


Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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767 FXUS63 KDLH 032343 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 643 PM CDT Thu Jul 3 2025 .KEY MESSAGES... - Isolated strong to severe storms are possible late this evening into Friday morning, mainly for northwest Wisconsin and far north-central Minnesota. Localized damaging wind gusts and small to marginally severe hail are the main threats. - Very warm and humid on July 4 (Friday). Heat Advisories have been issued. - Strong to severe thunderstorms are possible during the afternoon/evening on July 4 (Friday) and Saturday afternoon/evening. Heavy rain could lead to some flash flooding concerns as well. && .DISCUSSION... Issued at 223 PM CDT Thu Jul 3 2025 Current Conditions - Tonight: Prominent southerly flow through the day has lead to temperatures climbing into the mid and upper 80s this afternoon. Aside from some fair weather cumulus and some hazy skies in northern MN this rest of the afternoon continues to be quiet. Looking upstream we can see a cluster of precipitation over the Red River Valley tracking east. This area of interest is spurned from a shortwave rounding the apex of an upper level trough. 12Z suite of deterministic guidance brings this shortwave through the Brainerd Lakes region this evening and into NW WI overnight. CAMs are showing some increased consistency with this so we have introduced PoPs of 15% through the period. If convection does manage to develop there is a moderate amount of instability available with bulk shear of 40 kts. This convective parameter space would allow for a marginal threat (1 out of 5) for large hail and damaging winds to develop. As the night goes on there will be two features to be on the lookout for. A warm frontal boundary extending across WI and up through MN and an elongated low pressure system over the Northern Plains. CAMs are beginning to agree on showers and storms ramping up in the early morning hours along the warm frontal boundary and carrying this activity east. Meanwhile, back in the Northern Plains, another sector of showers and storms are set to fire up and move NE possibly clipping our northwest counties. A nocturnal low level jet will be ramping up overnight with speeds in excess of 40 mph further aiding the development and sustainability of convection. While still conditional the convective parameter space is conducive to a marginal risk (1 out of 5). Damaging winds is the primary concern with any storms that would develop in these early morning hours. Friday - This Weekend: Several impactful weather concerns for the Friday/Saturday timeframe: 1) Heat and humidity for Friday, 2) Strong to severe thunderstorm potential Friday and Saturday afternoons/evenings, and 3) Heavy rainfall and flooding potential Friday evening into Saturday. Independence Day (Friday) has seen a continued slight upward trend in the temperature and dewpoint forecast as the apex of the upper- level ridge slides overhead. Remnant storms in northern MN and northwest WI will be sliding east of the area by late morning, which may complicate the high temperature forecast a bit depending on the duration of lingering cloud cover, though strong warm air and moisture advection should still offset this a bit. Widespread dewpoints in the upper 60s to low 70s and high temperatures away from Lake Superior in the upper 80s to locally mid 90s are expected, though high temperatures in the 70s to mid 80s from the Twin Ports up the North Shore near Lake Superior are expected due to winds off the Lake. This will lead to widespread heat indices in the low to upper 90s away from Lake Superior, and maybe even some pockets of 100F heat indices. Heat Risk values will also be widespread Moderate values (heat affects most individuals sensitive to heat) to some pockets of Major values (heat affects anyone without effective cooling or adequate hydration). A Heat Advisory has been issued for all of the Northland aside from the North Shore for late Friday morning through mid evening. Because of this oppressive heat and humidity is occurring on Independence Day when outdoor events will be more common, it will be particularly important to plan ahead and ensure that you and those close to you have plenty of water and places to go to keep cool. Regarding precipitation/storm potential, scattered shower and thunderstorm development and potential isolated strong to severe storms return as early as later this afternoon into tonight. A low pressure system approaching from the Northern Plains/Canadian Prairies on Friday should put most of the Northland solidly in the warm sector of the low pressure. A capping inversion should hold across most of the area as the better synoptic forcing for ascent remains moreso over the Dakotas. By late Friday afternoon/early evening, the cold front/surface trough should be situated from central South Dakota northeast towards International Falls as falling heights aloft and low level convergence begins to initiate storms along and just ahead of the front. Storms should then slowly spread southeast