Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
506 FXUS63 KGRR 032326 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 726 PM EDT Wed Jul 3 2024 .KEY MESSAGES... - Warm and Partly Cloudy Independence Day - Showers and Storms Likely Friday - Unsettled Pattern Next Week && .DISCUSSION... Issued at 254 PM EDT Wed Jul 3 2024 - Warm and Partly Cloudy Independence Day Not much change to this part of the forecast. Dry weather is expected with rain chances creeping into far southwest Lower Michigan beginning well after dark on July 4, so little to no disruptions to nighttime fireworks are expected at this time. Dewpoints should be in the lower 60s during the day, resulting in apparent temperature/heat index readings in the mid 80s, which is near or slightly below expected highs in the upper 80s for areas away from the lake. - Showers and Storms Likely Friday The primary timeframe to watch for impacts will be late Friday morning into the afternoon. Synoptically, a positively tilted trough approaches the area causing a surface low to deepen as it passes to our northwest. The dynamics are decent with a 50 knot westerly mid- level jet and 30 knot southwesterly low-level jet setting up across lower Michigan. Ample moisture will be in place and dewpoints climb near 70 with PWAT values exceeding 1.5 inches. The key to severe potential will be the extent of morning convection ahead of the front. Current trends support an earlier frontal passage (late morning into early afternoon) supporting less instability, as well as more showers and storms ahead of the front. These outcomes would limit potential for strong storms even with decent deep layer shear. However, if we can get some instability to build (which won`t be difficult given the high dewpoints), ample moisture and the strong kinematics mean some gusty winds from water loaded downdrafts cannot be ruled out. This will need to be monitored closely over the next day or two to see if trends more towards a severe weather risk. Regardless of any severe weather potential, showers with embedded thunderstorms are likely as the front moves through so will keep the high PoPs in place for Friday. - Unsettled Pattern Next Week The shortwave and associated surface low take their time to exit west Michigan so rain showers continue into Saturday. A brief break comes in late Saturday into early Sunday as high pressure pushes through the state. The overall pattern remains quite unsettled Sunday into mid next week. A longwave trough sets up across the eastern half of the CONUS while strong ridging sets up across the western half. The general expectation in these kinds of patterns is for shortwaves to rotate through the larger scale flow pattern; bringing occasional chances for showers and storms. However, at this range, exact timing of any precipitation is uncertain as it depends on how the upper-low evolves in terms of its strength and position. Even though several chances of rain are possible, dry weather will be predominant much of the time. The other good news is that while temps will be slightly cooler, significant drops in temperature are not expected due to the low amount of change in the predominant airmass temperature. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 726 PM EDT Wed Jul 3 2024 VFR will persist through the forecast period as high pressure rolls into the region. There are signals that MKG may see fog early Thursday morning but there is low confidence that visibility will be greatly impacted. Winds turn calm overnight then build to around 5 knots Thursday. && .MARINE... Issued at 254 PM EDT Wed Jul 3 2024 Main concern in the very short term is persistent and localized shallow marine fog being noted by some of our webcams in the Holland to South Haven vicinity. Expectation is that this will scour out later today based on visible satellite trends. Fog could return again tonight, but if it does, it`s not expected to be widespread enough to warrant headlines. The immediate lakeshore could see some rapid changes though. Otherwise, winds and waves are expected to remain below advisory criteria through the period. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...TJT/Thomas AVIATION...Thielke MARINE...TJT