610 FXUS63 KMQT 092109 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 509 PM EDT Sat Apr 9 2022 .SHORT TERM...(This evening through Sunday) Issued at 333 PM EDT SAT APR 9 2022 A high amplitude ridge is creating an area of subsidence over Upper Michigan this afternoon and resulting in clearing skies across the western and central parts of the UP so far. Satellite imagery shows this clearing now beginning in south-central areas, and more slowly towards the east. Much of the region will have clear skies by late evening. Temperatures are expected to drop off tonight, mainly in the interior regions, from the combination of the recent light to moderate snowfall, lower surface dewpoints and generally fair winds under passing surface high pressure. Dewpoints could hold on in southern Schoolcraft and southern/eastern Luce counties overnight and result in some patchy fog formation by early Sunday morning so this wx type was added to the grids over a few hour period early tomorrow. Elsewhere, the MinT forecast relied more on a bias-correction blended back to the previous forecast to result in the areas of low to mid-teens in those interior spots of the UP. Southeasterly winds will increase tomorrow morning across the central and western UP. Some gusts up to 20 mph are likely for Sunday afternoon. There is a bit uncertainty in the MaxT's for tomorrow afternoon in Ontonogan, southern Houghton and eastern Baraga counties from increasing sky cover through the day, so future edits may be necessary and will be monitored. At this point though, mid-fifties are in the grids for localized areas of south-central and western Upper Michigan. These southeasterly winds are the result of an area of low pressure moving into southern MN and western WI by Sunday evening. Chances for precip across the region spread from west to east beginning later Sunday for anyone traveling back home after a weekend away. .LONG TERM...(Sunday night through Saturday) Issued at 508 PM EDT SAT APR 9 2022 During the upcoming week, pattern over N America will feature an amplifying western trof early in the week, moving to the central U.S. midweek and then drifting e late week as it weakens. Ahead of the amplifying trof, a vigorous shortwave tracking from the central Rockies tonight to Upper MI/Lake Superior and northern Ontario on Mon will produce some shra across the area Sun night/early Mon. GFS was the first to catch on to the stronger solution for this wave. A minor wave could produce some light pcpn late Mon aftn/night, but attention will be turning to the amplifying western trof which will go on to produce a unusually deep central U.S. system for the midweek period. Across Upper MI, the late Tue to early Thu period will probably feature frequent shra and at least some mdt rainfall at times as deepening low sends associated warm front n toward Upper MI with cold front or occluded front passing on Thu. GFS and its ensembles continue to represent a more progressive solution with the ECWMF/CMC and their ensembles continuing to represent a deeper (unusually deep for this time of year), slower solution, a solution that will be favored. The CMC/ECMWF ensemble means both show very impressive 500mb height anomalies of 330-350m over MN on Thu. As this system then slowly unwinds and drifts eastward, Upper MI will continue to be affected with at least some sct pcpn thru Fri and maybe Sat as well. There are indications that another shortwave will drop into the central U.S. and possibly spin up another low pres system somewhere in the Mississippi Valley/Ohio Valley/Great Lakes region over the weekend/early in the following week, but as would be expected at such a long time range into the model runs, there is vast spread in solutions for that possibility. As for temps, despite the strength of the wave passing on Mon, it will not bring significant cooling due to the amplifying western trof working to force rising heights downstream. As a result, expect temps around normal on Mon rising to above normal thru midweek in advance of the developing deep central U.S. system. Temps late week will fall back to blo normal under the weakening mid-level trof moving to the Great Lakes. Looking farther ahead for the week of Apr 17th, the last several days of CFSv2 means have had a strong signal for blo normal temps during that week due to Great Lakes troffing. Beginning Sun night/Mon, shortwave moving across the central Rockies tonight will take on a negative tilt as it swings across western Lake Superior/Upper MI into northern Ontario late Sun night/Mon. Associated sfc low organizing over the Central Plains on Sun will lift ne, likely tracking across far western Lake Superior early Mon. There is some question about whether moisture return will be sufficient, but given the vigorous deep layer forcing indicated by q- vectors, expect at least sct -shra development during Sun night. There is small chc that there could be a little snow mixed in over the nw fcst area due to evaporative cooling. Some light rain may linger across the w and n into Mon morning under cyclonic flow in the wake of the low. During the late aftn/evening, trailing minor shortwave and a little instability may yield isold -shra spreading out of MN/nw WI into western