Sunrise 6:46 AM   Sunset 8:37 PM Moonrise 9:49 PM   Moonset 6:20 AM

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LMZ844 St Joseph To South Haven Mi- 405 Pm Edt Thu Apr 25 2024
Through early evening - North winds 10 to 15 knots. Sunny. Waves 1 foot or less. Tonight - Northeast winds 5 to 10 knots veering southeast 10 to 20 knots after midnight. Mostly clear. Waves around 1 foot. Friday - Southeast winds 15 to 20 knots. Partly Sunny with a chance of rain showers. Waves 1 to 2 feet. Friday night - Southeast winds 15 to 25 knots veering south toward daybreak. Rain showers and a chance of Thunderstorms. Waves 2 to 4 feet.Saturday - South winds to 30 knots. Partly Sunny with a chance of showers and Thunderstorms. Waves 3 to 5 feet. Saturday night - South winds 20 to 25 knots. Partly cloudy with a chance of showers and Thunderstorms. Waves 3 to 5 feet. Sunday - South winds 20 to 25 knots. Partly Sunny with a chance of rain showers. Waves 2 to 4 feet. Monday - South winds 20 to 25 knots. Rain showers likely. Waves 2 to 4 feet. Tuesday - West winds around 15 knots backing southwest late in the day. Sunny. Waves 1 to 3 feet.

LMZ800
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FXUS63 KIWX 251926 AFDIWX

Area Forecast Discussion National Weather Service Northern Indiana 326 PM EDT Thu Apr 25 2024

KEY MESSAGES

- Much warmer temperatures this weekend with highs around 80.

- Periodic chances for rain and a few storms, particularly Friday night and Monday.

- The risk of severe weather is low at this time.

DISCUSSION
Issued at 315 PM EDT Thu Apr 25 2024

On the heels of a freeze warning and frost advisory from this morning and with the shifted pattern for tonight, a good question to posit is if we return to frost conditions again tonight. Well, as opposed to being in the trough with various areas of mid level vorticity to support high clouds last night, tonight will have mid level ridging around with NAM and GFS bufkit soudings indicating decoupling is possible. This is in frost formation's favor, however, increasing gradient is not. As an upper level low pressure system lifts northeast out of the Southern Plains, the gradient starts tightening after 6z from west to east and a low level jet approaches by 12z Friday. This also may be able to spread some high clouds in west of US-31 to also stunt any remaining cooling after 6z there. Temperatures could also crater not too long after sunset with the dry air around. With these thoughts in mind, have hoisted a frost advisory to cover areas generally north of US-30 and east of US-31.

Moving forward, for Friday, a warm front encroaches on the area spreading moisture into the area. PWATs between 1.25 and 1.5 inches which is 1 to 3 SDs above climatological norms help indicate the moisture to be tapped into. Surface convergence arrives during the afternoon especially for areas along and south of US-30 and then continues moving northeastward through 6z. While some embedded thunder may be possible as this front passes through, much of the instability will stay to our west through 12z Saturday. Given this and the fact that the better moisture still hasn't arrived yet, QPF totals stay below 0.5 inch and taper off quickly southeast of our 2nd tier of counties away from Lake MI.

For Saturday, more instability looks to be able to work into areas west of I-69 with the best instability looking to be in the aforementioned lake-adjacent counties. West of I-69, better columnar moisture looks to move in with surface dew points surpassing 60 degrees and 850 mb dew points surpassing 10C. However, we lose the better forcing between 12 and 18z with it going northeast of the area so would expect coverage of rainfall to decrease unless we can get an outflow boundary to move through. If we can get some thunderstorms to form, it looks like there'll be around 30 kts of effective shear to work with. SPC has those aforementioned lake-adjacent counties covered with a marginal chance of severe weather for Saturday. The shear would make damaging wind the most likely outcome from severe storms, but perhaps a tornado with SRH around 200 m2/s2 and sub- 1000m LCLs, as well as a few sporadic reports of hail with 6 to 7 C/km mid level lapse rates attempting to move in, but that moist low levels may remove that possibility.

Moving forward, for Saturday night, the moisture axis shifts from along our western counties to along and north of US-6 by Sunday morning, which would allow for a break for much of the forecast area from rain, especially those south of US-6. Now, there is still some 700 to 1500 J/kg of MUCAPE to work with on the ECMWF model Sunday so if there is a lingering boundary, perhaps we could tap into that for some storms then. We'll have to wait for a better chance for rain along an area of upper divergence as it swings through ahead of the main cold front late Sunday night/Monday. This area of moisture does look to stall out overhead and may be able to have some instability to work with. The GFS has an axis of 30 kts of effective shear east of I-69 during the afternoon so perhaps some severe weather could be had as well.

All told, through these sucessive rainfall events from later Friday into Tuesday morning, the NBM doesn't have more than 10 to 20 percent chance of 1 inch in 24 hours. Would think these percentages might be a little higher should convective rain be added to the equation. That helps to draw a picture for how little rain we get with the main limiting factor being the forcing.

While the GFS forms what appears to be convective rain with sporadic weak vort maxes moving through in the mid level flow, think that the next best chance for rain holds off until the Tuesday night through Wednesday time frame as another cold front moves through. With the speed of the front, perhaps a few thunderstorms could form early afternoon south of US-24 Wednesday as long as clouds break up to allow instability to form.

Temperatures during this forecast period trend warmer from today's 50s to tomorrow 60s to around 70 degrees. Then from Saturday through the end of the forecast period, 70s for highs will be in play. No threat for additional frost occurrences is forecast.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
Issued at 1255 PM EDT Thu Apr 25 2024

An expansive low level anticyclone across the eastern Great Lakes will continue to slowly push east as large scale longwave ridging shifts eastward. This will create an east-southeast gradient across the area overnight into Friday. Decoupling should keep wind speeds less than 10 knots overnight, and diurnal mixing on Friday should promote gusts to around 20 knots toward the end of this forecast valid period. The only sky cover of note this period will be some increasing high clouds late tonight into Friday morning. Rain chances will increase heading into later afternoon Friday as an elevated warm front approaches. This may bring some limited thunder potential late afternoon Friday, but instability should be quite limited overall.

IWX WATCHES/WARNINGS/ADVISORIES
IN...Frost Advisory from midnight tonight to 9 AM EDT Friday for INZ005>009-017-018-025>027-116-216.
OH...Frost Advisory from midnight tonight to 9 AM EDT Friday for OHZ001-002-004-005-015-016-024-025.
MI...Frost Advisory from midnight tonight to 9 AM EDT Friday for MIZ078>081.
MARINE...None.

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