Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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818 FXUS63 KDLH 101258 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 758 AM CDT Fri May 10 2024 .UPDATE... Issued at 756 AM CDT Fri May 10 2024 The Frost Advisories and Freeze Warning expire at 8 AM this morning as temperatures have quickly warmed into the upper 30s to 40s early this morning. && .KEY MESSAGES... - Freeze Warnings continue for much of northwest Wisconsin and parts of the Arrowhead through 8 AM. Frost Advisories also persist through 8 AM for east-central MN into the Twin Ports and for northern St. Louis County. - Scattered showers expected today along and behind a cold front, with isolated to scattered thunderstorms also expected this afternoon into early evening. - A few stronger storms this afternoon into early evening could produce small hail and gusty winds to 50 mph, with the best potential south of a Grand Rapids to Cloquet to Hayward line. - Several additional chances for showers/thunderstorms this weekend and into next week with near to above average temperatures. A few stronger thunderstorms could produce small hail and gusty again on Sunday afternoon (mainly northwest Wisconsin). && .DISCUSSION... Issued at 449 AM CDT Fri May 10 2024 Early this Morning: High pressure over the Northland early this morning has led to the development of a favorable radiational cooling setup tonight with calm to very light winds and mainly clear skies. As a result, temperatures have plummeted into the upper 20s to low 30s in parts of the Iron Range, Arrowhead, and large parts of NW WI. Freeze Warnings are in effect for these areas until 8 AM this morning due to low temperatures below freezing. Frost Advisories are also in effect until 8 AM for the MN counties of Pine, Carlton, Northern St. Louis, and Southern St. Louis due to low temperatures dropping into the mid-30s. Temperatures begin to warm quickly within a few hours after sunrise. Today - This Evening: A mid-level shortwave trough currently located over southern Manitoba/northern Ontario as of 4 AM CDT will quickly dive south-southeast across the Northland today, with an attendant surface cold front sliding southeast across the area throughout the day. Expect a mix of clouds and sun with and behind the cold frontal passage today, with the development of scattered showers for much of the day into this evening and some isolated to scattered thunderstorm activity this afternoon into early evening. High-res model guidance highlights a broad development of 200-500 J/kg of SBCAPE this afternoon into early evening, though 0-6km bulk shear will be decreasing to 20-30 knots as the afternoon progresses. While this isn`t a lot of instability or shear, dry air and steep low-level lapse rates could drive some evaporational cooling to enhance downdrafts from any storms that form, leading to isolated wind gusts up to 50 mph in the strongest storms along with small hail (pea-sized). The area of best potential for these stronger storms would be generally south of a Grand Rapids-Cloquet-Hayward line where the deepest low-level mixing will be when storms move through. Shower and storm activity quickly drops off towards and after sunset today. Precipitation amounts today will scattered and mainly be on the order of 0.10-0.25" today for locations where showers or storms move overhead, though isolated pockets to 0.5" are possible in any stronger storms. Tonight: Clearing skies are expected from west to east tonight, which should allow for a good chance to see the northern lights tonight. See the Space Center`s webpage for more specific details about the northern lights potential tonight. The clear skies and lighter northwest winds tonight will once again lead to low temperatures falling into the mid/upper-30s for the MN Arrowhead and parts of NW WI. Frost probabilities in these areas are 30-40% or less at the moment, but Frost Advisories may be needed again tonight if forecast low temperatures drop another couple degrees lower than the current forecast. This Weekend: We see northwest flow with subtle mid-level shortwave ridging develop for the Upper Midwest on Saturday, leading to sunny skies to start before some diurnal cumulus develop Saturday afternoon amid deeper low-level mixing. There is a 30-50% chance for some scattered showers late Saturday afternoon and evening and perhaps an embedded thunderstorm during the evening, primarily in north-central Minnesota. No severe weather is expected and precipitation amounts are expected to be on the order of one- tenth of an inch. Expect a warmer day, with highs ranging from the mid/upper-60s in the eastern CWA to low/mid-70s in the western CWA. On Sunday, a shortwave trough and surface low moving across far northern Ontario will bring an attendant stronger surface cold front southeast across the Northland, mainly during the morning in MN and late morning/afternoon in NW WI. The exact timing of when this front moves across the area will dictate how much of the warm sector will still be located in parts of our area during the afternoon when showers and thunderstorm are expected to develop. Right now this warm sector area is forecast to be limited to east-central MN into the inland counties of NW WI. This is the area that could see the development of 500-1200 J/kg of SBCAPE due to steep mid- and low-level lapse rates. Deep- layer shear vectors will be weaker (15-25 knots) with this Sunday system, but the stronger instability and steep lapse rates could provide enough energy for a few of these storms to produce small hail and gusty winds. Thunderstorm coverage/potential drops off quickly by the evening as the cold front continues moving south. Next Week: Look for a drier day on Monday into most of Tuesday as another shortwave ridge moves through the Upper-Midwest while a more mature low churns over far northern Ontario. Mostly sunny skies and high temperatures in the 60s (cooler near Lake Superior) are forecast. Ensemble guidance shows general agreement in a stronger shortwave trough moving through the Upper Midwest sometime in the Wednesday-Friday timeframe, but varies on when exactly this trough will move through mid-late week. Nonetheless, expect more widespread chances (50-70%) for >0.25" of rain with this system, with a 20-40% chance for greater than 0.5". Temperatures remain somewhat seasonal most of next week, with highs in the 60s to around 70 degrees, though cooler near Lake Superior. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 703 AM CDT Fri May 10 2024 Mid-level clouds and scattered showers have begun moving into north-central MN and will continue to move southeast through the morning and afternoon. Winds veer to northwesterly in northeast MN by mid to late morning, while veering to northwesterly in northwest Wisconsin from midday into the afternoon. As the low- levels become mixed today, gusts will increase to 20-25 knots for most terminals, aside from KHYR, from midday through the afternoon. Some gusts at KBRD could reach up to 28 knots. Scattered showers move southeast across the Northland today with and behind the cold front. Isolated to scattered thunderstorms develop during the afternoon and diminish by mid-evening. Expect VFR ceilings/visibilities with most showers, though some brief MVFR is possible with the heavier showers and storms should they move over a terminal. Gusty and erratic winds up to 40-45 knots and small hail are possible with any of the stronger storms. Expect winds to quickly weaken mid to late evening and turn light overnight. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 756 AM CDT Fri May 10 2024 Light southwesterly winds early this morning increase to 7-12 knots by this afternoon out of the west with gusts less than 20 knots as a cold front moves through Lake Superior. Scattered showers and isolated thunderstorms are possible along and behind the cold front today, with the thunderstorms mainly during the afternoon into early evening. Winds turn northwesterly later this evening and tonight. South to southwest winds return on Saturday through Sunday morning, with gusts of less than 15 knots. Winds do turn northwesterly behind another cold front Sunday afternoon and evening. A few gusts along the North Shore could approach 20-25 knots Sunday afternoon and evening, so some Small Craft Advisories may be needed. 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. && $$ UPDATE...Rothstein DISCUSSION...Rothstein AVIATION...Rothstein MARINE...Rothstein