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LMZ874 Expires:202312091645;;158688 Fzus63 Kmkx 090920 Glflm
open lake forecast for lake michigan national weather service milwaukee/sullivan wi 320 am cst Sat dec 9 2023
for waters beyond five nautical miles of shore on lake michigan.
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the wave, along with the average height of the highest 10% of the waves which will occasionally be encountered.
Synopsis..
southeast winds will quickly come around to southwest through the rest of the morning hours and become gusty as a surface low rapidly deepens to 29.4 inches as it races from the southern end of lake michigan this morning, to just south of james bay by this evening. The rapid strengthening of the low will drive gales from 35 to 40 knots, primarily over the eastern parts of lake michigan closer to the shoreline of the state of michigan. These gales will race northward through the day from the southeastern to northeastern quadrants of lake michigan. Thus, a gale warning has been issued over the southern half and northern half of lake michigan in two separate time segments to capture this evolution.
breezy southwest winds to 20 knots will then continue in the wake of the low, until a cold front passes Sunday morning and winds rise slightly and shift direction, with gusts between 20 to 25 knots out of the northwest expected.

lmz080-669-671-673-675-777-779-870-872-874-876-878-091645- lake michigan from michigan city in to st. Joseph mi 5 nm offshore to mid lake- lake michigan from sheboygan to port washington wi 5 nm offshore to mid lake- lake michigan from port washington to north point light wi 5 nm offshore to mid lake- lake michigan from north point light to wind point wi 5 nm offshore to mid lake- lake michigan from wind point wi to winthrop harbor il 5 nm offshore to mid lake- lake michigan from winthrop harbor to wilmette harbor il 5 nm offshore to mid lake- lake michigan from wilmette harbor il to michigan city in 5 nm offshore to mid lake- lake michigan from whitehall to pentwater mi 5 nm offshore to mid lake- lake michigan from grand haven to whitehall mi 5 nm offshore to mid lake- lake michigan from holland to grand haven mi 5 nm offshore to mid lake- lake michigan from south haven to holland mi 5 nm offshore to mid lake- lake michigan from st. Joseph to south haven mi 5 nm offshore to mid lake- 320 am cst Sat dec 9 2023
sheboygan wi to pentwater mi south...
.gale warning in effect from 6 am this morning to noon cst today...
Today..South gales to 35 kt becoming west gales to 40 kt late this morning, then becoming southwest to 30 kt early this afternoon diminishing to 15 to 25 kt late. Chance of rain this morning, then slight chance of sprinkles this afternoon. Waves 6 to 9 ft occasionally to 12 ft subsiding to 4 to 7 ft occasionally to 9 ft.
Tonight..Southwest winds 15 to 25 kt becoming west. Slight chance of sprinkles in the evening, then slight chance of rain overnight. Waves 5 to 8 ft occasionally to 10 ft.
Sunday..Northwest winds to 30 kt diminishing to 15 to 25 kt. Chance of rain in the morning. Waves 6 to 9 ft occasionally to 12 ft.
Sunday night..Northwest winds 10 to 20 kt. Waves 4 to 7 ft occasionally to 9 ft subsiding to 3 to 5 ft.
Monday..West winds 10 to 20 kt becoming southwest. Waves 3 to 5 ft.
Monday night..Southwest winds to 30 kt. Waves 5 to 8 ft occasionally to 10 ft building to 7 to 10 ft occasionally to 13 ft.
Tuesday..West winds to 30 kt. Waves 7 to 10 ft occasionally to 13 ft subsiding to 5 to 8 ft occasionally to 10 ft.
Wednesday..West winds 10 to 20 kt becoming southwest 15 to 25 kt. Waves 3 to 5 ft.

LMZ800
No data

FXUS63 KGRR 091123 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 623 AM EST Sat Dec 9 2023

LATEST UPDATE...
Aviation

SHORT TERM
(Today through Sunday)
Issued at 301 AM EST Sat Dec 9 2023

There are two sets of impacts that we are focused on in the short term. These impacts are winds today, and then snow shower potential focused on very late tonight and on Sunday.

We will be issuing a Wind Advisory for the entire area through mid- afternoon. Rain showers are now developing over the area as the low level jet out ahead of the incoming cold front is moving through right now. The cold front is back across Central IL marked by a solid line of convective showers and a stark wind shift. We can expect on and off showers until the frontal passage which will be between 12 and 18z across just about all of the area. A rumble of thunder can not be totally ruled out as 925 and 850 mb based LI's are around 0c.

The bigger feature on concern is the wind immediately along and just behind the cold frontal passage. The thought all along has been for some gusty winds with a fairly tight pressure gradient and initial surge of colder air coming in. The trend has been for stronger winds with HRRR mean wind gusts 40-45 mph and Euro ensemble mean winds 40+ mph. These winds will not last especially long, but will be long enough and widespread enough to justify issuing a wind advisory for the entire area.

We should see mainly dry conditions for most of the afternoon behind the sfc front passage. This is due to the short wave ridging that builds in behind the initial wave. This will change then this evening as we see the secondary upper feature, a closed upper low that will rotate into the area. This will fire up a few rain showers initially with the wave.

The showers will transition from rain showers being associated directly with the the low, to more banded lake effect rain and eventually snow showers late tonight and through Sunday with long wave troughing/cyclonic flow in place. The set up for lake effect is marginal at best, with just a chance of some light accumulations on grassy areas considering the recent warmer weather has warmed up pavement temps.

The coldest of the air coming in is as low as about -10C for just a short time centered around the late Sunday time frame. That is sufficient for lake effect with the delta t's around 15-16C. The problem is that even lake modified soundings indicate that the dgz is barely saturated as there is just not that cold of air in the mid and upper levels to help with the convective heights and saturating the dgz. This will really limit the potential for any impactful accumulations, along with sfc temps well into the 30s all day Sunday.

LONG TERM
(Sunday night through Friday)
Issued at 301 AM EST Sat Dec 9 2023

Light lake effect snow showers should be winding down Sunday night into Monday morning as the thermal trough axis moves east and inversion heights lower below 5 kft.

An upper low swings 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.

AVIATION
(For the 12Z TAFS through 12Z Sunday morning)
Issued at 623 AM EST Sat Dec 9 2023

MVFR conditions with areas of IFR will prevail this morning along with low level wind shear. South and then southwest surface winds will increase with gusts over 30 knots expected this morning and into the afternoon. Conditions will be MVFR into the evening then slowly improve to mostly VFR overnight. Winds will go west and diminish this evening with gusts decreasing below 20 knots.

MARINE
Issued at 301 AM EST Sat Dec 9 2023

We will be hoisting a Gale Warning for the entire nearshore through early this afternoon for a solid, yet short duration event. We will be leaving the existing Small Craft Advisory in effect from the end of the Gale warning at 18z through early Monday morning.

Models have been trending higher with winds near and just behind the frontal passage today. There is good agreement in multiple sets of data that the entire nearshore will see 4-6 hours of Gale criteria being met. It will be going good during the event, and will diminish a bit fairly quickly later this afternoon. Winds will come up again with the next wave moving through later this evening and will hold up through Sunday.



GRR WATCHES/WARNINGS/ADVISORIES
MI...Wind Advisory until 2 PM EST this afternoon for MIZ037>040- 043>046-050>052-056>059-064>067-071>074.

LM...Gale Warning until 1 PM EST this afternoon for LMZ844>849.

Small Craft Advisory from 1 PM this afternoon to 7 AM EST Monday for LMZ844>849.

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