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Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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934 FXUS63 KDLH 061154 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 654 AM CDT Sat Jul 6 2024 .KEY MESSAGES... - Scattered showers and thunderstorms are likely this afternoon through Sunday evening. A few storms may be strong over northwest Wisconsin Sunday afternoon and evening. - Diurnal rain and storm chances persist through much of next week. - High water persists across the Rainy River Basin and a Flood Advisory is in effect through early next week. See the summary at www.weather.gov/dlh/RainyRiverBasin for more information. && .DISCUSSION... Issued at 440 AM CDT Sat Jul 6 2024 A ridge of surface high pressure extended northeast from the central Plains into northeast Minnesota early this morning. Skies were generally clear and areas of fog are expected through sunrise. Weak flow was found aloft with the latest RAP analysis indicating a ridge aloft through 400 mb. GOES-East water vapor imagery revealed a weak lobe of vorticity over north-central Minnesota and adjacent areas of northwest Ontario as of 09Z. A shortwave trough was located over eastern Montana, eastern Wyoming, the western Dakotas, and the Nebraska Panhandle. High temperatures today will be similar to Friday with values in the upper 70s to low 80s. The seasonal temperatures, combined with cool air aloft, and ample moisture, will lead to isolated to scattered thunderstorm development this afternoon and evening. MLCAPE of 500-1250 J/kg is forecast by late afternoon. Weak flow near the ground and aloft will result in upright convection, at least initially. As storms collapse, additional development will occur along resultant outflow boundaries. Cold pool mergers will eventually support more persistent convection. Weak deep layer shear and modest lapse rates will limit the severe weather potential. Brief torrential rainfall is likely with the storms and there is a small risk of pea to half-inch diameter hail. Storms should subside this evening as instability is consumed. Attention then shifts to the shortwave trough approaching from the west. A weak southerly LLJ is forecast to develop overnight and a few models rejuvenate convection over central and northern Minnesota during the 07-10Z timeframe. Elevated CAPE from parcels lifted from the 925 to 850 mb layer may find 500-1000 J/kg to work with. Additional showers and storms are expected over central and southern Minnesota as the shortwave trough advances into western Minnesota during the early morning hours. As the trough passes eastward across the region, shower and storm chances will persist through the day. Deep layer shear increases over northwest Wisconsin during the afternoon and there is a potential for a few stronger thunderstorms. The risk of severe storms may be locally enhanced over northwest Wisconsin by a remnant MCV which will likely develop from the nocturnal convection over the Dakotas early this morning. There will be a low, but not zero, tornado potential and a small chance of one inch hail. Mid-level lapse rates of 6.5 to 7 degC/km and high freezing levels will limit the hail potential. Downbursts with wind gusts of 40 to 60 mph will be possible considering the somewhat dry mid to low levels. Weak flow and relatively cool air aloft will persist through much of the upcoming week. Look for diurnal chances of showers and storms each day with temperatures on the warm side of the seasonal normal range. Wednesday and Thursday have the lowest chances of precipitation through next week. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 653 AM CDT Sat Jul 6 2024 Fog will lift this morning. Showers and storms develop late this morning and persist through tonight. Low visibility expected if showers/storms pass over the terminals. Areas of fog redevelop tonight at HIB and HYR. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 440 AM CDT Sat Jul 6 2024 Offshore winds this morning turn southwesterly away from the shoreline. A relaxed pressure gradient will persist over the waters into early next week with wind speeds of 3 to 12 knots. Winds will back northeasterly on Sunday. There are slight chances of afternoon and evening storms each day. Winds will back southwesterly again for Monday and remain relatively light. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .HYDROLOGY... Issued at 440 AM CDT Sat Jul 6 2024 A Flood Advisory continues across portions of the Rainy River Basin, extending as far east as Lac La Croix and as far west as the Rainy Lake outlet. Lingering high water from rains in June continue across the Rainy River Basin. Headwaters gauges on the Kawishiwi River, Basswood River, and Lake Vermilion have crested and are slowly but surely coming down (Lake Vermilion falling at a rate of a measly quarter inch a day). The Vermilion River is also beginning to fall once again, after taking a turn upwards after a second round of heavy rains at the beginning of July. This has allowed the lake level increases on Crane Lake to slow considerably, nearly flatlining just above minor flood stage. Lac La Croix levels continue to increase though, the product of not only the high water from the Basswood River but numerous Canadian tributaries coming out of the Quetico as well. Latest data suggest that inflow and outflow are nearly meeting on Lac La Croix, which could help levels begin to crest soon. All this high water has led to some decent rises on downstream lakes, notably Namakan/Kabetogama (Nam/Kab) lakes (minor flooding ongoing), as well as levels beginning to increase on Rainy Lake (still within rule curves). Per the latest IJC water level bulletin, dam operators are working to maximize outflow through the basin. However, the sheer volume of water moving through the basin will still result in additional rises on these lakes. As water levels upstream crest and begin to come down, rates of rise on Nam/Kab should begin to slow and eventually crest. We`ve already seen the rates of rise begin to demonstrate signs of slowing. From July 1 to 3rd, Nam/Kab Lakes were rising at 2- 2.5" per day, but have recently slowed to 1-1.5"/day in the last 48 hours or so. General guidance suggest peak levels on Nam/Kab could be possible this coming week, but that is uncertain. As is usual for this basin, water will move slowly and recessions will happen at glacial speeds. Additional rainfall may cause brief rises in tributaries and extend the period of high water in core lakes. Boaters should expect high water, potentially hidden underwater hazards, and strong currents in constricted areas. Generally light winds are expected, except for possible brief erratic gusts out of thunderstorms, so wave heights should remain fairly minimal. The Flood Advisory is in effect through Wednesday, but may need to be extended based on observed conditions. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. MARINE...None. && $$ DISCUSSION...Huyck AVIATION...Huyck MARINE...Huyck HYDROLOGY...JDS