Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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997 FXUS63 KDLH 212015 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 315 PM CDT Tue May 21 2024 .KEY MESSAGES... - The threat for severe thunderstorms has increased for late afternoon into late evening, mainly for northwest Wisconsin and Pine County in Minnesota. Primary threats are damaging wind and a tornado with a secondary threat of a large hail. Flash flooding will also be possible. - The deep low pressure system will continue to produce rain tonight which could lead to flooding over central to northern Minnesota and parts of northwest Wisconsin. - Chances for showers will continue Thursday into the weekend with Friday having the highest chance for widespread showers and thunderstorms (60-80%). && .DISCUSSION... Issued at 315 PM CDT Tue May 21 2024 A 995MB low was centered in southwest Iowa as of 20Z with water vapor showing a shortwave moving out of Nebraska. The low will deepen further as it moves north tonight. These features along with robust moisture and warm advection with a low level jet acting on high PWAT values will produce strong forcing. The RAP wraps PWAT values around 1.6" into northwest Wisconsin by early evening which are anomalously high for this time of year. There was partial clearing surging north through southern Minnesota which would arrive into our southern Wisconsin zones yet this afternoon. Instability was not impressive over the Northland as of early afternoon but it is forecast to increase late afternoon into the evening, especially from around Burnett County east northeast into at least southern portions of Ashland/Iron Counties. Favorable shear profiles exist with forecast hodographs showing plenty of low level curvature. Confidence has increased for severe thunderstorms affecting east-central Minnesota into northwest Wisconsin late this afternoon into late evening. The main threat will be damaging wind but given the hodographs, a tornado threat will exist along with some hail. CAM guidance supports the severe threat although there remains some uncertainty on storm mode. Discreet storms are possible but given the forcing, we`d expect the storms to congeal into a line. The tornado threat will remain even if a linear mode prevails given strong southerly 0-3KM shear vectors of 30 to 40 knots and a southerly storm motion. The severe threat should wane by late evening. Strong northerly winds will develop on the backside of the low this evening/overnight and they will become westerly on Wednesday. Forecast soundings at Walker and Brainerd show 40-50knot northerly winds 1-2kft off the surface by late evening they will back late into Wednesday morning as they move across the region. We increased winds some but don`t feel confident to issue a Wind Advisory at this time. It will be something to watch for though for much of the Northland. A flood threat will continue as well and we expanded the Flood Watch further into northwest Wisconsin to account for the threat with the strong to severe storms late afternoon/evening. Heavy rain has already fallen over portions of the Northland with spotter reports of 1-2" across the Brainerd Lakes region. Addition rainfall from this afternoon and tonight will be 1 to 3 inches, highest in far northern Minnesota and the North Shore. The surface low will move just north of the Arrowhead in northwest Ontario by 12Z Wednesday, continuing northeast through the day. Showers and a few thunderstorms will occur through the day, especially in northern Minnesota. It will be windy with gusts of 30 to 40 mph with the possibility of even higher gusts. Looking ahead, there will be additional shower/storm chances (20- 30%) on Thursday with a frontal boundary across the area. Another stronger shortwave will deepen the surface low Thursday night into Friday causing higher chances (60-80%) for showers/storms. A strong storm will be possible Friday and expected rainfall will be from a half to one inch for much of the Northland. We do continue some low POPS, 20-40%, through the weekend but coverage looks more limited. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1226 PM CDT Tue May 21 2024 IFR conditions covered most of the Northland and are expected to prevail through most of the period with some improvement at the end of the period. A strong low pressure system is still on track to produce widespread showers and thunderstorms this afternoon into Wednesday. The thunderstorm threat will be greatest this afternoon into the late evening hours. The threat for severe thunderstorms has increased over northwest Wisconsin with all hazards on the table, including damaging winds and a tornado. Fog will occur at times, especially around Lake Superior into tonight. Strong winds will occur around Lake Superior today and as the low pressure system moves through, strong northerly then westerly winds will develop for all areas. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 315 PM CDT Tue May 21 2024 Strong easterly winds with gale force gusts to around 40 knots will continue or develop this evening. The wind will briefly diminish late evening or early morning as they switch from easterly to westerly as low pressure moves through the region. West to southwest winds will ramp up with strong gusts of 40 to 45 knots on Wednesday. Winds will diminish Wednesday night into Thursday. Widespread rain and some thunderstorms will continue tonight but gradually decrease in coverage late tonight into Wednesday. Some fog will remain possible at times, especially when winds are easterly and we issued a Dense Fog Advisory from the Twin Ports to the North Shore. 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 MNZ010>012-018>021- 025-026-033>038. WI...Flood Watch through Wednesday morning for WIZ001-006. Flood Watch until midnight CDT tonight for WIZ002-007-008. MARINE...Small Craft Advisory until 7 AM CDT Wednesday for LSZ121-147- 148. Gale Warning from 7 AM to 7 PM CDT Wednesday for LSZ121-147- 148. Small Craft Advisory until 4 PM CDT this afternoon for LSZ140>146-150. Dense Fog Advisory until 7 AM CDT Wednesday for LSZ140>143. Gale Warning until 7 PM CDT Wednesday for LSZ140>146-150. Dense Fog Advisory until 3 AM CDT Wednesday for LSZ144-145. && $$ DISCUSSION...Melde AVIATION...Melde MARINE...Melde