Sunrise 6:33 AM   Sunset 8:46 PM Moonrise 3:46 AM   Moonset 3:46 PM

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LMZ844 St Joseph To South Haven Mi- 1005 Pm Edt Fri May 3 2024
Rest of tonight - Northeast winds 5 to 10 knots veering east toward daybreak. Mostly clear. Waves around 1 foot. Saturday - Southeast winds around 10 knots veering southwest, then veering north late in the day. Mostly Sunny with a slight chance of rain showers. Waves 1 foot or less. Saturday night - Southeast winds 5 to 15 knots veering west late at night, then veering northwest 15 to 20 knots toward daybreak. Rain showers likely and a slight chance of Thunderstorms. Waves 2 to 3 feet. Sunday - North winds 15 to 20 knots. Mostly Sunny. Waves 2 to 4 feet. Sunday night - North winds 10 to 15 knots veering northeast 5 to 10 knots after midnight. Partly cloudy. Waves 2 to 4 feet subsiding to 1 to 3 feet after midnight. Monday - East winds 10 to 15 knots. Mostly Sunny. Waves around 1 foot. Tuesday - South winds 15 to 20 knots. Rain showers. Waves 1 to 2 feet. Wednesday - Southwest winds around 15 knots. Mostly Sunny with a chance of rain showers. Waves 1 to 2 feet.

LMZ800
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FXUS63 KIWX 040432 AFDIWX

Area Forecast Discussion National Weather Service Northern Indiana 1232 AM EDT Sat May 4 2024

KEY MESSAGES

- Normal to above normal temperatures through the week, with highs in the 70s and low 80s, cooler near Lake Michigan. Lows will be in the 50s and 60s.

- There are chances for showers and thunderstorms at times between this afternoon and next week.

DISCUSSION
Issued at 220 PM EDT Fri May 3 2024

The main surface low pressure associated with an upper level low pressure shifts northeastward into south-central Canada and this pushes a cold front and associated weaker area of vorticity into the forecast area today. Fairly strong low lapse rates, surpassing 8 C/km are noted on the NAM12, but more like 7 C/km on the ECMWF, this afternoon out in front of this eastward moving cold front. Model discrepancy on placement of storm formation is likely as a result of the NAM having a surface boundary advect eastward from Lake Erie on east winds. The HRRR has a more subtle indication of this as well.
Cloud cover is a major factor in storm formation this afternoon because the area is without substantial shear. So, storm formation will have a better chance with reduced cloud cover.
The area yesterday had some shear to tap into and that likely helped sustain updrafts for that one severe cell to produce marginally severe winds and just sub-severe hail without sufficient mid level lapse rates. Well, today, we are without substantial shear and mid level lapse rates so agree with today's general thunder allotment from SPC. As a result, think gusty winds to 40 or perhaps 50 mph may be possible with storms and perhaps some heavy rain that could lead to ponding or flooding with potentially training storms.

Models indicate the main temperature gradient associated with the cold front separates from the moisture gradient and shrinks westward, tonight. As such, could see some fog development, especially in areas where cloud cover scatters and allows for some radiative cooling. Areas west of I-69 would seem to be more conducive to this outcome.

It is interesting to see the ECMWF keep its moisture farther to the north and west in an area south of US-24 Saturday morning. Am a little skeptical of its precip output with a lack of forcing around, but will retain slight chance PoPs there. A somewhat better chance for showers and storms occurs Saturday afternoon and evening as a mix of sun and clouds allows for a reinvigoration of instability across the area. The greatest chance for this appears to still be south of US-24 and perhaps an axis west of US-31, but it's much drier over there. For whatever it's worth, the ECMWF does not have any afternoon showers/storms form Saturday afternoon, which is different from the rest of the model suite. With the stalled out baroclinic boundary to our west, models form a weak low pressure on it and that arrives Saturday evening. There will likely be a resurgence of showers and perhaps a thunderstorm along that boundary with the return of forcing. Instability looks to stay lower than 1000 J/kg and perhaps even lower than 500 J/kg which would restrict the thunder chance. Mid level lapse rates around 6 C/km may be able to help sustain convective rain overnight into Sunday morning. Highs in the 70s are expected across the area on Saturday.

The front moves eastward on Sunday and this likely restricts the thunder chance until Tuesday. Although, times of rain are still possible as weaker areas of vorticity travel along the front. As such will populate some of the time with slight and chance PoPs in the time periods where rain looks the most possible. Sunday and Monday afternoons are the most likely chance PoP periods.

A slow lumbering upper low within the Western CONUS trough comes far enough east to affect the area Tuesday. There is some disagreement on medium range guidance if the stalled boundary can move northward as a warm front allowing the area to be in the warm sector. The low level jet is expected to move into the area Tuesday afternoon and evening allowing 30 to 45 kts of effective shear to be an ingredient for developed storms to tap into. With the placement of the front in question, the chance for thunder is also in question. Instability appears to be the limiting factor with 500 to 1000 J/kg MUCAPE to tap into. 60F sfc dew points and 10C+ 850 dew points will be most possible south of US-24 or US-30, but the ECMWF actually has them over the whole forecast area. Boundary-parallel flow appears possible and various areas of upper jet support may support times of heavy rain from training/ backbuilding convective rain. Continued rain over this unsettled period is going to need to be watched as saturated soils could lead to standing water, especially in the more flood prone and urbanized areas where soil has been converted to less permeable concrete.

Either way, both models have a break in precipitation Wednesday morning. The question then becomes, when does the front move back northward again to cause more precipitation. A better chance for this appears to be Wednesday night. This period also appears to have shear and MUCAPE to tap into allowing for the possibility of more showers and thunderstorms that could be severe and produce heavy rain.

Chances for rain appear to be lower Thursday with instability being restricted to less than 500 J/kg. Shear is around though so if any thunderstorms are able to form in that meager environment, severe weather could be possible. Still a better chance for drier weather occurs Friday with little to no instability and shear. However, the upper low pressure center nearby may allow for a light shower still.
Friday also sees a return to mid to upper 60s for highs, which is normal to slightly below normal for this time of year.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
Issued at 1230 AM EDT Sat May 4 2024

Lingering boundary layer will likely allow a high MVFR to low VFR stratocu deck to settle in over KFWA through much of the forecast period. Drier air has worked into KSBN where lesser diurnal cu coverage is anticipated mid morning into the afternoon. Models do try to generate isolated showers in the vicinity of KFWA later this afternoon as weak surface based buoyancy develops on the western fringe of a stalled OH trough. However, point chances are too low for a mention in the TAF at this time. A sfc trough does approach KSBN toward the end of the period (3-6z Sun) with non-zero chances for decaying showers/iso storms. May opt to add in at least a VCSH with the 12z issuance if this signal persists.

IWX WATCHES/WARNINGS/ADVISORIES
IN...None.
OH...None.
MI...None.
MARINE...None.

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