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LHZ422 Inner Saginaw Bay Sw Of Point Au Gres To Bay Port Mi- 345 Pm Edt Thu Apr 25 2024
Tonight - East winds 15 to 20 knots veering to the southeast after midnight, then diminishing to 10 to 15 knots early in the morning. Clear. Waves 1 to 3 feet. Friday - Southeast winds 10 to 15 knots becoming east 15 to 20 knots early in the afternoon. Mostly Sunny. Waves 1 to 3 feet.Friday night - Southeast winds 20 to 25 knots increasing to 30 knots after midnight. A chance of showers in the evening, then showers after midnight. Waves 3 to 5 feet. Waves occasionally around 7 feet. A small craft advisory may be needed.Saturday - South winds to 30 knots diminishing to 20 to 25 knots early in the afternoon. Light showers in the morning, then a chance of showers and Thunderstorms in the afternoon. Waves 3 to 5 feet. Waves occasionally around 7 feet.
see lake huron open lake forecast for days 3 through 5.

LHZ400
No data

FXUS63 KAPX 252042 AFDAPX

Area Forecast Discussion National Weather Service Gaylord MI 442 PM EDT Thu Apr 25 2024

KEY MESSAGES

-- Elevated fire danger Friday afternoon.

-- Increasing confidence in rounds of showers and thunderstorms impacting northern Michigan from Friday night through Monday.

-- Chance for severe thunderstorms, particularly later Saturday into Saturday night across northern lower Michigan.

UPDATE
Issued at 435 PM EDT Thu Apr 25 2024

Per coordination with fire weather partners, and short term discussion below regarding low RHs and increasingly gusty winds Friday...will go ahead and explicitly add elevated fire danger wording to our messaging for Friday, especially Friday afternoon. Fire weather partners/experts not confident on fuel moisture aspect for widespread red flag conditions this time around, particularly with the anticipated rain this weekend...though isolated red flag conditions may not be totally out of the question Friday.



SHORT TERM /THROUGH SATURDAY/
High pressure still focused just to our east over Ontario...with PV maxima dropping across the CWA attm. Light and variable winds with lake breeze development today...and seeing a very few cu pop up over NE Lower, where some upsloping may be aiding in lift and saturation, combined with some slight moisture advection off the lake as that weak bit of PV moves through.

Expecting high pressure to remain over the area tonight...though return flow should rotate into the region going into Friday morning, and especially Friday afternoon, with increasing warmth aloft, as well as an increase in overall moisture
However
southeast flow hangs on into Friday as well, and antecedent dry air mass should preclude most, if not all, precip from reaching the ground over the region till beyond this period.

Primary Forecast Concerns:

Increasingly warm and breezy, remaining dry...Expecting temps aloft to increase through the day Friday, and with mixing up to around 850mb, think highs in the upper 50s to lower 60s are quite probable, especially considering we should remain largely clear...and temps will not fall as much tonight as they did last night. With better downsloping over NW Lower...think some upper 60s could be possible as well...though I do have to admit that we should start to get better mid/high cloud coverage into that area with time in the afternoon
Current dry air mass will take time to saturate
and suspect this may hold off even some of the cloud cover until later in the afternoon/evening; even less can be said for precip, which should hold off till Friday night and beyond. Some suggestion that another lobe of lower dewpoints could pivot over the region from north to south Friday, which could allow for afternoon RHs to fall even further below the usual 25 percent criteria for fire weather thresholds. Have not gone quite this aggressive, but have elected to keep dewpoints (and subsequently, RHs) a touch lower even so.
Additional concerns for fire weather as pressure gradient begins to strengthen with system tracking across the Plains; expecting 5-10kts sustained winds, which could gust as high as 20-25kts by evening.
Admittedly, this is more of a warm advection setup for winds, which typically would not be as favorable for gustiness...though do think the antecedent dry air mass and good potential for mixing could aid in better gusts this time around...at least, while the sun is out.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
Pattern Synopsis / Forecast: Active baroclinic zone will really get its act together over the course of the weekend as a complex setup of shortwaves and associated surface low pressure centers / frontal boundaries pass through the upper Great Lakes region, dispatching the dry influences of surface high pressure progged to be moving off the Atlantic coast of New England. The action begins Friday night as a surface warm front moves into the region, bringing a round of showers and potentially some thunder too. The next car in the metaphorical atmospheric train will be surface low pressure advancing east from Wisconsin into the U.P., drawing in a warmer and potentially much more unstable airmass before a surface cold frontal boundary moves into the region and sparks off another chance for showers and storms late Saturday, some of which could be strong to severe. This frontal boundary largely becomes stationary over the region by Sunday, continuing unsettled weather potential Sunday into Monday as yet another low pressure center works into the Great Lakes. The passage of this low pressure center should mark the end of the active stretch of weather, with surface high pressure progged to intrude into the Great Lakes as we move closer to midweek.

