133 FXUS63 KMQT 211842 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 242 PM EDT Sat Aug 21 2021 .SHORT TERM...(This evening through Sunday) Issued at 242 PM EDT SAT AUG 21 2021 Water vapor imagery and RAP analysis show a vigorous, well-defined shortwave lifting ne into nw Ontario. Extending southward from the associated 992 mb sfc low is a pre-frontal sfc trough into central Upper Mi with the cold front lagging back into western Lake Superior and nw WI. Ahead of the trough, an area of stratocu is noted over central Upper Mi on visible satellite imagery. A broken/narrow line of convection (shra with some embedded isold thunder) is noted on radar from eastern Lake Superior into western Alger and eastern Delta counties where dewpoints are around 70F and MLCAPEs are noted in the 500-1000 j/kg range. As time goes on this afternoon, the better instability (MLCAPEs up to 1000 j/kg) will continue to get pushed into the eastern counties of the U.P. As a result, have generally confined convective PoPs the rest of the afternoon into the east half counties per latest 18Z HRRR run, which seems to have the best handle on the ongoing convection. Afternoon temps thus far under partly cloudy to cloudy skies have risen into the upper 70s to lower 80s. The vigorous shortwave over southern Manitoba will continue lifting ne, reaching Hudson Bay tonight. With best forcing/height falls shifting ne with it, forcing will be diminishing with the cold front moving across the fcst thru this evening. Expect breezy s winds gusting up to 25-30mph ahead of the cold front, strongest at Grand Marais in downsloping southerly flow. Postfrontal westerly winds will likely gust to around 40mph on the Keweenaw based on potential momentum transfer from mixing off fcst soundings. With incoming pres rises around 4mb/3hr providing an isallobaric wind component aligned with the gradient wind, would not be surprised if some gusts to around 45mph occur at times for a few hrs late afternoon/early evening. The southerly winds up Lake MI in advance of the cold front today will continue to build waves this afternoon so the high swim risk along the Lake MI beaches of Schoolcraft County still looks warranted into this evening. Shower potential will continue over the eastern fcst area this evening until the cold front exits. In the wake of the front, high pres will build toward the Upper Lakes tonight, bringing cooler and drier air into the area. Temps tonight should slip down into the upper 40s over the interior w trending up to around 60F along Lake Superior. Sunday, expect dry, cooler and less humid conditions as sfc high pressure builds in quickly from the west in the wake of the cold front. Max temps will probably be slightly cooler than seasonal normals with highs from the upper 60s/lower 70s north to the mid 70s interior west and south central. The cooler air in combination with dew points falling back into the upper 40s to mid 50s should make for a comfortable day. Waves generated from fairly gusty nw-n winds behind the front will likely warrant a high swim risk for Alger County and probably a moderate swim risk for Marquette County. .LONG TERM...(Sunday through Friday) Issued at 327 AM EDT SAT AUG 21 2021 Through the extended fcst period, models indicate mean troughing over western Canada, and at times over the western CONUS, as a series of shortwaves eject eastward across the northern CONUS and Upper Great Lakes region in a progressive flow through next week. Based on dynamics and available moisture, it looks like the more promising chances for widespread showers would not be until mid to late next week. Temperatures will fluctuate from near to above normal through much of the period. Beginning Saturday night into Sunday, models indicate any remaining showers ending in the evening over the eastern portion of the cwa, then dry, cooler and less humid conditions thereafter into Sunday as sfc high pressure builds in quickly from the west behind Saturday's shortwave/cold front. Min temps Sat night will fall back into the more comfortable 50s for most locations. Sunday's max temps will be closer to seasonal normals with highs in the 70s and dew points in the upper 40s to mid 50s. Waves generated from fairly gusty nw-n winds behind the front will likely warrant a high swim risk for Alger County on Sunday. The next shortwave moving across the Northern Plains on Sunday will weaken as it lifts into northern Ontario by Monday morning. Models show a weaker pcpn signal with this weakening wave compared to the wave on Saturday. Even though GFS soundings indicate MLCAPE values increasing to 500-1000j/kg Mon ahead of the front, warm nose of nearly 17C temps aloft and fairly significant CIN may prohibit convective development on Mon across much of the area. In the end, the better chc of pcpn with this wave looks to be late Sun night/early Mon over the w in association with an approaching, but weakening 30 kt low-level jet. Otherwise, nothing more than low chc/schc pops are warranted late Sun night/Mon. Max temps will rise back into the lower to mid 80s most locations on Monday and Tuesday. Latest models indicating perhaps a better signal for showers/t- storms with the next shortwave due in late Tue into Wed. Trends indicate better shortwave dynamics and stronger WAA/moisture transport ahead of the system. With MUCAPE values approaching 1000- 1500 j/kg and deep layer shear 40-50 knots there certainly could be some strong to marginally severe storms associated with this system. High pressure building in behind this system should result in dry and cooler conditions on Thursday. Models certainly differ on the timing/strength details but there does appear to be a pretty consistent signal that a broader, deeper trough will dig in from the Northern Plains late next week/weekend bringing more opportunities for rainfall. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 135 PM EDT SAT AUG 21 2021 A cold front will sweep across west and central Upper MI this afternoon. Some shra and isold tsra will be possible but it looks like most of that activity now will be east of the terminals, so have taken any mention of shra out of the 18Z TAFs. There will be a brief period of MVFR cigs at KSAW ahead of the fropa early this afternoon. Otherwise, expect VFR conditions to prevail at all terminals in Sunday as drier air moves into the area behind the front. Winds will be gusty today to 20-30kt. Strongest winds will occur at KCMX where wnw winds after fropa will gust perhaps above 35kt later this aftn/early evening. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 242 PM EDT SAT AUG 21 2021 A cold front will sweep across this afternoon and evening. After frontal passage, incoming pres rises from the w will give postfrontal west winds a boost. Until the axis of the pres rises passes, there will be the potential for some gale force gusts to around 35kt for a few hrs late aftn/early evening, particularly at higher obs platforms. The area from just w and n of the Keweenaw Peninsula toward Granite Island/Stannard Rock should be favored for the higher wind gusts. Winds will then diminish to under 20kt from w to e overnight thru Sun morning as high pres arrives. At the moment, it appears winds will remain generally under 20kt Mon thru Wed. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Beach Hazards Statement until 10 PM EDT this evening for MIZ014. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...JAW AVIATION...Voss MARINE...Voss