Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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520 FXUS63 KMQT 040856 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 456 AM EDT Sat May 4 2024 .KEY MESSAGES... -Rain overspreading the UP from west to east today as a low pressure system approaches from the central Plains. -The UP remains under the preferred path for low pressure systems, with multiple notable features passing through the next week. -In between systems, dry conditions will be expected, though mostly low winds and antecedent rainfall should broadly limit fire concerns. && .SHORT TERM /TODAY/... Issued at 454 AM EDT Sat May 4 2024 Increasing clouds continue to stream into western portions of Upper Michigan early this morning per latest water vapor imagery. As a low pressure system continues its northeastward propagation toward the UP from the central Plains, that cloud cover will continue to overspread the eastern half of the forecast area as well today. And, an uptick in isentropic ascent will commence over the western counties by mid-morning as well, resulting in 30-50% rain chances by Sat 15Z in the Ironwood area. Just like the cloud cover, these rain showers will make their way eastward through the morning and afternoon hours with increasing rain probabilities over much of Upper Michigan by late afternoon. Nonetheless, the eastern third of the UP should have enough time to warm into the low 70s, unlike the western third which will struggle to reach 60 degrees with earlier onset of rain. Currently, temperatures across the area are ranging from the upper 30s across the interior to as high as the upper 40s to mid 50s along the Lake Superior lakeshore. && .LONG TERM /TONIGHT THROUGH FRIDAY/... Issued at 436 AM EDT Sat May 4 2024 Starting tonight, a broad trough will expand over the Upper Midwest and central Canada with a ridge over the eastern U.S. coast and a closed low over the western U.S. coast. A shortwave riding the middle trough will be progressing eastward over the U.P. with another shortwave not long behind it over Manitoba. The associated cold front finish progressing east across the U.P. by Sunday morning, bringing a line of showers eastward as well as a brief period of northeast gusts to 20-25 mph; a few rumbles of thunder are possible mainly earlier in the period. Lows overnight are expected in the mid 30s to mid 40s, warmest east where the cloud cover is expected to hold on the longest. The second shortwave passes just north of Lake Superior on Sunday, but no precip is expected as sfc high pressure builds in over the Upper Great Lakes. This should see cloud cover diminish, light winds, and highs in the mid 50s to mid 60s; warmest south central. Mixing increasing in the afternoon, stronger over the interior west, will bring RHs down around 40% in the east/Keweenaw with near 30-35% in the interior west. No fire weather concerns are expected at this time. With mid level ridging moving east over the Great Lakes and high pressure shifting to expand over the entire basin, the quiet weather continues with lows in the mid 30s to low 40s. Meanwhile, the closed low will have made it onshore and moved east over the Rockies, beginning to open up into a trough and take on a negative tilt. By Monday morning, the trough will be situated just over the lee side of the Rockies. High pressure means another dry day with better mixing up to ~850 mb. Stronger winds mixing down from aloft are not going to be an issue, but lower dew points will be. Minimum RHs are expected around 30-35% in the afternoon/evening hours. With highs in the upper 50s to low 70s, cooler by the lakeshores, we flirt with borderline elevated fire weather conditions. Will want to monitor these conditions in future forecast packages. The trough is expected to pivot northeast over the Plains through Monday night supporting sfc low cyclogenesis, but the U.P. stays dry yet. Monday night will be warmer than the previous night with temps only settling into the 40s, warmer in the west as clouds increase ahead of the next system. Chances for showers increase in the far west on Tuesday with increasing q-vector convergence, but likely will hold off until late morning/early afternoon when the trough begins to develop back into a closed low over the northern Plains. PVA over our region increases at this point into Wednesday morning as a shortwave cycles around the low, eventually passing northeast over the Upper Great Lakes. An approaching left exit region of the upper level jet also looks to support additional cyclogenesis over the Central Plains Tuesday night. This second sfc low then lifts northeast on Tuesday, crossing northeast over the Great Lakes Tuesday night resulting in an uptick in PoPs Wednesday night. Meanwhile, the stronger sfc low associated with the mid level low will spin over the Northern Plains. With the given spread in the guidance, opted to leave the NBM PoPs Tuesday onward. There is a chance for thunderstorms on Tuesday and Wednesday, but confidence remains low at this point given the spotty instability noted in the guidance; best chances are on Tuesday when the mid level lapse rates and bulk shear are higher. Slight chances for showers gradually diminish through the end of the work week as we begin to see a pattern shift. Longer range ensemble guidance hints at positive 500 mb height anomalies over the western U.S. with negative height anomalies moving toward the east coast toward the latter part of May. This means less moisture from the Gulf of Mexico to support precip chances and cooler northwest flow over the Great Lakes. The drier trend is captured well by CPC precip outlooks out to 3-4 weeks with a cooler pattern more within the next 8-14 days. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 128 AM EDT Sat May 4 2024 VFR conditions continue into Sat morning as weak ridging continues to affect the area. Starting late tonight, another low pressure over the Central Plains lifts northeastward towards the Upper Midwest and brings more rainfall to the west as soon as Saturday afternoon. This incoming rainfall will bring MVFR and possibly lower conditions to across KIWD, MCMX and KSAW by the end of the TAF period. && .MARINE... Issued at 436 AM EDT Sat May 4 2024 Southwest winds this morning become northwest mid morning over the west half of Lake Superior as a weak low pressure lifts northeast into the region. Winds across the rest of the lake turn northeast behind a cold front this evening as the low lifts northeast into northern Ontario. The eastern portions of Lake Superior could briefly see some northwest wind gusts up to 25 kt tonight into Sunday morning. As high pressure settles over the lake Sunday and Monday, winds will be below 20 kt until Monday afternoon. A strong low pressure system over the Northern Great Plains will cause gusty northeasterly winds to funnel towards Duluth Harbor to around 20-25 kts monday afternoon into Monday night. Meanwhile, a second weaker low pressure develops over the Central Plains, lifting northeast toward the Upper Great Lakes on Tuesday. The track and timing of this secondary low is still not totally solid, but east winds to 20-30 kts are likely Tuesday into Tuesday evening as it moves through the Great Lakes Basin. Probability of Gales remains low at this time. (<20% chance of winds exceeding 34 kts). Winds look to hold around 15-25 kts through the rest of the work week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TDUD LONG TERM...Jablonski AVIATION...07 MARINE...Jablonski