textproduct: Detroit/Pontiac

KEY MESSAGES

- Milder with widespread showers developing tonight.

- Stretch of warm conditions throughout the work week with daytime temperatures in the 70s each day for most locations.

- An active pattern will bring periodic chances for showers and thunderstorms Monday night through Thursday.

- There is a Marginal Risk of severe thunderstorms Monday night and Tuesday morning.

- Locally heavy rainfall potential also increases during the mid week period.

DTW THRESHOLD PROBABILITIES

* High for ceilings aob 5000 feet late tonight into Monday morning.

* Low for thunderstorms late tonight into early Monday morning.

PREV DISCUSSION

Issued at 337 PM EDT Sun Apr 12 2026

DISCUSSION...

Prolonged period of mid level southwest flow featured north of a sprawling southeast conus upper ridge sets the stage for an increasingly mild, moist and intermittently active pattern heading into early next week. Increasing depth to southwest flow downstream of organizing northern plains low pressure effectively drawing the attendant warm frontal structure northward across lower Michigan late this afternoon. Modestly mixed emerging warm sector will maintain gusty conditions into the evening hours, intermittently reaching excess of 30 mph at times. Narrow window for possible weak boundary layer destabilization across central lower mi maintains a lower probability for shower/t-storm production over mainly the Saginaw valley through early this evening. Attention then turns to an inbound mid level wave and plume of higher quality moisture noted on water vapor shearing across the mid Miss valley. Fueled by 50+ knot inflow at 850 mb, this will establish favorable conditions for roughly a 6-hour period of widespread rainfall overnight. Probabilistic output highlights a broad qpf footprint of .1 to 25" /highest north/, with lower likelihood for upwards of half an inch across the Saginaw valley and northern thumb.

The first in a series of seasonably warm days entrenched starting Monday as low level southwest flow sustains periodic bouts of more meaningful thermal advection. Highs pushing well into the 70s except along the immediate lake Huron shoreline. Background environment generally unsupportive of convective development through the daylight period despite some degree of diurnal destabilization, owing to a lack of tangible forced ascent as shortwave upper ridging briefly governs conditions. Outgoing forecast will continue to promote simply a low end pop mention through early evening. Renewed deeper moisture transport initiates upstream again Monday night, possibly aided by some form of remnant convective wave ejecting through the warm sector. While greater convective organization and expansion expected to focus along/north of a surface low and warm front across parts of MN/WI and eventually northern MI, the probability does exist for sufficient mid level destabilization to occur as higher theta-e lifts through to initiate convection locally during the overnight hours. An uptick in deep layer shear could offer some organized updraft potential should activity emerge and root within a steepening lapse rate environment in the mid levels. SPC Day 2 Outlook maintains a marginal risk to highlight the potential for large hail Monday night.

A muddled picture yet in terms of convective potential across the Tuesday-Wednesday periods. The ambient environment will be virtually unchanged Tuesday, still defined by southwest flow of considerable depth south of a frontal boundary that now anchors over northern lower mi. This will again support highs well into the 70s. The overall environment still lacks in discernible forced ascent outside of the front, unless a yet defined trailing MCV makes an appearance from overnight convection upstream. Outgoing forecast will continue to highlight a broader, mid range probability for rainfall Tuesday afternoon, but suspect some downward revision may occur across at least southern areas as confidence grows in the frontal positioning holding from the Saginaw valley/northern thumb northward. Convective initiation and expansion most likely Tuesday evening across central and northern lower mi as the boundary gradually retreats northward and also upstream under more supportive conditions. Plausible the midwest activity funnels downstream in some fashion nocturnally for the overnight period. The underlying thermodynamic and kinematic profiles suggests an organized convective episode is possible, with the latest SPC Day 3 outlook offering a broad Slight Risk for Svr Wx encompassing all of lower Michigan. Warmer mid April conditions persist through the latter half of the week. This combined with continued high quality moisture content will maintain a favorable background environment thermodynamically for additional episodes of convective development within the Wed=Thu periods, particularly as greater height falls and an associated frontal passage offer greater large scale forced ascent. Dry and very mild Friday - temperatures possibly making a run toward 80 degrees.

MARINE...

Southerly gradient winds continue to strengthen this evening as a low pressure system tracks through Lake Superior and Ontario, while high pressure remains stalled off the Mid-Atlantic coast. A warm front associated with the low continues to lift northward, trailing an even warmer elevated front. This provides stability, preventing 40-50 knot 3-5 kft winds from mixing down to water level. Locally higher winds and waves are still possible across the northern half of Lake Huron given ongoing convection along the warm frontal boundary. Small Craft Advisories remain in effect for the southern Lake Huron nearshores as waves respond to increasing winds tonight. Expanded the advisory to include Lake St. Clair and western Lake Erie since gusts are now expected to exceed 25 knots. Potential still exists for brief gusts to gales late tonight into Monday as a 65+ knot low-level jet crosses portions of the central Great Lakes. The main area of concern is still Saginaw Bay after flow veers southwesterly and funnels/converges off-shore, but also near The Straits where potential for deeper mixing exists. Several additional rounds of showers and thunderstorms are likely throughout the week due to a series of troughs, low pressure systems, and fronts.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 AM EDT Monday for LHZ421-422-443.

Small Craft Advisory until 10 AM EDT Monday for LHZ441-442.

Lake St Clair...Small Craft Advisory until noon EDT Monday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until noon EDT Monday for LEZ444.