during the remainder of the evening into overnight hours mainly in central to northeastern MN on a more widespread basis. Some of these storms should be strong to severe on a more widely scattered basis with 0-6km bulk shear values of 30-35 kt and 1500-3000 J/kg of MUCAPE to initially work with, though instability does drop off with time later in the evening and overnight and storm mode becomes a more messy cluster rather quickly. The primary hazard would be damaging wind gusts given plenty of downdraft CAPE, with large hail as a secondary threat, particularly initially in the late afternoon/early evening when storms have yet to congeal before the hail threat quickly decreases. There is also a period of time late afternoon into the late evening where storms could be surface based and have just enough low-level helicity for a non-zero tornado threat (2%, the lowest SPC Convective Outlook threshold for tornado mention) across far northern Minnesota near the front. This tornado threat remains very limited at best. A deep layer of southwest winds aloft being parallel to the surface cold front would point to a heavy rain and at the very least a localized flash flooding potential Friday evening into Saturday. PWATs increase to around 2" and the surface to freezing level depth being around 13-15,000 feet will create a threat for training storms to produce efficient, heavy rainfall rates with multiple waves of thunderstorms from the afternoon/evening storms and then continued thunderstorms as the cold front actually slides through the Northland overnight into Saturday morning. It still doesn`t look like flooding would be an issue for most locations, but some portions of the Brainerd Lakes into the Iron Range and Arrowhead would be favored the most for 1-2" of rainfall, with potential localized amounts of 2"+ (25-35% chance in the Iron Range) for Friday through Saturday. Rainfall probabilities drop off with southeastward extent into the Twin Ports and northwest WI. Probabilities of >1" of rainfall in the Twin Ports are around 40-50% and taper off to 20-40% in northwest WI through Saturday. WPC has upgraded our excessive rainfall outlook from a marginal risk (5% chance of flash flooding) to a slight risk (15% of flash flooding). As the cold front continues trekking southeast through the Northland on Saturday, with noticeably less hot temperatures with highs in the upper 70s to low 80s. There remains a short window of time Saturday afternoon and evening where a few strong to severe storms will be possible once again, primarily in northwest WI along and ahead of the cold front depending on how cloud cover and lingering precipitation from overnight storms impacts instability. Largely cooler and drier for Sunday behind the cold front with highs in the 70s and more comfortable dewpoints in the 50s to around 60. Early Next Week: Zonal mid to upper-level flow for early next week turning northwesterly for mid-week. It looks like there will be periodic shortwaves moving through this flow pattern aloft, which should bring additional shower and thunderstorm chances at times with seasonal high temperatures. There doesn`t appear to be any strong signal at this time for strong to severe storm potential early next week. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 640 PM CDT Thu Jul 3 2025 VFR conditions expected through the period with the exception of a period of time roughly between 08z and 14z when a round of thunderstorms may impact most of the terminals. Thunderstorms may develop in the vicinity of terminals as a warm front lifts to the northeast during this time. Therefore, timing remains somewhat uncertain, but most likely within that 08z to 14z interval. It is looking likely that BRD may not see any storms at this time, so thunder probabilities were left out of that TAF. There is also a slight possibility (10% chance) that some fog and low clouds could impact DLH in that same approximate time range as well with upslope flow. Winds become southerly into Friday with some gusty winds up to 20-25 kt expected through the afternoon. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 223 PM CDT Thu Jul 3 2025 Northeast winds across the lake will continue through the overnight period with the strongest winds being found at the head of the lake. Overnight there will also be some storms that may develop along a warm frontal boundary and pass over the Lake during the early morning hours. Activity will taper off before once again ramping up in the overnight period where more widespread storms and showers will be possible. Winds will also switch from out of the east to the southwest Friday night. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...Heat Advisory from 11 AM to 8 PM CDT Friday for MNZ010>012-018- 019-025-026-033>038. Beach Hazards Statement until 10 PM CDT this evening for MNZ037. WI...Heat Advisory from 11 AM to 8 PM CDT Friday for WIZ001>004- 006>009. Beach Hazards Statement until 10 PM CDT this evening for WIZ001. MARINE...Small Craft Advisory until 10 PM CDT this evening for LSZ143>146. && $$ DISCUSSION...Britt AVIATION...JDS MARINE...Britt