


Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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463 FXUS63 KDLH 151713 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 1213 PM CDT Tue Jul 15 2025 .KEY MESSAGES... - Multiple 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. - Temperatures for the latter half of the week into the weekend will be more mild with additional chances for precipitation late Friday into Saturday. && .UPDATE... Issued at 1210 PM CDT Tue Jul 15 2025 Expanded the Flood Watch to include Aitkin County, as well as most of the Arrowhead and Twin Ports in addition to the original Flood Watch that had Pine County and most of northwest Wisconsin. Latest high-res model guidance shows a concerning signal for training convection along and just north of a stationary front currently situated from the Brainerd Lakes northeast into the Twin Ports and portions of the North Shore. Expect thunderstorm initiation this afternoon, initially starting as scattered discrete storms with a threat of large hail to ping pong ball (1.5") size, 60 mph wind gusts, and heavy rainfall that could lead to flash flooding. Latest atmospheric parameters show PWAT values of 1.5-2" (higher side of climatology for this time of year), MLCAPE of 1500-2500 J/kg, and effective shear of 35-45 kt. Storms should grow upscale into a southeastward-advancing line of storms, with the primary threat transition to wind gusts of up to 65 mph, large hail to quarter size, and heavy rainfall that could lead to flash flooding as the line tracks into northwestern Wisconsin this evening. Can`t rule out a low-end tornado threat for east- central Minnesota into northwest Wisconsin late this afternoon and evening as the 0-1km and 0-3km helicity appears a bit more marginal, though there should be some low-level vorticity in the vicinity of the front that could be stretched by strengthening updrafts. Particularly for 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 latest HREF 12Z 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. The flash flooding threat should transition into east- central MN and northwest Wisconsin this evening as storms track southeast with time. && .DISCUSSION... Issued at 526 AM CDT Tue Jul 15 2025 A line of thunderstorms has developed early this morning across the northern portion of the CWA. 06z sfc analysis from WPC revealed a warm front draped across northern MN, which has been the primary forcing mechanism for this morning`s convection when combined with the influence of a 30+ knot southwesterly LLJ at 850mb. This LLJ and stalling warm front will continue showers and thunderstorms through the early to mid morning hours today, mainly impacting northern MN. High PWATs to around 1.7" as well as training storms this morning has led to high rainfall rates and minor flooding concerns. In addition, large hail to 1" will also be a concern for the next several hours as MUCAPE values remain elevated in the 2000-2500 J/kg range. Damaging winds are a minimal concern early this morning as CAM model soundings show a stable layer in the low-levels and DCAPE is only at 500 J/kg or less. An active synoptic pattern is expected today as a series of shortwaves propagate through the CWA within zonal flow at 500mb. At the sfc, a quasi-stationary front over the CWA will provide necessary forcing in additional to the larger synoptic lift. Deep moisture advection is expected to occur today with PWAT increasing to 1.5-2" by this afternoon, especially within the warm sector over northwest WI and Pine County in MN. The orientation of this moisture advection to the quasi-stationary cold front will likely result in training thunderstorms developing this afternoon and continuing into tonight as another LLJ around 30 knots in magnitude develops. CAMs reflect this potential for training thunderstorms with decent agreement on an overall pattern of training convection. The primary concern for this afternoon into tonight is flash flooding due to the high amount of PWAT, in the 90-97th percentile per NAEFS and ECMWF climatology, and the potential for training thunderstorms. Model soundings from the CAMs in KHYR show that a deep warm cloud layer in excess of 10,000ft will be likely combined with a long and skinny CAPE profile around 900-1200 J/kg. These two factors are very favorable for heavy rainfall rates, which is reflected in global ensembles showing signals for 1-3" inches of rainfall by 12z Wednesday. In addition, probability matched mean QPF from the 00z HREF suggest that locally higher amounts to 4" will be possible over northwest WI, which could lead to flash flooding concerns. With the ingredients in place for flash flooding, a Flash Flood Watch was issued for most of northwest WI and Pine County in MN due to the potential this afternoon through tonight. At this time, the greatest uncertainty lies in exactly where these training storms will develop due to spatial discrepancies in the CAMs. While flooding is the primary concern, severe thunderstorms will also be possible this afternoon as instability increases in excess of 1000 J/kg with 0-6km bulk shear of 20-30 knots. Primary severe hazards this afternoon and evening will be large hail up to 1" and sporadic wind gusts to 60 mph. A Slight Risk remains in effect for portions of the CWA today due to this potential for strong to severe thunderstorms. Overall, today into tonight will be a period to keep an eye on the weather. Precipitation will be slow to exit the CWA on Wednesday into Wednesday night, with CAMs continuing to show additional rounds of showers and thunderstorms on Wednesday. Wednesday`s precip will be synoptically forced by a 500mb shortwave, which will move through the CWA on Wednesday night. In the wake of this shortwave, a brief period of high pressure will be possible on Thursday. This will bring a brief break in the rain on Thursday before additional chances for showers and thunderstorms arrive late Friday into Saturday. Expect more mild high temps for the latter half of the week into the weekend. && .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 526 AM CDT Tue Jul 15 2025 Winds today will be around 10 knots or less before shifting northeast and increasing on Tuesday night to 10 to 20 knots with gusts to 25 knots, highest in the western arm and the Apostle Islands. These winds will also generate waves in these areas of 2 to 5 feet. A Small Craft Advisory has been issued for these nearshore waters starting late this evening. Winds then diminish to 5 to 15 knots on Wednesday night. Multiple rounds of thunderstorms are expected today into Wednesday. A few stronger storms will be possible this afternoon and evening across western Lake Superior. Large hail and wind gusts to 50 knots are the primary concerns in stronger storms along with 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 10 PM this evening to 7 PM CDT Wednesday for LSZ121-143>148-150. && $$ UPDATE...Rothstein DISCUSSION...Unruh AVIATION...Rothstein MARINE...Unruh