609 FXUS63 KMQT 110903 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 503 AM EDT Thu Oct 11 2018 .SHORT TERM...(Today and tonight) Issued at 502 AM EDT THU OCT 11 2018 Sfc low passed across central Upper Michigan earlier tonight and is now over eastern Lake Superior btwn STDM4 and the 45006 (eastern Lk Superior buoy) at 08z/4 AM EDT with pressure of 994mb. Drier air in low-levels has wrapped in behind the exiting low, temporarily diminishing pcpn across all but eastern Upper Michigan. Widespread low-mid level moisture on colder side of the low and within upper level trough axis is poised to sweep across Upper Michigan today before exiting into Quebec tonight. Deep moisture and cold air advection resulting in snow over northern MN this morning and we'll see rain/snow changing to snow over western and ncntrl Upper Michigan today. 00z RAOB from INL shows favorable upstream lake effect profile with H85 temps of -7c and deep moisture up to H7/9kft AGL. As this airmass within a cyclonic flow regime behind the sfc low advects across western Lk Superior (water temps on average around 8C, expect to see widespread lake enhanced showers. With wetbulb zero heights falling blo 500 ft, higher terrain areas of west should change to mainly snow by early aftn. Shortwave sliding across into this aftn along with the deeper moisture/cyclonic flow should result in greater intensity to the lake effect with some wet snow accums over higher terrain of far west (Ironwood, Porcupine Mts/Bergland) up to 1 inch. Snow amounts elsewhere over west and north central higher terrain should be just coating as aftn temps will be in the low-mid 30s and precip intensity will be weaker. Will see lake effect develop over east as well this aftn, but sfc temps will only fall to near 40F by aftn so only looking at rain, maybe some graupel in the heavier bands. Otherwise today, will be blustery and turning colder all areas. Strongest wind gusts over 30 mph will be on the Keweenaw/near Lake Superior. Enough over-water instability for lake effect to continue tonight as sfc-H85 delta t/s are 15-16c. However, lake effect should be less enhanced at a weaker intensity as deep moisture pulls out, large scale subsidence moves overhead and low-level flow is less cyclonic. Higher terrain areas in the west and central favored by northwest winds will see the best chances for the lake effect and there may still be some light snow accums (less than 1 inch) over higher terrain of the west as sfc temps fall below freezing. Could also be a stronger lake effect band over Alger/Schoolcraft county, but again marginal temps would result in mainly rain/graupel for those areas. Away from the lake effect may be some partial clearing scntrl toward Menominee county with downsloping wnw winds. Lows temps away from the interior west will be mostly in the mid 30s. .LONG TERM...(Friday through Wednesday) Issued at 402 AM EDT THU OCT 11 2018 Thru the upcoming weekend, a mean ridge will remain over the Gulf of AK, extending n thru AK and far nw Canada at times. Operational medium range guidance and ensemble means are still pointing toward slight progression of the ridge into western Canada during next week. This will force a mean Rockies to central N America trof to shift e to eastern N America as next week progresses, and this will lead to a drier pattern (a trend to blo normal pcpn amounts) taking hold across the Upper Lakes next week under developing nw flow. Although there will still be periodic pcpn episodes associated with a series of shortwaves progressing thru the mean trof during roughly the first half of the week, pcpn amounts associated with each wave will be light. As for temps, solidly blo normal temps will prevail now thru much of next week as mean troffing gradually shifts e, placing the Upper Lakes under chilly nw flow. Over the last few days, medium range models/ensembles have generally suggested that the ridge drifting into western N America will broaden farther downstream, which would allow for some overall warming at the end of the week. Beginning Fri, A weak shortwave is fcst to swing across the Upper Lakes. Despite this, fcst soundings show no real response in inversion/moisture depth on Fri. With inversions around 6kft, 850mb temps of -7/-8C, and Lake Superior water temps roughly 6 to 8C, conditions will be supportive of continued lake effect, and would think the shortwave would provide a slight temporary boost to coverage and perhaps allow showers to spread farther inland than would otherwise occur. On the negative side, curvature of the low- level flow is neutral to slightly anticyclonic. In any event, expect sct -shsn on Fri in the usual areas that see lake effect under wnw winds veering more westerly. In areas exposed to the moderating influence of a long fetch across the lake, ptype will be more of a rain/snow mix. Obviously, it will be a cold day for mid Oct. High temps will only be in the mid 30s w and n central high terrain. Expect upper 30s/lwr 40s elsewhere. Sct lake effect -shsn will linger into Fri night, but drying air mass/lowering inversion/waa ahead of the next shortwave dropping into the Dakotas should spell an end to any pcpn, at least over the w as the night progresses. Shortwave that drops into the Dakotas Fri night will shift to the Upper Lakes by Sat evening. WAA/isentropic ascent and rather vigorous deep layer forcing should support some -shra spreading into western Upper MI during the aftn. Sat will be a warmer day though still blo normal. High temps will be in the 40s. A period of isold to sct -shra will acccompany the shortwave across the area Sat night. A trailing stronger shortwave arrives Sun, but with track of vort max over or just n of Upper MI, main forcing with this wave will pass by to the n. Still, it should provide for some lake enhancement on Sun under 850mb temps of -5 to -7C. If boundary layer is cold enough during the day, some minor wet snow accumulation would occur over the w. LES will then follow into Sun night under 850mb temps falling toward -9C. With a fairly sharp sfc trof sweeping s across the lake with passage of shortwave, there will be an opportunity for a period of somewhat heavier shsn that could provide some minor snow accumulations Sun night. Passage of sfc high pres ridge will bring an end to lingering lake effect from w to e Mon aftn into Mon evening. Medium range models are in quite good agreement with the next shortwave to drop se into the Upper Lakes on Tue, bringing the next round of -shra/-shsn. Sct lake effect will then follow into Wed. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 144 AM EDT THU OCT 11 2018 Lower conditions with the rain and fog will slowly imrpove at all sites through this forecast period. Will be some improvement to MVFR conditions by late Thu morning. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 502 AM EDT THU OCT 11 2018 As low pressure exits eastern Lake Superior, expect winds to become WNW 20-30 kts across Lake Superior today, with gales of 35-40 kts over the east half into this evening. Winds diminish to 15 to 25 knots into Friday morning then relax below 20 knots Friday evening into Saturday morning. Another system crossing Lake Superior later Saturday will result in winds to 30 kts on western Lake Superior Saturday aftn into Saturday night then across all areas on Sunday. Could even see a marginal gale over parts of Lake Superior on Sunday. Winds diminish to 20 kts or less later Sunday night into Monday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning from noon today to 11 PM EDT this evening for LSZ250-251-265>267. Lake Michigan... None. && $$ SHORT TERM...JLA LONG TERM...Rolfson AVIATION...07 MARINE...JLA