Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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417 FXUS63 KDLH 211133 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 633 AM CDT Sat Sep 21 2024 .KEY MESSAGES... - Scattered to numerous showers and thunderstorms this morning over portions of the Northland. The storms are not expected to be severe this morning. - Additional thunderstorms will develop this afternoon into the evening as a cold front moves through the region. Strong to severe storms will be possible, mainly over portions of northwest Wisconsin. - Cooler temperatures develop Sunday into Monday then they will warm a few degrees through the week. A mostly dry period is expected Sunday through late week. && .DISCUSSION... Issued at 319 AM CDT Sat Sep 21 2024 A low level jet, as seen at 850mb, of 35 to 45 knots is forecast by the RAP from eastern South Dakota into central Minnesota. Area VWPs support this forecast as seen at KFSD/KMPX. The warm air advection and convergence with the low level jet has caused showers and thunderstorms to expand in coverage early this morning with a larger area from around Walker south and east toward Siren, WI. This is more widespread than the CAMS and much of the guidance is struggling this morning. We`ve increased POPs quite a bit and pushed chances this morning further north and east and increased values using the low level jet as guidance. Additional short term adjustments will likely be needed over the next few hours and we`ll monitor radar closely. The bulk of these showers/storms should either lift north and east or diminish later this morning as the low level jet continues north and east. A shortwave, as seen on water vapor imagery, will move from the northwest North Dakota/Manitoba/Saskatchewan border early this morning into northwest Minnesota by early afternoon then continue east/northeast brushing northern parts of Minnesota. A surface cold front will also push east today through central to northern Minnesota by early afternoon and through far eastern Minnesota and far northwest Wisconsin by late afternoon finally clearing the rest of northwest Wisconsin early to mid evening. Instability will build this afternoon ahead of the front, especially from east- central Minnesota into northern Wisconsin with PWAT values rising to around 1.3". Deep layer shear will be 30-35 knots with mid-level lapse rates from 7-7.5 C/km. These parameters along with the forcing from mainly the cold front will be enough to produce some strong to severe thunderstorms from mid to late afternoon through about 02Z this evening. SPC has a marginal risk, 1 out of 5, over parts of northwest Wisconsin. The main risks are hail to 1 inch in diameter and damaging wind to 60 mph. The showers/storms will end overnight with cooler temperatures moving in on gusty west to northwest winds. A quiet stretch of weather is expected from Sunday through most of next week. An upper ridge will move onto the West Coast early in the week progressing east toward the Northland mid-late week. A weak shortwave is forecast to move through the region Tuesday, but it should not produce much for precipitation and we kept the forecast dry. Nearly all 80 ensemble members of the ECMWF/GFS keep Tuesday dry. Temperatures will be closer to normal Sunday/Monday then warm a bit through the week. Some frost will be possible in spots Sunday night. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 633 AM CDT Sat Sep 21 2024 Scattered showers and a few thunderstorms were occurring across much of the Northland this morning. They are more numerous and made it further north and east than earlier expected thanks to the low level jet. These showers/storms will continue for a few more hours but should decrease in coverage but may not end altogether. Low level wind shear will continue at KDLH/KBRD/KHIB this morning. Some brief dips to low MVFR or even IFR will be possible in the stronger showers/storms. Additional development of showers/storms will then occur along a cold front this afternoon into this evening. A few of the storms may be strong to severe, especially from east central Minnesota into northwest Wisconsin. The front will clear northwest Wisconsin this evening. Winds will switch from southerly ahead to west then northwest behind the front. Some stronger gusts will occur both preceding the front and behind. We will expect some low MVFR ceilings to occur behind the front but they are not expected to be widespread enough at this time to add to the forecast. If they were to occur, they`d be most likely at KINL and KHIB late this afternoon and early evening and at KHYR this evening. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 319 AM CDT Sat Sep 21 2024 The wind is expected to become easterly for a time today from 5 to 15 knots ahead of a cold front. Winds will switch to west then northwest behind the front, increasing in speed to 10 to 20 knots with gusts around 25 knots tonight. Thunderstorms will be possible today into this evening with the main threats cloud to surface lightning and gusty and erratic wind. We issued a Small Craft for all areas from Saturday evening into the Sunday morning. The wind will be lighter on Sunday, roughly from 10 to 15 knots. 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...Small Craft Advisory from 10 PM this evening to 7 AM CDT Sunday for LSZ121-140>142-147-148-150. Small Craft Advisory from 10 PM this evening to 4 AM CDT Sunday for LSZ143>146. && $$ DISCUSSION...Melde AVIATION...Melde MARINE...Melde