Sunrise 6:13 AM   Sunset 9:09 PM Moonrise 5:30 PM   Moonset 3:38 AM

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LMZ849 Pentwater To Manistee Mi- 1005 Pm Edt Sun May 19 2024
Rest of tonight - East winds 5 to 10 knots veering southeast 10 to 15 knots toward daybreak. Partly cloudy. Waves 1 foot or less. Monday - South winds 10 to 20 knots. Rain showers likely and a chance of Thunderstorms. Waves 1 to 3 feet. Monday night - Southwest winds 10 to 15 knots. Mostly cloudy with a chance of showers and Thunderstorms. Waves 1 to 3 feet. Tuesday - Southeast winds 10 to 15 knots. Mostly cloudy with a chance of rain showers and a slight chance of Thunderstorms. Waves 1 to 2 feet. Tuesday night - Southeast winds 10 to 20 knots becoming south to 30 knots after midnight. Rain showers and a chance of Thunderstorms. Waves 2 to 3 feet building to 6 to 8 feet after midnight. Wednesday - Southwest winds to 30 knots. Mostly Sunny with a chance of rain showers. Waves 6 to 8 feet. Thursday - Southwest winds 15 to 25 knots. Sunny. Waves 2 to 4 feet.Friday - Southeast winds 10 to 15 knots veering southwest. Sunny. Waves around 1 foot.

LMZ800
No data

FXUS63 KGRR 200730 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 330 AM EDT Mon May 20 2024

KEY MESSAGES

- Marginal Risk for Severe Thunderstorms Today

- Warm and Humid Tuesday

- Severe Weather Risk Tuesday Night

- Dry and Pleasant Late Week Period

DISCUSSION
Issued at 330 AM EDT Mon May 20 2024

- Marginal Risk for Severe Thunderstorms Today

A fairly complex mesoscale pattern will evolve across our area today as a warm front just south of our area early this morning moves slowly north. Meanwhile well off to our west convection across eastern IA early this morning will continue moving ene. A consensus blend of latest CAMs and 00Z HRRR suggest that this convection will reach our west to northwestern fcst area by mid to late morning.

Severe wx is unlikely with this first round of rain and embedded convection given limited instability and fairly weak shear as well as unfavorable timing. However this complex of rain and convection may inhibit the warm front from moving much further north then perhaps the I-96 corridor.

Our main risk for marginally severe wx then comes for this afternoon and evening as instability builds in the warm sector.
SB/MU cape values should reach around 1500 j/kg near to south of I-96 by mid to late aftn with potential for convective development with relatively strong updrafts by then as suggested by the 00Z HRRR.

Localized damaging wind gusts are the primary svr wx threat from mid aftn through the evening as fcst soundings show potential for dry adiabatic low level lapse rates and dcapes to reach 1000 j/kg.
Localized large hail is also possible looking at fcst soundings and we also can't rule out potential for an isolated weak spinup in the vicinity of the warm front where enhanced updraft helicity is expected. A diurnally driven gradual decrease in convection is fcst late this evening and overnight.

- Warm and Humid Tuesday

It will be warm and quite humid Tuesday and most of the day will be dry. We do expect some scattered showers and thunderstorms to begin to develop from mid to late afternoon coincident with the peak in diurnally driven instability (sb/mu capes potentially reaching close to 2k j/kg).

However convective potential is somewhat mitigated by the lack of a stronger focusing mechanism for convective development to occur.
An upper shortwave moving in from the wsw could focus some convective initiation from mid to late afternoon before we get back into some mid to upper level nva.

- Severe Weather Risk Tuesday Night

A QLCS emanating from the upstream SPC Day2 ENH risk area is expected to make a run at wrn Lwr MI on Tuesday night with the main threat being damaging wind gusts. The severe weather risk should gradually wane overnight as this feature eventually loses steam with eastward extent due to declining instability.

Some question as to the areal extent of convection on Wednesday since the sfc boundary may slip south of the area, but best pops will be focused south and east of GRR and especially near JXN. It's possible much of the area dries out with stable low level westerly flow becoming established.

- Dry and Pleasant Late Week Period

A period of dry and pleasant weather looks likely for the end of the week as sfc ridging takes over and a drier air mass with dew pts in the 40s arrives. Also an amplifying upper level ridge is shown to be overhead by Friday.

Pops appear to ramp up again over the holiday weekend as the ridge moves east and warm front returns, although confidence regarding the timing and coverage of convective events is low at this time.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 200 AM EDT Mon May 20 2024

Upstream convection over eastern Iowa at 06Z extrapolates into MKG/GRR shortly after 12Z, although some question as to whether or not it impacts the terminals south and east of GRR later this morning.

Other isolated/scattered diurnal development of showers/storms expected in the afternoon before a more widespread coverage of storms occurs this evening (between 00Z and 06Z Tue). In general expect VFR today with periods of MVFR/IFR possible in any showers and storms.

Wind fcsts are somewhat complicated today due to potential impacts from convection and eventual position of incoming warm front, but in general we should see southerly winds increasing to 10 to 20 kts by afternoon.

MARINE
Issued at 330 AM EDT Mon May 20 2024

Winds and waves will remain rather minimal and below Small Craft Advisory levels ealry this week. However locally higher winds and waves are possible in thunderstorms today through Tuesday night.

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

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