Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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001 FXUS63 KGRR 230554 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 154 AM EDT Sun Jun 23 2024 .KEY MESSAGES... - Strong/severe storms this evening into tonight - Round of storms possible for late Monday night into early Tuesday && .UPDATE... Issued at 855 PM EDT Sat Jun 22 2024 A marginal threat for severe weather, chiefly in the form of damaging wind gusts, will continue for southwest Lower MI until shortly after midnight. Severe convection moving east across southern WI at this time appears to be congealing into a line and we would expect a continued linear storm mode as this activity crosses Lake MI into Lower MI. The downstream thermodynamic and kinematic environment over Lower MI is not overly favorable for sustaining intense thunderstorms. Typically we would want to see substantial DCAPE and steep low level lapse rates over Lower MI. Neither of these features is present at this time. Moreover, the upper jet as depicted on WV imagery suggests the best PV forcing will pass north of the area and there is no downstream upper jet to provide any sort of coupled forcing for ascent. We still have to monitor the threat for localized flooding however, especially if the boundary associated with the congealing line of convection becomes oriented more west to east overnight. && .DISCUSSION... Issued at 234 PM EDT Sat Jun 22 2024 - Strong/severe storms this evening into tonight The combination of decent ML CAPE values of 500 to 1000 J/kg, 100 to 125 J/kg of 0 to 3 km ML CAPE and increased surface convergence along a warm front has produced a favorable setup for some storms with rotating updrafts over northeast parts of the CWA. The low level convergence is progged to weaken over the next hour or two so that may limit the coverage of storms. By 23z, the storms in WI may be working into western parts of the CWA. Overall the low level convergence is still shown to be weak but high res models are showing another area of storms arriving in the 01z to 03z window. This is when the mid level jet is pushing in from the west. As a result these storms do have a potential for enhanced wind gusts if they do indeed form. Its not until 12z Sunday that the cold front moves in so another round of storms will be possible then. - Round of storms possible for late Monday night into early Tuesday Models are showing a mid level wave dropping down from the northwest during this time. MU CAPE values are over 1000 J/kg with favorable deep layer shear values. Thus a potential exists for a round of thunderstorms during this period. Given the combination of shear and instability the convection could become organized. Tuesday afternoon, MU CAPE values top 2000 J/kg and favorable deep layer shear is shown to exist but the models are also showing a cap. For now we will maintain a low risk for storms then. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 154 AM EDT Sun Jun 23 2024 A few more hours of showers and thunderstorms will be followed by a period of IFR cigs Sunday morning as a cold front comes through. Cigs lifting to MVFR levels by afternoon behind the front then scattering out/turning VFR late in the day (except earlier at MKG... shortly after 18Z). VFR prevailing on Sunday night. Winds shifting northwesterly with the passage of the cold front Sunday morning and increasing to 15 to 25 kts for the afternoon. Winds gradually subsiding Sunday evening after 00Z. && .MARINE... Issued at 234 PM EDT Sat Jun 22 2024 Southwest winds out ahead of the main wave may gust over 20 knots at times this afternoon but stronger winds will be possible tonight into Sunday as the wave moves in. Thus we will maintain the marine an beach hazard headlines for tonight into Sunday morning. && .HYDROLOGY... Issued at 234 PM EDT Sat Jun 22 2024 The PWAT values are up around 2 inches and area soundings are showing low lcl`s along with thin deep CAPE, especially for northwest zones. Favorable 925 to 850 mb moisture transport exists through southern WI and into our northwest zones including the Pentwater to Ludington region. The deep wave moving in from the west will encounter an unstable air mass here in MI for this afternoon and into tonight leading to showers and storms with heavy rain. Already there has been 1.5 to 2.5 inches for parts of Mason, Oceana and Lake counties. High res models show swaths of heavier rain still to come with locally over another 1.5 inches looking likely. Given the risk for additional heavy rain in combination with the rainfall which has already fallen, there could be some flooding from these cells so we will keep the flood watch going. For the larger rives, they are relatively low. Projected rainfall amounts keep the forecast points under action stage at this time. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until noon EDT today for MIZ050-056-064- 071. MARINE...Small Craft Advisory until noon EDT today for LMZ844>847. && $$ UPDATE...TJT DISCUSSION...MJS AVIATION...Meade MARINE...MJS HYDROLOGY...MJS