176 FXUS63 KMQT 310808 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 408 AM EDT Mon Jul 31 2023 .UPDATE... Issued at 724 PM EDT SUN JUL 30 2023 The forecast remains on track tonight. Diurnal cumulus streets continue to diminish this evening, and skies should be clear across most of the UP overnight. The exception will be in the eastern UP, as patchy cloud cover from upstream convection is expected to move southeast across Superior tonight. A few showers may even reach the far eastern UP into the pre-dawn hours. Temperatures hover in the lower to mid 70s still, but should be able to quickly fall back through the 60s and 50s after sunset with another cool night ahead. && .SHORT TERM...(This evening and overnight) Issued at 138 PM EDT SUN JUL 30 2023 GOES Water Vapor and RAP analysis highlight well the ridge/trough pattern across CONUS today. Within this flow, Upper Michigan has been under the influence of surface ridging and northwest flow aloft. This has supported a cloudy period around mid-day thanks to a shortwave dropping southeast through the forecast area. Behind the wave, diurnally driven strato-cu has developed. Daytime highs have warmed mostly into the 70s across the region, and diurnal mixing has supported minimum RH values in the region dipping into the 40s and in some places, the high 30s. Expecting skies to trend toward clear in the evening as we loose the daytime heating. With the main synoptic drivers and dry air still in place, expecting a cool night with lows in the upper 40s and 50s in interior locations and upper 50s to near 60F by the lakeshores. A stretched out PV streamer tied up in northwest flow aloft may be able to support a stray shower or two by morning near Copper Harbor and east of Munising, but confidence is low. .LONG TERM...(Tonight through Sunday) Issued at 406 AM EDT MON JUL 31 2023 Generally near- to above-normal temperatures and precipitation are favored throughout the long term forecast period. The best potential for strong to severe thunderstorms remains in the Wednesday afternoon thru Thursday evening time frame. Friday and Saturday look mostly dry and pleasant, but another period of unsettled weather appears to be increasingly likely for next Sunday-Monday. Starting with tonight, a ~1022 mb surface ridge shifts east across Upper Michigan with it lingering across the east half thru Tuesday morning. Interior east locations are likely to cool well into the 40s by sunrise on Tuesday whereas more western locations may reach their lows earlier in the night then slowly warm during the early morning. Patchy fog is possible for the coolest spots. Sunny skies save for hazy/smoky skies should allow temps to warm to around 80F by Tuesday afternoon. Surface winds become southerly but remain light allowing for lake breeze development. Southerly winds push the Lake MI boundary across most of the UP whereas the Lake Superior boundary struggles to move inland. HREF means indicate 500-750 J/kg SBCAPE in the vicinity of these lake breezes that should be adequate for isolated (~30%) diurnal shower development with a few (10-15%) embedded thunderstorms possible. HREF guidance shows precip chances increasing mainly across the central UP between 18-21z Tuesday afternoon before diminishing as sunset approaches. While it is very unlikely at this time, bulk shear values are supportive of organized thunderstorms if higher CAPE solutions (e.g. NAM 3km) materialize. Warm air advection associated with a weak low level jet Tuesday night should keep temps around 60F or 10-15F warmer than Monday night. A disturbance tracking into Ontario should allow for some PoPs Tuesday night, mainly across Lake Superior. Forecaster confidence diminishes for the Wednesday-Thursday time frame, but the synoptic scale pattern appears favorable for at least one round of strong to severe thunderstorms. At this time, chances should be higher across the west half on Wednesday and across the east half on Thursday. Mean surface to 500 mb bulk shear values on 00z EPS guidance are generally 25-30 knots for Wednesday and 35+ knots for Thursday implying a greater severe threat on Thursday. However, cold front timing differences continue to plague various model solutions and it's possible that better shear on Thursday may not align with sufficient instability. A noticeably cooler/drier air mass moves in behind the cold front leading to a pleasant Friday and Saturday before the next system approaches. By Saturday morning, 00z EPS guidance shows a surface low across the Dakotas that tracks over MN on Saturday, the Upper Great Lakes on Sunday, then Quebec by Monday night. While it's too early to assess potential impacts of this system, roughly 10% of EPS ensemble members produce over an inch of rain during the Sunday- Monday time frame. Additionally, potential for a sub-1000 mb surface low implies blustery conditions. Finally, this system appears to carve out a longwave trough across the Great Lakes region that may result in a prolonged period of active weather. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 110 AM EDT MON JUL 31 2023 VFR conditions prevail through the forecast period, with just some midlevel cloud cover around CMX and possibly SAW tonight, and high- level smoke from upstream wildfires leading to filtered sunshine for Monday. Some hit and miss sprinkles or showers cannot be ruled out at CMX tonight, but no real impacts are expected. Light and variable winds tonight will come in from the west/northwest for Monday, peaking at around 5 to 10 knots. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 406 AM EDT MON JUL 31 2023 Winds should generally be less than 20 kt for most of the forecast period. A low level jet Tuesday night brings the potential for south- southwesterly gusts around 20-25 kt over the higher platforms of the eastern lake that continues into Wednesday. A cold front Wednesday night or Thursday shifts winds northwesterly with gusts around 20 kt behind the front. Thunderstorm chances shift from west to east across the lake late Tuesday night through Wednesday night with chances lingering over the eastern half on Thursday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ UPDATE...LC SHORT TERM...JTP LONG TERM...EK AVIATION...LC MARINE...EK