Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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526 FXUS63 KDLH 280606 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 106 AM CDT Fri Jun 28 2024 .KEY MESSAGES... - Widespread moderate to locally heavy rainfall will return Thursday night, ending Friday afternoon. The heaviest rainfall is most likely along and north of the Iron Range into the Arrowhead of far northern Minnesota. - Isolated severe thunderstorms are possible (risk level 1 out of 5) in northeast Minnesota and northwest Wisconsin Friday afternoon and evening. - Residual showers Saturday in northeast Minnesota give way to a dry Sunday before the next round of moderate to locally heavy rainfall is forecast to return Monday into Tuesday. && .DISCUSSION... Issued at 339 PM CDT Thu Jun 27 2024 A beautiful partly sunny day has given way to some increasing clouds as the high pressure responsible for our brief dry weather slides off to the east towards Wisconsin. On tap is a low pressure system coming in from the west with an attendant warm front. This warm front is currently located over South Dakota and is snaking its way down into central Nebraska and will continue to lift northward eventually making it to our area Friday. This warm front will be responsible for the showers and storms that arrive in the area overnight into Friday. For those wondering about the heavy rainfall threat with this setup, the overall threat is lower than previous events which is certainly good news for us considering the recent heavy rainfall and continued saturated soils across the entire Northland. The reasons are as follows 1) while the moisture transport certainly is there, the moisture is not completely coming straight from the Gulf of Mexico but rather is being slightly modified from the Desert southwest. As such this limits how much moisture will be brought up into our area. 2) The best forcing looks to be up along the warm front near the Borderlands of Minnesota and also south of us along the Minnesota River valley. The various 6z and 12z model suites consistently paint a swath of heavy rain (2-4 inches) near the Borderlands although focused into Canada with the warm front. However, the caveat being if the warm front does not make it as far north as the models indicate then this could spell trouble for our area as this is likely where thunderstorms could end up training over the same areas. As such WPC does have all of the Northland in a marginal risk for excessive rainfall. When looking at the CSU machine learning probabilities both the ARI and UFVS both show a higher possibility (15-30%) of excessive rainfall. Again something to certainly keep an eye on particularly if the front does not make it as far north as predicted. Overall, widespread rainfall amounts of 0.50-1.00 inches are expected across most of the Northland, with locally higher amounts of 1-2 inches for the North Shore which terrain influences, and also along the International Border closer to the warm front. Given high uncertainty in the placement of higher totals, a Flood Watch was not issued. However, this will have to be closely evaluated for locations near the International Border. Regarding the severe thunderstorm threat Friday, while forcing from the mid levels is present, the threat is muted some by weak mid level lapse rates and a narrow window of CAPE values in the 1000- 1500 j/kg range. Cloud cover from morning storms will also be a concern for how much afternoon buoyancy develops. Deep layer shear of around 40-55 knots is certainly sufficient for organized convection which both the GFS and RAP 13 deterministic models show. Much of the Northland is in a SPC marginal risk (risk level 1 of 5) with a slight risk (risk level 2 of 5) further south into central and southern Minnesota which is where the better forcing and instability will reside. This coincides well when looking at the CSU machine Learning probabilities which paints a swath of 5% wind and hail probabilities for the Northland for a more marginal and condition severe risk. Looking ahead, Sunday will bring a respite from precipitation with sunny high pressure in place across the Northland. However, this break is short lived as the next wave approaches the Upper Midwest Monday into Tuesday. While details will still have to be worked out, the setup has a similar appearance to previous events the past couple of weeks with a heavy rain and severe thunderstorm risk that will have to be closely watched. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 106 AM CDT Fri Jun 28 2024 A wave of showers and embedded thunderstorms is poised to move across the terminals overnight, bringing deteriorating conditions. Currently VFR to MVFR ceilings extend across the area, with IFR ceilings expected to develop over the next few hours, and MVFR to IFR visibilities with the areas of rain. Brief LIFR conditions are possible, but confidence is low that they will be widespread. Winds will increase out of the south with this system, with gusts of 20 to 25 kts in the morning. Conditions will slowly improve as the system moves west to east beginning around 18z, with KHIB, KDLH, and KBRD terminals returning to VFR beginning around 21z. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 339 PM CDT Thu Jun 27 2024 Winds for tonight will shift from onshore flow to southeasterly winds late tonight. The winds will begin to pick up as night falls, with stronger winds of up to 15 kts and gusts of 20 kts possible. Wave heights may reach up to 2 feet with the strongest winds. Rain showers tonight will continue into Friday with embedded thunderstorms. For Friday, as the storm system from the west continues eastward winds will switch to southerlies and be strongest around noon, being up to 20 kts with gusts of up to 25 kts possible on the Southern Shore. Thunderstorms and rain are still likely throughout the morning. Wave heights may reach up to 3 feet on the North Shore. The winds and wave heights will decrease into tomorrow night. Small Craft Advisories may (30-50% chance) be needed on Friday. 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...CJM AVIATION...LE MARINE...AP