Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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756 FXUS63 KAPX 050757 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 357 AM EDT Fri Jul 5 2024 .KEY MESSAGES... - Multiple rounds of showers and storms expected into this evening. Low chances for severe storms this afternoon. - Periods of Rain/storms through the weekend - Rain/storm potential Monday/Tuesday? && .SHORT TERM /THROUGH TONIGHT/... Issued at 356 AM EDT Fri Jul 5 2024 Pattern Synopsis: Longwave troughing will gradually pivot across the north-central CONUS into this weekend as a seasonably strong jet rounds its axis and punches over the southern Great Lakes today. Forcing provided by this feature aloft will support a deepening cyclone that is expected to trek across the lower peninsula this afternoon and evening, eventually departing east of the region later tonight. Forecast Details: Multiple rounds of showers and storms, low chances for severe -- Scattered showers across parts of northern Michigan will continue to expand in coverage from west to east this morning as the aforementioned system moves closer to the region. While some rumbles of thunder cannot be ruled out with activity this morning, numerous showers and storms are expected to form across the area beginning shortly after noon. Thunderstorm clusters are expected to be more disorganized in nature with relatively weak effective shear (~20-25 kts) in place given relatively low ELs/tropopause height. While forecast hodographs do display streamwise vorticity in the lowest few kilometers, weak low-level shear (~10 kts 0-1km shear) should lead to shrunken hodographs with <100 m2/s2 0-1km SRH -- leading to very low confidence in any tornado potential despite the potential for some weakly rotating storms should any become more organized. Damaging wind gusts and large hail will be possible with any strong storms, but confidence remains low in these hazards as well. Aforementioned low cloud tops will keep the majority of the profile warmer than -10 to -20 C, making it even more difficult for large hail formation given already relatively weak effective shear. Strong wind gusts will be possible, but <20 kt flow through the lowest several kilometers of the profile also decreases confidence in this potential. The primary hazard will most likely be lightning given the fact that there is an influx of people across northern Michigan here to enjoy outdoor activities for the holiday weekend. Those planning any outdoor activities should be paying close attention to the forecast, and have multiple ways of receiving weather information and warnings -- primarily this afternoon and early evening when thunderstorms are most likely. Thunder chances will diminish into tonight with lingering chances for showers lasting into Saturday morning. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 356 AM EDT Fri Jul 5 2024 PATTERN SYNOPSIS/FORECAST: Broad troughing over the northern Plains attm...with ridging over the West Coast...and southeastern US. Southwesterly flow crossing the central US; abundant moisture (pwats of 2in or more) and some convection along and ahead of a surface boundary stretching from TX into the OH Valley. PV max over MN within broader troughing; this feature has spawned some convection upstream amid slightly better moisture and better forcing...along and ahead of a low over MN with small warm front over S. WI...and cold front extending back into northern TX. Otherwise...a rather nebulous pattern over the Upper Great Lakes...with a NW-SE oriented cold front well to our north in Canada. It remains reasonably mild, however, with 850mb temps in the 15C range...and temps yesterday topped out largely in the low 80s as a result. Low over WI expected to slowly meander ENE-ward through the start of the actual weekend...not fully departing the region till later Saturday afternoon as a secondary trough axis slips through, leaving the potential for showers and storms in the forecast to start the weekend. Break in the action behind this may only be brief...with chances for activity poised to return Sunday afternoon as another niblet of energy swings in...though not a full washout by any means. Will then be looking for another round to approach the area going into Monday...as upstream trough axis strengthens; this feature is currently progged to swing across the Upper Midwest (including Northern Michigan) Tuesday...as remnants of T.C. Beryl meander inland somewhere over the southern portion of the continent. Beyond this...expecting upstream pattern to break down and allow ridging to spread eastward into the central US going into the middle of next week and beyond. Primary Forecast Concerns: Periods of rain/storms through the weekend... Saturday...not necessarily the most impressive setup, but appears we could be unstable enough to get some convection to redevelop, especially along and ahead of the secondary trough axis swinging in Saturday afternoon...especially if we get enough diurnal heating to destabilize the lower levels enough to overcome somewhat more stable layers in the mid-levels. It will also help if we end up more moist from rain today/tonight...as this could further boost destabilization potential with diurnal heating. Probabilistic guidance currently points toward development of a few hundred joules of CAPE attm, which is worth keeping an eye on, noting the abundance of outdoor activities going on over the region today. This would more likely be skinny CAPE, which could promote better rainfall rates, with freezing levels still up around 3km or so. Do wonder if these will be soggy showers moreso than thunder threats, though thunder will still be a threat, particularly if we are able to get better surface heating during the afternoon ahead of the front. Weak shear/wind profiles Saturday suggest a general lack of organized severe threat, though not impossible some could pulse up and produce some small hail and/or gusty downbursts. Additionally, think storm motion/propagation could end up driven more by mesoscale/storm-scale outflow boundaries than anything else (e.g., not impossible we could get a lake breeze on the Lake Huron coast Saturday afternoon), such that storm motion may not be as predictable as normal, which could be problematic for people out and about this weekend. Furthermore, if cells are able to sit over an area for an extended amount of time, not impossible it could lead to some localized flooding concerns at worst-case scenario. This idea also remains unclear depending on how this event ultimately ends up evolving...but is also worth keeping an eye on. Sunday...think the better organized activity will remain to our west, closer to better forcing...though environment still supports potential for diurnally-driven showers and perhaps a rumble of thunder or two over interior northern Lower in particular. Another day with generally weak flow suggests these, too, will be the kind of showers/storms that just meander here and there, moving relatively slowly, and periodically pulsing up in intensity as outflow boundaries from other storms move through (and/or lake breeze development helps boost things). Kind of a stereotypical summer storm idea. Rain/storm potential Monday/Tuesday?...Though it`s still quite a ways out...think we`ll have to keep an eye on Monday/Tuesday of next week for our next major chance of rain/storms. Current setup suggests southwest flow into the Upper Midwest; with some potential to tap into tropical moisture depending on where Beryl ends up tracking, think heavy rains could again become a concern if this idea holds going forward. However...there are currently some signals the axis of moisture transport could remain to our south, which could shift the focus out of our area. Certainly something to keep an eye on as we look forward into the start of next week, though again...at this hour, nothing definite yet by any means. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1145 PM EDT Thu Jul 4 2024 Vertically-stacked low pressure will slowly slide thru the Western Great Lakes region thru Friday night. Chances of showers and thunderstorms will steadily increase overnight thru Friday. Prevailing conditions will remain VFR for the next 24 hours...but may briefly drop to MVFR/IFR within any heavier showers/storms. Light/variable surface winds overnight will become easterly under 10 kts on Friday. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ SHORT TERM...DJC LONG TERM...FEF AVIATION...MLR