FXUS63 KMQT 301942 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 342 PM EDT Fri Jul 30 2021 .SHORT TERM...(This evening through Saturday) Issued at 342 PM EDT FRI JUL 30 2021 NW flow aloft continues over the Upper Great Lakes between a negative tilt ridge covering much of the western and central CONUS and a trough over Quebec. A short wave embedded within the flow over far northern Ontario and associated cold front is kicking off some showers and thunderstorms. GOES GLM shows all of the lightning still back in Manitoba right now; the showers that are approaching Thunder Bay are just plain rain for now. Tonight, initially clear skies will become cloudy with the approach of this front. Showers should reach the Keweenaw by around 02-04z, but everywhere else they'll hold off until well after midnight. Models show a packet of elevated instability advecting in from the west late tonight ahead of the front with an enhancement i the westerly low- to mid-level flow. If that materializes, there could be some rumbles of thunder, but overall MUCAPE values look unimpressive. Therefore, have capped thunder chances at slight chance for tonight. The increased cloud cover will lead to warmer lows tonight than last night by 10 degrees or more, especially in the downslope areas where a southwesterly breeze will be maintained through the night. Tomorrow, the front hangs up over the area, becoming west-to-east oriented and perhaps enhanced by the lake breeze. It's hard to tell whether the convergence signal is from the lake breeze, the cold front, or a secondary surface trough, but whatever it is the signal is definitely there in all of the guidance. The question will be how quickly the convergence zone drops southward out of the area. If it holds up like in the slower NAM solution, could see up to 1000 J/kg of MLCAPE build which along with low-level lapse rates of around 7-8 C/km and effective shear vectors around 25-30 kts could support some marginally organized, locally gusty showers and storms. However most of the CAMs are more bearish, particularly the WRF-ARW, NSSL-WRF, and CMC Hi-res. In addition, there will be a second area of showers/storms farther north and later in the day forced by dCVA out ahead of a more potent short wave dropping southeastward through the mid-level flow. This wave is expected to be near Thunder Bay by around 00z tomorrow evening, so that batch of showers and storms should remain over western Lake Superior, perhaps just clipping the Keweenaw by late afternoon. Look for highs in the mid to upper 70s across the area. .LONG TERM...(Saturday through Thursday) Issued at 356 AM EDT FRI JUL 30 2021 Amplifying trough rotating down from Ontario at the start of this forecast period will allow for showers and thunderstorms to be possible this weekend. Given the lack of defining features for the precip to follow/latch onto, difficult at this time to pinpoint locations that will actually receive rain, forcing to take a bit more of a broad-brush approach with PoPs. So, although there are PoPs nearly everywhere Saturday into Saturday night, not all will get the rain as these chances will be more hit-and-miss in nature. As for thunder chances, they will exist given the availability of sufficient instability, but latest indications are that these storms shouldn't end up being severe as other parameters are lacking. Just enough shear in the area at the time could make storms a bit pulsy, but again, looking to remain below severe criteria. Once that trough loses its impact over Upper Michigan later in the weekend, it will yield the opportunity for surface high pressure to briefly build in. Therefore, expect generally subdued, dry weather by the second half of Sunday through much of Monday for nearly everyone. The next chance of rain arrives Tuesday due to another trough scooting by, but with this one even weaker-looking and further east compared to the previous one, chances are on the lower-end. The back-and-forth of precip chances and dry weather yet again emerges mid-week, although what previously looked like models agreed on the reasoning (upper ridging moving in) seems to have broken down in agreement for these latest runs. Stuck with the dry weather period Wednesday into early Thursday with perhaps some precip starting to shift back in late Thursday into Friday. Temperatures through the period will waffle on either side of normal for this time of year, with the coolest day occurring Sunday (highs topping out in the 60s to low 70s) but then a warming trend next week, culminating in the warmest day looking to occur on Thursday (highs well into the 80s). Lows will respond accordingly with the coolest night occurring Sunday night into Monday morning. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 129 PM EDT FRI JUL 30 2021 VFR conditions are expected this TAF period. High pressure over Wisconsin with just fairweather cu this afternoon will give way to a mid-level ceiling building in from the north late tonight/early Saturday with an approaching cold front. There will be showers with the front as well, mainly at CMX and SAW. Could be an isolated/embedded weak thunderstorm, but not enough to warrant a mention in the TAF at this point. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 342 PM EDT FRI JUL 30 2021 Winds are expected to remain light (generally 15 kts or less) tonight and tomorrow as they veer from southerly to westerly to NW with the passage of a cold front. Saturday night into Sunday will likely see some 20-25 kt winds northerlies, especially central and east. After that, light winds of 20 kts or less are expected again through at least the middle of next week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...lg AVIATION...RJC MARINE...RJC