Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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868 FXUS63 KDLH 192341 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 641 PM CDT Thu Sep 19 2024 .KEY MESSAGES... - Strong to severe thunderstorms are ongoing across parts of northeast Minnesota and northwest Wisconsin, with storms gradually weakening and tracking east through the evening. - Another chance for showers and thunderstorms on Saturday. Depending on timing and placement, a few strong storms could occur. - Seasonable temperatures return Sunday and into next week. && .DISCUSSION... Issued at 145 PM CDT Thu Sep 19 2024 As expected, a stacked upper level low continues to steadily march along the International Border this afternoon, pushing a north-south cold front into and across Minnesota. As instability builds and our cap erodes, quick upscale growth is expected as storms ignite along the cold front, taking advantage of 2000-3000 J/kg SBCAPE and 25- 40knots bulk shear. Storms are expected to ignite first in southern Minnesota and unzip to the north through the Twin Ports. A secondary area of storms closer the upper level low should also pop off across the Iron Range and into the MN Arrowhead. CAMs are still in decent agreement for ignition in the Northland in the 4-6pm timeframe, then pushing east through 10-11 PM across the Arrowhead and NW WI. Across the board, large hail, damaging winds, and a couple tornadoes are possible hazards. An initially discrete mode is expected to become kind of messy as it evolves into clusters. Bulk shear is expected to wane into the evening hours, reducing the chance for a true QLCS type system to be realized. The one exception might be in the MN Arrowhead where locally high shear close to the low could help more of a linear system come to fruition. Slightly more backed winds in the northern portion of the CWA could lead to enhanced SRH and better low level curvature in hodographs, which will need to be monitored for an isolated tornado threat. Otherwise marginal SRH and already fairly southerly winds further south may lead to a reduced tornado threat. Large hail up to ping pong size in diameter remains possible, especially in the first couple hours of convection initiation. Damaging winds up to 60 mph are possible, especially with any more linear clusters or decaying storms. In addition to the severe threat, some quick downpours and locally heavy rain is possible, thanks to our very moist environment. PWATs at International Falls were 1.46 inches this morning, which is a new daily max for the 12z sounding. Some high rainfall rates are likely with storms, and were already observed in some of our morning convection. However, with antecedent dry conditions, 1 hour flash flood guidance is 2-3 inches across much of the area expected to see heavy rain this afternoon and evening, so we would need very impressive rates in order to get any minor flooding. Beyond today, the Northland finds itself stuck between a high pressure over the southern Plains and an upper level trough bearing down from Canada. Global models have come into better agreement on an oblong trough brushing over northern Minnesota Saturday, bringing our next chance of precipitation, most likely in the afternoon and evening. Some instability is present and if the cap can be eroded a cold front would have access to over 1000 J/kg of MUCAPE (mostly in NW WI) which could produce some stronger afternoon thunderstorms. Much to the approbation of summer lovers, above normal temperatures are expected to continue through Saturday with highs rising into the 70s and low 80s. We are still on track to see more normal temperatures return Sunday behind Saturday`s front with highs in the 60s and overnight lows in the 40s and 50s. These relatively cooler temperatures should continue into next week. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 641 PM CDT Thu Sep 19 2024 Thunderstorms will impact several TAF sites this evening, with patchy fog developing overnight as storms diminish. A period of gusty west winds and scattered clouds Friday afternoon. In the next few hours, strong to severe thunderstorms will impact DLH and HYR causing reductions to IFR or worse conditions as heavy rain, strong winds, and possible hail impact at DLH 00z to 02z or so and HYR around 01z to 04z. Elsewhere VFR conditions will prevail this evening, with patch fog developing at HIB and HYR causing reductions to MVFR visibility. Fog will quickly lift on Friday morning, but low level moisture will cause initially MVFR stratocumulus clouds to develop at INL and possibly HIB on Friday morning into the afternoon, lifting to VFR ceilings before eventually clearing out. Otherwise conditions at other sites remaining VFR through the day Friday. South to southwest winds around 5 knots overnight becoming westerly around 10 knots gusting to 15-20 knots on Friday. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 145 PM CDT Thu Sep 19 2024 A cold front brings a chance for thunderstorms late this afternoon into the evening hours. Strong winds and large hail are possible along with frequent lightning. Thunderstorms should be past Western Lake Superior by late evening and winds begin to turn southerly. Friday, expected southwesterly winds with some breezy afternoon gusts behind today`s cold front. Some gusts of 15-20 knots are possible, but Small Craft Advisory criteria are not expected to be met. South to southwest winds continue Saturday, mostly less than 10- 15 knots, and there is a chance for some showers and thunderstorms in the afternoon and evening. Winds become northwesterly Sunday, fairly light around to less than 10 knots. 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...Levens AVIATION...JJM MARINE...Levens