117 FXUS63 KGRR 091039 AFDGRRArea Forecast Discussion National Weather Service Grand Rapids MI 639 AM EDT Tue Sep 9 2025
.KEY MESSAGES...
- Dry and mild through Friday
- Rain chances arrive Saturday
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.DISCUSSION... Issued at 320 AM EDT Mon Sep 8 2025
- Dry and mild through Friday
No changes needed to the forecast through Friday. The front to our west and northwest is still expected to weaken significantly before it pushes through our area as mainly a windshift line on Wednesday. This weakening is the result of the upper wave supporting the front dampening out as the long wave ridge to our west becomes the dominant feature over the region. Increasing subsidence and a lack of moisture advection into the area will only dry the atmosphere out more than it is already.
Temperatures continue to look like they will stay stable, and not really cool off behind the front. 850 mb temperatures ahead of the front will be 10-11C, while they will stay around 11C behind the front. The only noticeable change will be the drier wind coming in from the ENE.
- Rain chances arrive Saturday
Model ensemble means are starting to fine tune the details for the rain chances coming this weekend. The main issue to resolve was the interaction of the upper ridge building ENE from the SW, while northern stream energy is forecast to dive SE toward the region also.
The latest ensemble means show that the northern stream low will not be nearly as amplified as the Euro and its ensemble members had been showing. This now looks like it may stay just NE of the region. This scenario then looks to allow the upper ridge to build a bit more toward us, and for our area to see some showers and storms at the nose of a low level jet associated with a southern stream wave riding over the upper ridge on Saturday.
Now, with the upper trough largely staying to our NE with the northern stream weaker, we may end up under increasing subsidence again with the upper ridge building in for Sunday. The Euro ensemble mean has gravitated toward the ensemble means of the GEFS and GEPS. This could bring the area back to warmer temps and dry conditions by Sunday, and hold through Monday.
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.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 638 AM EDT Tue Sep 9 2025
This forecast period will continue to feature little to no impact to aviation interests. We will see high clouds over all of the terminals through the period. Some mid clouds may approach right at the end of this period, but not a big deal since VFR conditions are expected. Winds will shift from light SE early, to SSW this afternoon, then going back to SE overnight.
The only real impact that will be possible will be some patchy fog at KJXN once again. The light winds at the site in a low area will be conducive for fog once again.
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.MARINE... Issued at 320 AM EDT Mon Sep 8 2025
No changes are needed with the marine/beach headlines at this time. The flow from the SW increases a bit with the approach of the weakening cold front, especially the further north you go. The highest waves will be found at Little and Big Sable Points today.
Once the imminent event diminishes tonight, we are looking at a few days of quiet weather. High pressure will be over the area, and a flow offshore will keep conditions fairly tame through Friday. Saturday is looking like the next best chance of some rainfall.
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.GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until 6 PM EDT this evening for MIZ037- 043. MARINE...Small Craft Advisory until 6 PM EDT this evening for LMZ848-849.
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DISCUSSION...NJJ AVIATION...NJJ MARINE...NJJ
NWS grr Office Area Forecast Discussion