Primary Forecast Concerns:

Friday Night Convection: Despite warm / moist advection moving into the region, there will be some barriers to overcome as we progress into the overnight hours. Stout low level dry layer will impede the initial advances of a stratiform rain plume well ahead of the surface warm frontal boundary. It wouldn't be overly surprising for this plume to pass through the region with more of a whimper considering progged soundings display dewpoint depressions as high as 30 Celsius across the southwest part of the CWA around 00z Saturday. The most appreciable rainfall from this frontal passage will come later in the overnight when steepening lapse rates aloft (up to 7 Celsius / km) and 850mb warm advection drive elevated instability associated with the warm front. In theory, would like to see steeper lapse rates to drive instability up for better thunder coverage, but the moistening airmass should provide better rainfall potential for places that see repeated shower passages Friday night regardless. While instability is low (generally 100-400 J/kg), suppose an embedded rumble of thunder or two cannot be ruled out.
Overall, looks like most spots probably see a general 0.25" or less Friday night, though localized areas that see repeated downpours could observe 0.75"+. At this time, severe weather potential looks quite low Friday night into Saturday morning.

Saturday - Saturday Night: Uncertainty begins to riddle the forecast as we progress into Saturday, particularly with respect to the position of the surface warm frontal boundary. Most guidance has the surface warm front clearing the Straits and stalling out somewhere between the Bridge and the Soo, but there is a modest amount of guidance that has the front stalling out around the M-32 area. The former solution would generate more clearing / destabilization potential amid warmer temperatures across northern lower into the day Saturday, possibly as high as the upper 70s for some, while the latter solution brings about a cloudier and cooler solution (upper 50s and lower 60s) with a stable layer in the low levels and thus suppresses the majority of surface based convection to the south and west. Considering favorable low pressure position based off severe climo for northern Michigan and the 500mb ridge axis located just to our east, this in theory should allow for an easier warm frontal passage, despite the suppressing efforts of the colder Great Lakes.
In the event that this solution pans out, this opens a Pandora's Box of convective potential across the region.

Being in the vicinity of the triple point of the system will lead to favorable dynamics aloft to contribute to severe weather potential later Saturday into Saturday night as the surface low and associated cold front move into the region. Bulk shear increases considerably with the intrusion of the triple point (as high as 40-50kts). In addition, SRH values balloon above 200 m^2/s^2, indicating ample potential for rotating updrafts to materialize with any surface based storm that initiates. The final thing that will need to come together will be the maintenance of surface / low level moisture.
Guidance wants to keep dewpoints well into the 50s and even into the lower 60s, which would lower cloud bases and bypass the potential suppressing nature of warmer air aloft in the profile. If we can achieve the higher end of this dewpoint range, coupled with the other aforementioned favorable dynamics, this could lead to all hazards being on the table Saturday evening / early overnight, with heavy emphasis on wind and hail (non-zero chance for these hazards to be locally significant if a more discrete / supercellular storm mode can be realized). Tornadic activity will be somewhat questionable owing to shear vectors being more parallel to the cold front as opposed to normal to the boundary as it approaches northern Michigan (thus leading to the eventual stationary nature of the front), but risk still remains non-zero. Additionally, the parallel relationship of shear vectors and frontal orientation could set up a heavy rain sequence with any potential training thunderstorms as PWATs swell to 1.00-1.25 (200-300% of climo normal).

This setup has a very low floor, but a high ceiling that can't be overlooked despite ongoing forecast uncertainty. This is reflected by SPC already electing to place northern lower Michigan within the Day 3 Slight Risk (level 2/5) for the conditional threat of severe weather. Numerous more updates are to be had in the coming forecast cycles as details on the evolution of this sequence become clearer.

Rest of the Period: The cold front will stall out overhead and become stationary by Sunday, and with additional disturbances expected to ride this area of forcing, this spells additional rounds of showers and storms at times Sunday into Monday, bringing additional rainfall. Eventually, low pressure will pass through the region and the stalled front will be forced eastward by intruding high pressure. By Tuesday, conditions look to be drier but still on the mild side, with highs in the upper 50s to upper 60s and lows generally in the 40s. One final note- considering that we will be dealing with warm daytime temperatures and mild nights coupled with mild temperatures accompanying rainfall, this should spell the arrival of spring greenup in the next week or so, particularly across northern lower Michigan. This could open the door for any frost / freeze impacts beyond the forecast period to be amplified.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
High pressure in the area today with generally clear skies...though a few high based cu has been developing over NE Lower near APN, Y31 in the last couple hours. Won't be impossible to see these develop elsewhere...but for now anticipate skies remain clear at TAF sites into Friday morning. Winds today largely 10-15kts from the southeast...except lake breeze has developed at mbL and TVC, with onshore winds developing accordingly. Expecting light winds tonight...with land breezes again, esp at mbL and perhaps APN. Winds strengthen toward end of TAF period, and esp beyond.

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

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