Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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909 FXUS63 KDLH 012055 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 355 PM CDT Sat Jun 1 2024 .KEY MESSAGES... - Widely scattered showers and isolated thunderstorms this afternoon last into early evening today. - Fog is expected to form tonight in parts of inland northwest Wiscosin and especially across north-central Wisconsin, potentially reducing visibility to 1/2 mile into early Sunday. - Isolated general storm chances Sunday gives way to the next round of possible severe weather and expected heavy rainfall starting Sunday evening in north-central Minnesota and spreading eastward Sunday night. - The active pattern continues Tuesday daytime into Tuesday night for possible severe weather again and heavy rainfall. Scattered rain showers last into the end of next week. && .DISCUSSION... Issued at 356 PM CDT Sat Jun 1 2024 A shortwave trough centered in northwest Ontario this afternoon is rotating through a deep central Canadian mid- to upper-level low pressure center and dragging a weak cold front across far northern Minnesota this afternoon. Pre-frontal, diurnally-aided rain showers have formed as a result right ahead of the front. Surface observations show high cloud bases from 5000-7000 feet above ground level, with a very dry air mass in the low levels underneath those showers very likely limiting any rainfall to sprinkles a few hundredths of an inch of rain into early evening today. Those showers and isolated thunderstorms exit the area then by the mid to late evening hours. Weak surface high pressure sets up tonight over northern Wisconsin to create calm winds. Some moistre from rain showers that wrapped up over the last few hours should remain trapped under that surface high and aid in fog formation later tonight for inland northwest Wisconsin and mainly north-central Wisconsin. Have placed patchy and areas of fog in the grids for most Wisconsin zones through 8-9 AM Sunday morning. Some guidance has visibility dropping down to 1/2 mile so an overnight land-based Dense Fog Advisory cannot be ruled out for our far southeastern counties (highest chances in Price or Iron Counties bordering WFOs Green Bay, LaCrosse and Minneapolis). While fog is ongoing in northern Wisconsin tonight, a 30-35 knot low-level southerly jet builds into western Minnesota tonight to rapidly increase precipitable water values Sunday from west to east. The exception will be in the eastern Arrowhead where a drier Canadian high-pressure dominated airmass lingers Sunday afternoon to keep minimum relative humidity still down to the mid-20 percent ranage. Blended in 10th percentile guidance into the dewpoint forecast for that part of the Arrowhead as a result. Isolated strong thunderstorm chances (capable of near-severe hail) build first in the afternoon hours Sunday in north- central Minnesota along the warm front of a deepening surface low pressure centered in southern Manitoba. In this time period, severe thunderstorms fire over central North Dakota and slowly spread eastward into northwest Minnesota as the low pressure lifts into the Manitoba/Onatario border region of Canada by late Sunday afternoon and the cold front trailing into the Red River Valley of the North basin. The severe thunderstorms eventually are progged to form a line of severe thunderstorms reaching north- central Minnesota between 7-10 PM Sunday evening. In this time period, damaging wind gusts of 70 mph is the primary hazard and is most likely in the greater Itasca / Cass / Crow Wing / Aitkin County region of north- central Minnesota lasting into the early overnight hours (12-2 AM). Depending on environmental stability factors and the organization of the line of storms, a tornado (also large hail) could not be ruled out in this general locations of Cass to Crow Wing to southern Itasca County either. Further eastward into northeast Minnesota still has the potential to see damaging wind gusts to 60 mph, but the southern trend of this severe weather tomorrow evening keeps those lower. Heavy rainfall is likely (80% chance) to create anywhere from 0.5 to 1 inch of rainfall with this system tomorrow evening and overnight. An few reports of 1.5 inches would not be surprising either in the Brainerd Lakes or east-central Minnesota region by Monday morning, creating minor ponding of water. Scattered showers and storm chances last into Monday, but the next potential round of severe weather sets up Tuesday daytime as a deep trough digs through the US Plains and a surface low pressure over the Dakotas deepens to create an even more moist and unstable environment over the Northland. The best instability and shear to support severe weather hazards would be placed across northeast Minnesota and especially northwest Wisconsin with the Tuesday round of storms that has potential to last into early Tuesday night depending on how fast the support aloft lingers or speeds up to eject out of the Northland Tuesday evening. An area of strong to possibly isolated severe thunderstorms will have to be monitored for Wednesday daytime as the deep low pressure is currently progged to move through northwest Ontario. This scenario may then create an environment over mainly north- central and northeast Minnesota with meso-forcing aloft, increasing mid-level lapse rates to 7.5 C/km, CAPE of 800-1200 J/kg and shear of 25-30 knots to support a large hail threat Wednesday daytime. Ensemble guidance shows a 40-50% chance of west-northwest winds gusting 35-45 mph beginning Wednesday night into Thursday and may need a future Wind Advisory if this scenario persists, largely dependent upon the synoptic pressure gradient from a building high in the central CONUS and low over the Great Lakes. Scattered thunderstorms and shower chances last into the end of next week as slightly above normal temperatures persist. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Updated at 240 PM CDT Sat Jun 1 2024 Breezy west winds through 00Z Sunday become light and variable backing southerly 12-15Z Sunday. Mist resulting from overnight marine fog off Lake Superior may (30% chance) drop visibility at terminals along and right near the shorelines, including DLH, along with radiation fog forming in inland northwest Wisconsin affecting HYR tonight. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 245 PM CDT Sat Jun 1 2024 Dense marine fog lingers along the North Shore today and expected into tonight. Extended the far North Shore fog Advisory into early Sunday morning for the expectation of overnight linger dense fog. Some guidance brings similar reduced visibility back into the Apostle Islands later tonight again so altered those zones to run from late evening today to early Sunda ymornign as well in a fog Advisory. Winds shift to easterly tomorrow, gusting towards 20 knots in the southwestern arm of the lake and builds wave heights to 2 feet tomorrow afternoon. The next round of heavy rain and strong thunderstorms likely affects the lake after Midnight Sunday night and lasts into Monday morning. Easterly winds 10 to 20 knots last into Monday with wave heights from 2 to 3 feet. 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...Dense Fog Advisory until 7 AM CDT Sunday for LSZ140-141. Dense Fog Advisory until 8 PM CDT this evening for LSZ142-143. Dense Fog Advisory from 10 PM this evening to 7 AM CDT Sunday for LSZ147-150. && $$ DISCUSSION...NLy AVIATION...NLy MARINE...NLy