FXUS63 KMQT 040537 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 1237 AM EST Wed Dec 4 2024 .KEY MESSAGES... - Quick-hitting clipper arrives tonight, bringing widespread snowfall of 2-4 inches, locally up to 6-8 inches in the east by Wednesday morning. - Gusty southwesterly winds ahead of the cold front to gales of 35 kt over western Lake Superior tonight. - Heavy lake effect snow bands will develop Wednesday for the northwest belts, shifting to the northerly belts Wednesday night into Thursday. The combination of heavy snow and blowing snow will lead to dangerous travel conditions and near-zero visibility in heavy snow bands. Winter Storm Warnings and Winter Weather Advisories have been posted. - Blustery northwest winds, gusting up to 30-45 mph are expected late in the day Wednesday through Thursday morning, especially near Lake Superior and in the Keweenaw. During this period, wind chills drop to near 0 over the east and into the single digits below 0 central and west. - A low end gale up to 35 knots is expected over the west tonight, while storms to 50 knots develop across the entire lake Wednesday afternoon through Thursday morning. && .UPDATE... Issued at 1007 PM EST Tue Dec 3 2024 The deepening clipper low continues to move eastward into Ontario tonight, with the cold front analyzed over western MN. Light snow is filling in across the UP courtesy of warm advection and isentropic ascent out ahead of the front. Snow is steadiest across the eastern UP with lake enhancement off of Lake Michigan with SSW flow. Much of the UP remains on track to receive a few inches of snow by sunrise, when this initial burst of system snow begins to wrap up. && .SHORT TERM /THROUGH TONIGHT/... Issued at 230 PM EST Tue Dec 3 2024 General weather pattern for today will be dictated by broad 500mb troughing over the eastern CONUS with ridging over the Pacific Northwest with a subtle shortwave coming out of the Canadian Rockies. This is reflected at the surface by an expansive surface high pressure over the Mississippi River Valley at around 1037 mb and a developing clipper low of near 1004 mb approaching Lake Winnipeg. Closer to home, winds have shifted westerly to southwesterly in response to the shifting of the pressure systems, and KMQT radar returns show only a single remaining lake effect band in the east half lingering over the Grand Marais to Luce County shores while light snow continues off and on over the Keweenaw per the KCMX METAR. Both features look to lift to the north throughout the day, so the current Winter Weather Advisories for lake effect snow have been allowed to expire at 18Z. Tonight, the aforementioned clipper will rapidly transit the Canadian Prairie, deepening to a Euro-ensemble mean of 996mb over the north-central shores of Lake Superior by 12Z Wednesday. Precipitation ahead of that cold front will arrive over the western UP shores of Lake Superior in earnest around 00Z tonight, with hourly PoPs over 75% for all of the UP except the MI/WI state line communities overnight. Despite the fast speed of the low, the strengthening nature of the low indicates strong forcing and snow is expected to overperform relative to other clipper lows of that strength. The HREF shows 30-60% chances of widespread 6-hourly QPF rates exceeding 0.15 inches with a lake-enhanced band of over a quarter-inch 40-60% probable from the tip of the Keweenaw southeast to Manistique overnight. With approximately 15:1 snow ratios, this will lead to snow accumulations by 12Z Wednesday of widespread 2-4 inches (lower along the state line) but locally higher amounts to 6- 8 inches or higher possible in the east half depending on the exact setup of lake-enhancement. && .LONG TERM /WEDNESDAY THROUGH TUESDAY/... Issued at 435 PM EST Tue Dec 3 2024 Synopsis: A strong Alberta clipper dives southeast from central Canada into the Great Lakes Basin late Tuesday through Wednesday, introducing widespread light to moderate snow across the area before transitioning to LES as the surface low pressure deepens and tracks east of Lake Superior. Along with LES, gusty northwest winds upwards of 45-50 knots in the open waters of Lake Superior and along the lake shores are likely following the system's cold frontal passage, potentially dangerous travel conditions in blowing snow for the northwest to north wind snowbelts late Wednesday into Thursday. Additional chances for snow and some rain are possible this weekend into next week. System snow will be ongoing at the start of the long term forecast period as low pressure just north of Lake Superior aids in isentropic ascent and widespread light snow, with a slight boost in the adjacent Lake Michigan counties. Through the late morning into the afternoon, snow will taper off across the central UP as the dry slot moves overhead; however this break in snow will be short lived as the trough swings southeast, sending a shot of arctic air across Lake Superior transitioning precipitation to pure lake effect snow. 850 temps near -15 to -20 will be more than sufficient for strong lake effect snow bands across the northwest snowbelts beginning late Wednesday night. Surface temperatures quickly drop to the single digits in the far interior west Wednesday night with wind chills below zero. Winds back to the north wind snowbelts overnight into Thursday morning. At the same time, guidance highlights areas of the central and east UP could see snowfall rates 1-1.5" per hour as lake induced ELs climb to near 3-4k ft in connection with Lake Nipigon. Combined with winds near 45-50 mph along the lakeshores, travel will become increasingly dangerous with visibility