229 FXUS63 KAPX 101743 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 143 PM EDT Wed Oct 10 2018 .UPDATE... Issued at 1020 AM EDT Wed Oct 10 2018 The storm system which has been organizing over the Plains since the weekend, will slowly continue its trek up across the western Great Lakes today, which will continue the unseasonably warm and muggy conditions across northern Michigan through the afternoon. Thunderstorm chances linger across northern Michigan into this evening due to abundant low and mid lvl moisture (sfc dew pts in the 60s and 850mb dew pts around 14c) and sufficient instability (0-3km MuCape nearing 500 j/kg and 850/700mb lapse rates nearing 6 c/km). Overall current forecast trends are in line, with chances confined to areal coverage and timing this morning. && .NEAR TERM...(Today through Tonight) Issued at 332 AM EDT Wed Oct 10 2018 High impact weather potential: More scattered thunderstorms. Marginal risk for severe storms with damaging winds the main threat. Pattern synopsis and forecast: The pattern is still basically the same as the last few days, for now. Deep upper troughing was over the western conus, as a more defined shortwave has now pushed into the Central Plains. This has kept the upper ridging and warmth over the eastern conus. In between, strong SW flow aloft has continued to pump impressive deep moisture of 1.50" to 1.70" PWATS from the Plains into nrn Michigan. This moisture advection and convergence was fed by a 30-40kt LLJ along and ahead of a frontal boundary that stretches from nrn Michigan back to low pressure deepening in Iowa, and along and ahead of this system's cold front that extends into the srn Plains. Widespread rains have developed north of the frontal boundary and sfc low across the nrn Plains, upper Mississippi valley and upper Michigan, as well as out ahead of the cold front. Forcing continue to be applied by the whole gamut, DPVA, FGEN and deformation north of the low pressure, and theta-e advection and convergence with upper divergence in a now double jet structure for all areas. Few- several hundred j/kg of MUCAPE was still allowing for embedded rumbles of thunder from eastern upper back to the convection ahead of the sfc low's cold front. Specifically closer to home, the frontal boundary was slowly lifting north in increasing srly low level flow as the low pressure is lifting NE. To the north of the front, sfc/low level moisture was abundantly stuck under a strong inversion, resulting in dreary low clouds and fog. South of the front in the warm sector, clouds were much higher and skies were becoming increasingly clearer. The shortwave upper troughing will lift into the Mississippi valley by late today and then through nrn Michigan tonight, while also becoming more negatively tilted. The sfc low pressure lifts into Wisconsin today and the warm front lifts further north into the Straits region, putting most all of nrn lower into the warm sector. The sfc low then tracks across eastern upper Michigan tonight, allowing the strong cold front to blow through overnight. There will be a lull in any shower/storm action in the warm sector through this morning, while periods of showers and isolated rumbles of thunder with dreary low clouds persist across eastern upper. By afternoon, the aforementioned forcing increases across the region, along with deeper moisture advection (PWATS to around 1.80") and continued few to several hundred j/kg, to result in widespread showers and scattered thunderstorms that will continue into early this evening. Despite the lack of good instability, wind fields will be pretty strong, with 0-6km bulk shear 40-45kts. This leaves us in a marginal risk for a severe storm or two with damaging winds being the threat. The deep moisture strips out aloft as the cold front plows through overnight with H8 temperatures dropping all the way down to 2-6C by daybreak Thursday. This will result in a transition to maybe a little drizzle to ultimately the chance for lake effect rain showers late tonight. Highs today will have quite the range one more time again, with low 70s to maybe some low 80s in nrn lower, and mid 50s to mid 60s in eastern upper, and a crazy thermal gradient somewhere around the Straits region. A very warm start to the night will end with temperatures in the upper 40s west to the lower half of the 50s east. && .SHORT TERM...(Thursday through Friday) Issued at 332 AM EDT Wed Oct 10 2018 ...Much cooler; lake effect rain and maybe even snow chances... High Impact Weather Potential...None expected. Steady cold air advection Thursday into Thursday night with cold air lingering into Friday as an upper level trough digs into the region. 850 mb temperatures bottom out at around -6 C early Friday yielding awesome delta Ts in the 20+ range. Moisture looks okay with 850-700 mb rh generally between 50 and 60 percent except for a short wave that ramps moisture up to near 70 percent Friday afternoon. This should all add up to lake effect rain showers, which will mix with and possibly change over to snow showers in the higher terrain. .LONG TERM...(Friday night through Tuesday) Issued at 332 AM EDT Wed Oct 10 2018 ...Still unsettled and remaining on the cool side... High Impact Weather Potential...None expected. With the exception of a bit of short wave ridging for part of Saturday, the pattern looks to remain rather active. Short wave after short wave (and associated shots of cold air) move through the flow likely bringing more lake effect/lake enhanced showers. It even looks marginally cold enough for rain showers to mix with or even change over to snow showers at times. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 142 PM EDT Wed Oct 10 2018 A very active period across the Great Lakes during the nxt 24 hours, as gusty winds shift from the southwest this afternoon to west to northwest Thursday, as a strong system lifts up across the western Great Lakes. Mainly MVFR/VFR cigs and vsby expected this afternoon and early evening with scattered convection, before a better chance for pcpn and IFR cigs and vsbys this evening across northern Michigan TAF sites as the storm system prepares to exit northeast toward Quebec. The Lake Michigan shoreline TAF locations (KMBL, KTVC and KPLN) will become largely dominated by lake induced pcpn and clouds in northwest flow Thursday, with some lake snow possible Thursday night. && .MARINE... Issued at 332 AM EDT Wed Oct 10 2018 Deepening low pressure and a strong cold front in the Central and Southern Plains will lift through nrn Michigan tonight. This will pull a warm front into the Straits for the daytime. Easterly winds will reach advisory levels from the Straits north, while some advisory southerly winds will be noticed from the Manitou Islands south. Showers and isolated to scattered thunderstorms will be overspreading all of the region this afternoon into early this evening before the strong cold front blasts through overnight tonight. Precipitation tapers off, but some lake effect rain showers are expected late tonight through the next several days. The main story will be the extreme overlake instability that develops in the strong cold advection. Gale force winds are expected for most all nearshore waters late tonight through at least Thursday evening. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LHZ348-349. GALE WATCH from Thursday morning through Thursday evening for LHZ347. GALE WATCH from late tonight through Thursday evening for LHZ345- 346. LM...GALE WARNING from 10 PM this evening to midnight EDT Thursday night for LMZ323-341-342-344>346. LS...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LSZ322. GALE WATCH from Thursday morning through Thursday evening for LSZ321. && $$ UPDATE...SR NEAR TERM...SMD SHORT TERM...AS LONG TERM...AS AVIATION...SR MARINE...SMD