FXUS63 KMQT 090830 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 330 AM EST Sat Dec 9 2023 .SHORT TERM...(Today and tonight) Issued at 330 AM EST SAT DEC 9 2023 Key Messages: - Rain spreads north across Upper MI this morning, except possibly the far west around Ironwood, then mostly lifts out of the area during the afternoon. - The rain may mix with or change to sloppy, wet snow over portions of the west half of Upper MI, but accumulations will be minimal, under 1 inch. - Another area of rain and snow will move into western Upper Michigan this afternoon, spreading e through tonight as the precipitation transitions to all snow. - 1 to 4 inches of wet snow accumulation expected west and north tonight, greatest high terrain of the west. Water vapor imagery and RAP analysis shows mid-level troffing over the Plains and Rockies early this morning. A well-defined wave was over western MN. Another wave is lifting ne into northern IL, and this will be the main feature of interest for today. The wave over MN will be of interest for tonight. With the southern wave, an expanding area of rain is currently developing/spreading out of eastern IA/northern IL into WI. Closer to home, it's been a quiet, unseasonably warm night for early Dec. Temps across Upper MI are currently in the mid 30s to lwr 40s F, several degrees above normal max temps for this time of year, but a few spots in Delta County have fallen to around 30F. Some fog, locally dense, is noted closer to Lake MI. Shortwave currently lifting into northern IL will quickly head nne into northern Ontario, to the n of Georgian Bay, by evening. As it does, vigorous forcing/12hr 500mb height falls of around 140m combined with anomalous precipitable water increasing to 200-250pct of normal will support rain spreading nne across the fcst area this morning. Only far western Upper MI around Ironwood may escape being affected by the rain associated with this wave. Although the sfc low will track nne across eastern Upper MI and despite it being Dec, the mild antecedent conditions across the area, including dwpts in the mid 30s F, will make it difficult for rain to switch over to accumulating snow in the western portion of the pcpn shield. In addition, since the wave is not phasing with the MN wave, cooling will not arrive soon enough to ensure a quick change to snow. Fcst will reflect a mix of rain/snow roughly w of an Iron Mtn to Marquette line, but since temps/dwpts won't likely be lwr than the mid 30s F during the pcpn, little if any snow accumulation will occur (under 1 inch), and no travel impacts are expected. Rainfall amounts over most of the e half of the fcst area will be at least one-half inch in general, and possibly up to 0.75 inches or so. Pcpn associated with the wave will lift out to the ne of the area in the aftn. However, the MN shortwave will shift to WI late aftn/evening, and this will support additional pcpn developing/spreading into Upper MI from the w. A weak sfc trof will also develop wsw from the departing sfc low and ahead of a cold front that will sweep se across the area this evening thru the early overnight period. Both of these features will further aid the second round of pcpn development. 850mb temps over western Lake Superior falling to -4C by evening and to around -8C by midnight will also add an increasing lake enhanced component to the pcpn. Initially as this next area of pcpn develops into western Upper MI, wetbulb zero heights will range upwards to as high as 1400ft agl. So pcpn over the w will begin as mix of rain/snow, more rain than snow closer to Lake Superior and more snow than rain in the high terrain. A transition to all snow will occur from w to e tonight as the pcpn spreads across the entire area. Fcst soundings continue to show bulk of upward motion blo the DGZ, and that combined with temps around freezing during best forcing will hold snow accumulations down. SLRs should be down on the order 10-13 to 1. Overall, expect 1 to 4 inches of snow accumulation tonight across the w and n, greatest in the high terrain of western Upper MI. A few spots may top out around 5 inches from the Porcupine Mtns to Ironwood and also in a small area of the high terrain around Herman in ne Baraga County. Will issue a winter wx advy for Gogebic County given the expectation of exceeding the 3in/12hr snowfall threshold for low SLR snow. Will let dayshift reevaluate whether greater coverage of 3+ inch snow accumulations will occur tonight over western Upper MI, warranting expansion of advy. .LONG TERM...(Sunday through Friday) Issued at 319 AM EST SAT DEC 9 2023 Key messages: - Light northwest wind lake effect ends west to east through day Sunday. - Next shortwave/cold front bring gusty west winds especially Lake Superior/Keweenaw late Monday night/Tuesday. - Other than near normal temperatures Sunday and Tuesday, above normal temperatures will continue through the upcoming week peaking out at 20+ degrees above normal Thursday and Friday. -No widespread, significant system snowfalls across Upper MI over the next 10 days. As shortwave exits south and east of the area early Sunday, deeper moisture will quickly depart. 85H temperatures of -10 to -12 will yield some light lake effect but alignment of DGZ and lowering inversion heights will keep accumulations between 1-3 inches mainly east. LES will diminish from west to east through the day. Ridging overhead on Monday will yield a tranquil December day. Next shortwave will dive southeast into northern Ontario and Upper MI later Monday night. WAA/isentropic ascent ahead of this wave should lead to some light snow developing across the north and east Mon night, followed by west northwest flow lake effect for Tuesday as 850mb temps drop to -16C. Dry air mass moving in behind the front and quick moving nature of the trough will keep lake effect in the 1- 3 inch range...mainly east. Tight pressure gradient will lead to gust west winds across the Keweenaw perhaps up to 40 mph making it feel even chillier...especially given how mild its been so far this early winter. Ridging returns midweek with a significant warming trend. 85H temperatures anomalies could approach 30 degrees C above normal across western Ontario Thursday into early Friday before next mostly dry front arrives for the weekend cooling things back down. Record highs for late in the week are in the upper 40s to around 50. Not out of the question, especially if there is any sunshine on Thursday. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1203 AM EST SAT DEC 9 2023 Flight categories will hover around the MVFR/VFR mark early this morning at IWD and CMX. SAW, however, will predominantly be MVFR as a low pressure system approaches Lake Michigan. All TAF sites will deteriorate further though during the Sat 12-14Z time frame as that system moves into the area, spreading snow and then a rain/snow mix across the TAF sites. Flight retrictions will be most impactful at SAW where visibilities and cigs will dip into the LIFR range. Elsewhere, IWD and CMX should hold steady at IFR. Do not expect much improvement though in this TAF period. In addition, winds will increase out of the northwest at IWD and CMX this evening with gusts up to 24 kts. Will not, however, mention any blowing snow at CMX due to the heaviness of this snow. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 319 AM EST SAT DEC 9 2023 A compact area of low pressure lifting northeastward across the eastern Lake could lead to a short duration of some northwesterly gale gusts to 35 knots over the far eastern Lake near Whitefish Point and east late this afternoon. Then a cold front will sweep across Lake Superior this evening with winds shifting to the northwest with a few gale gusts to 35 knots likely especially across the north central part of the Lake. Winds will slowly diminish through the afternoon Sunday as ridging builds in from the west and persist through the day Monday. Another cold front approaching late Mon will cause southwest winds to ramp up to increase to 20-30kt by late afternoon. After the cold front passed late Monday night, west northwest gales between 40-45 knots are likely through much of the day Tuesday. Winds should be 30 knots or less Wednesday before another southwesterly gale is possible Thursday into Friday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory from 5 PM this afternoon to 3 AM CST Sunday for MIZ009. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...MZ AVIATION...TDUD MARINE...MZ