Sunrise 5:58 AM   Sunset 8:54 PM Moonrise 6:17 PM   Moonset 3:40 AM

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LHZ464 Expires:202405220400;;616408 Fzus63 Kdtx 211952 Glflh
open lake forecast for lake huron national weather service detroit/pontiac mi 352 pm edt Tue may 21 2024
for waters beyond five nautical miles off shore on lake huron
waves are the significant wave height - the average of the highest 1/3 of the wave spectrum. Occasional wave height is the average of the highest 1/10 of the wave spectrum.
Synopsis - A warm front lifts north today as a low pressure system moves into the great lakes from the plains. This low, 29.10 inches, reaches western lake superior Wednesday morning with the associated cold front moving through the central lakes during the day. High pressure then builds in through Friday.
lhz363-462>464-220400- lake huron from sturgeon point to alabaster mi beyond 5nm off shore- lake huron from port austin to harbor beach beyond 5nm off shore- lake huron from harbor beach to port sanilac beyond 5nm off shore- lake huron from port sanilac to port huron beyond 5nm off shore- 352 pm edt Tue may 21 2024
Tonight - East winds 5 to 10 knots veering to the southeast after midnight - .then increasing to 10 to 15 knots early in the morning. Waves 1 to 3 feet. Wednesday - South winds 10 to 15 knots veering to the southwest late in the afternoon. Waves 2 to 4 feet. Wednesday night - Southwest winds 10 to 15 knots decreasing to 5 to 10 knots in the late evening and overnight. Waves 3 to 5 feet subsiding to 1 to 3 feet in the late evening and overnight. Thursday - Southwest winds 5 to 10 knots increasing to 10 to 15 knots in the late morning and afternoon. Waves 1 to 3 feet. Thursday night - South winds 5 to 10 knots. Waves 1 to 3 feet. Friday - South winds 5 to 10 knots backing to the southeast late in the morning - .then becoming east 10 to 15 knots late in the afternoon. A chance of showers and Thunderstorms late in the afternoon. Waves 1 to 3 feet. Saturday - Southeast winds 10 to 15 knots veering to the southwest until early evening - .then becoming west 5 to 10 knots in the late evening and early morning. A chance of showers and Thunderstorms early in the morning - .then a chance of showers until early evening. Waves 1 to 3 feet. Sunday - Southwest winds 5 to 10 knots backing to the southeast early in the evening - .then backing to the northeast in the late evening and early morning. Waves 1 to 3 feet.

LHZ400
No data

FXUS63 KDTX 211943 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 343 PM EDT Tue May 21 2024

KEY MESSAGES

- Isolated storms are possible this afternoon/evening south of I-69, while locations along I-69 are most favored for development.

- Strong to severe storms are unlikely, but cannot rule out an overachieving storm or two that pose a marginally severe wind (60 mph gust) or hail (up to 1 inch diameter) threat.

- Marginal to Slight Risk of severe storms remains for Southeast Michigan late tonight for damaging wind potential, but latest model trends support weakening activity upon arrival.

- One more chance for showers/storms Wednesday before a cooler and less humid airmass arrives late Wednesday into Thursday.

- Brief warm-up Friday with some additional chances for showers and storms through the weekend.

DISCUSSION

A strong differential heating boundary has setup along I-69 this afternoon as clouds struggled to mix out north of the interstate where 2m temperatures are still in the 70s (60s for The Thumb). Near- full insolation further south has helped guide readings into the mid 80s as dewpoints across Southeast Michigan settle in the low to mid 60s. 21.12Z KDTX RAOB revealed another low-level inversion which initially caps surface-based convection, but given that the 925 mb inversion is 3C cooler than Monday's with a higher 2m Td, SBCAPEs should eventually build into the 1000-1750 J/kg range (see 12Z HRRR ensemble mean and SPC MesoAnalysis). Main limiting factors are attributed to the initial synoptic setup and the 750-550 mb lapse rates.

Regarding the former, shortwave ridging is in-place for the start of the forecast period which delayed the development of a diurnal cumulus field. Resultant subsidence signal is well-defined in forecast soundings and contributes to a muted convection response in the 12Z CAMs. The mid-level lapse rate issue suggests very isolated coverage of thunderstorms late this afternoon as a secondary/weak warm layer could further suppress convective depths and CAPE values.
All told, the afternoon forecast narrative lends heavily on a surface convergence axis tied to the aforementioned thermal gradient. This serves as the primary focus for CI, but weak 0-6 km bulk shear limits overall lifecycles as storms generally drift toward the northeast. Did make some slight adjustments to PoPs to include a minimum of Slight Chance mentions across the region and a wider swath of Chance PoPs along the boundary. Additional convective development is also possible further south where free-convection may arise from the strongest surface heating. Localized outflow boundaries and lake breezes interactions could also spur additional convective action late today. Strong to severe storms are unlikely based on the current setup, but cannot rule out an overachieving storm or two that pose a marginally severe wind or hail threat.

