FXUS63 KDLH 041147 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 647 AM CDT Sat May 4 2024 .KEY MESSAGES... - Light to moderate rain continues through this morning and afternoon before tapering off this evening last in the Arrowhead and northwest Wisconsin. An isolated thunderstorm is possible (20% chance) near the Iron Range this afternoon. - Mostly clear skies and a colder air mass overhead tonight are expected to aid in fog and frost formation tonight. - Dry conditions Sunday giveway to a warmup near 70 F Monday when there is a 40% chance of near-critical fire weather conditions as breezy southerly winds occur with minimum relative humidity in the low to mid-30% range. - The next round of rainfall begins Monday night into Tuesday, with non-severe thunderstorms most likely in northwest Wisconsin. && .DISCUSSION... Issued at 248 AM CDT Sat May 4 2024 The slow moving, weak cold front that moved into the region overnight is producing an axis of low to mid-level convergent flow from the Brainerd Lakes into the Arrowhead early this morning. Combine this forcing with a southerly moist jet with Gulf air, the widespread light to locally moderate rainfall within the convergent axis has brought up to a few tenths of an inch of rainfall overnight so far. Rainfall rates and amounts will increase during the daylight morning hours for the I-35 counties in MN and US Hwy 53 counties in WI though as the mid- level frontal forcing pushes eastward within the deeper mid to upper level trough to align better with the moisture. A quarter to half-inch of rainfall is expected for those locations by late this afternoon. Frontal-associated rainfall exits the region by mid-afternoon as dry air in the mid-levels pushes into the southern half of the Northland from the west and the front exits the region. In far northern Minnesota (north of US Hwy 2), a secondary vort max drops into north-central Minnesota from the north by mid-day today. Residual wrap-around moisture (0.5" PWAT progged in guidance), mid-level lapse rates of 7.5 to 8.5 C/km, around 100 J/kg of MUCAPE and 20 knots of effective shear may (20% chance) support isolated thunderstorm development from Bemidji- Grand Rapids- Hibbing and northward. The most likely hazards in those thunderstorms would be very localized moderate rainfall and pea size hail. Other locations in the Arrowhead, Brainerd Lakes and Twin Ports are expected to see another period of scattered rain showers in this afternoon time period. As the secondary vort max exits the Arrowhead by mid-evening later today, dry air subsidence ends all shower chances overnight tonight. Deterministic guidance progs the 850 mb air mass from 0 to -2 C for far northern Minnesota. Combine this cold air mass, light winds under surface high pressure and residual moisture trapped in the boundary layer, there is potential (40% chance) of fog development in the region Saturday night into Sunday morning. If locations closer to the Brainerd Lakes that see precipitation end earlier today and the dry air mixes out the surface layer enough, then frost could instead form tonight for those locations. A dry day on Sunday sees temperatures rebound into the low to mid-60s across the region as surface high pressure exits the region to the east and a mid-level ridge builds overhead from the west; promoting southerly air advecting into the region beginning Sunday night. Gusty southeasterly low-level winds mix out Monday morning to create breezy conditions around 15 mph with gusts to 30 mph for parts of east-central and north-central MN. Relative humidity in the low to mid-30 percent range may (40% chance) create a period of near-critical fire weather conditions Monday afternoon as temperatures are forecast to peak around 70 F. The fuel guidance from land management agencies will also be monitored for input due to recent rainfall and how the spring "green up" proceeds in this early week period. Precipitation chances build Monday evening as a low pressure moves out of the Northern Rockies and into the Northern Plains Monday afternoon. The warm front passes over the region Monday night to create a period of likely (80% chance) widespread rainfall and possible (30% chance) thunderstorms late Monday night into Tuesday afternoon as the low pressure retrogrades in the Northern Plains. The best chance of non-severe thunderstorms will be in northwest Wisconsin Tuesday afternoon. In all, there is a 60-70% chance of at least 1/2 inch of rainfall for northwest Wisconsin and east-central and the Arrowhead in MN. The upper-bound of isolated rainfall is 1-1.25" with a 20% chance of occurrence in localized areas of east-central MN and northwest Wisconsin Tuesday. Ensemble cluster analysis shows high confidence on the vertically stacked low pressure center remaining over the Northern Plains, which may (20-30% chance) keep the Northland in a continued wet pattern into next week as well before the deep low ejects eastward by late next week. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 647 AM CDT Sat May 4 2024 A band of moderate rainfall is ongoing over most of northeast Minnesota currently and will extend into northwest Wisconsin over the next couple of hours. VFR conditions presently are expected to drop at terminals as higher rainfall rates produce lower visibility and ceilings lower by 14Z in NE MN, towards 15Z in NW WI. Conditions improve from 16 to 19Z west to east. After the widespread rainfall chances taper except in the Arrowhead by this afternoon, scattered rain showers form in north-central Minnesota first late this morning and work eastward towards HIB this afternoon. An isolated thunderstorm producing moderate rain and pea size hail could not be ruled out near and north of a line from GPZ-HIB-ELO in Minnesota from mid to late afternoon hours today. The last rain showers exit the Arrowhead after 00-02Z this evening. Areas of fog, although location highly unsure still at this time, are expected starting late Saturday night and lasting into early Sunday morning. Have placed mist in the HYR TAF at this time for the best chances (40% chance) of this fog development towards the end of that TAF period, but other terminals may need it in future issuances as well. && .MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/... Issued at 640 AM CDT Sat May 4 2024 A band of persistent light to moderate rainfall today and tapering this evening may (60% chance along the South Shore and 40% chance for the North Shore) result in marine fog Saturday night into Sunday morning. No headlines are expected currently, but if dense fog does form tonight then some could be necessary. Otherwise, light winds under high pressure prevail through Sunday morning before becoming west-southwest at 10-15 knots. 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...NLy AVIATION...NLy MARINE...NLy