Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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967 FXUS63 KDLH 171147 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 647 AM CDT Mon Jun 17 2024 .KEY MESSAGES... - Overall threat for flash flooding has decreased a bit due to forecast uncertainty. Heaviest rainfall has shifted north since last update and the Flash Flood Watch extended north as a result. Today`s severe threat reduced as well. - A cold front will bring chances for strong to severe storms for Tuesday as it works across the region. - Additional chances for rain and storms this weekend. && .DISCUSSION... Issued at 540 AM CDT Mon Jun 17 2024 A complex pattern was in place across the central CONUS early this morning. A large area of low pressure was located over northern Manitoba with with a cold front trailing into far northwestern Ontario, far southwestern Manitoba and into North Dakota. Another area of low pressure was analyzed over northern Lake Superior with a cold front trailing into northwestern Wisconsin, southeastern Minnesota and northwestern Iowa before turning into a warm front across Nebraska. A large area of showers and thunderstorms was located along and behind this front from southern and eastern Minnesota into northwestern Iowa, eastern South Dakota and eastern Nebraska and was moving east-northeast along the front. Multiple rounds of showers and thunderstorms are expected to move along this front today into tonight. CAMs are showing a break during the midday hours before activity ramps back up tonight. Overall model trends have backed off on QPF amounts over the region today and tonight and have shifted the area of highest QPF further north. A surge of northward moving higher PWATs are forecast to reach areas along and north of the Iron Range overnight with values of 1.5-1.8" which would be near the top of climatology for the date. However, CAMs continue to struggle in the placement of showers and storms overnight, although northern areas are favored on the latest HRRR and NAMNest runs. Rainfall amounts of 0.25-1" are currently forecast for today and tonight, which is quite a bit lower than our previous package. WPC has outlined the entire area in a slight risk for excessive rainfall for today and tonight and given the reduction in QPF amounts, this seems warranted. Have held on to the Flash Flood Watch currently in place, but have extended it north based on the shift in highest QPF to the north. Have left the southern part in place due to continued uncertainty. A few stronger storms cannot be ruled out at times today with hail up to 1" and damaging wind gusts to around 55 mph being possible. An isolated tornado cannot be ruled out across far southeastern Sawyer County and southern Price County this evening, but overall chances for any severe storms is around 10% or less in this area. Tuesday will see a Colorado low lift northeastward across the eastern Dakotas and western Minnesota and drag a cold front across the region during the evening and overnight hours. Additional rounds of showers and thunderstorms are expected through the day with a final push during the late afternoon and evening hours in association with the front. The heaviest rainfall looks to occur in areas along and north of the Iron Range in the vicinity of a warm front during the morning and early afternoon hours. Another surge of higher PWATs will move in ahead of the cold front with values over 2" in some spots which would exceed the climatological max for the day. While rainfall amounts of 1.5-3" will be possible along and north of the Iron Range, amounts up to around an inch will be possible elsewhere. There still remains uncertainty in the where that warm front will set up and if it remains south of the Iron Range, the heavy rainfall threat will shift south as well. As mentioned above, have keep the Flash Flood Watch in place to the south despite the lower QPF amounts due to this uncertainty. However, the threat for 3" or rainfall or greater has fallen below 10% at this time for the entire event. Instability along the cold front may build to around 1000-2000 J/kg with effective shear around 35 knots. Given the nearly unidirectional wind field along the front, quick upscale growth into a line of storms is expected. This storm mode will favor damaging wind gusts to around 60 mph and small hail. SRH is forecast to be over 300 m2/s2, so a few tornadoes will be possible embedded within the line. As this line pushes eastward into northwest Wisconsin during the evening hours an overall downward trend is expected. Some of the severe threat may be tempered if clouds and rainfall linger through the morning and early afternoon ahead of the front, but should any breaks in the clouds occur, temperatures in the 80s and Tds in the low 70s will quickly build instability. High pressure will then build in for Wednesday and Wednesday night giving the region a break from the active weather. However, the pattern will remain active with additional chances for showers and thunderstorms for the end of the week and into the weekend. Temperatures through this period will be near normal to start with a slow warming trend into the weekend. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 647 AM CDT Mon Jun 17 2024 Periods of showers and thunderstorms are expected over the next 24 hours. Current batch will bring MVFR ceilings and perhaps some MVFR VSBYs through this morning before a break in the rainfall. Additional showers and storms arrive for this evening and overnight with IFR ceilings and MVFR VSBYs. Winds will gust to around 15 to 20 knots outside of storms starting later this morning and continuing into tonight. A low level jet will begin to move into the southern part of the region late in the period and bring some low level wind shear to BRD and HYR. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 540 AM CDT Mon Jun 17 2024 Periods of showers and thunderstorms will be the primary concern over the next 48 hours as winds outside of storms remain around 20 knots or less. However, southerly winds Tuesday morning into Tuesday afternoon may gust to around 24 to 28 knots at the head of the lake and may lead to a brief period of conditions hazardous to small craft. Gusty winds to around 40 knots will be possible in any storms today into Tuesday with higher wind gusts to around 50 knots possible Tuesday afternoon with a line of storms. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...Flood Watch from 1 PM CDT this afternoon through Wednesday morning for MNZ010-011-018-019-025-026-033>038. WI...Flood Watch from 1 PM CDT this afternoon through Wednesday morning for WIZ001-006-007. MARINE...None. && $$ DISCUSSION...BJH AVIATION...BJH MARINE...BJH