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LMZ847 Grand Haven To Whitehall Mi- 1105 Am Edt Sat Sep 23 2023
Rest of today..Southeast winds 5 to 15 knots. Sunny. Waves 1 foot or less.
Tonight..East winds 10 to 20 knots. Partly cloudy. Waves 1 to 2 feet.
Sunday..Southeast winds 10 to 20 knots backing east 5 to 10 knots late in the day. Partly Sunny. Waves around 1 foot.
Sunday night..East winds 15 to 20 knots. Partly cloudy. Waves around 1 foot.
Monday..East winds around 15 knots. Mostly cloudy with a slight chance of rain showers. Waves around 1 foot.
Tuesday..East winds around 15 knots. Partly Sunny. Waves 1 foot or less.
Wednesday..East winds around 15 knots. Partly Sunny. Waves around 1 foot.

LMZ800
No data

FXUS63 KGRR 231351 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 951 AM EDT Sat Sep 23 2023

LATEST UPDATE...
Update

UPDATE
Issued at 951 AM EDT Sat Sep 23 2023

No changes to the going forecast with high clouds currently moving across lower Michigan. These high clouds are associated with an upper- level shortwave visible on water vapor imagery moving across the Upper-Midwest. Both the 12z DTX and APX soundings give continued confidence in dry conditions across West Michigan today given the substantially drier nature of these soundings compared to the 00z soundings from last night. The substantial dry air in place along with subsidence from 500 mbar ridging overhead creates an environment much more hostile to convective precipitation compared to yesterday.

Scattered mid to high level clouds expected to continue through the day as the aforementioned shortwave rounds through Wisconsin.
Highs today will be in the mid 70s with drier low-level easterly flow supporting dewpoints in the upper-forties to low fifties.

Main forecast concerns with the afternoon package will be evaluating any fog potential tonight as well as precipitation potential for the start of next week. No significant impacts are expected with this precipitation.

SHORT TERM
(Today through Sunday)
Issued at 315 AM EDT Sat Sep 23 2023

Very quiet short term period expected. Dry low level easterly flow will dominate this weekend. Scattered mid/high level cloud cover is possible as an upper low moves into the Upper Midwest through the period. While a few isolated showers managed to pop yesterday, that won't be the case today as surface dewpoints continue declining into the upper 40s for many areas. The majority of cloud cover looks to move in Sunday afternoon and evening. High temperatures look to be in the mid 70s, with the warmest readings across the western portion of the region given the low level easterly flow.

LONG TERM
(Sunday night through Friday)
Issued at 315 AM EDT Sat Sep 23 2023

A fairly low confidence forecast is shaping up for the long term period which essentially encompasses the upcoming work week. There are model differences between the operational runs of the GFS and the ECMWF. The upper low in the short term over the Northern Plains gradually moves into the Great Lakes region in the long term with varying speeds. This low is moving into and through a mean ridge position that stretches from the Mexican subtropics including the Baja of California northward through the Southern Plains and into Eastern Canada. The plains low moves east and gradually fills with time as it moves into the ridge. The GFS is quicker moving the wave into the ridge with the ECMWF lagging a bit. The ECWMF looks more reasonable with the evolution of the upper pattern.

As for lower in the atmosphere, at the surface and especially at 850mb there is a warm front situated in the region with the ECMWF showing the potential for occasional precipitation on many of the days in the long term. We feel the GFS is a bit too quick bringing precipitation into the area early in the week (Sunday night through Monday night). The ECWMF holds the precipitation off more into Tuesday and this seems reasonable. The ECMWF would suggest at least some chance of light precipitation from Tuesday through the end of the week. Overall confidence is low in when we see precipitation given the model disparity and overall weak features at both the surface and aloft. 70s for highs look pretty common next week which is above normals for this time of year.

AVIATION
(For the 12Z TAFS through 12Z Sunday morning)
Issued at 642 AM EDT Sat Sep 23 2023

VFR for this TAF period. A few high clouds are likely at times through the period. Fog threat is very low through Sunday morning as drier air works into the region. Light east winds continue.



MARINE
Issued at 204 AM EDT Sat Sep 23 2023

Prolonged period of waves of 1 ft or less continues to be expected. This is due to a long duration period of easterly flow over Lake Michigan. Winds and waves are expected to stay below SCA criteria through the weekend and into early next week.



GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
LM...None.

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