637 FXUS63 KAPX 091727 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 127 PM EDT Tue Oct 9 2018 .UPDATE... Issued at 1043 AM EDT Tue Oct 9 2018 Warm front remains stalled over our northern CWA and extends from Eastern Upper Michigan thru Central Wisconsin into the Central and Southern Plains. Virtually all convection associated with this front remains north and west of this boundary. Thus...our CWA is precip free for the moment. Latest near term models still suggest afternoon destabilization (MUCAPES of 500-1000 J/kg) combined with dwpts well into the 60s will result in the development of scattered showers and possibly a few thunderstorms across just about anywhere in our CWA this afternoon and evening. No real mechanism to will be in place to organized this convection with the stationary front to our NW. Wind fields will begin to strengthen a bit today...but overall shear is not very impressive. Expect any storms that do develop will remain below severe limits. Do expect an unusually warm mid October day for many places...but temp gradient will be rather tight. Afternoon highs will range from the 60s in Eastern Upper Michigan to near 80 degrees around Saginaw Bay. && .NEAR TERM...(Today through Tonight) Issued at 348 AM EDT Tue Oct 9 2018 High impact weather potential: Chance of thunderstorms today and tonight. Severe storms not expected. Dense fog over portions of the SE CWA into this morning. Pattern synopsis and forecast: Deep upper troughing continues in the Rockies, with strong ridging over the eastern conus. In between, strong sw flow aloft has continued to pump impressive of 1.30" to 1.70" into our neck of the woods, highest across eastern upper. This moisture advection and convergence was fed by a 35-45kt LLJ along and ahead of a frontal boundary that stretches from the Central Plains through the Upper Mississippi valley and nrn Great Lakes. Pockets of theta-e advection and convergence, combined with a series of shortwaves/vorticity and resulting DPVA and upper divergence in the right entrance region of a 140kt upper jet in eastern Canada, was resulting in periods of rain showers associated with individual weak sfc low pressures across this region. Embedded within these showers was periodic rumbles of thunder as well, with a few hundred j/kg of MUCAPE. There was also a corridor of dense fog in lower lying areas along and SE of a line from from Houghton Lake to Alpena, where there was more protection from the winds that have increase at the sfc and especially just above ground. The high dew points and good radiational cooling has led to these poor visibilities. The above stated pattern has been steady for awhile, but things are going to start to change, but the general concept will remain the same. A more defined and large chunk of the upper troughing from the Rockies will lift NE and into the Central Plains today and into tonight. A more impressive area of low pressure develops in the Central Plains and works it's way into Wisconsin. The series of individual weaker shortwaves/vorticity maxima will continue to bring periods of showers and potential embedded thunder to primarily Lake Michigan and eastern upper. Also, the BL in the warm sector becomes well mixed across nrn lower today (taking longer in the SE after fog burns off), and is likely to result in diurnally induced showers and thunderstorms, despite any focusing mechanism, as the atmosphere is expected to remain uncapped. MLCAPES will be several hundred to possibly greater than 1000j/kg, but with WBZ/FZL near 12kft and less than impressive mid level lapse rates of around 6c/km, doubt we are looking at any severe threat, despite 0-6km bulk shear of 40kts. The diurnally driven showers/storms will fade with nightfall, but as the aforementioned more developed low pressure approaches Wisconsin, additional showers and potential rumbles of thunder may continue and/or redevelop in nrn lower, forced by a little better LLJ and upper divergence forcing. Meanwhile, more of the same for eastern upper and Lake Michigan, with periods of showers and storms persisting. Highs today will have quite the range again, with mid 50s to mid 60s along/near the front in eastern upper, to the 70s in nrn lower Michigan, possibly some lower 80s closer to Saginaw bay. Lows tonight will be quite mild again, but with a good range as well. Low to mid 50s in eastern upper to the very mild lower to middle 60s in nrn lower. && .SHORT TERM...(Wednesday through Thursday) Issued at 348 AM EDT Tue Oct 9 2018 ...And the bottom drops out... High Impact Weather Potential...Thunderstorms possible Wednesday afternoon with a small chance for a severe storm or two south of M- 32. Pattern Synopsis/Forecast...A potent negatively tilted H5 trough will lift into the Upper Midwest on Wednesday, interacting with a soupy airmass for early October. Its associated deepening surface low is progged to trek through the UP into southeast Ontario Wednesday night into Thursday morning, dragging a strong cold front across northern Michigan. Very strong cold air advection develops behind the front by late Wednesday night and continues through the day Thursday. Primary Forecast Concerns...Temperatures, shower/storm potential, and Thursday's winds. A fairly tight thermal gradient will linger near the Straits on Wednesday. It will be another day of unseasonably warm temperatures over northern Lower, where 850mb temps will continue to hover around 15C. There should be some peeks of sun across northeast