Any afternoon/evening convective development should decay by 10 PM followed by a period of dry/calm conditions. Attention then turns upstream to a negatively tilted amplifying shortwave trough closing off over SD/IA/MN. Impressive flow within its broad cyclonic shield will spread eastward overnight driving a flanking boundary and a line of well-organized convection across Lake Michigan, into western Lower. Questions remain regarding the integrity/longevity of the expected QLCS, but SPC has maintained the Marginal to Slight Risk of severe storms for Southeast Michigan through the early morning hours on Wednesday. With the exception of the FV3, CAMs are quite bearish on storms (and even showers) surviving to the western CWA border late tonight as the boundary washes out and moisture quality degrades rapidly.

Upper level pattern becomes more progressive Wednesday as the upper low interacts with a stalled trough over Saskatchewan, a unified jet streak and the associated height falls work across Lower Michigan as the main cold frontal boundary gets shoved into the Great Lakes.
Can't rule out a bit of shower activity, but a low-impact FROPA is most likely. Post-frontal conditions offer a drier and cooler forecast for Thursday.

A well-advertised Pacific wave crosses the High Plains into Minnesota Friday with the warm advection arm extending into Southern Lower. Ensembles have trended higher with max temperatures Friday peaking in the mid 80s. Storms are also possible during the evening and overnight hours with the next cold front. Surface ridge builds in across the eastern Plains Saturday morning, expanding into Michigan as the day progresses. This draws a cooler and drier airmass until a VortMax ejects across the Mid-Mississippi Valley and into the Ohio Valley Sunday bringing areas of rainfall to close out the weekend with near-seasonable temperatures. Thermal troughing hangs around early next week before strong longwave ridge amplification gets underway across western CONUS. Omega block configuration is possible through the end of next week.

MARINE

A strengthening low pressure system will lift from Iowa through western Lake Superior Wednesday morning while pulling a warm front northward through lower Michigan. There is a chance of some isolated showers or thunderstorms this afternoon and evening but chances increase tonight ahead of an approaching cold front. The cold front will pass through on Wednesday with showers and thunderstorms possible tonight and Wednesday ahead of it. Winds increase out of the south to 25 knots ahead of the associated cold front Wednesday, then veer to the west Wednesday night into Thursday but settling back down to 15 knots. A small craft advisory will be needed for Saginaw Bay Wednesday as the winds funneling out of the bay have a higher chance to reach 25 knots.

CLIMATE

Here are the record high temperatures for May 21-22:

May 21st: Detroit 92 (set in 1977)
Flint 93 (set in 1921)
Saginaw/Tri-Cities 94 (set in 1977)

May 22nd: Detroit 90 (set in 1994)
Flint 91 (set in 1934)
Saginaw/Tri-Cities 89 (set in 1992)

Here are the record high low temperatures for May 21-22:

May 21st: Detroit 71 (set in 2013)
Flint 67 (set in 1934)
Saginaw/Tri-Cities 66 (set in 2021)

May 22nd: Detroit 67 (set in 1941)
Flint 65 (set in 1977)
Saginaw/Tri-Cities 68 (set in 1977)

PREV DISCUSSION
Issued at 127 PM EDT Tue May 21 2024

AVIATION...

Morning low stratus has begun rapidly clearing early this afternoon over the northern portions of the area as a diurnal cu Field expands in from the south. Uncertainty in thunderstorm potential this afternoon is still fairly high however a thermal gradient is set up between PTK and FNT from differential heating today from the aforementioned stratus lingering in the north. Should convection develop, it likely will be focused along/near this boundary. Given some high-res model guidance is picking up on this especially towards PTK< just enough confidence to switch to a Tempo group. FNT confidence not high enough to make the change at this point but will amend as needed this afternoon based on observational trends.
Decaying line of showers and storms possible late tonight/early Wednesday morning though high uncertainty still exists in how well this activity can maintain itself as it moves across the state at the diurnal instability minimum.

For DTW/D21 Convection... There remains a low chance at convection this afternoon though best potential looks to hold north of DTW towards PTK/FNT instead. Decaying Midwest convection is expected to work across the state overnight however given the unfavorable diurnal timing, high uncertainty how much, if any, reaches Detroit.
That said, even in model outcomes where rain reaches DTW early Wednesday morning, thunder chances are very limited so have opted for a Prob30 SHRA mention instead.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms this afternoon and again late tonight.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory from 8 AM to 10 PM EDT Wednesday for LHZ421- 422-441.

Lake St Clair...None.
Michigan waters of Lake Erie...None.

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