Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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072 FXUS63 KDLH 142018 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 318 PM CDT Fri Jun 14 2024 .KEY MESSAGES... - Showers and thunderstorms will develop across the Northland Saturday into Saturday night. The threat for severe storms is low but there may be heavy rain in spots, mainly over northwest Wisconsin. - More thunderstorms expected Sunday into Sunday night with the potential for strong to severe storms, most likely for portions of the Northland that are south of the Borderlands and Iron Range. Heavy rain will also be a threat. - A wet pattern will continue next week with the potential for both severe storms and heavy rain leading to flooding. The Monday/Monday night period is looking like the best chance for very heavy rainfall. && .DISCUSSION... Issued at 318 PM CDT Fri Jun 14 2024 Tonight... Upper ridging and surface high pressure will move through and east of the Northland tonight into Saturday. Dry conditions are expected for most tonight with a few showers possibly making it into far western portions of the Northland late. Saturday into Saturday night... Showers and thunderstorms will increase in coverage from southwest to northeast Saturday into Saturday night with persistent warm air and moisture advection occurring along with forcing from a shortwave. A low level jet at 850MB is forecast to increase to 40-50 knots Saturday evening. Instability Saturday will be limited but will build to 200-800 j/kg Saturday night. A few stronger storms are expected to develop into northwest Wisconsin late Saturday night. The storms will be capable of producing heavy rain with PWAT values around 1.75", in the 90-99th percentile. Sunday into Sunday night... Showers and thunderstorms may be ongoing Sunday morning as a shortwave exits the area. A cold front will be just entering our western area Sunday afternoon and a warm and moist airmass will exist ahead of it. We have highs in the eighties with dewpoints from the mid-sixties to around seventy. PWAT values will again be around 1.7" and MUCAPE values will rise to 1500-3000j/kg. There is also adequate shear in place ahead of the front along with mid-level lapse rates from 7-8c/km. The convective parameters are favorable for severe storms Sunday afternoon/night. However, forcing will be limited with subsidence in the wake of the exiting shortwave occurring in the late morning afternoon. 500MB heights will also be rising Sunday afternoon/night. Convergence along the front is not particularly strong either. If a few storms do develop, then severe weather will be possible given the shear/CAPE in place. If enough storms do develop, heavy rain may also occur given the moisture in place and with deep southwest flow aloft which will become nearly parallel to the surface boundary. Monday into Monday night... A greater threat for heavy rain and flooding will occur Monday into Monday night. The surface front will return north as a warm front, moving into northern Minnesota Monday night, and deep southwest flow aloft will continue to be nearly parallel to it. FGEN will strengthen during the day with increasing southerly flow south of the front which backs on the cooler side of the front. The theme of this forecast continues to be the presence of high PWAT air and values around 1.8" are expected which are in the 90-99th percentile. Instability isn`t real impressive over the Northland but the forcing and moisture will make up for that and there is a greater pool south. Strong southerly low level flow, high moisture, and some instability are all supportive of multiple rounds of strong to severe thunderstorms. I`m getting more concerned that very heavy rain may occur which may lead to flash flooding and possibly longer term flooding of rivers/streams. The ECMWF ensemble forecasts a 20-40% chance for rainfall of 2"+ just Monday/Monday night over parts of central to northern Minnesota. There will likely be localized even higher amounts due to training strong thunderstorms. Tuesday through Friday... Southerly flow aloft on Tuesday will continue but a shortwave will push a cold front into the Northland Tuesday into Tuesday night. Warm and moist air will remain in place ahead of the front with shear/instability/moisture all supportive of strong to severe storms and more heavy rain. Wednesday looks be the driest day of the period with the front moving just east and south of the Northland and weak high pressure over northern Minnesota. Confidence in the forecast beyond Wednesday is lower than average and we continue to have chances for showers/storms Thursday/Friday. Summary... Much of the Northland has seen rainfall much above normal since mid-May. There will be plenty of moisture available with PWAT values in the 90-99th percentile developing this weekend and lasting into at least next Tuesday. There will be several rounds of thunderstorms that occur this weekend into at least Tuesday night with a severe and heavy rain threat. Concerns are growing that very heavy rainfall may occur Monday into Monday night leading to flooding. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1217 PM CDT Fri Jun 14 2024 VFR conditions are expected through the period for most of the Northland. Afternoon cumulus will vary from scattered to broken at times but bases will remain VFR. Some patchy fog may develop (~15%) tonight, mainly around and inland from Lake Superior. A chance for showers and a few thunderstorms will develop late tonight into Saturday from southwest to northeast. For now we just added VCSH at KBRD starting Saturday morning. Southerly winds will strengthen on Saturday. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 318 PM CDT Fri Jun 14 2024 Easterly winds will be at or less than 15 knots tonight into Saturday but they are expected to back to more southerly along parts of the South Shore tonight. East to southeast winds will occur Saturday night into Sunday from 10 to 20 knots. There will be a chance for thunderstorms Saturday night into Sunday. 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...Melde AVIATION...Melde MARINE...Melde