Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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407 FXUS63 KDLH 121840 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 140 PM CDT Wed Jun 12 2024 .KEY MESSAGES... - Strong to severe thunderstorms are likely to develop this afternoon and evening. Hazards include very large hail up to 3" in diameter, damaging winds to 70 mph, and a low chance for a tornado. - Much of the Northland is under an Enhanced Risk (3 out of 5) for severe weather today. Storms will be beginning around mid- afternoon today and move east-southeast through the afternoon and evening. - Cooler temps on Thursday and high pressure on Friday. Additional shower and thunderstorm chances likely this weekend into early next week. && .DISCUSSION... Issued at 140 PM CDT Wed Jun 12 2024 This afternoon and evening: Destabilization has been occurring early this afternoon as skies have (or in the process of becoming) cleared in the wake of showers and thunderstorms that moved through earlier this morning. High MLCAPE values of 2000-3500 J/kg are expected this afternoon and evening in the warm sector ahead of an approaching cold front. Aloft, a steep elevated mixed layer around 8-8.5 degC/km will be advecting into the CWA this afternoon. At the surface, moisture advection provided via a strong southwesterly LLJ at 850mb of 40-45 knots has increased dewpoints across the MN portion of the CWA to around the low to mid 60s. Previously, there was some concern that the convection that is currently moving through southern MN would reduce the amount of available moisture and reduce the severe thunderstorm potential. However, recent obs have shown that the strong LLJ has been able to overcome this barrier. Latent heat release from the morning and ongoing convection being advected northward is also likely contributing to the strong instability that will be seen today. Thunderstorms are expected to have strong and quickly-developing organization today as very favorable wind shear occurs over the CWA. A strong 500mb jet maxima will result in 0-6 km bulk shear today of 50-55 knots. Storm mode today is expected to initially begin as discrete supercells over north-central MN, primarily northwest of the Iron Range. As convection propagates eastward, storm mode is expected to transition to becoming more quasi-linear. Recent runs of the CAMs suggest that while storm mode will become more linear this evening, large hail will continue to be a threat as cells remain somewhat discrete. Timing wise, strong to severe convection will be starting as soon as 3 PM in far north-central MN and move east- southeast through the region this afternoon and evening. Any strong to severe thunderstorms should be downstream of the CWA around midnight tonight. All severe thunderstorm hazards will be possible this afternoon and evening, expect for flash flooding. The primary concern is very large hail, which is forecast to be up to 3 inches in diameter across the MN portions of the CWA and adjacent counties in northwest WI. Damaging winds up to 70 mph are also a concern today, as model soundings show dry air in the low-levels and DCAPE values of around 1000-1500 J/kg. While the potential is low, a tornado or two also can`t be ruled out this afternoon and early evening as 0-1km SRH increases to around 100-150 m2/s2. The one limiting factor to the tornado potential today will be somewhat high LCL heights of around 2000 feet AGL in the area where discrete supercells are most likely in far north-central MN. LCL heights will be lowering to around 350- 750 feet AGL farther east late this afternoon and evening, but with storm mode becoming more linear, this will lessen the tornado threat. Flash flooding is unlikely to occur today as the strong to severe thunderstorms will be fairly progressive across the CWA. Thursday into Friday: Cooler temps are expected tomorrow following the cold frontal passage tonight. Scattered showers will be possible, mainly in the Arrowhead. Isolated thunderstorms in the afternoon hours will be possible, but severe weather is not expected. Quiet conditions develop on Friday as high pressure builds over the Northern Plains. Weekend into early next week: Low pressure developing in the lee of the Rockies Friday evening will propagate into the Upper Midwest on Saturday. This will be bringing widespread showers and thunderstorms through much of the weekend. Strong WAA occurring over the weekend will result in high temps on Sunday reaching into the low to mid 80s with uncomfortable dewpoints in the 60s. Monday will see shower and thunderstorm activity continue as a strong shortwave trough propagates eastward through the central CONUS. There are early indications that Monday`s system could bring strong to severe thunderstorms, especially in north-central MN. However, it is still too early for specifics. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1247 PM CDT Wed Jun 12 2024 VFR conditions are expected early this afternoon ahead of an approaching cold front and developing thunderstorms. Strong to severe thunderstorms will be developing around mid-afternoon in far north-central MN and move east-southeastward through the afternoon and evening hours. These storms will be capable of producing very large hail up to 3 inches in diameter, gusty winds to 70 mph, and a low chance for a tornado or two. IFR, and even LIFR, visibility will be possible within the thunderstorm cores. Once storms exit the region this evening into tonight, expect VFR conditions to return for most terminals. However, IFR conditions resulting from fog will be possible in HYR tonight into early Thursday morning. Northwest winds are expected to be breezy tomorrow following a cold frontal passage. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 140 PM CDT Wed Jun 12 2024 Strong to severe storms may produce hail and gusty winds across western Lake Superior this late afternoon and evening ahead of a cold front. Following the cold frontal passage, winds increase out of the northwest on Thursday with gusts to near 20 knots - a Small Craft Advisory may be needed. Winds weaken Thursday evening into Friday as an area of high pressure builds across the Upper Great Lakes. This weekend into early next week a more active weather pattern develops with a few chances for precipitation. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. MARINE...None. && $$ DISCUSSION...Unruh AVIATION...Unruh MARINE...JJM