dropping to near zero at times. North-northwest lake effect snow weakens through Thursday evening. As snow showers taper off, overall snow amounts could reach 4-10 inches across much of the northern UP with locally higher amounts up to a foot and half where the heaviest snow bands set up. Looking beyond Thursday into the weekend, descending high pressure and backing winds will lift LES out over Lake Superior on Friday. Some WAA/isentropic ascent on Friday ahead of another weak clipper low may bring back some light system snow. That said, the spread in guidance is still noteworthy at this time, lowering confidence in the forecast. There is growing potential for an additional clipper low late in the weekend/early next week to bring more system snow/possibly rain mixing in. Ensemble guidance spread is even greater with that system and any additional lows ejecting into the Great Lakes next week in our active pattern. Otherwise, temps continue to remain mainly below normal this week into the weekend, but a brief warm up to near or above normal temps is expected for Sunday and Monday. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1222 AM EST Wed Dec 4 2024 The initial batch of snow is moving through the UP tonight with a clipper low quickly tracking into Ontario. MVFR ceilings will be favored at all terminals through the forecast period, but visiblity remains more variable. MVFR to occasional IFR visiblity is expected with light to moderate snow tonight, then a brief improvement in visibility is possible into the early morning hours at IWD and SAW with a brief dry period. However, visiblity restrictions likely hang on at CMX the rest of tonight as winds veering more to the west kick off lake effect snow there. Winds continue to veer to the NW into Wednesday, bringing in lake effect snow and associated MVFR/IFR visibility back into IWD and SAW. As winds turn to the NW by Wednesday afternoon, they'll become gusty with 30 kt gusts becoming likely (60+%) at all terminals after 18Z. The combination of wind and snow could create a BLSN threat especially at KCMX Wednesday afternoon. && .MARINE... Issued at 435 PM EST Tue Dec 3 2024 There are two gale events expected during the forecast period. The first one will be a low end event of 35 kt gales across the western lake tonight while the second one will be a widespread Storm 45 to 50 kts Wednesday afternoon to Thursday evening. Winds this afternoon and evening increase to 20-30 kts for tonight with some gales to 35 kts expected in the west tonight ahead of the approaching Alberta Clipper low pressure system. On Wednesday, the clipper low passes north of Lake Superior and winds become northwest behind the associated cold front. Winds increase behind the front to storms 45 to 50kts from west to east Wednesday afternoon and evening. North-northwest gales Thursday morning gradually fall below 34 kts in the afternoon. 20-30 kt winds gradually fall to around 15- 25 kts for Thursday night, backing west by Friday morning. West winds continue through Friday night, veering northwest for Saturday, then backing south for Sunday. Waves tonight build up to 5-10 feet, higher over the west half. Behind the cold front on Wednesday, waves build up to 10-15 ft. Wave heights over the west begin to settle Wednesday night while waves over the east continue to increase to up to 15-20 ft by Thursday morning. Waves then fall below 4 ft in the west Thursday evening and Thursday night in the east. Across the lake, waves between 3-6 ft are expected on Friday and Saturday. With the cold airmass surging in Wednesday night and increasing waves, some freezing spray is also expected. The main area of concern for freezing spray is the west half of the lake Wednesday afternoon and Wednesday night. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Storm Warning until 1 PM EST Thursday for MIZ001-003- 006-007-014-085. Winter Storm Warning from 10 AM EST /9 AM CST/ this morning to 7 AM EST /6 AM CST/ Thursday for MIZ002-004-009-084. Winter Storm Warning from 1 PM this afternoon to 7 PM EST Thursday for MIZ005. Winter Weather Advisory from 1 PM EST /noon CST/ this afternoon to 1 PM EST /noon CST/ Thursday for MIZ010-013. Lake Superior... Gale Warning until 5 AM EST /4 AM CST/ early this morning for LSZ162-263-264. Gale Warning from 4 PM this afternoon to 1 PM EST Thursday for LSZ251-267. Gale Warning from 10 AM EST /9 AM CST/ this morning to 1 PM EST /noon CST/ this afternoon for LSZ162-241-242-263. Storm Warning from 1 PM EST /noon CST/ this afternoon to 4 AM EST /3 AM CST/ Thursday for LSZ162-241-242-263. Heavy Freezing Spray Warning from 1 PM EST /noon CST/ this afternoon to 7 AM EST /6 AM CST/ Thursday for LSZ162- 240>242-263. Gale Warning from 10 AM EST /9 AM CST/ this morning to 7 AM EST /6 AM CST/ Thursday for LSZ240. Gale Warning from 10 AM this morning to 7 PM EST this evening for LSZ243-244-264. Heavy Freezing Spray Warning from 4 PM this afternoon to 7 AM EST Thursday for LSZ243-244-264. Storm Warning from 7 PM this evening to 7 AM EST Thursday for LSZ243>246-249-250-264>266. Gale Warning from 1 PM this afternoon to 7 PM EST this evening for LSZ245-246-265. Heavy Freezing Spray Warning from 7 PM this evening to 7 AM EST Thursday for LSZ245>248-265-266. Gale Warning from 1 PM this afternoon to 10 AM EST Thursday for LSZ247-248. Gale Warning from 2 PM this afternoon to 7 PM EST this evening for LSZ249-250-266. Lake Michigan... Gale Warning until 5 AM EST early this morning for LMZ221-248- 250. Gale Warning from 4 PM this afternoon to 1 PM EST Thursday for LMZ221-248-250. && $$ UPDATE... SHORT TERM...GS LONG TERM...BW AVIATION...LC MARINE...BW