FXUS63 KAPX 282011 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 411 PM EDT Wed Jul 28 2021 .NEAR TERM...(Through Tonight) Issued at 221 PM EDT Wed Jul 28 2021 ...Monitoring severe storm and heavy rain potential tonight... High impact weather potential: Some concerns for isolated severe storms and heavy rainfall totals tonight across parts of the area. Pattern synopsis and forecast: Northern Michigan continues to lay at the inflection point between Intermountain West/High Plains centered ridge axis and northeast NOAM centered troughing. Overhead northwest flow the result, with subtle shortwave troughing digging southeast within this flow across northern Minnesota. Environment ahead of this trough taking on all the characteristics to support a high end severe weather event...with tight instability gradient and burgeoning enhanced low level convergence axis tucked under deepening upper level divergence bullseye. Maturing/increasing northwest flow through the deepening convective layer supports rapid upscale convective growth later this afternoon and evening across the northwest Great Lakes, with those organizing wind fields supporting intial discrete supercells taking the form of a mature MCS (perhaps derecho?) as it digs southeast along instability gradient/convergence axis tonight into the lower Great Lakes. Primary forecast concerns/challenges: Addressing severe storm and heavy rain potential tonight. Details: As mentioned above, expect thunderstorms to rapidly increase in both areal coverage and intensity to our west and northwest the remainder of this afternoon and evening as digging shortwave trough reaches max instability gradient and area of enhanced low level convergence. Expect intial more discrete cells to continue to grow upscale, with deep layer shear values supporting transition to an MCS as storms dig southeast. Pattern recognition of ridge/trough inflection point placement and both instability gradient/developing low level jet mass field adjustments all support latest convective allowing guidance of taking most severe complex of storms to our west and southwest this evening and early overnight. Still, definitely not completely out of the woods yet for our area, with upwards of 1K joules/kg of mixed layer cape and effective shear values exceeding 40s knots, particularly south of the Grand Traverse Bay region. So while not expecting the widespread significant severe event expected back across Wisconsin into southwest lower Michigan, could still see some more isolated severe storms. Latest SPC Day One Convective Outlook concurs, keeping moderate risk wording to our west and southwest, with just slight chance wording clipping the southwest third of the area, and marginal wording across the remainder of northern Michigan. While high precipitable water values (nearing/exceeding 2 inches far southwest) definitely supports some hydro concerns, expected transient nature of activity and deepest convection staying to our west argues otherwise. While we could see some localized heavier rain totals (in excess of an inch), currently do not expect any widespread flooding concerns. && .SHORT TERM...(Thursday through Saturday) Issued at 408 PM EDT Wed Jul 28 2021 ...Showers ending Thursday, then cooler and dry Friday... High Impact Weather Potential...Minimal Pattern Synopsis/Forecast...Western ridging persists with troughing across the northeast. The upper level jet is pushed into southwestern Canada, before dipping back south across the Great Lakes. A couple weak PV- anomalies will scoot southeast across southern Ontario, dampening the eastern periphery of the ridge and shunting the jet more fully over Michigan. At the surface a frontal boundary is laid out from southern Wisconsin into the Ohio Valley, and a weak area of low pressure is progged to move east along it. Most of the more intense convection associated with this should remain to our south through the morning hours, but we may still have some lingering showers with embedded thunder. Forecast/Details: By Thursday morning the best moisture axis will have shifted south but we'll still have PWAT's just over 1.0" over our area, right around climatological norms for late July. This combined with decent instability and mid-level lapse rates, along with bulk shear between 40 and 45 kts will allow any lingering showers to contain thunder, mainly in the southern section of the CWA. The potential for showers exists in the U.P. and far northern lower as well, as another weak upper level impulse moves through and another cold front moves through from the northwest. Confidence in any showers north of M-55 is low however. Post-frontal mixing should lead to gusty winds Thursday afternoon and early evening. Thursday night into Friday an area of high pressure will sink through the upper Great Lakes...leading to drying conditions and calming winds. The rest of the day Friday looks quiet and dry with perhaps a few fair weather cumulus in the afternoon. Highs Thursday should be in the mid to upper 70's followed by cooler air Friday with highs mainly in the low 70's. && .LONG TERM...(Saturday night through Wednesday) Issued at 408 PM EDT Wed Jul 28 2021 High impact weather potential: Minimal Additional rounds of shortwave energy drop into the upper Great Lakes through the weekend, with western ridging becoming more amplified. Saturday brings another chance of rain as a cold front sweeps across the area. This will be followed by generally quiet conditions Sunday (perhaps some isolated light showers) with high pressure sliding by to our west. Heading through early next week there are signals that an upper level cutoff starts to set up over the region, which could bring in additional shower chances, but for now guidance is fairly dry. Overall cooler air moving in with 850mb temperatures dropping to 10 C or lower through much of the extended...highs look to be mainly in the low 70's. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 221 PM EDT Wed Jul 28 2021 VFR conditions expected into this evening. Growing complex of showers and thunderstorms expected to drop southeast across the area later this evening into the overnight. Best chance for significant storms expected to occur west of our area, although cannot completely rule some stronger storms, especially at KTVC and KMBL. Any of these stronger storms will be capable of producing gusty winds and periods of heavy rain. Low clouds expected to build in behind this convective complex Thursday morning, likely resulting in widespread MVFR to even IFR conditions. Light winds outside of any thunderstorms through tonight. Winds become northwest and increase in speed during Thursday morning. && .MARINE... Issued at 221 PM EDT Wed Jul 28 2021 Outside of some gusty winds and heavy rain associated with passing thunderstorms, not expecting any widespread marine concerns through tonight. Pressure gradient tightens Thursday, producing increasingly gusty northwest winds and potential for small craft advisory conditions, especially on northern Lake Michigan. Winds begin to subside later Thursday night into Friday. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ NEAR TERM...MB SHORT TERM...STJ LONG TERM...STJ AVIATION...MB MARINE...MB