Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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790 FXUS63 KAPX 211444 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 1044 AM EDT Fri Jun 21 2024 .KEY MESSAGES... - Shower and Thunderstorm Chances continue today and tonight - Heavy rainfall with amounts of 2-4"+ possible Saturday into Saturday night. - Isolated severe storms also possible Saturday into Saturday night. - Less active, cooler weather possible next week. && .UPDATE... Issued at 1039 AM EDT Fri Jun 21 2024 Current satellite/radar imagery shows diminishing showers across the region with cloud cover attempting to erode, especially south of M-55. Anomalous moisture is in place, with thie mornings 12Z RAOB showing 1.71" PW. This moisture will remain through this afternoon with isolated to scattered thunderstorms, especially south of M-32 and east of I-75 in northern lower Michigan. Areas of locally heavy rain will be possible. Showers and storms continue into the overnight hours due to a disturbance aloft and approaching frontal boundary. Heavy rain is likely Saturday and Saturday night with isolated instances of flooding not out of the question. && .SHORT TERM /THROUGH TONIGHT/... Issued at 336 AM EDT Fri Jun 21 2024 Pattern Synopsis and Forecast: Current satellite and obs depict light and generally east to northeast winds around northern MI this morning. Low clouds are around the region with some areas of haze/fog likely (although obs show this at the moment). This overrunning of moisture over the cooler airmass near the surface will continue into the morning hours. CAM guidance is mixed on suggesting how long clouds and light rain will linger. Confidence is in it taking most of the morning to exit northern lower, and possibly lingering over eastern upper through the afternoon hours. Southerly winds will form over the southern and central part of the state, possibly creating an area of convergence late this afternoon. Some CAMs are showing isolated convection sprouting from this boundary and around ~700 j/kg of SBCAPE in the environment. The main hazards with any storms that do form later this afternoon will be heavy downpours, lightning, and possibly small hail and locally gusty winds. Mild overnight temperatures with chances for fog formation again as anomalous moisture hangs around. Primary Forecast Concerns/Key Messages: Guidance shows the uncertainty in the morning, more for what will happen to the upper level moisture overrunning a slightly cooler airmass near the surface. 00z KAPX sounding had 1.67 PWAT, which is near the daily max. The environment is very moist, and nothing really scours it out. Clouds will likely persist over eastern upper and near the tip of the mitt today as convection upstream will continue to bubble and throw clouds overhead. Areas closer to the central part of the state will get a good shot at clearing. If this happens and they warm into the low 80s, there is a good chance a few isolated non-severe storms will form along a low level convergence zone. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 336 AM EDT Fri Jun 21 2024 Pattern Synopsis: Low-amplitude ridging will depart east of the Great Lakes as troughing slides overhead this weekend. A lead shortwave looks to punch across the region Saturday with a much stronger, more prominent shortwave set to dig across the Great Lakes Sunday/Sunday night. Forcing provided by these features aloft will support a seasonably-strong cyclone that is expected to trek across northern Michigan Saturday into Sunday. Subsidence on the backside of this system as it moves out will likely build surface high pressure into the region on Monday before another wave enters the picture closer to the middle of next week. Forecast Details: Heavy rainfall possible Saturday into Saturday night -- Scattered showers and embedded thunder is expected to be ongoing at the start of the period as warm, moist advection will already be underway ahead of the approaching system. Strongest advections tied to 35- 45kt 850-700mb flow will arrive later on Saturday, helping to pump PWAT values to 2" or higher -- an impressive number for northern Michigan. This would far exceed the max moving average for any time of year (~1.8") and could possibly be sampled as a top-25 all time PWAT value at the 00Z Sunday 6/23 launch based on SPC sounding climatology. To no surprise, forecast soundings display moist adiabatic profiles through the depth of the troposphere with 500- 1,500 J/kg MLCAPE in place into the evening hours. With the warm front draped west-east across the lower peninsula, mean cloud-layer flow oriented parallel to the boundary, and aforementioned buoyancy in place, ingredients appear to be aligning themselves to support a heavy convective rainfall event across northern Michigan. Very efficient rainfall is expected over a several hour stretch for most locations -- and perhaps over the bulk of an 8-12 hour period for a swath of northern Michigan Saturday afternoon into Saturday night. Training convection will lead to the potential for some areas to see several inches of rain by Sunday morning. Based on latest guidance, parts of northern Michigan have high chances (70+ percent) to see at least 1" of rain, medium chances (40-60 percent) to see at least 2" of rain, and even low chances (10-30 percent) to see at least 4" of rain. Exact locations of heaviest rainfall are still uncertain, but current confidence has shifted further south than previous thought -- with best chances for heaviest rainfall lying between M-72 and the bridge. Flood potential will be monitored closely with this system given how favorable the environment in place will be to support efficient heavy rainfall over an extended period of time. Isolated severe storms possible Saturday into Saturday night -- While the primary, highest-confidence threat is heavy rainfall Saturday into Saturday night, isolated severe storms will also be possible during that time. Buoyancy will support convection, but aforementioned moist adiabatic profiles with buoyancy struggling to extend much past freezing aloft will hinder hail potential. Best chances for any severe storms may be late afternoon/evening as the wind field strengthens with the cyclone working into the region. This 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+. While a largely unfavorable convective mode is expected at this time -- and will limit overall severe threat -- aforementioned shear magnitudes, if/when combined with any partial clearing to foster elevated low- level CAPE, will support both a damaging wind and low-end tornado threat across northern lower Michigan. Less active, cooler weather next week -- Rain/thunder chances look to wind down through the second half of the weekend as high pressure builds in to start the week, bringing about a reprieve from rain chances on Monday. Rain chances look to return closer to the middle of the week, but the overall pattern appears to be less active for the Great Lakes through the end of the period. High temperatures in the upper 70s/low 80s to start the week look to cool back closer to 70 through back half of the period. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 746 AM EDT Fri Jun 21 2024 Few areas of MVFR and locally IFR cigs at terminals this morning. Skies mostly BKN010 to BKN050 with patchy HZ/BR. -RA moving out of eastern upper and tip of the mitt terminals. Winds generally VRB AOB 10kts through the period. Chances for skies to breifly lift and scatter especially over northern lower terminals from 16Z through 20Z. VCSH chances after 20Z, with higher confidence -RA/RA chances after 03Z for most terminals. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE... SHORT TERM...ELD LONG TERM...DJC AVIATION...JZ