Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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137 FXUS63 KDTX 230423 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1223 AM EDT Thu May 23 2024 .KEY MESSAGES... - Windy conditions subside this evening but become breezy again Thursday to around 20 mph. - A brief warm-up is expected Friday with a 50 to 70% chance for showers and storms late Friday into early Saturday. - Slightly cooler conditions early next week with additional showers and storms likely late Sunday into Monday. && .AVIATION... A significant spoke of absolute vorticity pushed across the forecast area between 00-04Z. Subsidence in the wake of the shortwave and loss of daytime heating has caused the cumulus to dissipate this evening. Relatively neutral temperature advection with increasing confluent flow aloft will result in low sky fraction the duration of tonight. A cooler and drier morning is expected to result in a slow development of boundary layer cumulus late Thursday morning. DTW THRESHOLD PROBABILITIES... * None && .PREV DISCUSSION... Issued at 346 PM EDT Wed May 22 2024 DISCUSSION... Stacked low pressure just north of Lake Superior is sending a cold front across the region this afternoon. The cumulus field noted ahead of the front (now positioned from Bad Axe to Adrian) continues to exhibit very little vertical development, indicating the lack of low-level convergence and upper support as well as modest capping are sufficient to suppress convection despite 1000+ J/kg MLCAPE analyzed across the region. Deep mixing and a tight pressure gradient associated with the low are responsible for gusts in the 30 to 40 mph range. The windy conditions will subside with the loss of daytime heating, but remain breezy to around 15 to 25 mph this evening. Surface dew points settling into the lower 50s behind the front will bring a noticeable improvement in humidity over the next few hours. With a much drier column settling in, precipitation-free conditions are forecast this evening into tonight. An area of PV advection and modest height falls tied to the mid-level low over central Ontario will pass over the state late this evening but with little consequence other than a reinforcing shot of cooler air. 850mb temps settle to near 8 to 9 C, down from the 14.4 C observed in the 12z DTX RAOB. This sets the stage for Thursday AM lows to fall to the mid to upper 50s under mostly clear skies. Daytime Thursday will be spent positioned between the Ontario low moving over James Bay and high pressure building in across the Ohio Valley. This keeps a light southwest breeze going but with wind speeds much lower than today - around 10 to 20 mph. The relatively cooler air mass will have short residence time with near full late May sun helping boost temps into the around 80, still on the high side of the seasonal norm. The Canadian low sends one more lobe of vorticity across the northern Great Lakes Thursday night, pushing a shallow cold front across Lake Huron and possibly into the Thumb/Tri-Cities Friday morning. This will encounter a still very dry environment with PWATs near or below 0.50 inches, so not expecting more than a northeast wind shift with this feature. The next low emerges over the northern High Plains Thursday night, quickly deepening on Friday as it lifts northeast across the Dakotas. This squeezes a shortwave ridge over the Great Lakes and maintains the dry conditions through most of the day. The ridge axis passes overhead by late afternoon with developing southwest wind quickly advecting in a wedge of higher theta-e. Convective trends for Friday evening/night are unclear at this stage and will be reliant on how upstream activity gets going along the warm front. For now it appears the best chances for showers/storms arrive after midnight when the better height falls/synoptic forcing align with deeper moisture. Saturday shows a decreasing precip trend through the day after a cold front clears the area from west to east. High pressure fills in behind this system to keep late Saturday into early Sunday dry and seasonable. A deeper low then ejects out of the Plains late Sunday into Monday, bringing a high likelihood for showers and storms. Still some timing specificity to work out with this system, but if 12z model trends hold it looks like the more widespread rain may occur overnight Sunday night into early Monday morning before a dry slot brings more of a scattered coverage for the Memorial Day holiday. This system will usher in a cooler air mass for early next week with highs in the 70s likely. MARINE... A strengthening low pressure system will stall over Ontario today offering a stronger gradient wind. The systems`s cold front has moved through resulting in breezy westerly flow for most of the Central Great Lakes. Mainly dry conditions are expected the rest of today with winds and waves over Saginaw Bay dropping below Small Craft Advisory criteria late this evening. Winds flip to the east over the weekend and remain rather as a surface ridge builds in across the eastern Plains, expanding into Michigan as the day progresses. Another wave ejects across the Mid-Mississippi Valley and into the Ohio Valley Sunday, but most of the showers/storms should remain to the south with favorable marine conditions through the period. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....YO DISCUSSION...TF MARINE.......KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.