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Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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384 FXUS63 KDLH 031110 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 610 AM CDT Wed Jul 3 2024 .KEY MESSAGES... - Scattered showers and a few isolated storms this afternoon and early evening. - Slow-moving system will bring a chance of moderate to heavy rainfall to northwest Wisconsin and portions of central and east-central Minnesota July 4 afternoon and evening through Friday morning. - Several chances of showers and storms forecast during the next 7 days. - Near-normal temperatures throughout the forecast period. && .DISCUSSION... Issued at 426 AM CDT Wed Jul 3 2024 A few isolated showers were located along the International Border early this morning. A cool front stretched from an area of low pressure over far northern Ontario across the Arrowhead to near Aitkin and then west into southeast North Dakota. A few surface pressure troughs were found both ahead and behind the front. Look for those showers to move eastward and gradually dissipate over the next several hours. GOES-East Bands 8, 9, and 10 water vapor imagery reveals a broad area of cyclonic flow over the Canadian Prairies into the Upper Midwest early this morning. Of particular note are several small-scale vorticity maxima from southeast North Dakota west into north-central Montana. Cold air advection is forecast over the Northland today, strongest over northern Minnesota. Look for scattered showers and a few thunderstorms to develop late this morning into the afternoon and persist through this evening. Forecast MLCAPE of 250-750 J/kg will be found with 0-6 km deep layer shear of 25 to 35 knots. The weak instability will limit the potential for strong to severe storms. One or two storms may produce pea-size hail. Severe weather is not anticipated and locally heavy rainfall is unlikely. The train of smaller vorticity maxima should propagate eastward into central MN and northwest WI this afternoon and may provide enough lift to generate isolated showers over those areas. Have added small PoPs with this update to account for that potential. Temperatures today are forecast to reach the middle 70s north to the low 80s in the St. Croix River Valley and adjacent areas of the I-35 corridor and northwest Wisconsin. Partial clearing is expected tonight which should allow for areas of patchy fog to develop. Looking ahead to Thursday, July 4, temperatures will be near normal once again with highs in the middle 70s to low 80s. A shortwave trough with a weak area of surface low pressure will propagate eastward from the central Plains into the Upper Midwest during the day. Rain and a few thunderstorms are forecast to accompany the system as it slowly moves eastward. Instability will be limited due to forecast cloud cover and relatively warm temperatures aloft. Look for MLCAPE in the 250-1000 J/kg range with very limited deep layer shear of 20 to 25 knots. Forecast soundings show deep moisture and PWATs are forecast to be 1.25 to 1.5 inches over central Minnesota into northwest Wisconsin. Locally heavy rain will be possible with the storms given a slow propagation and "warm rain" processes. The main mitigating factor for the risk of heavy rain will be the general lack of focused ascent. A warm front will remain south of the Northland, over southern Minnesota and southern Wisconsin. If the front advances farther north than currently forecast, the risk of heavy rainfall over portions of the I-35 corridor and northwest Wisconsin would increase. Aside from increasing cloud cover, morning festivities on Independence Day should be unaffected with rain chances trending higher in the afternoon and evening. Areas of northern Minnesota, generally north of US-2, have the lowest chance of additional precipitation on Thursday. Showers and storms are expected to persist over portions of central Minnesota and northwest Wisconsin on Friday as the upper-level trough gradually propagates eastward. Rain chances will decrease by evening as a narrow axis of ridging passes over the Northland. Rain chances return to the forecast on Saturday as another trough of low pressure aloft and surface low pressure propagate eastward across the region. Deterministic guidance seems to be a little slower with the arrival of rain chances over the past 24 hours. If the trend continues, much of Saturday may end up dry with rain holding off until late afternoon or evening. There will be several additional chances of showers and thunderstorms Sunday through next week. The upper-level flow remains progressive with numerous shortwave troughs and vorticity maxima moving generally west to east across the Canadian Prairies and the Upper Midwest. Temperatures will remain near normal for early July. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 610 AM CDT Wed Jul 3 2024 Scattered showers and a few thunderstorms are forecast late this morning through early this evening. INL has the greatest chance of a thunderstorm and have maintained the VCTS mention with this forecast. Added VCSH to HIB, DLH, and HYR. Think BRD will be west of the showers. Gusty west winds today subside tonight. IFR visibility with light winds likely at HIB, INL, BRD, and HYR after 04.09Z. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 426 AM CDT Wed Jul 3 2024 A weak cool front will advance eastward across western Lake Superior today. Winds will turn southwesterly in the wake of the front. Wind speeds will increase to 10-20 knots with gusts of 15 to 25 knots. The long fetch along the North Shore will allow waves to build to 2 to 5 feet near and east of Grand Marais. A Small Craft Advisory remains in effect from Grand Marais to Grand Portage primarily for the hazardous waves. Wind speeds and waves will diminish this evening and should remain relatively light while backing northeastward for Independence Day Thursday. By Thursday evening, the pressure gradient will tighten north of a strengthening area of low pressure over southern Minnesota, northeast Iowa, and southern Wisconsin. Northeast winds of 5 to 15 knots with gusts of 10 to 20 knots are forecast by Friday morning. Waves may become hazardous near the Twin Ports by late Friday morning. Winds and waves will gradually diminish through the afternoon and evening as the surface low to the south moves farther away from the region. 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...Small Craft Advisory from 10 AM this morning to 10 PM CDT this evening for LSZ140. && $$ DISCUSSION...Huyck AVIATION...Huyck MARINE...Huyck