Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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505 FXUS63 KAPX 202000 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 400 PM EDT Fri Sep 20 2024 .KEY MESSAGES... - Rain/thunder chances through this evening - Rain/storms Return Sunday && .SHORT TERM /THROUGH SATURDAY/... Issued at 359 PM EDT Fri Sep 20 2024 Pattern Synopsis: Weak troughing will continue to slide over the Great Lakes this evening and tonight as much stronger upstream troughing pivots across the northern Great Plains through Saturday. Meanwhile, short wave ridging looks to work over the region to start the weekend, providing subsidence aloft to help temporarily build surface high pressure across the Great Lakes. Forecast Details: Rain/thunder chances through this evening -- Scattered showers and isolated thunderstorms will continue to work across northern Michigan into this evening. While coverage has diminished some over the last 1-2 hours, additional showers/storms may still initiate across northern lower this afternoon. With a few hundred J/kg of MLCAPE and around 30 kts of deep layer shear in place, a strong storm or two cannot be ruled out -- but current confidence is that these chances are low. Chances will diminish this evening into tonight as the weak front moves through and forcing aloft becomes less favorable with time. Otherwise, cloud cover will begin to clear from west to east tonight, allowing for efficient radiational cooling with weak/calm winds in place. Rainfall today is expected to provide sufficient moisture to help patchy/areas of fog develop later tonight into Saturday morning. After morning fog burns off as diurnal mixing ensues, a summer-like day is in store for Saturday with mostly sunny skies and high temperatures in the upper 70s to mid 80s. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 359 PM EDT Fri Sep 20 2024 PATTERN SYNOPSIS/FORECAST: Finally starting to see a bit of a pattern breakdown...with largely zonal flow across the northern tier of the US...though southern stream troughing over southern California trying to keep the ridge in place over the southern Plains...further aiding in zonal flow into the Midwest. Trough axis and attendant surface occluded front punching through the Upper Great Lakes this morning...with a decent plume of moisture (morning sounding pwats of 1.28" (compared to 0.37" a few days ago)) stretching northward into Canada...where southerly flow remains strong between parent PV swirly over Manitoba...and upper level ridge centered near Hudson Bay. For a change...with this zonal pattern, starting to see some signals of cold advection aloft across the northern tier of the country, especially back over the Rockies, where 120+kt upper jet diving southeastward is aiding in development of a decent blob of PV there. Troughing continues to plod through the Great Lakes today/tonight...with ridging briefly returning for Saturday. However...aforementioned blob of PV over the Intermountain West/Canadian Rockies is expected to trek eastward this weekend, approaching the Great Lakes for Saturday night into Sunday. Looks like the upper low over SoCal will eject this weekend as well...which could lend to a SW-NE oriented boundary setting up across the Midwest for early next week. Beyond this...increasing uncertainty in how things play out, as guidance is still struggling on how troughing develops/moves through the Great Lakes toward midweek next week...though signals do point to the potential of troughing settling into the eastern US/Upper Great Lakes in some fashion. Assuming this idea comes to fruition...this suggests things should begin to cool down to more seasonable levels (perhaps a bit below normal if we were to end up with upper troughing settling directly overhead). Stay tuned to see if this idea does develop further in the coming days. Primary Forecast Concerns: Rain/storms Sunday into Sunday Night. Cold front drops into the area starting Sunday morning. Should be some decent forcing along this front through the day...and do think the boundary will stall out from NE to SW over the Great Lakes...which could allow rain to stay focused over an area for several hours. Think it will rain, too...given that the antecedent dry airmass we thought we had over the area has not been able to keep rain from getting to the surface today. Radar estimates suggest that some areas today could have seen up toward a half inch in 6hrs, which we haven`t heard reports on yet...so might have to wait till tomorrow morning to find out for sure how well the moisture is getting wrung out today...given that pwats will be similar on Sunday as they are now (1-1.5 inches)...though forcing might be a little better, which could be more favorable for rainfall production than today. Not a ton of instability for deep convective purposes, though do think we should have some thunder...with deep layer shear around 30kts being on the marginal side regarding storm organization purposes. So not impossible there could be some stronger storms Sunday...but nothing widespread by any means. Some concern for rain to focus over part of NE Lower near Saginaw Bay as a low/wave tracks up the boundary...where there could be better deformation to promote better rainfall rates. Interestingly...some of the more typically bullish guidance really wants to bullseye some 6-hr rainfall totals around or in excess of an inch Sunday night; probabilistic guidance is sort of hinting at better probabilities of this as well (30-40 percent chance of 6-hr rainfall totals of an inch or more Sunday night)...though admittedly, I`d prefer to play things more conservatively than the going deterministic forecast suggests, at least at this time. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 141 PM EDT Fri Sep 20 2024 Mainly VFR conditions are expected to persist across northern Michigan TAF sites through this evening. Showers and a few embedded thunderstorms will continue to work across the area this afternoon before chances wane this evening. Any heavy showers/storms that pass over TAF sites could briefly drop VSBYs to MVFR/IFR. Otherwise, rainfall today followed by clearing skies and weak/calm winds tonight is expected to lead to patchy/areas of fog development across northern Michigan tonight. Drops to IFR/LIFR VSBYs will be possible late tonight/early Saturday morning before lifting after sunrise. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ SHORT TERM...DJC LONG TERM...FEF AVIATION...DJC