Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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733 FXUS63 KDLH 102121 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 421 PM CDT Mon Jun 10 2024 .KEY MESSAGES... - Rain showers and thunderstorms will move along a cold front late tonight through the day Tuesday. Isolated severe storms are possible later in the afternoon in portions of northeastern Minnesota. - Above average temperatures will be present Wednesday ahead of another cold front bringing another round of showers and storms. Severe weather is expected Wednesday. - More chances for showers and dry conditions in between will follow for the late week through the weekend. && .DISCUSSION... Issued at 151 PM CDT Mon Jun 10 2024 Our beautiful day will come to an end late tonight as a weak cold front with a closed low moves east across the Northern Plains into the Northland. Rain showers and embedded thunderstorms are expected, but should not be severe for this first round. As the day continues and the first round of showers move east, southwest flow and WAA at the surface resumes. Increasing surface moisture from the southwest flow and/or leftover from the morning showers and increasing instability could lead to strong to severe storms in the afternoon in our southern area, especially along the I-35 corridor and far northwestern Wisconsin. MUCAPE values 1000-2000 J/kg and marginal values of shear at 25-30 kts with good upper level forcing are expected by the afternoon in these areas. However, this is highly conditional that skies clear and therefore allows instability to build behind the weak cold front. It will be close timing, as the first line of showers are not forecasted to move passed the area until early afternoon, and clearing 1-2 hours after the rain ends. Storms will come to an end late Tuesday evening. Southwest flow bringing WAA and gulf moisture transport will start up again Wednesday morning ahead of our second system for the week. Most of the day will feel a bit sticky, as dewpoints will reach the upper 50s and lower 60s by the afternoon. A few models hint at isolated showers in the morning due to the WAA, but should not affect activity expected in the afternoon. Like Tuesday, a weak cold front will initiate showers and thunderstorms in the afternoon. MUCAPE values in the 1500-3000 J/kg range, lapse rates at 7-8 C/km, and strong shear upwards of 50 kts present across the Northland. Storm motion is expected to be mostly perpendicular to the front, which will lead to discrete supercells at the beginning of the event. The combination of high instability and strong, unidirectional shear above a couple kilometers are indications of large hail (2+ inches), which will be the main threat for Wednesday afternoon. Large hail is most likely in the southern half of the area. Despite hodographs showing good turning at the low levels and SRH > 100 m2/s2, LCLs are a bit high for tornados. However, a tornado or two is not out of the question. As the sun goes down and we lose daytime heating and surface instability, storms will transition to a linear mode and the threat will shift to more of a wind threat. Thursday, a small shortwave and a stationary front will lead to additional chances for showers and thunderstorms, especially in the afternoon. Currently, shear at 40-50 kts and steep lapse rates support severe weather, but the instability will be lacking at <1000 J/kg. For Friday, an upper level ridge will build in the west half of the CONUS and only grow taller and move eastward as the day goes on. Winds across the Northland will be mostly from the N and NW at about 5-10 mph. While an ridge running impulse is possible, no severe weather is expected as CAPE is practically zero with deep moisture yet to return. On Saturday, the ridge bulges more and continues on its eastward trajectory. Rain and thunderstorms are possible across the Northland starting in the afternoon due to transport of moisture from the Gulf, bringing up 50 F dewpoints by Saturday night. Thunderstorms are expected with the higher dewpoints and buoyancy with forcing supplied by a wave embedded in the ridge. Winds aloft are not fast enough to support severe weather as the shear will not be conducive enough. Finally, for Sunday the ridge will have moved eastward. Temperatures into the higher 70s can be expected, some reaching 80 F with favorable mixing. There is a possibility for a strong mid level jet south of low pressure across Canada, coupled with Gulf moisture transported northward. Since this is so far out, severe likelihoods are still uncertain. The timing between the GFS and Euro models are different, but they both seem to bring a strong mid level jet with a wave after the departing ridge along with increasing Gulf of Mexico Moisture. CSU Machine Learning probabilities also highlight a non-zero severe threat late this weekend into next week with southwest flow aloft. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1226 PM CDT Mon Jun 10 2024 VFR conditions with light winds will last through the day and tonight. Early Tuesday morning, a cold front will move eastward across the Northland bringing showers and thunderstorms. MVFR/IFR ceilings will accompany the heaviest rain and ceilings should lift an hour or two after the front has passed in the late afternoon and early evening. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 151 PM CDT Mon Jun 10 2024 Light and variable winds today will shift to the south along the South Shore and east along the North Shore for Tuesday. Showers and storms are possible Tuesday afternoon, though no strong to severe storms are expected. Ahead of another system, Wednesday will be warm and winds will shift to the southwest and increase, with gusts up to 20 kts. Hazardous small craft conditions are not currently expected, but will need to be monitored. Another round of storms Wednesday evening and overnight may be strong to severe over western Lake Superior. 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...KML/AP/PA AVIATION...KML MARINE...KML