Lower, but otherwise expect more cloud cover than Tuesday. Highs will likely climb into the mid to upper 70s across most of northern Lower, perhaps a few upper 70s down towards Saginaw Bay. North of the front with greater cloud cover and rain potential, eastern Upper highs will range from the mid 50s to mid 60s. Under the influence of strong cold air advection, Thursday's temperatures will struggle for any recovery and will likely drop through the 40s by afternoon (perhaps a few 50s lingering near Lake Huron). Humidity will continue to rise on Wednesday with dewpoints climbing into the mid 60s south of the Straits. PWATs will rise to ~1.9" Wednesday afternoon ahead of the approaching cold front, which could potentially set a new APX synoptic sounding record for October. This anomalous moisture combined with mild temperatures will promote some convective instability, but it will be limited as forecast soundings show low-mid level lapse rates becoming near moist adiabatic by afternoon (i.e. tall, skinny CAPE profiles). Only looking at <500 J/kg MLCAPE by afternoon, highest across northeast Lower. Strongest forcing will occur Wednesday afternoon into early evening as a corridor of low-mid level fgen sweeps through ahead of the cold front and upper divergence slides overhead in advance of the main trough. Thunderstorms will certainly be possible, and deep layer shear will be adequate for perhaps some organized convection given the strong forcing that will be in play. The only limiting factor will be instability, but wouldn't rule out isolated gusty wind potential with any stronger cells that might develop. SPC has introduced a Day 2 marginal risk generally south of M-32. Heaviest rain will fall between Wed afternoon and very early Thursday morning as the cold front sweeps through. Amounts do not look out of hand for northern Lower, generally between a half inch to locally 1 inch on Wednesday, but eastern Upper will likely receive in excess of 1 inch. As strong cold air advection develops behind the cold front and strips out moisture from the mid levels, we'll transition into a WNW flow lake effect pattern for Thursday. Inversion heights up to 5-6 kft look plausible, but low level lapse rates will vary as surface temperatures fluctuate. Expect scattered lake induced rain showers developing Thursday morning and continuing into Friday. Final concern will be potential for gusty winds on Thursday behind the departing low and cold front. The strong CAA will promote good boundary layer mixing by Thursday afternoon, tapping into 30-40 knot winds aloft. Could easily see 30-35 mph gusts reach the surface Thursday afternoon, but potential for gales looks very limited. .LONG TERM...(Thursday night through Monday) Issued at 348 AM EDT Tue Oct 9 2018 High Impact Weather Potential...Minimal. Lake induced shower setup will continue into Friday as winds remain out of the WNW. High pressure passing through the Ohio Valley will extend into northern Michigan late Friday night into Saturday and will bring an end to the showers (perhaps with a bit of light snow mixed in for some areas Friday night?). Focus then turns to later in the weekend as a clipper system and southern stream low both converge over the Great Lakes, potentially bringing more widespread rain and gusty winds. Another shot of colder air behind this system looks to set the stage for additional lake processes heading into && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 127 PM EDT Tue Oct 9 2018 A warm/stationary front will hold just north of Northern Lower Michigan thru tonight. Warm/moist air riding northward thru Lower Michigan will keep chances of hit and miss showers and storms in the forecast thru tonight. Chances of showers/storms will increase later tonight and Wednesday as the main surface low lifts NE out of the Southern Plains and into the Western Great Lakes region. Cigs and vsbys will drop to MVFR/possibly IFR as more widespread precip develops. Winds will remain generally from the S/SW at 10 to 15 kts for most locations...with the exception of PLN where winds will be more variable closer to the stationary front. && .MARINE... Issued at 348 AM EDT Tue Oct 9 2018 A frontal boundary will waver around eastern upper/far nrn lower Michigan today through Wednesday, before an area of low pressure and a strong cold front cross the region Wednesday night. The majority of the showers and embedded thunderstorms will primarily impact Lake Michigan and all of eastern upper Michigan, but scattered activity is expected over much of the nearshore waters this afternoon into this evening. More widespread showers and storms are anticipated Wednesday night as the low pressure and it's strong cold front cross the region. There is even a small risk for a few storms to have some damaging winds. The warmer SW winds ahead of the cold front will produce some low end advisory wind speeds, mainly over Lake Michigan despite neutral to slightly stable overlake conditions. There is just too much uncertainty to be sure of when and where headlines are needed at this point. More widespread advisory level wind speeds expected behind the cold front Wednesday night into Thursday with the potential for gales in spots as overlake instability grows substantially. This is pretty far out into the forecast, and will hold on for headlines for this scenario as well. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ UPDATE...MR NEAR TERM...SMD SHORT TERM...MK LONG TERM...MK AVIATION...MR MARINE...SMD