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LMZ846 Holland To Grand Haven Mi- 405 Am Est Sun Dec 10 2023
.small craft advisory in effect through Monday morning...
Early this morning..West gales to 35 knots. Cloudy with a chance of rain and snow showers. Waves 6 to 9 feet.
Today..Northwest gales to 35 knots decreasing to 30 knots. Cloudy with a chance of rain and snow showers. Waves 6 to 8 feet.
Tonight..Northwest winds 15 to 25 knots. Cloudy with a chance of snow showers. Waves 3 to 5 feet.
Monday..West winds 15 to 25 knots backing southwest late in the day. Partly Sunny. Waves 2 to 4 feet.
Monday night..Southwest winds to 30 knots increasing to gales to 35 knots after midnight. Mostly clear. Waves 3 to 5 feet building to 6 to 9 feet after midnight.
Tuesday..West gales to 35 knots. Mostly Sunny. Waves 7 to 10 feet.
Wednesday..Northwest winds 15 to 25 knots. Sunny. Waves 3 to 5 feet.
Thursday..Southwest winds 20 to 25 knots. Sunny. Waves 3 to 5 feet.

LMZ800
No data

FXUS63 KGRR 100746 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 245 AM EST Sun Dec 10 2023

LATEST UPDATE...
Short Term/Long Term/Marine

SHORT TERM
(Today through Monday)
Issued at 245 AM EST Sun Dec 10 2023

Our main focus in the short term portion of the forecast is on the shower activity into this evening, some of which could produce some light accumulations on grassy areas. The trends have remained consistent in showing this should have little to no impact through tonight.

What was once the parent low with this system is now opening up and rotating NE through the northern portion of the state. A few sprinkles/light showers are moving through the area early this morning. Moisture is not very deep, only around 7-8k ft agl, and the dgz is only partially saturated. The lake does not look to be helping much so far per radar trends, with delta t's only around 10- 12C at this time.

We will see the lake contribution increase through the morning and into the afternoon as 850 mb temperatures drop down to around -9 to -10C by this evening. This will increase delta t's to the mid teens C, and will help in the production of lake effect showers. Sfc temps well into the 30s will help keep some rain mixed in at times until the sufficiently cold air arrives and changes all showers to snow.

Even when the coldest of the air is here, and best over lake instability is present, we still do not expect much in the way of any accumulation. Even with a lake modified parcel with better instability, the top of the convective layer barely gets into the dgz. This will really limit snowflake generation and size, and thus accumulations. We believe that some of the most organized snow showers could drop a few tenths of an inch on grassy areas across the north and west. Ground temps are in the 30s after the recent warmer weather, and with solar radiation warming road sfcs, roads should be largely just wet until sunset.

The snow showers are forecast to wind down later tonight. The long wave cyclonic flow aloft moves out, and we will lose the marginally cool air aloft that was here. It does look like we will keep lake effect cloud cover in through most of Monday as moisture gets trapped in. The dgz is pretty much unsaturated, so it should just mainly be clouds.

LONG TERM
(Monday night through Saturday)
Issued at 245 AM EST Sun Dec 10 2023

An upper low moves through SE Canada Tuesday into Wednesday with troughing extending south into the central Great Lakes but forecast soundings are dry and the polar jet remains north of the area, so we will maintain the dry forecast through Thursday.

Slight chance POPs on Friday and into the weekend are the result of an approaching clipper. Forecast soundings show little moisture to work with and the mean path of the sfc low remains north of the forecast area, so little if any QPF is expected.

AVIATION
(For the 06Z TAFS through 06Z Sunday night)
Issued at 1251 AM EST Sun Dec 10 2023

VFR conditions have been dominant over the past few hours at all of the terminals. We are now seeing MVFR ceilings working back in over the area from the west as another front approaches the area.
There are a few light showers scattered about, and more widespread showers will start moving over the terminals toward 12z. Initially they will be mostly rain, and then will mix with snow at times, before changing to all snow showers this afternoon. We expect that most of the showers will be accompanied by MVFR visibilities and ceilings. Some spotty IFR will be possible and isolated once showers turn to all snow, and under the heaviest showers.

The snow showers will then migrate back closer to the lake this evening as winds become more from the NNW. This will allow for VFR to be more likely inland, and MVFR toward the lake.



MARINE
Issued at 245 AM EST Sun Dec 10 2023

The Small Craft Advisory in effect through 12z Monday looks good, and we will keep it as is for this forecast cycle. Winds along the coast look generally between 25 and 30 knots early this morning.
These wind speeds should persist through much of the morning before they taper off then through tonight.

We will see a brief break in the winds and waves later tonight and for the first half of Monday. Winds will then come up later in the day, with waves following suit shortly thereafter with an onshore flow expected.

GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
LM...Small Craft Advisory until 7 AM EST Monday for LMZ844>849.

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