Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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116 FXUS63 KGRR 080746 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 346 AM EDT Mon Jul 8 2024 .KEY MESSAGES... - Occasional Showers and Storms Through Tuesday - Rain showers, some heavy, possible Tuesday night into Thursday - Unsettled, warm weather continues into next weekend. && .DISCUSSION... Issued at 343 AM EDT Mon Jul 8 2024 - Occasional Showers and Storms Through Tuesday Regional water vapor imagery shows a weak vorticity maxima across Wisconsin that will slide into lower Michigan over the next few hours. Combined with upper-level divergence showers will develop across the northwest CWA near daybreak. An isolated rumble of thunder is possible but confidence is low. More widespread shower and thunderstorm chances arrive this afternoon into the evening as a shortwave ahead of a parent trough initiates convection off of a lake breeze convergence zone draped across the CWA. We remain in the D1 general thunder as while MLCAPES exceeding 750 J/kg are expected with MUCAPEs exceeding 1000 J/kg, deep layer shear is marginal at 25-35 knots. Model soundings also show modest mid-level lapse rates which means updrafts will struggle somewhat as they develop. Cannot rule out isolated strong storms (wind/hail risk) but that would be the exception and not the norm. Showers and storms then subside overnight. Latest trends Tuesday suggest that a front crossing into the area stalls as the mid-level wave driving it shears out, as well as the front undergoing frontolysis. Scattered showers and storms are possible, mainly across the southeastern CWA where the dying front stalls, however much of the area will be dry. While instability is present, shear under 30 knots aided by near moist adiabatic mid- level lapse rates will keep the occasional embedded thunderstorm non- severe (if any convection can develop at all). Approaching 00z Tuesday, the deformation rain bands associated with the remnants of Beryl begin to approach the I94 corridor. - Rain showers, some heavy, possible Tuesday night into Thursday The models continue to hone in on the track and course of Beryl. As Beryl becomes extra tropical and moves to the northeast, there continues to be run to run variability in both the ensembles and in the operational models on the track. The NHC cone overall covers most, if not all, of these potential outcomes. The biggest driver for Beryl will be two fold. First the 300mb jet stream will move through the midwest with a 100 kt jet moving over Michigan by Wednesday night. Stepping down to 500 mb the remains of Beryl becomes engulfed in the trough and should ride up into a weak negatively tilted ridge. The biggest question is where the core of the low goes from there. Ensembles and latest models continue to waffle between various courses. However, even given the differences between the runs, the overall course brings persistent tropical moisture and showers through southern Michigan Tuesday night through Wednesday and into Thursday. WPC has the region in a slight risk for excessive rainfall and half one to two and a half inches over time frame. So while some potential changes lurk on the horizon, a wet period is ahead through mid week. - Unsettled, warm weather continues into next weekend. No major changes through the latter half of the week with slightly warmer than normal Max temperatures ahead with periods of showers and storms possible as a zonal flow will bring successive troughs through the region. This should allow for potential for afternoon convection through the latter half of the week and into next weekend. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 145 AM EDT Mon Jul 8 2024 Overall VFR will dominate the pattern today. However, some showers with an isolated thunderstorm will continue to move eastward from Wisconsin early this morning. As storms should be north of any TAF sites, not foreseeing any reductions this morning. Storms forming this afternoon into the early evening could briefly reduce Vsbys/cigs with the best chance at AZO and BTL. && .MARINE... Issued at 343 AM EDT Mon Jul 8 2024 Weak gradient winds keep winds and waves below small craft advisory/beach hazard statement levels today into Tuesday. The next timeframe of concern will be Wednesday and Wednesday night as the remnants of Beryl approach the Central Great Lakes. Notable uncertainty in the track of this system, and by extension the positioning and strength of the gradient pattern exists. The trend across 00z guidance is for a more easterly low track which would reduce the impact of gradient winds across the lake. However, the NAM and to some extent the Canadian model do suggest northerly winds at least approaching small craft criteria. Bottom line is marine interests may be impacted by the remnants of Beryl mid-week, however uncertainty in the extent of this remains high. Stay tuned to future forecast updates as the low track becomes clearer. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ceru/Thomas AVIATION...Ceru MARINE...Thomas