Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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722 FXUS63 KDTX 120753 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 353 AM EDT Sun May 12 2024 .KEY MESSAGES... - Temperatures return to normal values today and a few degrees above normal Monday. - Showers and scattered thunderstorms move in late tonight and Monday as a cold front drops into the region. - Locally heavy rainfall is possible Monday afternoon and Monday night as the front stalls across southern Lower Michigan. - Showers and thunderstorms continue Tuesday as the front exits the region. Cooler than normal temperatures follow Tuesday and Wednesday. && .DISCUSSION... Sunshine through patchy cirrus starts the day across SE Mi as weak high pressure slides through the central Great Lakes. The high is then shunted quickly eastward as the next sizable low pressure system moves from central Canada to the upper Midwest and northern Great Lakes by afternoon. An expansive pattern of warm advection precedes the system first noted as a further increase of cirrus coverage and then late morning to early afternoon thickening mid level clouds across southern Lower Mi. Moisture transport/theta-e advection is adequate for the cloud cover but a bit too shallow for rain this far south, although radar indications of virga are likely toward the Tri Cities. Temperatures finally return to near normal conditions for early/mid May with the help of SW wind gaining traction across the area, however afternoon highs are held in check by the early expansion of cloud cover. Boundary layer growth likely comes up short of the 800 mb shown in model soundings that would otherwise support a larger 70+ temperature footprint. Preference leans toward slightly cooler guidance leading to afternoon highs in the upper 60s most areas. SW flow continues to support mild conditions tonight as the system warm sector builds fully across the central Great Lakes while also setting up at least somewhat receptive conditions for late arriving showers and thunderstorms. Upper Midwest activity developing off this afternoon`s diurnal cycle has a chance to survive the evening and reach SE Mi after midnight, although on a steady weakening trend. Model projections of surface based instability drop off in typical nocturnal fashion while 700-500 mb lapse rate hovers in the 6-7 C/km range. More notable is the 40 kt warm sector low level jet setting up within the 850 mb theta-e ridge having potential to support scattered elevated convection by late evening both in the warm sector and then closer to the cold front as it settles into northern/central Lower Mi toward sunrise. Inherited entry level likely/numerous POPs cover this well from the Tri Cities and northern Thumb down to the I-69 corridor by sunrise Monday. The front entering northern Lower Mi Sunday night is still projected to stall somewhere in central to southern Lower Mi during Monday ensuring an active early week period across the region. Predictability is higher than average on the larger scale weather structures such as the presence of the frontal zone in general, the James Bay and KS/OK mid level circulations, and the 1 inch PW moisture supply between them. The combination of these elements is favorable for increased confidence in a heavy rainfall scenario but with low predictability on QPF location and magnitude. The pattern will have a substantial convective component, both surface based and elevated/nocturnal, which will also be able to manipulate the effective position of the larger scale front. Assuming those uncertainties and taking the 00Z model consensus at face value favors a potential heavy rainfall area generally north of the M-59 corridor and south of the M-46 corridor from Monday afternoon through Monday night. The southern stream wave brings surface low pressure into the Ohio valley by Tuesday and this gives the front a chance to become more progressive north to south across Lower Mi. Showers are likely with a chance of thunderstorms along the front but farther south toward metro Detroit and the Ohio border region. If we again assume the latest model timing then this activity moves south of the border Tuesday evening. A dry period during mid week allows time for some recovery before another system moves in during the late week period. && .MARINE... High pressure slides across the central Great Lakes this morning. It brings favorable marine conditions until another low approaches late in the day. This system offers the potential for enhanced southwest flow over Saginaw Bay where gusts could briefly touch 25 knot Small Craft Advisory threshold. Otherwise, showers and storms arrive across Lake Huron and Lower Michigan tonight and continue through the early week period as a cold front stalls across the area. && .HYDROLOGY... An active period of weather will be centered on a cold front moving into Lower Michigan late tonight which then stalls in central to southern Lower Michigan Monday and Monday night. Showers and thunderstorms will be numerous along the front, especially Monday afternoon and Monday night, when locally heavy rainfall possibly exceeding 1 inch is possible. Predictability is moderate on the overall rainfall scenario but still low on precise threat areas and total amounts needed to factor in for flooding hazards. A broad area of minor flooding potential is centered on the Monday night time period for Southeast Michigan. && .PREV DISCUSSION... Issued at 1108 PM EDT Sat May 11 2024 AVIATION... The western edge of a low pressure system is lingering due to slower departure speed, therefore SCT VFR clouds linger across some of the terminals until late tonight. Winds hold from the northwest with decreasing speeds as a ridge of high pressure briefly crosses through the region. This helps to reinforce column stability and a clearing trend into Sunday. Winds flip toward the south-southwest Sunday afternoon upon arrival of a northern Great Lakes low pressure system`s warm front. Can`t completely rule out a few sprinkles or showers as the elevated portion of the front encroaches, but this scenario is mainly reserved for FNT/MBS. Minimal impact to ceilings and visibility anticipated, thus VFR conditions likely persist. The cold front arrives Sunday night with showers and low-end potential for a few embedded thunderstorms to form ahead of the boundary, sometime after 03Z. For DTW/D21 Convection...Thunderstorms are possible after 03Z Monday with an approaching cold front. Storms will be isolated to widely scattered. Some potential exists for a more linear structure to organize along the cold front, but low confidence exists in the magnitude of instability and ability organization at this time. DTW THRESHOLD PROBABILITIES... * Low for thunder after 03Z Monday. * Low for ceiling at or below 5000 feet tonight. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...BT MARINE.......DG HYDROLOGY....BT AVIATION.....KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.