Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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055 FXUS63 KMQT 062258 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 658 PM EDT Mon May 6 2024 .KEY MESSAGES... -Quiet weather through tonight. -Complex mid-week weather pattern with rain chances increasing on Tuesday and multiple passing low pressures keeping rain in the forecast through the end of the week. && .SHORT TERM /THROUGH TODAY/... Issued at 142 PM EDT Mon May 6 2024 Upper air pattern consists of a 500 mb trough in the central Rockies and a shortwave in the mid Mississippi River Valley. The trough heads northeast and develops a closed 500 mb low that moves into the Dakotas by 12z Tue. Weather will be quiet through tonight with very few changes made to the going forecast. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 344 PM EDT Mon May 6 2024 The extended forecast is largely dominated by a trough currently approaching the Northern Great Plains and its complex evolution and influence on the surface lows moving across the CONUS through the upcoming week, which will keep precipitation chances in the forecast throughout the forecast period. For Tuesday, the negatively tilted trough forms a closed off low over the Northern Plains as the shortwave continues northeast from Iowa to the Upper Great Lakes. This stacked low will be stalled over the Dakotas Tuesday through Wednesday morning, but a shortwave rotating around the base of the low aloft will be the focus for the weather pattern heading into the midweek. This shortwave will get jet support as it becomes coincident with a right-entrance region of a ~125 kt 300mb, giving enough synoptic support for showers over the UP beginning Tuesday late-morning in the west and overspreading the UP by the end of the day. This continues a model trend of precipitation arriving later with each major model run. With bulk shear low (20-35 kts) and mean 12Z HREF MUCAPE of around 100mb, not many thunderstorms are expected, but a few rumbles of thunder can`t be ruled out. With moisture advecting in and cloud cover ahead limiting mixing potential, minimum RHs barely fall into the 30s ahead of the approaching showers, so fire weather shouldn`t be a concern, and with a WPC Marginal Risk of Excessive Rainfall, any minor fires that may start should be extinguished naturally. The pressure falls associated with the shower activity Tuesday will become a discrete surface low pressure by Wednesday morning and depart the region by the afternoon. As it does, the original closed low over the Dakotas will weaken from a peak strength of near 980mb Tuesday morning to near 1000mb by midday Wednesday as it slides southeast. As it does, it will phase with another weak lee cyclone off the Rockies, with ensembles tracking this new low generally around Lake Michigan and Illinois by overnight Wednesday into Thursday. Precip will be the forecast if the northern clusters verify, but the UP could be high and dry if a more southern solution materializes. By Friday, anomalous ridging over coastal British Columbia will be contrasted with anomalous troughing over the Lower Great Lakes, putting the UP in a northwesterly flow regime. Some deterministic and ensemble guidance suggests a clipper-type low late in the week into the weekend, keep PoPs in the forecast, though uncertainty is high in any specifics as the complex setup has a lot of variables to work out first. Confidence is increasing that this ridge will shift over the Great Lakes by the midweek of next week, warranting the CPC to favor below normal precipitation for the second half of May. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 658 PM EDT Mon May 6 2024 VFR conditions continue through tonight as an occluding front approaches the U.P. from the south, arriving Tuesday. This front will degrade conditions at KIWD to IFR by the early afternoon and MVFR at KCMX and KSAW late in the afternoon as rainfall moves into the area. Some LLWS is expected over KIWD late tonight as the front approaches. While there is a small chance (20%) for LLWS to develop around 12z Tuesday over KCMX, given the that the stronger winds will more than likely not reach KCMX until the late morning to early afternoon hours (when they will be able to mix down to the surface), LLWS isn`t expected for KCMX. && .MARINE... Issued at 344 PM EDT Mon May 6 2024 With high pressure over the Upper Great Lakes, resulting stability will keep winds mainly below 20 kts through tonight for the vast majority of Lake Superior. The exception to this would be over the far western portion of the lake near the Duluth Harbor where some northeast channeling may yield some gusts up to 25 kts. An approaching low pressure Tuesday morning will force northeasterly to east winds to funnel over the western half of Lake Superior to 25 kts by noon Tuesday with a few gusts to 30 kts in the far west and along the Minnesota shorelines. Winds across the east half of the lake increase to around 20-25 kts Tuesday afternoon. A brief break in 20+ kt winds is expected Tuesday night. Periodic chances for winds in the 20-30 kt range dot the forecast through Thursday as multiple weak low pressure systems pass through the Upper Great Lakes region, but uncertainty still remains. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...07 LONG TERM...GS AVIATION...TAP MARINE...GS