Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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946 FXUS63 KMQT 212301 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 701 PM EDT Fri Jun 21 2024 .KEY MESSAGES... - Patchy fog develops tonight, continuing into Saturday. - Wet pattern continues tonight, becoming widespread rain Saturday into early Sunday. - The heaviest rainfall should stay south of the UP, but there is still a marginal chance (5% chance) for locally heavy rain resulting in minor flooding impacts across southern Upper Michigan. - Another round of showers/thunderstorms possible Sunday and Monday night into Tuesday. && .SHORT TERM /THROUGH TONIGHT/... Issued at 353 PM EDT Fri Jun 21 2024 Current RAP analysis this afternoon highlights the mid level trough out over the Canadian Prairie Provinces with a weak shortwave over the UP and a deteriorating sfc high pressure over the Upper Great Lakes. Sfc obs show the warm front has lifted into southern WI already and WAA light showers light up the radar data across much of the central and eastern UP. This round of showers continues moving east across the UP with the weak shortwave, diminishing over the east this evening. A brief dry period is likely in the north half of the UP following this round of showers into tonight while isolated to scattered showers continue over the south-central as an additional weak shortwave traverses the UP supported by WAA. Showers then increase from the south late tonight into Saturday ahead of the main shortwave on Saturday. Given the ample moisture and light easterly winds mainly below 10 mph, some patchy fog is expected to develop tonight and continue into Saturday. Some rumbles of thunder can`t be ruled out in the south-central through tonight, however instability is lacking (6/21 12Z HREF mean MUCAPE stays around 100J/kg over Menominee County) and the frontal boundary will stall out over central WI tonight so strong storms are not expected. Lows are expected in the 50s with cooler temps in the Keweenaw and eastern Lake Superior shores. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 304 PM EDT Fri Jun 21 2024 Deterministic and ensemble guidance packages continue to highlight the potential for multiple rounds of showers and thunderstorms in the extended forecast period as Upper Michigan sits primarily under near-zonal to northwest flow aloft. During this period, daytime temperatures will start off cool, but trend back into the 70s and 80s for the first half of the work week. Beginning Saturday, surface low will lift northeast along a warm front into the Great Lakes as a shortwave presses east through Minnesota. This will support a deepening surface low Saturday afternoon into early Sunday as the low transits Wisconsin and lower Michigan. Precip along and north of the boundary will build into the region through the day as PWATS remain 1.75-2 inches. Recent NBM and LREF guidance suggests a high (>75%) chance of exceeding 1 inch of rain across the southern half of the forecast area, with 30-60 percent chance across the north half. While most deterministic guidance suggests a widespread 0.5-2 inches through Sunday morning, GEFS and EC ensemble means suggesting the same supports the higher confidence in a potential notable and widespread rainfall event. This generally matches the EC EFI and SOT, which paints much of the south half with 0.8-0.9 EFI and 2 for SOT, indicating a potential extreme rainfall event outside of climatology. It should be noted though, that even if widespread 1-2 inches of rain does occur, recent RFC flash flood guidance suggests 2+ inches of rain in 1-6 hours would be needed to raise flash flooding concerns. Given that this is not the case with this event, flash flooding is not a concern. With that being said though, given recent rainfall, I`d expect some ponding of water in low lying locations and some additional river rises through the next few days if we do experience this rainfall. Additionally, rainfall amounts will be dependent on where the low tracks and where the warm frontal boundary stalls across Wisconsin, which a general clustering analysis of the EC and GEFS ensembles still suggests a range of locations. Model soundings suggest a mostly capped atmosphere across the area, with some elevated instability noted across the south. With this in mind, some embedded thunderstorms can`t be completely ruled out, but strong or severe thunderstorms aren`t expected at the moment. Daytime highs Saturday should be in the 60s to near 70F while overnight lows dip into the 50s to upper 40s across the forecast area. Precip should end Sunday morning from west to east as the low pulls away and weak mid-level ridging transits the area. This break appears to be short-lived though, given the clipper-like shortwave pressing southeast across Ontario/Lake Superior in the afternoon/evening. The GFS and NAM suggest the morning rain should end early enough to enable small daytime destabilization through the day, which would support thunderstorms to accompany the afternoon/evening wave. At the moment, strong or severe weather aren`t anticipated. High pressure over the area Monday should keep the region dry while upstream, a ridge rolling impulse moves east through the Dakotas/Minnesota and a surface low tries to develop. By Monday night, precip chances increase for Upper Michigan as a cold front extending south of a low moving through Manitoba and the low moving through southern Minnesota press closer. These swing into the Great Lakes on Tuesday. Ahead of the front, daytime temps could warm into the 80s across much of the region Tuesday. High pressure and dry conditions builds in Wednesday into Thursday. Beyond this, guidance differs greatly on the timing and position of the next wave. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 701 PM EDT Fri Jun 21 2024 Next round of showers will move in overnight and will bring deteriorating conditions with them. IWD will be MVFR tonight and then IFR Saturday. CMX will be VFR until later tonight when fog could develop and take them down to MVFR. By late Saturday afternoon, rain moves in there with LLWS and MVFR condtions at times. SAW will be VFR until later tonight when rain moves in and then drops to MVFR. By late Sat afternoon, heavier rain and IFR/LIFR conditions move in. && .MARINE... Issued at 304 PM EDT Fri Jun 21 2024 A deepening low pressure system will gradually lift into the region tonight and Saturday, before exiting into Ontario Sunday morning. As this transit occurs, expect winds to shift to northeasterly/easterly across Lake Superior tonight before becoming northerly Saturday night and northwesterly by Sunday morning. Light winds of 20kts or lower are mostly expected in this event, although northeast winds going down into the Duluth Harbor Saturday may climb to near 25 kts at times. Additionally, as winds shift to the north Saturday night, expecting an increasing to 25-30 knots across central and eastern Lake Superior as the peak pressure gradient force shifts through. Winds lighten to 20kts or less Sunday and predominately remain there until at least Tuesday. At this point, expecting southerly winds to increase to near 25 kts ahead of a transiting cold front. Thunderstorms will be possible, mainly Sunday afternoon/evening and then again on Tuesday. Winds may be erratic near these, but at the moment, strong or severe thunderstorms are not expected. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Jablonski LONG TERM...JTP AVIATION...07 MARINE...JTP