428 FXUS63 KAPX 211940 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 340 PM EDT Sat Aug 21 2021 .NEAR TERM...(Through Tonight) Issued at 340 PM EDT Sat Aug 21 2021 ...Chance for showers/t-storms returns... N-s cold front is advancing across western upper MI and eastern WI. This front remain on target to cross northern MI tonight. There is isolated convection ahead of the front, with decaying showers over Lake MI west of MBL/FKS, and actual t-storms just east of Munising. No precip over this forecast area yet, but a line of agitated cu is evident on satellite from Wellston to Northport. Daytime heating, the surface cold front, and weak heights falls aloft as a shortwave transits the area, will all contribute to spotty precip this evening and early overnight. MlCape values are analyzed at around 500j/kg, a little higher west and lower east. Pretty decent agreement amongst the CAMs that current activity will grow somewhat upscale, with sct showers and a few t-storms across eastern upper and far northern lower MI this evening. A stray shower ahead of the main frontal band is a possibility, especially along the bands of agitated cu already in place. Instability wanes completely by the time the front reaches se sections. No svr potential noted, with meager instability, and 0-6km bulk shear values of 20kt or less. A period of mostly cloudy skies will be seen post-fropa. Those will clear out of eastern upper MI overnight, but most of northern lower MI will still be on the cloudy side at sunrise Sunday. && .SHORT TERM...(Sunday through Tuesday) Issued at 340 PM EDT Sat Aug 21 2021 High Impact Weather Potential: Minimal attm... Pattern Synopsis/Forecast: By Sunday morning...upper-level shortwave that set off our cloud cover and a few showers/storms this afternoon will be well to our north in the vicinity of Hudson Bay. To our southeast...tropical cyclone Henri will be poised to move onto the New England coast...with broad troughing just behind it...while ridging across eastern Canada remains at anomalously strong levels further downstream. Meanwhile...troughiness in the western US will continue to be supported by various bits of energy dropping through the flow. Troughing that just moved into the Pacific northwest today (21/12z) should be located near the eastern side of the Rockies by Sunday morning as well...progressing quickly across the northern Plains and Upper Midwest through the remainder of the day. This may be our next potential weather maker for Monday into Monday night. As ridging downstream dampens...will look for Henri to begin to press eastward as well...allowing some semblance of ridging to attempt to build across the Great Lakes through the remainder of the period...ahead of the next shortwave swinging through the flow. Primary Forecast Concerns: Rain/storm chances through the period...potentially low afternoon RHs Monday...? Not quite sure what to think of this forecast... Thinking back on last weekend, if I remember correctly, some of the ensemble guidance suggested it could be active for mid-week this past week...which ultimately did not turn out to be the case (though part of that was related to uncertainty/lack of pattern progression due to tropical systems in the flow...from Fred to Grace to now Henri). A glance through that same ensemble guidance today has a similar idea...suggesting the coming week could be somewhat active again as upstream energy heads eastward with time. That being said...initial conditions this weekend are different than last weekend...with the main concern last weekend the dry weather moving in, whereas today we're watching a few showers move in, not to mention different positions of tropical systems...so it's hard to say whether or not the same precip-dwindling trend may continue into next week. More or less just conjecture/food for thought at this time. In the meantime...looking at what current guidance is putting out there, and what can legitimately be discerned from that...looks like there is still some uncertainty going forward, first in how long post-frontal moisture lingers across our southeast counties Sunday morning...as this could lead to a cloudier day across our southeast...and perhaps keep temps from reaching their potential maxes. The surface front should be well to our south Sunday morning...but the cold front aloft may not quite exit as quickly, allowing an inversion aloft where RHs may be high enough for some stratus-y clouds to form. Might also not be out of the question for some showers/drizzle(?) to linger across our southeast Sunday morning as well...though much of the area should remain dry (and less humid). Looks like both boundaries may ultimately get hung up in the region...as Henri moves onshore in New England and holds up the pattern across the Great Lakes (i.e., southwesterly flow/weak ridging aloft...with most of the shortwave activity passing to our north along the flow). This idea may allow the cold front to slow down a bit more...keeping rain chances in the area a tad longer into Sunday than initially planned, too. Next shortwave looks to track across the northern Plains Sunday night...approaching the Great Lakes by Monday morning. Similar to what we're dealing with today...looks like best moisture and dynamics should remain well to our north in Canada...such that our precipitation chances stay minimized...if we get anything at all beyond increased clouds. Going into Tuesday and beyond...will have to keep an eye out as upstream shortwave troughing (which should also pass to our north) allows a surface system to deepen across the Plains and track eastward. This may impact us as early as Tuesday...if anything is able to develop along the warm front lifting in...though not entirely certain on that yet. && .LONG TERM...(Tuesday night through Saturday) Issued at 340 PM EDT Sat Aug 21 2021 High Impact Weather Potential: Minimal attm... Much uncertainty remains in the exact details in the coming days...though attm...our next decent chance of rain and/or storms may occur toward the start of the long term period...with the aforementioned surface system moving eastward. This would be potentially associated with an increase in moisture and instability, assuming we end up in the warm sector. Can't get too bogged down in the details attm...as they'll likely change to some degree...but it is something worth keeping an eye on in future shifts to see if this idea continues. As mentioned above at the start of the short term...not sure if my earlier conjecture will turn out to be reasonable, or just blowing hot air. Will have to see how guidance ultimately handles the pattern in the coming days. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 133 PM EDT Sat Aug 21 2021 Cold front will cross northern lower MI tonight, with a skinny band of showers/perhaps TSRA just ahead of it. Best chance for rain will be at PLN, then perhaps TVC/MBL. Brief period of MVFR cigs is possible right behind the cold front. VFR on Sunday. Somewhat gusty southerly winds this afternoon. Winds abruptly veer nw/nnw late tonight. && .MARINE... Issued at 340 PM EDT Sat Aug 21 2021 Southerly winds are gusty in spots this afternoon, especially on Lake MI and Whitefish Bay. A cold front crosses the area tonight, and somewhat gusty nw-erly winds will be in place Sunday. Additional small craft advisories will likely be needed in some areas. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LMZ344>346. LS...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LSZ321. && $$ NEAR TERM...JZ SHORT TERM...FEF LONG TERM...FEF AVIATION...JZ MARINE...JZ