Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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311 FXUS63 KDTX 231958 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 358 PM EDT Thu May 23 2024 .KEY MESSAGES... - Friday brings more nice weather to kick off the holiday weekend, mostly sunny with highs in the lower 80s. - Showers and thunderstorms move in Friday night (60-70%) and continue into Saturday morning. - Rain ends Saturday afternoon through Saturday night. - Showers are likely again with a chance of thunderstorms Sunday afternoon and Sunday night. - The Memorial Day outlook calls for cool temperatures with showers likely Monday and Monday night. && .DISCUSSION... Ohio valley surface high pressure is demonstrating full control of conditions today resulting in ideal mid to late May weather across Lower Mi. Most locations enjoy full sun and breezy SW wind during mid to late afternoon, both of which help lift temperatures to highs near 80. Temperature trends follow a mostly clear sky with light and variable wind tonight taking advantage of a low humidity air mass and favorable radiational cooling. Lows in the lower 50s with a few upper 40s in the usual cooler locations look good at the lower end of the guidance range. The low pressure system in the Rockies/High Plains tonight moves toward the upper Midwest to start Friday. It helps build the mid level short wave ridge downstream that in turn directs high pressure into more of a south to north position across the central Great Lakes for another day of full sun and low humidity in SE Mi. Temperatures also reach about a category higher into the lower 80s before high clouds thicken late in the day. Thunderstorm trends become the forecast highlight for the Great Lakes Friday night as multiple convective systems are likely to occur upstream with the Plains to Midwest low pressure system. The surface low is positioned with good model agreement in northern MN by Friday evening and is connected to the primary warm frontal zone that has been stalled across the Ohio valley. The system draws the warm front northward Friday evening but only toward the southern Mi border. Farther north progress is restricted by secondary low pressure within the occlusion over WI thus setting up a sharp west to east instability gradient shown best in the 12Z HREF mean MUCAPE that holds sub 1000 J/kg across Lower Mi. The system continues to pinch the surface based moisture/instability axis southward during the night which helps explain a general weakening convective trend in Hi-res solutions across the Great Lakes while remaining MCS structures propagate into the OH/TN valleys toward the instability axis. There is enough elevated instability to maintain a generous coverage of showers with scattered ordinary storms across Lower Mi judging by the corridor of 700-500 mb lapse rate averaging 7.5 C/km that sweeps overhead and eastward during Saturday morning. The rest of Saturday and Saturday night turn out Ok as a broad short wave ridge and associated surface high pressure cover the Great Lakes. However, the large scale mid and upper air pattern is zonal and progressive which keeps short wave systems on the move through the weekend. Consensus of extended range models projects the next Plains low pressure system arriving late Sunday. It picks up the Ohio valley front once again for another textbook low level jet driven moisture transport scenario into Lower Mi Sunday night through Memorial Day. && .MARINE... The central Great Lakes are positioned between a low pressure system over southern Hudson Bay and a ridge of high pressure spreading across the Ohio and Tennessee Valleys. Winds remain somewhat breezy through the rest of the daylight period with gusts eventually trending lower overnight. An upper level ridge works in aloft Friday offering dry and stable conditions. Gradient winds veer northerly, becoming variable, and eventually easterly with lower speeds. Shortwave feature ejects across the Upper Midwest Friday night into Saturday with a secondary surface low developing along the system`s cold front. This offers opportunities for some thunderstorms and a period of Small Craft Advisory conditions across Saginaw Bay during the afternoon. An occluded low then tracks across Wisconsin and into The UP Sunday night and Monday which drags an energetic LLJ across the waterways. Expect a broader representation of Small Craft Advisories marked by gusts approaching 30 knots. && .PREV DISCUSSION... Issued at 123 PM EDT Thu May 23 2024 AVIATION... Mainly clear sky conditions today with the exception of a few diurnal cumulus and some high cirrus. High pressure to the south keeps stable, dry conditions in place. Westerly winds remain gentle through the rest of the day today, with occasional gusts reaching 15 knots. Light and variable winds in the early morning hours tomorrow as the center of the high pressure centers overhead. Winds flip to become southeasterly tomorrow behind the high, with skies remaining clear. The next system is expected to move in Friday night/Saturday morning and bring showers and storms, although the start time for these storms remains just outside the TAF period for now. DTW THRESHOLD PROBABILITIES... * None && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...BT MARINE.......KGK AVIATION.....BC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.