DISCUSSION
Issued at 147 PM CDT Fri Jul 26 2024

High pressure over the Great Lakes continues to very slowly push eastward through this weekend as a stout low sweeps over central Canada, bringing an extended frontal zone over the Northern Plains and Upper Midwest over the next 3-4 days. We're just beginning to see the effects of this setup, with a line of clouds and precipitation over North Dakota, and the first day of robust WAA into the Northland along with good moisture return. Temperatures are rising into the upper 70s and low 80s today with dewpoints soaring into the 60s. To our west this afternoon is a taste of what's to come tomorrow - temperatures in the high 80s to near 90 and dewpoints in the upper 60s to low 70s (resulting in heat indices in the 90s across the board). Generally temperatures in the 80s should continue, not just this weekend but through much of next week as well. There wont be much recovery overnight, with overnight lows largely in the 60s through that same time period. Widespread HeatRisk values of 3 on Saturday, and a couple isolated areas of 4 mean that folks without access to adequate cooling and hydration will likely be affected. CPC graphics outline our region in good chances for above normal temperatures through at least early August.

The other impact of our frontal system will be chances for showers and thunderstorms. Overnight tonight, the first couple areas of showers and storms could brush portions of Koochiching County, but latest trends have this overnight convection backing off in space and time so we may not see any precipitation in the CWA until closer to midnight at which point an isolated storm could intensify to severe levels along a CAPE gradient with up to 30 knots of bulk shear. As instability dissipates overnight so too should any storm coverage. With a lot of warm moist air coming in Saturday, redevelopment is expected over north-central MN in the afternoon and evening hours. Robust MLCAPE and bulk shear of 30-45 knots could lead to some isolated severe storms once again with all hazards possible (severe threat for Itasca, Kooch, Cass, Crow Wing, and central/northern St. Louis Counties). Additionally, training storms are possible which could lead to some heavy rain. We are working with a very moist atmosphere with forecast PW values of 1.5-2", deep saturation and freezing levels in excess of 10kft. Some of these storms on Saturday may be outrunning the best synoptic support and could be somewhat scattered or discontinuous leading to more splotchy coverage of the heaviest rain. However, some bullseyes of 2"+ could be possible, best chance in Koochiching County.

Sunday, we get the "best" of all worlds with widespread heat, moisture, and synoptic support for much of NE MN. Still some model discrepancies to work through for the Sunday-Monday timeframe, but generally some isolated severe storms could be possible in the areas of best instability and shear (currently around the Brainerd Lakes area). With good synoptic support as the frontal area moves over the area, training storms could be prevalent with PW near 2", deep warm cloud layers (over 10kft), areas of slow Corfidi vectors, and deep layer parallel flow. Sunday-Monday will be a time period to monitor for heavy rain and flash flooding potential for portions of north- central and northeast Minnesota, especially areas along and north of the Iron Range which may receive some areas of heavy rain before this round. Additionally, areas from Int. Falls to Ely are some of the few that are still running around to above normal for precipitation over the last 30 days and have normal to above normal streamflows persisting. Should the trend for heavy rain continue and confidence in placement increases, a Flood Watch may be needed.

Through the rest of next week, heat persists with passing shortwaves and 500mb vort maxes bringing chances for showers and thunderstorms.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
Issued at 1241 PM CDT Fri Jul 26 2024

A fairly broad area of MVFR stratocumulus clouds is affecting HYR/BRD/DLH/HIB this afternoon associated with warm air advection. Most models suggest these will scatter out in the next 2 to 3 hours, but models have also been handling their presence poorly so it is not out of the question that they could linger a bit longer into the afternoon. Breezy southerly winds are expected through the period. There is a 40 percent chance for showers and storms at INL tonight in the vicinity of a cold front to the west, but latest models suggest most of these showers and storms will remain west. A broad area of MVFR ceilings and perhaps some fog is expected to develop at most terminals late tonight into early Saturday morning. These clouds are expected to scatter out in the morning, leading to VFR conditions.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
Issued at 147 PM CDT Fri Jul 26 2024

Winds out of the south to southwest will persist through the weekend, with gusts up to 20 to 25 knots in the afternoon and early evenings, and gusts of 10 to 15 knots during the overnight and morning hours. This persistent south wind will lead to increased wave heights, especially for portions of the North Shore, but even just off shore on the South Shore waves of 1 to 3 feet are possible.
From Taconite Harbor to Grand Portage, waves up to 5 feet could be possible Saturday into Sunday, and a small craft advisory may be needed. With current warm lake water temperatures, it is unlikely that these stronger winds would stay aloft. Showers and thunderstorms possible Sunday afternoon into Monday. Some upwelling could be possible along the North Shore by Sunday afternoon and evening, but there is a robust warm water layer to move offshore before that can occur. Monday, winds should begin to quiet as the pressure gradient weakens.

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.