Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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615 FXUS63 KGRR 300143 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 943 PM EDT Mon Apr 29 2024 .KEY MESSAGES... - Scattered Showers/Storms into early evening - Best Chance for Showers and Storms Thursday into Friday - Above Normal Temperatures for Early May && .UPDATE... Issued at 936 PM EDT Mon Apr 29 2024 The surface cold front is currently over Lake Michigan. Any leftover showers ahead of the front will mainly be confined to areas east of I-69. Removed thunder mention for the remainder of the night. A gradual decrease in cloud cover from west to east overnight will allow for temperatures to bottom out in the mid 40s north and low 50s south and east. && .DISCUSSION... Issued at 258 PM EDT Mon Apr 29 2024 - Scattered Showers/Storms into early evening One batch of showers was pushing through the Lansing to Jackson region at this time. ML CAPE values were relatively low in our CWA and that has limited the thunder risk potential. The coupled upper level divergence/low level convergence area along this line of showers was pushing northeast of the CWA. Projected surface based instability(<500 J/kg) and lift through the remainder of the afternoon hours suggest only a limited potential for showers/storms exists going into the early evening hours. Most of this lift will be associated with the surface cold front that pushes in from the west. Isolated showers/storms could develop near and ahead of this front. Also, there is one batch of showers/storms in southeast IL/west central IN will likely clip the area southeast of a Battle Creek to Lansing line over the next few hours and that is the region where we will feature the highest probabilities for measurable precipitation this afternoon. - Best Chance for Showers and Storms Thursday into Friday Wednesday looks to be dry for West Michigan as any minimal rain chances Tuesday night quickly evaporate after daybreak. The next notable chance of rainfall across West Michigan is Thursday into Friday. A warm frontal boundary lifting north across the state provides some potential for showers during the day on Thursday, especially closer to the low towards Muskegon and Ludington. Precipitation becomes more widespread Thursday Night into Friday as a cold front drops across the region with a shortwave off of the parent trough moving through. Depending on when the front comes through, we will need to monitor for the chance of thunderstorms. The NAM (which is just coming into range) along with the GFS, both suggest most unstable CAPE values in excess of 1000 J/kg are possible Thursday afternoon. Predictability in the longwave pattern decreases notably into next weekend. Cluster analysis shows a trough somewhere in the vicinity of the region Saturday into Sunday, however there are discrepancies in the amplitude of this feature and whether deeper troughing directly affects lower Michigan. In one camp you have most GEPS members along with approximately 40 percent of the GEFS/EPS members suggesting a greater amplitude trough and by extension better forcing for precipitation, making up about 50 percent of the grand ensemble. On the other hand, the other approximately half of the grand ensemble supports a more zonal pattern with the better height falls staying out of the area. This would support lower precipitation chances across West Michigan. Given the uncertainty, will leave the current 30% PoPs from the NBM as is. - Above Normal Temperatures for Early May Highs in the 70s are expected for the long term period. The warmest day will be Thursday as southwest flow causes 850mb temps to rise into the 12-16C range. NBM max temperature probabilities suggest a 50 percent or more chance of exceeding 80 degrees Thursday south of M46. Low temperatures should generally be in the 50s. This will be above our normals of mid to upper 60s for early May highs and mid 40s for lows. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 810 PM EDT Mon Apr 29 2024 Mainly VFR is expected, exceptions being MVFR ceilings near and south/east of JXN the next few hours and also a couple hour period of MVFR ceilings possible tonight with a cold front passing through everywhere else. Winds become west with gusts 16 to 20 knots during the day Tuesday, with VFR likely. && .MARINE... Issued at 810 PM EDT Mon Apr 29 2024 Dense fog in the nearshore has cleared up, and south winds this evening will shift westerly overnight with passage of a cold front. During the day Tuesday, west winds will back southerly late in the day. The cooler waters of Lake Michigan, compared to the relatively warmer air mass, will maintain a stable marine layer and prevent stronger winds aloft from gusting over the lake. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...Hoving DISCUSSION...MJS/Thomas AVIATION...CAS MARINE...CAS