548 FXUS63 KAPX 051815 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 215 PM EDT Mon Oct 5 2020 .NEAR TERM...(Through Tuesday) Issued at 213 PM EDT Mon Oct 5 2020 ...Gusty winds and scattered shower chances tonight... High impact weather potential: Minor lakeshore flooding impacts continue through tonight. Pattern synopsis/forecast: Broad/weak mid-level ridging is draped overhead this afternoon with shortwave troughing and associated surface low pressure centered across northern Manitoba/Ontario. To our southeast, sprawling surface high pressure remains in place, leaving northern Michigan trapped between the two systems with a tightening pressure gradient and attendant occasionally gusty southwest winds as a result. While the aforementioned area of low pressure across central Canada will pass well to our north tonight, this system is expected to drag a cold front across the area locally, perhaps bringing some scattered/light showers, especially to northern sections of the forecast area. Shortwave troughing tonight will continue to shift east towards the eastern seaboard Tuesday morning. However, hot on its heels, an impressive 150+kt jet streak will be making headway into the area late in the day Tuesday/Tuesday night, aiding to deepen a cyclone across the Great Lakes region (discussed more in the short term section below). Primary forecast concerns/challenges: Gusty southwest winds today into tonight. Shower chances tonight. Southwesterly return flow continues to ramp up across northern Michigan this afternoon, which will continue to be the case right on into tonight. Frequent gusts up to 40 mph are expected along the Lake Michigan shorelines, diminishing to 25-30 mph as you head inland. No changes planed to the current gale warning or lakeshore flood headlines. By mid-evening, cloud cover is expected to be thickening/lowering, especially across the northern half to two-thirds of the forecast area. This coinciding well with an uptick in moisture ahead of the aforementioned cold front tied to the system centered near Hudson Bay. Not overly impressed with precip chances through this time frame, purely given our displacement from better forcing, but none the less, at least scattered/light showers are expected across portions of the forecast area this evening into the overnight hours. Most numerous shower activity expected to be across eastern upper into the Tip of the Mitt, but not much anticipated in the way of QPF. Near-zero thunder chances given virtually no instability. Tonight's lows in the 40s for most. Any lingering small shower chances early Tuesday morning quickly shift eastward with partly sunny skies, occasional breeziness and moderating high temperatures being the rule (highs in the upper 50s to mid-60s area-wide). Do expect an uptick in cloud cover late in the day beginning across eastern upper/northwest lower as our next system quickly approaches from the northwest...crossing the area Tuesday night. && .SHORT TERM...(Tuesday night through Thursday) Issued at 213 PM EDT Mon Oct 5 2020 ...Strengthening clipper Tuesday night into Wednesday... High Impact Weather Potential: Gusty winds through Wednesday. Synopsis/Forecast: The upper level jet strengthens and shifts south over the U.S-Canadian border heading into midweek. A weak wave treks through southern Canada Tuesday, inducing a clipper system in Northern Saskatchewan that drifts southeast...by Tuesday night it will be strengthening (to sub-995mb) as it moves just north of the SOO, bringing us rain Tuesday night into Wednesday with cool northwest flow. Heights start nudging upward Wednesday night into Thursday, with surface high pressure and drier air moving in. Details/Concerns: Expect rain to be the most persistent and widespread in the north, with chances decreasing to the south. In fact, some areas south of M55 may only see sporadic light showers for much of Tuesday night. Moisture will be a bit above average, (PWATs 0.7 to 0.9") but it will be quick hitting (just like the synoptic forcing), so not expecting any prolonged wide spread heavy rain; less than half and inch expected across the area through Wednesday. Individual showers could produce some heavy downpours though. Concerned with gusty wind potential, especially with any stronger updrafts...the best lapse rates remain in the northern half of the area, with the best bulk shear to the south. Bulk shear looks increase to at least 50 or 60 kts (likely even more) through the night as the very strong upper level jet moves in. We have a couple hundred Joules of elevated CAPE, along with 40+ kts of 0-3 km shear. Thus any beefier showers and storms will need to be watched for strong and possibly damaging winds, if there's any chance for winds penetrating the near- surface stable layer. Showers linger through Wednesday morning, with overlake instability kicking in. These lake effect showers will likely stay in the western half of the CWA. We could stay stuck under stratus through the afternon/early evening with moisture trapped under a 5 kft inversion. We may finally get enough clearing for clouds to start clearing out closer to sundown. Heading into Thursday we dry out and clear out thanks to incoming surface high pressure. Highs on Wednesday will be in the mid to upper 50s, cooler than Tuesday thanks to a reinforcing shot of cold air behind the clipper (possibly in the form of a cold front washing out across the area). Highs Thursday will depend on the center of the high passing directly overhead or sliding just to our southeast; either way we may drop a couple more degrees thanks to 850mb temps sinking to -1 or -2 C. && .LONG TERM...(Thursday night through Monday) Issued at 213 PM EDT Mon Oct 5 2020 We continue the progressive pattern across the CONUS with the upper level jet pushing north into southern Canada. A wave pushes north of the Great Lakes Friday into Saturday with rain chances associated with a surface low moving by to our north. Then amplified ridging builds into eastern sections of the CONUS with a sharp -PNA pattern briefly setting up. Anomalously strong midlevel heights should lead to mild days with plenty of sun. Some guidance even has some areas pushing 70+ by mid next week. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1232 PM EDT Mon Oct 5 2020 A cold front tied to low pressure near Hudson Bay will approach the western Great Lakes this evening, crossing northern Michigan Tuesday morning. South-southwest winds will continue to strengthen this afternoon, remaining gusty at times through tonight leading to LLWS developing at the majority of northern Michigan TAF sites. A few showers may also dot the map at times tonight into very early Tuesday morning, primarily at PLN, and to a lesser extent at the remaining terminals. && .MARINE... Issued at 213 PM EDT Mon Oct 5 2020 Gusty southwest winds remain the rule this afternoon through tonight ahead of a low pressure system progged to pass well to our north. Occasional gale force wind gust potential remains through this time frame, especially on the open and nearshore waters of Lake Michigan while SCA criteria should be the rule across Lake Huron, Whitefish Bay and the St. Marys River. Chances of rain showers will increase this evening and tonight...mainly for nearshore areas along and north of M-32. Another potent low pressure system crosses the Great Lakes region Tuesday night into Wednesday, perhaps bringing another round of gale force winds to the nearshore waters of northern Michigan. && .APX WATCHES/WARNINGS/ADVISORIES... MI...LAKESHORE FLOOD ADVISORY until 5 AM EDT Tuesday for MIZ016-020- 025-031-088-095-096-098. LH...SMALL CRAFT ADVISORY until 11 AM EDT Tuesday for LHZ347>349. SMALL CRAFT ADVISORY until 11 AM EDT Tuesday for LHZ345-346. LM...GALE WARNING until 5 AM EDT Tuesday for LMZ323-341-342-344>346. LS...SMALL CRAFT ADVISORY until 5 AM EDT Tuesday for LSZ321-322. && $$ NEAR TERM...MG SHORT TERM...STJ LONG TERM...STJ AVIATION...MG MARINE...MG