Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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358 FXUS63 KGRR 250200 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1000 PM EDT Mon Jun 24 2024 .KEY MESSAGES... - Strong to severe storms possible late tonight/Tuesday morning - Dry Most of Wednesday into Early Friday - Rain Returns Friday into Saturday && .UPDATE... Issued at 1000 PM EDT Mon Jun 24 2024 No significant fcst changes are needed this evening. A consensus of latest CAMs corroborated by recent rgnl radar trends the past hour or so suggest that the complex of thunderstorms over south central/se WI will continue to diminish late this evening. Our primary svr wx threat will come during the early morning hours Tuesday (around 08Z-13Z) as severe thunderstorms over northern MN attm congeal into a well developed MCS/squall line that moves se along the instability gradient. There is some question as to how much instability will be present by the time the convection moves into our area. However a favorable kinematic environment will likely compensate for diminishing instability and bring potential for damaging wind gusts particularly across our western/nw fcst area by around 08Z-10Z Tue and lasting through mid morning. && .DISCUSSION... Issued at 330 PM EDT Mon Jun 24 2024 - Strong to severe storms possible late tonight/Tuesday morning Bottom line up front: Storms capable of producing damaging winds and large hail will be moving through the region tonight through Tuesday morning. A line of storms will sweep through the region early Tuesday morning between 5 AM and 10 AM. Latest CAMS have several rounds moving through. The first should be a cluster of storms that moves through between midnight to 2 AM timeframe. That cluster has strong enough updrafts with 7 to 8 C/km lapse rates through the mid levels where damaging hail is a concern. The biggest threat tomorrow will be a long line of storms that will be extending from an upper level wave moving through the region overnight. This squall line will feature a strong pressure gradient with strong low level winds aloft accompanying this system. There is potentially over 50kts of winds between 5 to 10kt feet moving onshore after 5 AM. The question is whether or not it will be able to mix to the sfc. The strong southerly flow will keep stable air in place along with a strong inversion that could keep any convection at bay. Given all of this, the line is not purely thermodynamically driven but the strong kinematics will assist in downdraft potential. This line will move through Tuesday morning and exit the region moving to the southeast early Tuesday afternoon. There will be another round of storms possible later Tuesday, however given that the region will be fairly mixed it will lessen the potential for any storms. - Dry Most of Wednesday into Early Friday The long term forecast will be dominated by two key longwave features. The first being ridging across the southern CONUS and the second being longwave troughing across northern Canada. This places lower Michigan in a quasi-zonal longwave pattern with two main periods of active weather. Our first active period will continue from Tuesday night as showers wind down during the morning hours Wednesday with a shortwave exiting the area. Cannot rule out an isolated rumble of thunder near JXN given low-level LIs near but confidence is low as instability ramps up as showers depart. Surface high pressure and mid-level ridging then build in for the rest of Wednesday and continue into the start of the day Friday bringing dry weather and highs in the upper 70s to low 80s. - Rain Returns Friday into Saturday By Friday the ridging shifts east with a 30-35 knot SW low-level jet setting up a warm air advection pattern. As expected in the day 5-6 range, some small differences in timing and placement of key surface and upper-level features exist, though the overall idea has good model consensus. Showers and thunderstorms develop potentially as soon as Friday afternoon in the warm air advection pattern, with the best chance Friday night into Saturday as a shortwave trough and associated cold front move through. High pressure returns behind the departing cold front later Saturday into Sunday returning dry weather to Mid-Michigan. Highs in the 80s Friday and Saturday fall into the 70s Sunday behind the cold front. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 615 PM EDT Mon Jun 24 2024 VFR conditions will continue at all the terminals through late this evening. A line of thunderstorms will move across Lake MI from the northwest overnight and will impact our western terminals from around 08Z-10Z early tomorrow morning. The storms could bring brief reductions to IFR and brief but very gusty winds to near or potentially in excess of 50 kts. At this time there is not enough confidence that thunderstorms will hold together and impact our eastern terminals. Those terminal forecasts will be updated overnight based on radar and convective trends overnight. VFR conditions are expected at all the terminals from mid to late Tuesday morning through the afternoon. We will have to monitor for potential redevelopment of a few showers and storms tomorrow afternoon and evening. However at this time there is not enough potential for that to occur to warrant mention in any of the terminal forecasts. && .MARINE... Issued at 340 PM EDT Mon Jun 24 2024 Southwest winds will increase tonight behind a warm front and that will result in wind and waves that will become hazardous to small craft. High Confidence in several rounds of thunderstorms developing over the lake after midnight tonight with the potential for damaging winds and a chance for large hail. Along with these storms rip currents may persist after thunderstorms Tuesday morning due to possible water level fluctuations. Chance in storms Tuesday afternoon into Tuesday evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from 2 AM EDT Tuesday through Tuesday evening for MIZ037-043-050-056-064-071. MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for LMZ844>849. && $$ UPDATE...Laurens DISCUSSION...Ceru AVIATION...Laurens/Thomas MARINE...Ceru