Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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804 FXUS63 KAPX 141919 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 319 PM EDT Wed Aug 14 2024 .KEY MESSAGES... - Shower and thunderstorm chances Thursday night and Friday. Locally heavy rainfall possible, with non-zero chance at severe storms Friday afternoon. - Another showery weekend && .SHORT TERM /THROUGH THURSDAY/... Issued at 320 PM EDT Wed Aug 14 2024 Pattern/synopsis: High pressure over lower MI will move eastward, to the eastern lakes and then approaching the mid- Atlantic coast. Return flow will gradually increase behind the high, ahead of a mature low and occluded front crossing the upper MS Valley. Forecast: Keeping an eye on some well-developed cu in eastern upper MI, along the lake breeze convergence zone. Not expecting to cook off up there, though. Quiet for tonight, though cloud cover will start to increase from the sw. That increase continue thru Thursday, with gradual moistening in increasing return flow. Initially dry air will take some work to overcome, and the main push of precip occurs Thu night and beyond. Filtered sunshine will not result in any SbCape here on Thursday; we`re too dry ahead of initial precip band. Some showers could work into nw lower MI beginning toward midday. Pops increase thru the afternoon and evening, again mainly nw lower MI. Marginal elevated instability develops ne-ward across central Lake MI late in the day. A chance for some thunderstorms emerges by early evening, mainly west of TVC-CAD, with locally heavy rain possible. Lows tonight mid 50s to lower 60s. Highs Thursday upper 70s to low-mid 80s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 320 PM EDT Wed Aug 14 2024 Pattern Synopsis / Forecast: Frustratingly complex forecast in the cards to close out the week. Slow moving 500mb shortwave and associated surface low pressure / frontal boundaries will slowly make their way through northern Michigan Thursday night through much of the weekend. Moisture rich nature of this complex system will lead to potential for heavy rain at times, particularly Thursday night. A non-zero risk for severe storms may materialize Friday afternoon as the cold front passes through near / during peak heating. With moisture slow to erode on the backside of the system, showers will continue to be possible Saturday and perhaps Sunday too. High pressure briefly returns early next week before another disturbance makes a run at the upper Great Lakes toward the middle of next week. WPC Excessive Rainfall Outlook: Day 2 (Thursday morning-Friday morning) Marginal Risk- Focused across much of the CWA, with the exception of areas east of an Oscoda to Paradise line. Day 3 (Friday morning - Saturday morning) Marginal Risk- Focused primarily north / east of the M-115 corridor. Storm Prediction Center Severe Thunderstorm Outlook: Day 3 (Friday morning-Saturday morning) Marginal Risk (Level 1/5) essentially along and east of I-75 in both northern lower and eastern upper Michigan. Primary Forecast Concerns: Heavy Rain Potential: Moisture advection will be in full swing as the surface low and associated warm frontal boundary approaches. Latest guidance is certainly remaining bullish on moisture concentration, with PWATs as high as 1.5-1.8 (at or slightly above a 2 sigma anomaly for mid August) in the moisture pooling region along the passing warm frontal boundary. Two distinct elements will be at play with this rain: convective generation and synoptic generation. Convective element will certainly be going strong across Wisconsin through the day Thursday, but is expected to diminish somewhat as the instability plume becomes stunted by loss of daytime heating across northern Michigan. Some guidance tries to continue to force some storms across NW lower, but wouldn`t anticipate this area gutting much past I-75 and much farther north of M-72 Thursday evening. Some of these storms could drop a quick 2.00"+ of rain, which could certainly lead to some localized ponding of water, but any convection should be transient enough to mitigate more serious hydrological issues. As the low continues its movement into the region, there are some relatively strong signals for a synoptically forced area of steady efficient rainfall Friday night into Saturday along the warm frontal boundary, basically between M-72 and the Bridge. Excellent divergence aloft from associated jet streak and an 850mb jet of 35- 45kts parallel to the front should provide ample lift along the warm frontal boundary, generating the aforementioned area of enhanced rainfall. There are some signals for some spots to see amounts in excess of 2.00" of rainfall where this band of rain sets up... though the longevity may mitigate a majority of flooding issues, there will still be potential for low-lying / poor draining areas to pond up during this outburst of rain Thursday night into Friday. Friday Afternoon / Evening Severe Potential: As the low pressure center works overhead and some daytime heating can materialize in the dry slot, there will be potential for destabilization Friday afternoon as the attendant surface cold frontal boundary makes its way into the region. Some guidance is painting rapid destabilization across northeast lower... in the event clearing can materialize. Given the dynamics of the dry slot (steeper lapse rates, 0-6km shear approaching 25-30kts), in the event convective temperatures (likely anywhere from 76-80 degrees) can be realized, certainly enough there to force a severe threat with primary hazards of damaging winds and perhaps some hail too. This is highlighted by the Day 3 SPC outlook putting NE lower and far eastern upper in a Marginal Risk. With all that being said... wouldn`t be surprising to see a majority of this activity hold south of the CWA (where better surface heating is present) despite the expansive Day 3 outlook. More details to come in the ensuing forecast cycles. Rest of the weekend: Following the passage of the cold front, continued cyclonic flow will allow for the prolonging of shower activity into Saturday as moisture associated with the system is slow to exit. Probably not a washout, but certainly a fitting day for what has been a summer full of wet weekends. It does look like the back half of the weekend will be drier, or at least have lesser shower coverage. Given proximity of the system to the east, the best / longest lasting shower chances on Sunday would favor NE lower. We eventually dry out Monday. Temps: Humid with highs in the 70s Friday and Saturday, humidity begins to ease Sunday and especially Monday with highs still in the 70s. Lows range from the 60s Thursday and Friday nights, eventually into the 50s and 60s Saturday night, and low-to-mid 50s Monday night and beyond. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 126 PM EDT Wed Aug 14 2024 Mostly VFR, though some fog possible MBL late tonight. High pressure, centered over MI today, will slowly drift eastward. Mainly clear skies into this evening. Clouds do start to increase late tonight and Thursday. Still is a chance for IFR fog at MBL late tonight, but do not have vsbys dropping as low as they did this morning. Better precip chances arrive at MBL/TVC just beyond this TAF period. Light winds into tonight. Southerly breezes increase on Thursday. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ SHORT TERM...JZ LONG TERM...HAD AVIATION...JZ