Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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988 FXUS63 KDTX 011722 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 122 PM EDT Sat Jun 1 2024 .KEY MESSAGES... - Dry weather for most of the day with rain moving in late this evening through Sunday morning. Rainfall totals generally range between 0.25" to 0.5". - Warming trend through the weekend with drier conditions developing Sunday afternoon through Monday. - Unsettled weather returns Tuesday and lasts through mid-week with periods of showers and thunderstorms possible. && .AVIATION... VFR conditions and high cirrus holding ahead of approaching showers. Cigs will gradually lower ahead of the approaching system, with rain beginning around 0Z tonight. Showers will bring widespread IFR conditions, mainly during the early morning hours. Some light fog will also have the potential to develop and hang around into Sunday morning, especially near DTW/DET/YIP where southeasterly winds will bring moisture from Lake Erie over land. After the rain, borderline MVFR/VFR cigs return and visibilities come back up. For DTW/D21 Convection...Very Low chance for a rumble of thunder overnight. DTW THRESHOLD PROBABILITIES... * Low for thunderstorms this evening and tonight. * High for ceilings at or below 5,000 feet tonight. && .PREV DISCUSSION... Issued at 404 AM EDT Sat Jun 1 2024 DISCUSSION... Pattern shift is underway this morning with GOES-16 infrared imagery showing bands of cirrus spilling overhead in advance of a prominent stream of Gulf moisture. Most of the daytime hours remain dry with just thickening cloud cover, supporting a transition from filtered sunshine to overcast skies by this afternoon. Daytime highs in the mid to upper 70s settle right around normal for the first day of June. Radar mosaic shows a broad precipitation shield extending from a cut off low in northern Missouri to the Gulf of Mexico, which will slowly migrate and pivot north throughout the day as the low opens and attempts to merge with longer wavelength troughing across northern CONUS. The northward surge of this system draws a plume of Gulf moisture into lower Michigan this evening, characterized by forecast PWAT near 1.5" (90th percentile for this time of year) and surface dewpoints above 60 degrees. Models still struggle to resolve the northern and eastern extent of this moisture advection, however, given the pervasive dry air that is currently in place (for reference, current dewpoints are in the 40s). Other predictability concerns arise with the amount of convection that is ongoing upstream over the Mississippi Valley, which may further interrupt northward moisture transport in addition to altering system dynamics. As the rain shield lifts toward southern Michigan, there will be a degree of low level entrainment that may delay precipitation onset until well after 00z (8 pm local) and/or evaporate portions of the band itself. With this in mind, most areas will see between 0.25" to 0.5" of rain by Sunday morning with highest amounts west of I-75. One area to monitor for overachievement potential is the Tri Cities, where a decaying frontal zone/convergence axis and more reliable moisture transport could lead to a locally enhanced rain band although the bulk of model guidance keeps this feature northwest of the cwa. Further south, deformation prospects will be tied to low/mid-level closed circulations (925-700mb) that trail behind the deep layer moisture, which will be cut off by a sharp mid-level dry intrusion that follows immediately behind the wave. So while showers may linger in these southern convergence zones, do not expect heavy rainfall after 12z in these areas given the shrinking moisture depths. By Sunday afternoon, moisture will be confined to just a shallow layer of diurnal cloud with clearing anticipated overnight. High pressure briefly builds in for Monday alongside a warming trend. Unsettled weather then develops for mid-week as we transition into another closed upper low pattern, with energetic flow in both the low and upper levels and thunderstorm chances as this transition occurs. MARINE... Influence of high pressure wanes this morning as it drifts further over the mid-Atlantic. Low pressure lifting into northern Ontario drags a cold front into the Great Lakes with a secondary area of low pressure developing along this boundary over the western Ohio Valley today. Secondary low is set to track northeast into southern Great Lakes this evening into the first half of Sunday bringing widespread shower chances with a thunderstorm or two will be possible south of Port Huron. Diffuse pressure gradient however results in generally lighter winds (below 20kts) with this system. Weak high pressure then briefly builds in late Sunday and Monday. Additional active weather arrives midweek as a series of systems traverse the northern CONUS. HYDROLOGY... Showers and possibly a stray thunderstorm move into SE Michigan this evening as a deep supply of Gulf moisture converges with a weakening cold front late this evening through Sunday morning. Rainfall amounts expected to range between 0.25" to 0.5", although localized higher amounts in excess of an inch are not out of the question around the Tri Cities region. Minor flooding of urban and low-lying areas, ponding of water on roadways, and rises in area rivers will be the main impacts should an axis of heavy rainfall develop. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BC DISCUSSION...MV MARINE.......KDK HYDROLOGY....MV You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.