated convection over the NDak/SDak/MN border. Think these storms will continue to percolate over the next several hours and advance east-southeasterly along the front. MLCAPE of 2000-3500 J/kg was found south of the warm front. While the elevated convection is unlikely to tap all of that instability, there should be enough energy available to support strong to severe storms. Another area of thunderstorms stretched from northwest Ontario west into Manitoba ahead of an approaching shortwave trough. The LLJ will continue to support convection and push it eastward with time this morning. The jet will gradually veer and weaken after 14Z, which should result in storms weakening if not dissipating entirely. A few strong to severe storms appear possible from Pine River east to the I-35 corridor this morning. Within the last hour quarter-size hail was reported in Fargo. Outflow from the early morning convection will serve to sharpen the the warm frontal gradient. The front will lift northward and should be oriented from around Lake of the Woods to the Twin Cities by 15Z and perhaps a little farther north by early afternoon. The convection over the Canadian Prairies may weaken by late morning, but storms should redevelop in the 17Z-19Z timeframe ahead of the shortwave trough, over southeast Manitoba, northwest Minnesota, and adjacent areas of northwest Ontario. There will be ample instability and deep layer shear for severe thunderstorms this afternoon through this evening along the warm front. I’ll defer to the SPC SWODY1 for more detailed mesoscale analysis of the convective parameters. Storm mode will initially favor discrete supercells with all modes of severe weather possible. Storm motions will be southeasterly along the front. There is a potential for a few tornadoes while storms remain discrete, especially those which can ride along the frontal boundary. LCLs initially will be high initially, but should lower with time due to ingestion of RFD moisture. Very large hail up to baseball size and damaging wind gusts to 70 are possible with the discrete storms. Deep layer shear of 40 to 55 knots is forecast, which should lead to eventual upscale growth into an MCS. Once that transition occurs, the hail threat will diminish while the wind potential will increase. Gusts of 80 to 90 mph will not be out of the question at the apex of any bowing segments which develop. QLCS tornadoes are not out of the question, either. Torrential rainfall may lead to localized flash flooding before storm motions increase with the transition to an MCS. With recent rainfall over NW WI, even after the transition there may be a risk for flash flooding. Precipitable water of 1.5 to 2 inches with storms oriented parallel to the front will make storms efficient rain producers. In addition to the severe weather risk today and tonight, hot temperatures are on tap. Portions of the Northland will experience heat indices of 95 to 100 degrees this afternoon from the Brainerd lakes east into the I-35 corridor south of Moose Lake and into the St. Croix Valley near Grantsburg and Siren, WI. There is a question whether temperatures will be able to reach the low to middle 90s required to push heat indices over 100 with the morning clouds and storms. Should clouds clear by mid to late morning, afternoon temps may need to be increased a few degrees for those areas. Quieter weather is on tap for Thursday along with cooler conditions. Another round of showers and storms is possible for Friday afternoon through Saturday as a shortwave trough passes through the region on northwest flow. A weak cool front will accompany the trough and should be able to touch off a few showers and storms. At this time the risk of severe weather appears low. Temperatures will be in the 70s for most locations Saturday through Monday. Tuesday will see temperatures warm up a few degrees and there could be a few showers or storms during the afternoon and evening. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1255 PM CDT Wed Jul 28 2021 Convection is the main concern for the next 6-9 hours over the terminals, with tempo groups for both an initial set that will continue to affect KDLH and KHYR for the next couple hours, followed by another round now initiating around KINL and will spread southeast through the afternoon and early evening hours. Strongest storms should bring damaging winds and large hail, along with at least IFR if not LIFR conditions with the heavy rainfall. Once the storms move out of the area VFR conditions should return to the area. Expect that we may get some fog and stratus for KDLH and KHYR again tonight, but uncertainty is kind of low at this time and have put in some lower visibilities and stratus for now, but expect to be modifying this with later updates. && .MARINE... Issued at 1044 AM CDT Wed Jul 28 2021 Convection remains the main concern for the forecast today. The current convection over northern MN may affect the western tip of Lake Superior during the late morning/early afternoon, but then another round of storms is expected to develop over northwest MN and slide to the southeast during the late afternoon and evening hours. Both rounds of storms may bring damaging, gale force gusts or higher, large hail, and locally higher waves. Outside of storms, do not expect waves to get above 2 feet through tonight. After tonight winds turn to the northwest and should settle down to 10kts or less for Thursday. && .PRELIMINARY POINT TEMPS/POPS... DLH 79 61 80 55 / 70 70 0 0 INL 83 57 79 50 / 70 10 0 10 BRD 94 61 83 57 / 100 40 0 0 HYR 85 61 81 51 / 70 80 0 0 ASX 86 61 80 53 / 80 80 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ UPDATE...LE DISCUSSION...Huyck AVIATION...LE MARINE...LE