Upper MI. The wave passing late Sun night/Mon has the signature of being a high wind producer as it swings negative tilt across the area. Although the isallobaric wind component, owing to a healthy 5 to 7mb/3hr pres rise and 5 to 7mb/3hr pres fall, will largely pass before much daytime heating occurs, it will be favorably aligned with the gradient wind to give winds a boost. Strong caa will be an important missing factor, and the cold lake waters will further inhibit efficient mixing over the Great Lakes. That said, isallobaric wind component, caa and increasing daytime heating as clouds scatter out will lead to increasing mixing over the land to support gusts to around 30mph and possibly up to 40mph at times in some areas during the morning to mid aftn. Keweenaw will see strongest winds as winds veer to a more favorable westerly direction for that area. High wind advy criteria (gusts to at 45mph) may be met there. If mixing is better than currently anticipated, gusts will exceed 50mph for a time. High temps Mon should range from the lwr 40s Keweenaw to mid 50s F s central. If there are any shra Mon evening, those will exit/dissipate overnight. Tue should mostly be a dry day, but expect increasing clouds as waa regime well ahead of the amplified western trof spreads ne. In addition, upper diffluence will overspread the area due to right entrance of 140tk upper jet extending from northern Ontario to southern New England. Rain may spread out of WI into Upper MI late in the day. Much of the area will see highs in the 50s on Tue, but temps will be quite a bit lwr where developing se winds have at least a component across the Great Lakes. Expect periods of shra Tue night thru early Thu, and it will be breezy right thru the day on Thu. Main pcpn push Tue night/Wed morning will be driven by strong waa/isentropic ascent/upper diffluence. Wouldn't be surprised if some thunder occurs with this round of pcpn as there will be some CAPE for parcels lifted from near the top of sfc based stable layer. While some shra will continue Wed, next more substantial round of pcpn will likely occur in association with passing occluded front Wed night/early Thu. Could be some thunder again. Sct shra will then be the rule Thu into Fri under deep cyclonic flow and cold pool. These -shra will mix with and probably change to all snow Thu night/Fri as 850mb temps fall to around -10C. Pcpn may linger into Sat, depending on how quickly the trof moves across the Great Lakes region. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 145 PM EDT SAT APR 9 2022 MVFR cigs have cleared at KSAW over the last hour with VFR conditions expected through this forecast period. Gusty north- northwesterly winds at KCMX and KSAW will decrease this evening ahead of a low pressure moving into Wisconsin overnight and then Minnesota by daybreak Sunday. Southeasterly winds up to 10 knots develop late this evening at KIWD and persist through tomorrow, with southeasterly winds building in the morning hours at KSAW and KCMX. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 508 PM EDT SAT APR 9 2022 Winds across Lake Superior will fall off to blo 15kt tonight as a high pres ridge moves to Lake Superior. As the ridge departs on Sun and low pres organizes over the Central Plains, easterly winds will be on the increase, up to 15-25kt by evening across w and central Lake Superior. Winds will increase further Sun night as the low approaches western Lake Superior. Stability over the chilly lake waters should work to hold winds back from their potential, but still expect se gales up to 40kt to develop over the e half of Lake Superior, extending to as far w as around Isle Royale. The low pres will then pass across far western Lake Superior Mon morning. System looks typical of one that produces high winds as the low lifts by the area, but stability will again be a factor that could limit winds from reaching their potential. Stability will be offset to some degree by incoming pres rises of 5-7mb/3hr. Result should be a period of wsw gales of 35-40kt across a wide swath of the lake on Mon, except far w and far e. Wind direction and the pres rise will favor the area just w and n of the Keweenaw Peninsula for strongest winds. While fcst currently reflects winds up to 40kt for that area, there is some potential that winds could gust to 45-50kt for a 2-4hr period just ahead of the incoming pres rise max. Winds will quickly diminish mid to late aftn with winds falling to blo 20kt by late Mon evening. Passing high pres ridge on Tue will lead to winds under 15kt. Winds will then increase as a deep low pres lifts from the western Plains Tue evening to the Upper Mississippi Valley for Wed/Thu. Winds of 20-30kt will be common during this period, and there will probably end up being a period of easterly gales for at least portions of Lake Superior at some point Wed into early Thu. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Watch from late Sunday night through Monday morning for LSZ267. Gale Watch from late Sunday night through Monday afternoon for LSZ264-266. Gale Watch from Monday morning through Monday afternoon for LSZ241>248-263-265. Lake Michigan... None. && $$ SHORT TERM...NLy LONG TERM...Rolfson AVIATION...NLy MARINE...Rolfson