


Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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076 FXUS63 KDLH 151949 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 249 PM CDT Tue Jul 15 2025 .KEY MESSAGES... - Several rounds of showers and thunderstorms are expected today into Wednesday. Rainfall amounts of 1-3" with locally higher amounts may lead to flash flooding concerns this afternoon into tonight in east-central Minnesota, the Arrowhead, and northwest Wisconsin. - Strong to severe thunderstorms will be possible this afternoon and evening with damaging winds to 65 mph and large hail up to 1.5" in diameter being the primary hazards. A low-end potential for a tornado or two also cannot be ruled out. - Temperatures for the latter half of the week into the weekend will be more mild with additional chances for precipitation Friday into Saturday. && .DISCUSSION... Issued at 248 PM CDT Tue Jul 15 2025 This Afternoon - Tonight: An initial round of thunderstorms has developed in far east- central MN into northwestern WI this afternoon in an area of low- level warm advection on the warm side of a surface stationary front. Storm motion has generally been parallel to the front here in a high PWAT environment (1.6-1.9") with storms slowly traveling northeast and training over the same locations. Effective shear has been about 30-35 kt, which should be enough for some of these storms to become organized and produce up to 60 mph wet-downburst winds, large hail to 1-1.5" in diameter, and a low-end (2% SPC outlook) for a tornado. Heavy rain rates with the training here could produce flash flooding, but will more likely prime portions of Douglas and Bayfield Counties for flash flooding potential with an additional round of storms this evening. Otherwise, expect the primary strong to severe storm potential to develop with and on the warm side of the slow-moving front draped from the Brainerd Lakes to around the Twin Ports later this afternoon and evening as model soundings point to MLCAPE of 1700-2700 becoming uncapped as subtle 500-mb shortwave energy traverses over the front. This environment will also be characterized by decent low and mid- level lapse rates around 7 degC/km, PWAT values around 1.6-2" (towards the upper-end of climatology for July), and effective bulk shear around 35-40 kt. This environment looks favorable enough for organized discrete (supercells) thunderstorm development initially, though front- parallel flow aloft should result in these storms growing upscale into a linear segment of storms towards this evening. Initial concerns with the discrete storms should be hail up to 1.5 inches in diameter and 60 mph damaging wind gusts in addition to heavy rainfall potential leading to flash flooding. As storms grow upscale into a line towards this evening and tracks southeastward into east-central MN and northwest WI, the threat should transition to damaging wind gusts up to 65 mph, hail up to quarters (though this threat decreases rather rapidly), and heavy rain that could lead to flash flooding. There will also be some more modest levels of 0-1km and 0-3km storm-relative helicity (SRH), but low-level vorticity in the vicinity of the front that could be stretched by strengthening updrafts and lead to a low-end (SPC 2% outlook chance) for a tornado or two this afternoon into early evening. Thunderstorm intensity should then diminish into late this evening over northwest WI as instability weakens and surface-based inhibition increases. Regarding the heavy rainfall potential, storms should repeatedly move over the same locations with efficient rates (1-2"+ per hour), leading to concerns for flash flooding due to rapid runoff. The 12Z HREF guidance shows 24-hour localized probability matched mean QPF of 1-3" with localized amounts to 4+ inches, with the best potential for the higher end of these rainfall amounts where the Flood Watch has been issued for in east-central MN into the Twin Ports, most of the Arrowhead, and northwest Wisconsin. The flash flooding threat should transition into east-central MN and northwest Wisconsin this evening as storms track southeast with time. While rainfall intensity in storms should drop off overnight, moderate rainfall rates on areas that already see heavy rain this afternoon and evening could keep the flooding/flash flooding threat persisting into the overnight hours, particularly in northwest WI. Wednesday: Rainfall will be slow to exit the Northland Wednesday into Wednesday night as a couple shortwave 500-mb troughs continue to traverse the Northland, though very modest instability should preclude any strong to severe thunderstorm development. Wednesday should also be much cooler as cloud cover and rainfall lingers, with highs in the upper 50s to upper 60s. Prominent northeast winds off of Lake Superior will also likely produce a high risk of rip currents at the Minnesota and Wisconsin Point Beaches, so a Beach Hazard Statement will likely be needed on Wednesday. Thursday: Brief surface high pressure with zonal flow aloft should give us a mild and dry day on Thursday, with high temperatures in the low to mid 70s. Friday - This Weekend: Zonal flow aloft continues on Friday, turning slightly more northwesterly on Saturday into Sunday. Weaker 500-mb shortwave energy will move across the Northland through this flow on Friday into Saturday, leading to additional shower and thunderstorm potential Friday and Saturday. At this juncture, there doesn`t appear to be much of an overlap between bulk shear and instability to produce any strong to severe storms for Friday into Saturday. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 1210 PM CDT Tue Jul 15 2025 A stationary front will bring showers and storms this afternoon and evening, with lingering showers and some embedded storms at times overnight into Wednesday. Most of northeast Minnesota has seen MVFR to IFR ceilings develop along and north of the surface front, with some reduced visibilities due to smoke at INL, as well, though VFR conditions are present elsewhere. Strong to severe thunderstorms capable of producing large hail, damaging winds, and heavy rainfall will be possible this afternoon and evening, with intensity weakening tonight. Expect erratic and gusty winds near any storms as well as quick reductions to MVFR/IFR conditions with the storms and heavy rain. Expect IFR to potentially LIFR ceilings to develop tonight behind the front, lingering through the end of the TAF period at DLH, east-central Minnesota, and northwest Wisconsin, while ceilings improve a bit quicker at INL/BRD farther behind the front on Wednesday morning. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 248 PM CDT Tue Jul 15 2025 Winds today will be around 10 knots or less the rest of today before increasing tonight out of the northeast at 10 to 20 knots with gusts to 25 knots, highest in the western arm of Lake Superior and the Apostle Islands. These winds will lead to increasing wave heights of 2 to 5 feet. A Small Craft Advisory continues for these nearshore waters starting late this evening and persisting through Wednesday. Winds weaken to 5 to 15 knots Wednesday night through Thursday. Several rounds of thunderstorms are expected today into Wednesday. A few stronger storms remain possible this afternoon and evening across western Lake Superior. Large hail and wind gusts to 50 knots are the primary concerns in stronger storms, as well as cloud to water lightning and heavy rainfall. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...Flood Watch through Wednesday morning for MNZ012-019>021- 035>038. WI...Flood Watch through Wednesday morning for WIZ001>004-006>008. MARINE...Small Craft Advisory from 11 PM this evening to 7 PM CDT Wednesday for LSZ121-143>148-150. && $$ DISCUSSION...Rothstein AVIATION...Rothstein MARINE...Rothstein