Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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071 FXUS63 KAPX 130735 CCA AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 335 AM EDT Sat Jul 13 2024 .KEY MESSAGES... - Warm and humid with shower and thunderstorm chances Sunday through Tuesday. - Trending drier, cooler, and less humid Tuesday night and beyond. && .SHORT TERM /THROUGH TONIGHT/... Issued at 331 AM EDT Sat Jul 13 2024 Pattern/synopsis: Surface ridging is trying to hold on across central and southern lower MI. Abundant return flow is in place to the west; 70f dew point air is as far north as Winnipeg. A cold front will advance across the Dakotas and into MN thru tonight. Aloft, there are weak impulses in the nearly zonal flow over the n central US; the more prominent waves will be generated by MCSs. Forecast: Weak synoptic sw-erly low level flow develops today, as surface ridging downstate gradually weakens. That flow increases tonight, and especially overnight, when theta-e advection ramps up locally. 900-850mb sw winds over northern Lake MI increase to 25-30kt after 06Z. For today, still light surface winds will allow lake breezes to develop (once early morning fog/stratus erodes). Surface dew points are a little lower early this morning (mid-upper 50s in parts of northern lower MI). This will hold thru the day today. Between that and the loss of the upper trof that was in place the past couple of days, and deeper instability will be largely lacking today. However, Lake MI will contribute a touch of moisture in upper MI, and once you get away from Lake MI/Huron more substantial heating will be realized. 500j/kg of MlCape is possible over central and northern Chippewa Co. A developing Lk Superior breeze will be the primary forcing mechanism. Have expanded slightly the pops that were previously in place here, from early afternoon into early evening. Elsewhere, mostly sunny (once morning fog/stratus is mixed out). Tonight, have a bit of a lull mid-evening, before return flow steadily ramps up. A stray cell or two could be possible in advance of any MCS from the west, and will have a small chance for a storm near Manistee as soon as midnight. Better pops will await more organized clusters of convection trying to push east, along with stronger/richer return flow. Best MuCape (above 1k j/kg) is going to remain a little south of our latitude late tonight, centered on the south half of Lake MI. Though an organized MCS is likely to track across WI late tonight, an expected ese-ward movement will mainly target central Lake MI and sw lower MI by Sunday morning. Will mention a few strong storms possible very late tonight in our far sw. Chance pops expand across most of northern MI after 2 am tonight, but hard to go with likely pops anywhere yet. The highest pops will occur after 12Z. Max temps today well into the 80s, though a bit cooler near Lake MI. Muggy lows tonight in the 60s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 331 AM EDT Sat Jul 13 2024 Pattern Synopsis / Forecast: Two dominant features will work together to create a corridor of speedy zonal flow out of the WNW, aimed directly at northern Michigan. The first will be an absolute unit of a ridge / upper level high over the western CONUS (currently driving record dismantling heat in the desert SW... Las Vegas has been 115+ for 7 days). The other feature will be well to our north: a deep longwave trough anchored over far northern Manitoba and Saskatchewan. This classic flow regime will be accompanied by deep Gulf moisture return... as pointed out by previous forecaster, Gulf plume has made the long journey into North Dakota, and with this current pattern, should easily be able to leak dewpoints well into the 60s and even perhaps low 70s into northern Michigan through the weekend and into next week... accompanied by temperatures well into the 80s and perhaps breaching 90 in places barring any convection suppressing warming in the morning hours. Given expected fire brigade of shortwaves / embedded height disruptions passing through zonal flow, it sure looks like a quality "MCS Mania" setup from Montana to the Great Lakes, and pending the exact trajectory / evolution of these convectively charged waves, could have implications on northern Michigan as early as late tonight into Sunday. Most pronounced wave looks to pass Monday night into Tuesday, with accompanying surface low pressure deepening while passing through Lake Superior as the aforementioned longwave digs southward through Ontario. This will result in a much more refreshing airmass after Tuesday, with highs returning into the 70s and nighttime lows ranging from near 50 to the upper 50s to close out the work week. Primary Forecast Concerns: Sunday: Admittedly a frustrating amount of uncertainty with the evolution of storms at this juncture. Following passage of morning line of storms (see Short Term for Sat. night details), looks like diurnal instability could make a return as partial clearing allows for sfc temps to build back into the 80s with a newfound surge of dewpoints, generally ranging from 65 - 73. This should drive MLCAPE values back up to 700-1,500 Joules, and thus should be enough to drive some returning showers and thunder. given lack of deeper forcing overhead, pattern recognition says initiation probably get limited to lake breezes, which, with a general WSW flow regime, should target the eastern Yoop and NE lower. Will have to watch for some of these storms to pack a punch... unidirectional WNW shear profile with an ESE storm motion suggests that these storms may have some streamwise vorticity to tap into, and thus could pose a damaging wind / hail threat. Certainly a tricky forecast, as morning convective activity could just slap a cloud deck over the region, leaving us in a proverbial sweat box of 70s air temps and dewpoints with little to no instability, and thus making me look like an absolute walnut for even mentioning returning convection Sunday afternoon. Safe to say that more concise updates will be had in the coming forecast cycles. Monday night - Tuesday: More pronounced wave and associated deepening low pressure progged to pass through Lake Superior Monday night into Tuesday, dragging a cold front through northern Michigan some time between later Monday night and Tuesday afternoon. Much like Sunday, uncertainties in timing and convective evolution cast instability into the forecast, but most guidance seems on board with this disturbance passing through. Conceptually, this brings more showers and thunder to the region given the presence of deeper moisture and better forcing. In the wake of this activity, cold air advection set to commence as stout troughing digs into the Great Lakes from Canada, with surface high pressure likely scouring out lingering moisture. This should lead to a stretch of pleasant temperatures by midweek and into the end of the week, with dry conditions accompanying the cooldown as well. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1149 PM EDT Fri Jul 12 2024 Shallow fog potential the concern for the overnight...KMBL already hinting at reduced visibilities. May be enough of a breeze at KCIU to prevent any issues...always a question at KPLN/KMBL given cold air draining and propensity to see some fog. Should not be a long-lived issue...with VFR conditions expected Saturday...perhaps with some convection north of KCIU. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ SHORT TERM...JZ LONG TERM...HAD AVIATION...JPB