995 FXUS63 KMQT 100820 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 420 AM EDT Wed Oct 10 2018 .SHORT TERM...(This evening through Wednesday night) Issued at 313 PM EDT TUE OCT 9 2018 ...Periods of heavy rain could result in flooding... Primary concern for tonight through late tomorrow will be the copious amounts of rain forecast to come into the Upper Peninsula of Michigan. Atmospheric moisture content (PWATs) has been far exceeding climatological norms for early to mid October, and near/greater than the daily max (from the GRB upper-air site). This well-advertised event continues to remain on track for this forecast issuance, with refinements made to QPF amounts. Locations within the Flood Watch continue to be where the heaviest precip axis is slated to occur tonight, with an additional 2 to 3+ inches expected, on top of what has already fallen. The eastern half of the U.P. has seen a break from the precip, as well as some locations in the central and western portions. However, radar imagery has been depicting the rain to be filling back in area-wide, with much more developing and on the way ahead of an approaching low. Ample moisture transport aligned with convergence zone overhead, and a boost for lifting from the deepening low and its attendant trough axis, all coupled with continuing WAA and a hint of instability is setting the stage for efficient rain to fall tonight. As mentioned yesterday, there is a secondary concern for trees to potentially come down, given how saturated the grounds are with all of the recent rain, and more to come. Locations along the shorelines of western Lake Superior into the Keweenaw Peninsula should be aware of the possibility of any stronger wind gusts moving in tonight/tomorrow having the potential to unset trees with weakened roots. Winds will be on the increase, particularly across the Lake Superior waters, but winds on land will also be on the increase. Although no headlines are anticipated at this time since winds are forecast to remain below the criteria for a Wind Advisory, the nearshore locations, particularly along the tip of the Keweenaw, could experience higher gusts as compared to locations further inland. The increased wind threat will shift to the eastern shorelines tomorrow night into Thursday. In spite of ample WAA aloft, the cloud cover and rain has moderated temps quite a bit, forcing a lack of too much movement between the highs and lows for most of the U.P. The warmest locations have, and will continue to be through tomorrow, the south-central and eastern half of Upper Michigan where there has been some breaks in the cloud cover and rain. Lows tonight will range in the 40s to lower 50s, with highs tomorrow remaining in the 40s for many locations across the west, but rising into the 60s where warmer air is able to advect and mix down in the south and east. Cooler temps arrive tomorrow night with the passage of a cold front, ranging from the 30s to 40s. .LONG TERM...(Thursday through Tuesday) Issued at 419 AM EDT WED OCT 10 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 point toward some broadening and slight progression of the ridge during next week. This will force a mean Rockies to central N America trof to drift e to eastern N America as next week progresses. In the end, 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. In the meantime, the pattern will continue to provide frequent opportunities of pcpn. Current amplified western CONUS trof/eastern CONUS ridge configuration will support mdt/hvy pcpn amounts thru today until the main shortwave currently lifting out across the Plains shifts thru the Upper Lakes tonight/early Thu. Thereafter, periodic pcpn events associated with a series of shortwaves progressing thru the mean trof will be much lighter for the remainder of this 7 day fcst. As for temps, solidly blo normal temps will prevail late week thru much of next week as mean troffing gradually shifts e, placing the Upper Lakes under chilly nw flow. Trends from the last 24hrs of operational medium range models/ensembles suggest the ridge drifting into western N America and the downstream trof over eastern N America may be a bit more amplified than suggested 24hrs ago. This would support cooler conditions, blo normal temps, persisting thru all of next week, though there still should be a tendency for some moderation at the end of the week. Beginning Thu, sfc low pressure will be over ne Lake Superior at 12z and will track to near James Bay by late aftn. Will be blustery and turning colder in the wake of the low under steady caa which drops 850mb temps from -4C w/2C e at 12z to -5 to -7C across the board by 00z. As a result, temps over the higher terrain of the w and n central will likely not get out of the 30s during the daylight hrs while temps e and s central fall to the lwr 40s. Under cyclonic flow, caa and deep moisture to 12-15kft, lake enhanced showers will already be ongoing into western Upper MI under wnw flow to start the day and will expand quickly eastward. With wetbulb zero heights falling blo 700ft, expect some shsn along with the shra over