Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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505 FXUS63 KAPX 220133 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 933 PM EDT Fri Jun 21 2024 .KEY MESSAGES... - Widespread showers and thunderstorms with heavy rainfall likely later tonight and especially into Saturday. Isolated areas of flooding will be possible. - Heavy rain threat continues into Saturday evening. - Additional shower chances at times next week. && .UPDATE... Issued at 932 PM EDT Fri Jun 21 2024 Diurnal instability developed today over central and southern lower MI. Precip coverage and amounts have thus been highest in our southern areas, along the north fringe of this unstable area. That instability is slowly waning. However, instability is also found over southern WI and places south and west. Sub-800mb winds from the sw increase in the western and central lakes tonight, gradually advecting that richer airmass into our area. That will fuel sporadic convection across the area tonight, and precip rates will potentially increase as moisture levels ramp up further. && .SHORT TERM /THROUGH SATURDAY/... Issued at 245 PM EDT Fri Jun 21 2024 Pattern Synopsis and Forecast: Energy aloft quickly moves into the area tonight with lingering/additional shower & storm development. The main story will be a short wave trough riding the north periphery of a ridge thus facilitating sfc low development across the Plains, Midwest, then Great Lakes later tonight through later Saturday. Additionally, warm front/stationary boundary will drape across northern Michigan. All the while, an anomalously moist environment will remain in place, and even increase into Saturday, facilitating the potential for heavy, efficient rainfall. Along with other aspects, this pattern described above takes after the classic "Upper Level Ridge" Maddox Flash Flood Pattern/Conceptual Model and is definitely food for thought in regards to this upcoming event. Primary Forecast Concerns: Real intriguing pattern upcoming from a heavy rain perspective. Anomalous moisture is already in place, as both sampled from this mornings 12Z sounding (1.71" PWs) in addition to anecdotal evidence via on/off-duty meteorologist observing very efficient, warm rain processes with this mornings rain in the vicinity of Gaylord and north. Thus, with the threat for increased showers and storms this afternoon/evening, especially if portions of the area clear out and some instability is able to manifest, very heavy rainfall will be possible, mainly south of M-32 and east of I-75 (where the best moisture/clearing will likely be). Quick 1 to 2 inches of rain cannot be ruled out. Pattern late tonight into Saturday night emulates classic "Upper Level Ridge" Maddox Flash Flood Pattern/Conceptual Model. Short wave rides the upper level ridge with stationary boundary and anomalous moisture in place. Plenty of lift, minor but long skinny CAPE, PWs in the vicinity of all time/top 10-20 or whatever values, and some pretty ridiculous warm cloud layer heights (11-13kft) for this region of the world. Conceptual model suggests the heaviest rainfall will be just to the north of the boundary on the "cool" side, which would put the heaviest rainfall across the northern half of northern lower, tip of mitt and vicinity generally. All of this considered, CAMs and global models suggest 2-4", some 6"+, especially north of M- 32. Pretty significant signal for efficient, very heavy rainfall especially in locations that have training storms/cells. Additionally, region from Torch Lake and East Jordan east to Alpena has seen 1 to 3 inches of rain the last 48 hours, so this region may be slightly more prone to flooding with this event. Thus, at this time, we think at least isolated instances of flooding will be possible Sat-Sat night, especially across flood prone regions and urban areas. This rich environment with heavy rain potential will continue into the overnight hours on Saturday, visit the long term discussion for more details. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 245 PM EDT Fri Jun 21 2024 Pattern Synopsis/Pattern Forecast: A period of transition as sub-tropical ridge slow retrogrades west into early next week, taking up it more familiar summer location across the Desert Southwest by the middle of next week. This forces/allows more northern stream influences into the northern Conus...including the Great Lakes...next week. Per the usual, such transitions often bring about some of our more active weather, and this one is no exception with periods of heavy rain and perhaps some severe weather to kick off this weekend. Primary Forecast Concerns/Challenges: Addressing heavy rain and severe thunderstorms concerns Saturday night. Secondary focus on additional shower chances and temperature trends through next week. Details: Heavy rain threat will continue as we head through Saturday night. Pattern recognition strongly suggests such, with a stalled baroclinic axis serving as a source of forced deep layer convergence within an exceptionally moisture rich vertical profile of the atmosphere (precipitable water values up and over 2 inches across parts of northern lower Michigan...nearing max potential for northern Michigan). Persistent low level jet forcing along primary baroclinic axis/stall warm front will only enhance deep layer convergence into Saturday evening as weak area of low pressure rides along the stalled frontal boundary. Efficient warm cloud processes will enhance rainfall rates, which could easily exceed an inch per hour a times...with pattern recognition again supporting potential for training of these heavier rainfall rates. While nearly all of northern Michigan remains within the slight risk category per latest WPC excessive rain outlook, current primary target areas based off deep layer convergence signature suggests areas between M-72 and the Straits remains the primary focal point. Combine this with the expected heavy rain on Saturday (see short term section above for all those good details) and very likely some areas will exceed 2 inches of rain by sunrise Sunday. Wouldn`t be terrible surprised to see some local areas exceed this amount be quite a bit given expectations set above. Secondary concern remains severe potential. While moist adiabatic lapse rates through nearly the entirety of the column, increased cyclonic curvature along and south of stalled frontal boundary will enlarge already cyclonically-curved low-level hodographs in an environment characterized by 0-1km shear of 35+ kts, 0-3km shear of 40+ kts, and effective SRH of 200+. Combine this with low lifting condensation levels and the potential for precipitation loading, and the stage is set for a low end tornado and gusty wind threat. Again, this remains a secondary concern...taking a back seat to the heavy rain potential. Honestly speaking...not a lot of time devoted to the rest of the extended forecast. More northern stream influence for sure, voiding our area of any more periods of prolonged heat. Passing waves within what looks to be a rather energetic/active flow regime should brings the threat for showers and thunderstorms at times. Exact timing of any individual waves subject to change of course. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 750 PM EDT Fri Jun 21 2024 Worsening conditions. Warm/moist air will gradually push into the region again, as a warm front now in northern IL moves north. SHRA/TSRA will become more numerous tonight, with occasional vsby restrictions possible. Cigs will also worsen, with MVFR and then IFR cigs becoming widespread overnight and into early Saturday. SHRA/TSRA may see a bit of a lull Sat morning, before become more widespread again in the afternoon. Light winds. && .APX WATCHES/WARNINGS/ADVISORIES... MI...Flood Watch from 2 AM EDT Saturday through Sunday morning for MIZ016>018-020>030-099. MARINE...None. && $$ UPDATE...JZ SHORT TERM...JLD LONG TERM...MSB AVIATION...JZ