DISCUSSION
Issued at 407 AM CDT Sat Jul 27 2024

Another hot and humid day today with sticky dewpoints in the upper 60s to around 70, and the warmest high temperatures of the week today. A weak cold front is sagging into the forecast area this morning, and ahead of the front temperatures will rise into the mid 80s to low 90s. The associated dewpoints will put our Heat Index values squarely into the 90s for a broad portion of the forecast area this afternoon. However, convection to our northwest will cause increased cloud cover, and with the breezy south winds expected today, expect that conditions may not be as miserable as it could be. The afternoon high temperatures, while well above normal are not near record values. The concern with this heat is not the highs, but also the overnight lows.
This morning temperatures have been so far staying above 70F, which is rather muggy for northern MN and WI, and are expected again tonight. Our new HeatRisk tool is recommending a heat advisory for today, but all the others are shy of making criteria. So, we will wait and see how things develop, and be prepared to issue should we get warmer than currently forecast.
Also of concern is the thunderstorms expected through the weekend. This afternoon and evening, not only do we get a decent warm sector and pool of instability over central and southern MN that can be drawn upon for the Northland, but deep layer shear of over 30 knots is also expected. There is a Slight Risk of severe storms, mainly over northwest MN and northeast ND, but these may spread into north central MN this evening and bring strong to severe storms. A shortwave moving through the upper level flow on Sunday together with a similar CAPE and shear set- up will affect southern portion of the forecast area Sunday afternoon and evening. 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 today 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. By Sunday, most of these parameters line up even better than they do today, and we are anticipating storms with heavy rainfall, and slow movements, increasing the risk for flash flooding. The greatest severe risk will be pushed a little farther south than for today.

Heat continues to be our major concern through the rest of the work week, with temperatures warming back into the mid-upper 80s again Tuesday into Wednesday as the cooler temperatures on Monday are pushed back out. Another day of cooler temperatures and shower and storm chances are expected Thursday through next Saturday, with a slow warming trend.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 631 AM CDT Sat Jul 27 2024

An area of MVFR/IFR stratus over most of the terminals this morning will gradually slide northeast this morning and gradually lift back to VFR between 15z and 18z this morning. The southerly winds will pick up to 10-15kts with gusts around 20kts after 14z, but then decrease again after 00z this evening.
Showers are currently over northwest MN, and may approach KINL until 14z, and have included a VCSH group. More showers and thunderstorms will develop during the day today, starting out near KINL, then spreading east to affect KHIB and KBRD close to the end of the TAF period. It appears that storms should stay out of KDLH and KHYR through this TAF period. Have only included VCTS groups for now.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
Issued at 407 AM CDT Sat Jul 27 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...Small Craft Advisory from 1 PM this afternoon to 4 AM CDT Sunday for LSZ144>147-150.