the w. May see some graupel as well, typical of earlier season lake effect. Pres rises are not particularly notable and will already be over the fcst area during the morning, so not really expecting an isallobaric enhancement to the post-frontal winds Thu. Given potential mixed layer winds, may see some 35-40mph gusts over the Keweenaw and along the lake from around Munising eastward. So, at this point, not anticipating that a wind advy will be needed Thu. Deeper moisture doesn't begin to depart until later Thu night/Fri morning. With 850mb temps of -6 to -8C and Lake Superior water temps running mostly 6-8C and locally up to 10C or so, wnw/nw flow sct lake effect showers will continue Thu night, and ptype will transition to just snow as wetbulb zero heights fall blo 700ft, except in areas exposed to the moderating influence of a long fetch across the lake. In those locations, expect a mix. Some light accumulations of snow (inch or less) will probably occur, mainly over the higher terrain. A weak shortwave passes on Fri, but fcst soundings show no real response in moisture depth. Nonetheless, the weak forcing overtop adequate instability over the lake (850mb temps around -7C) should continue to support some light w to nw flow lake effect showers on Fri. Will be another chilly day with w and n central not getting out of the 30s. Low to mid 40s expected elsewhere. A few lake effect showers may linger into Fri night, but drying air mass and the start of waa ahead of the next shortwave dropping into the Dakotas should spell an end to any pcpn. There is slight improvement in medium range guidance with regard to shortwave timing and amplitude early next week. A slightly faster trend is noted with the first shortwave arriving this weekend. While most of the area should still remain dry on Sat, waa/isentropic ascent ahead of the first wave may bring some -shra into the western fcst area in the aftn. Sat will be a warmer day though still blo normal. High temps will be in the 40s. Isold to sct -shra will acccompany the shortwave across the area Sat night with a trailing stronger shortwave arriving Sun. Given 850mb temps of -4C or lower, could see a short period of decent lake enhanced pcpn as this wave passes. If boundary layer is cold enough during the day, some minor wet snow accumulation would occur over the w. LES with a mix closer to shore will then follow into Sun night under 850mb temps falling toward -8C. At least one more shortwave will move across the area in the Mon-Wed time frame, probably on Tue, bringing an increase in sct shra. Otherwise, air mass will likely be cold enough for much of this time to support some isold/sct lake effect -shra/-shsn. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 141 AM EDT WED OCT 10 2018 Conditions are expected to deteriorate again overnight as abundant low level moisture north of a frontal boundary and low pressure system will support mainly LIFR conditions through the forecast period along with periods of rain. There may be brief periods where conditions drop below minimums at KSAW but any periods should be brief during intervals between areas of rain. Gusty northeast winds will also persist as the low approaches but diminish and become light at KSAW as the low center moves into Upper Michigan Wednesday evening. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 305 PM EDT TUE OCT 9 2018 Winds will pick up substantially tonight into tomorrow, with the western half of Lake Superior seeing the highest winds tonight, followed by the east half on Thursday. This is due to the approach and passage of a deepening low pressure system that will be crossing the Upper Great Lakes. These periods of increased winds through tomorrow evening have been highlighted in a Gale Warning, with an additional warning possible for the east half on Thursday. Sustained winds out of the NE tonight will start out in the 20-30 knot range, then increase to near/above 34 knots for the western half tomorrow. Gusts will approach 45 knots, with brief, localized gusts exceeding storm force possible. Greater than gale force gusts will persist into tomorrow night, with the focus shifting to the eastern half by Thursday, as mentioned. As the low passes across, expect the winds to swing around to out of the NW by Thursday. Winds will likely remain elevated into early Friday, before the pressure gradient slackens over the region. Look for less than 20 knot winds to prevail through the weekend. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Flood Watch through this evening for MIZ001>006-009>013-084. Lake Superior... Gale Watch from Thursday morning through Thursday evening for LSZ266-267. Gale Warning until 5 PM EDT this afternoon for LSZ266. Storm Warning until 5 PM EDT /4 PM CDT/ this afternoon for LSZ162. Gale Warning from 5 PM EDT /4 PM CDT/ this afternoon to 1 AM EDT /midnight CDT/ Thursday for LSZ162. Gale Warning until 1 AM EDT Thursday for LSZ263-264. Gale Watch from Thursday morning through Thursday evening for LSZ265. Lake Michigan... None. && $$ SHORT TERM...lg LONG TERM...Rolfson AVIATION...JLB MARINE...lg