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
463 FXUS63 KGRR 031431 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1031 AM EDT Wed Jul 3 2024 .KEY MESSAGES... - Chance of Passing Showers Today Then Clearing Clouds - Warm and Partly Sunny Independence Day - Risk for a Period of Strong Storms Friday && .UPDATE... Issued at 1031 AM EDT Wed Jul 3 2024 No changes to the current forecast are planned. The main forecast concern with the afternoon update will be regarding the potential for strong/severe convection Friday. && .DISCUSSION... Issued at 340 AM EDT Wed Jul 3 2024 - Chance of Passing Showers Today Then Clearing Clouds A weak cold front passing through the area this morning, along with remnant low-level moisture and meager elevated instability, may touch off a few showers (slight chance of isolated thunderstorm). By late in the morning, the chance will shift south and east of Grand Rapids toward Jackson. Most of the clouds are likely to clear away from NW to SE this afternoon, and deeper mixing will help temperatures climb higher than they were yesterday. - Warm and Partly Sunny Independence Day In between upper-level shortwave troughs on the 4th of July, there will be a diffuse surface pressure field resulting in light winds, while temperatures climb to slightly warmer than normal. The maximum heat index should stay below 90. Skies will be partly cloudy as high clouds stream in from convection to our west and a few cumulus clouds may bubble up. Some models develop isolated showers late in the day but the chance is about 10 percent for any given spot. - Risk for a Period of Strong Storms Friday Models continue to advertise a closed 500 mb low tracking through Lower MI during the afternoon. A stronger mid level jet streak on the south side of this system pivots through the CWA enhancing the deep layer shear. Surface instability plots show the atmosphere destabilizing during the late morning into the afternoon hours. Generally the models indicate that scattered convection will develop in the late morning to early afternoon hours before shifting the action east of the CWA by mid afternoon. The deep layer shear projections support organized convection, however the instability is shown to be somewhat limited. Ensemble surface based CAPE projections are mostly under 1000 J/kg which could be a limiting factor for the amount and strength of any convection that does develop. Close monitoring will be needed as we get closer to this period. For now, we will continue to feature relatively high POP`s for the late morning into the afternoon period. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 641 AM EDT Wed Jul 3 2024 The ceilings and visibilities are forecast to lower down into the MVFR category and even IFR for a few sites as a front tracks southeastward through the TAF sites. Showers will form out ahead of this front this morning. It will turn slightly unstable so an isolated thunderstorm could develop but confidence was not high enough for inclusion in the TAF`s at this time. As the wind veers to the west behind the front, ceilings and visibilities will rise to VFR levels this afternoon from west to east. && .MARINE... Issued at 1031 AM EDT Wed Jul 3 2024 Update... Will let the Beach Hazards and Small Craft Advisory expire at noon, although observations strongly suggest we`ve already dropped below hazardous criteria. Previous discussion follows... This forecast is lower than usual confidence for small craft and swimming hazards this morning, but at the very least it`s likely that moderate swim risk will be present along many beaches, with a fair enough possibility for high swim risk to issue a Beach Hazards Statement through noon. Ongoing Small Craft Advisory for gusts over 22 knots will be extended later into the morning as the wave field responds to briefly stronger southwesterly winds anticipated over the next few hours and lingers for a few more hours after the winds relax. Models have been varied in their solutions for early this morning regarding where, how strong, and for how long the stronger southwesterly surface winds will be. Stronger winds are present just 1000 feet above the lake, but it seems they will not fully mix down without the help of rain falling into the dry air at 1000 feet and cooling it down in tandem with the passing cold front. Even the most aggressive models relax the winds substantially no later than 8 or 9 AM, so any waves or currents hazardous enough for boats or swimmers should be diminishing by noon if not earlier. Independence Day will feature light winds and waves 1 foot or less. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until noon EDT today for MIZ037-043-050- 056-064. MARINE...Small Craft Advisory until noon EDT today for LMZ845>849. && $$ UPDATE...TJT DISCUSSION...MJS/CAS AVIATION...MJS MARINE...CAS/TJT