Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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289 FXUS63 KGRR 210610 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 210 AM EDT Fri Jun 21 2024 .KEY MESSAGES... - Risk for Severe Storms through this afternoon - Heat continues - One or more rounds of Strong/Severe Storms possible Saturday into Saturday night && .UPDATE... Issued at 927 PM EDT Thu Jun 20 2024 Radar indicates dwindling precipitation with low prospects for redevelopment overnight, so will lower PoPs this update. The only other concern of note will be the possible development of patchy fog overnight especially where the heavier precipitation had occurred. This would include the I-96 corridor from Grand Rapids to Lansing as well as areas from Rockford to Belding. && .DISCUSSION... Issued at 311 PM EDT Thu Jun 20 2024 - Risk for Severe Storms through this afternoon SPC`s meso page shows ML CAPE values around 1500 J/kg extending from near Grand Rapids to Lansing and down into the Jackson region. Low level convergence is enhanced in this region and as a result scattered storms have developed. These storms have produced outflow boundaries some of which have collided. Effective bulk shear was up to 25 knots and some organization has occurred with the cells. High res models suggest the cells will gradually build east so the risk for a few severe storms remains possible into the late afternoon hours. - Heat continues into Saturday The low level thermal ridge remains over the southern and central zones into Saturday. At the same time there will be plenty of moisture in this warm air mass with PWAT values hovering in the 1.75 to 2.00 inches. Progged heat index values are shown to continue to top out in the 93 to 97 degree range during this timeframe. As a result we will keep the head advisory going. - One or more rounds of Strong/Severe Storms possible Saturday into Saturday night Parameters are coming together to warrant a greater risk for severe weather during this time frame. Overall the models are generally showing a stronger mid level wave digging into the area in a pattern of stronger mid to upper level flow. A morning low level jet could set off an MCS, especially over northern parts of the CWA. A second low level jet arrives in the evening. Ensemble surface based CAPE values from the models are showing at least 1000 J/kg in the afternoon/evening. With the potential for stronger wind fields, favorable dynamics and instability, we may end up with organized storms with stronger/organized wind gusts being a main hazard. With several rounds of heavier rain possible, values could be excessive. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 210 AM EDT Fri Jun 21 2024 Areas of MVFR/IFR in fog/stratus expected through 12Z with a small chance of local LIFR vsbys as well, mainly at JXN and LAN. Conditions lifting toward VFR by afternoon, although a few t-storms possible in the afternoon at LAN and JXN. Once again the strongest cells may contain torrential rain, gusty winds and hail so if they directly impact a terminal there could be brief IFR or lower conditions and possibly a wind gust over 30 kts. Convection ending by 00Z this evening. && .MARINE... Issued at 311 PM EDT Thu Jun 20 2024 Overall, outside of any storms the winds and waves remain low into Friday. On Saturday its looking like the winds and waves will be building with a high potential for hazardous swim and boating conditions arriving by evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Heat Advisory until 8 PM EDT Saturday for MIZ056-057-064>067- 071>074. MARINE...None. && $$ UPDATE...TJT DISCUSSION...MJS AVIATION...Meade MARINE...MJS