Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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793 FXUS63 KDTX 210550 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 150 AM EDT Tue May 21 2024 .KEY MESSAGES... - Additional storms are possible this afternoon into the evening. Damaging wind is the greatest threat. - Warm and muggy conditions with high temperatures in the mid to upper 80s continue through mid week until a cold front moves through the region Wednesday. - There is one more chance for showers/storms Wednesday before a cooler and less humid air mass follows the front for the late week period. && .AVIATION... Outside of a very sparse rain shower, rain chances have abated in the wake of a passing upper-level wave. Nighttime satellite highlights extensive coverage of low-level stratus that has developed in the wake of the wave, presently situated over west- central Michigan. hi-res model guidance highlights low-level stratus spreading inland, extending into KMBS and possibly into KFNT, where MVFR to IFR cigs will be possible. This stratus deck will further be reinforced from a strengthening low-level inversion, which would maintain coverage into the morning hours. Sunshine will lift and scour out any stratus development by the late morning. For this afternoon, diurnally heating will provide the chance for shower and thunderstorms development, but confidence remains very low regarding timing and coverage potential. KPTK to KFNT have some signal for development in model output, where a PROB30 has been introduced. For DTW/D21 Convection... Outside of a stray shower, generally dry conditions are expected overnight. The chance for a shower or storm will return this afternoon and evening, but confidence is very low regarding coverage and timing. DTW THRESHOLD PROBABILITIES... * Low this morning, low this afternoon and evening. * Low for aob 5000 feet this morning. && .PREV DISCUSSION... Issued at 440 PM EDT Mon May 20 2024 DISCUSSION... The early afternoon convective cluster followed the warm front supported instability gradient along and north of the I-69 corridor this afternoon. Hourly mesoanalysis showed 0-6 km bulk shear sneaking up to around 30 knots as the storms increased coverage, just enough for some forward propagation and sporadic wind damage as the storms matured. The southward moving outflow then became the focus of a secondary development capable of its own sporadic wind damage and large hail before exiting into Ontario at press time. Yet another round of storms is on schedule to affect Lower/SE Mi this evening as upstream activity develops eastward. Mid afternoon satellite imagery clearly shows the outflow reinforced warm front beginning to recover northward or at least hold a position near the M-59 to I-96 corridors for the late afternoon. Surface pressure falls associated with the inbound MCV will be sufficient to draw instability northward into SW Lower Mi late in the diurnal cycle while the mid level circulation further supports organized convection. Maintenance of instability then becomes more questionable after midnight as the surface low slips through central Lower Mi. The surface low is a tracer for MCV support that carries the remaining convective clusters into Lake Huron before sunrise. The MCV subsidence wake appears as a substantial short wave ridge in model data to start off Tuesday. The effective frontal boundary sinks back south as well to leave conditions dry for the morning before a transition to return flow moisture transport occurs in the afternoon. Scattered showers and a stray thunderstorm are possible through the evening as the surface warm front sharpens up ahead of the next Midwest low pressure system. The southern stream circulation in today`s Pacific coast trough has good model agreement on a track into the Midwest where it deepens substantially by Tuesday night. The leading cold front becomes the subject of the next round of severe thunderstorm potential for our area, although the latest model trends exhibit a strong nocturnal limiting factor for eastward longevity. The 12Z HREF hi-res members show good agreement on a convincing weakening trend across Lower Mi late Tuesday night. This is a surprising solution given how strongly forced the pattern is on the background of the larger scale low pressure system. The SPC Slight/Marginal risk combo nicely depicts the decreasing potential for severe intensity into Wednesday morning. MARINE... A stalled boundary extends from southern Lake Huron to southern Lake Michigan with a mid level system rippling along it. This helped touch off a afternoon round of storms. Additional mid level support this evening will lead to another round of storms reaching the eastern lakes around midnight. The front will linger Tuesday which could help another round of storms in the afternoon. A stronger surface low will then lift northeast through northern Michigan Tuesday night into Wednesday, pulling a cold front through the region leading to yet another round of storms Wednesday. Conditions are expected to remain below Small Craft Advisory criteria tonight through Tuesday, though locally higher winds and waves will be possible within any thunderstorms. Winds increase out of the south to 20 to 30 knots ahead of the associated cold front Wednesday, then veer to the west Wednesday night into Thursday while remaining gusty to around 25 knots. Less humid air settles in for the late week as high pressure builds in. CLIMATE... Here are the record high temperatures for May 20th through May 22nd: May 20th: Detroit 91 (set in 1977) Flint 92 (set in 1934) Saginaw/Tri-Cities 93 (set in 1977) May 21st: Detroit 92 (set in 1977) Flint 93 (set in 1921) Saginaw/Tri-Cities 94 (set in 1977) May 22nd: Detroit 90 (set in 1994) Flint 91 (set in 1934) Saginaw/Tri-Cities 89 (set in 1992) Here are the record high low temperatures for May 20th through May 22nd: May 20th: Detroit 68 (set in 1934) Flint 65 (set in 1939) Saginaw/Tri-Cities 70 (set in 1975) May 21st: Detroit 71 (set in 2013) Flint 67 (set in 1934) Saginaw/Tri-Cities 66 (set in 2021) May 22nd: Detroit 67 (set in 1941) Flint 65 (set in 1977) Saginaw/Tri-Cities 68 (set in 1977) && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....AM DISCUSSION...BT MARINE.......DRK CLIMATE......BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.