Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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697 FXUS63 KDTX 120803 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 403 AM EDT Wed Jun 12 2024 .KEY MESSAGES... - Warming trend continues through mid-week with high temperatures in the mid 80s today and nearing 90 degrees for Thursday. - Scattered showers and thunderstorms arrive Thursday. Strong to severe storms will be possible during the afternoon and evening with damaging winds and large hail the main threats. Southeast MI is outlined in a Marginal to Slight Risk from SPC. - Higher than usual confidence in hot and humid conditions next week. Temperatures into the 90s Monday and Tuesday with relatively high humidity will likely bring the highest heat indices we have seen so far this year. && .DISCUSSION... A weak shortwave is passing over the region this morning with an associated tongue of theta-e responsible for the area of mid-level clouds passing overhead. The low levels remain dry evidenced by sfc dew point depressions of about 10 to 15 degrees, so the weak radar returns noted this morning have largely been virga save for a few light showers in the Thumb. Height rebounds commence around daybreak with a low amplitude shortwave ridge building directly overhead today. Steady southwest flow and increasing sunshine offer a net boost in mean thickness with 850mb temps rising to around 15C by 00z this evening. This supports high temps in the lower to mid 80s this afternoon. Surface dew points will likewise rise to near 60 degrees and provide a noticeably more humid feel than previous days. Did add a slight chance for a shower for interior areas as a weak surface trough/wind shift may produce enough convergence for disorganized convection during peak heating. A zonal jet streak crossing the northern Plains today will be the impetus for a round of convection over the upper Midwest this afternoon and evening as a cold front tracks across the region. Model guidance continues to offer moderate confidence that some of this convection will sustain itself along a veering 40 kt LLJ, reaching Lake Michigan tonight and eventually moving into northern Lower MI early Thursday morning. Elevated instability looks to advect in locally with 700-500mb lapse rates nudging up to around 6.5 C/km across the north. This would support MUCAPE of a few hundred J/kg and a chance for elevated thunder with highest confidence north of I-69 during the pre-dawn hours. Uncertainty remains with convective trends during the day Thursday, but generally expect any morning activity to wane in vigor as the convective shortwave passes east and favors a pocket of subsidence through midday. Continued southwest flow ahead of the inbound cold front will bring dew points into the mid 60s with temps rising into the mid to upper 80s. Forcing associated with the inbound upper jet exit region and attendant shortwave then begins to arrive during the afternoon and evening bringing better opportunity for convective redevelopment along/ahead of the cold front. This window offers potential for isolated to scattered severe storms with MLCAPE on the order of 1000 to 2000 J/kg (assuming early/mid day convection doesn`t stabilize the environment) and bulk 0-6km shear increasing to around 50 kt which would be supportive of damaging wind gusts and large hail as the primary threats, though an isolated tornado cannot be ruled out. Areas south of I-69 and west of I-75 are highlighted in the SPC Day 2 Slight Risk (2/5) with the rest of SE MI in a Marginal Risk (1/5). The front pushes across the area during the late evening and brings an end to any showers and thunderstorms around midnight. Cooler, drier, and more seasonable air settles in behind the front to bring comfortable conditions Friday and Saturday. High pressure will dominate the region, bringing mostly sunny skies and light winds. The next opportunity for showers and storms arrives Sunday as the ridge axis passes east and a shortwave lifts in from the central Plains. There are still significant timing differences among deterministic solutions stemming from this wave`s ejection speed out of the Four Corners region on Friday. A significant warm-up is still on track for next week with model guidance supporting a 592 dam 500mb ridge setting up across the SE CONUS Sunday and gradually expanding to encompass much of the eastern half of the continent through the week. Ensemble guidance shows mean 500mb height anomalies near 2 sigma by mid-week which supports a prolonged period of well above normal temps with potential for record heat. This is corroborated by ensemble progs showing 30 to 50% of LREF membership with apparent temps above 95 degrees each day from Monday to Thursday. Available soundings continue to suggest only weak capping, so the temperature forecast for any given day will remain subject to any MCS activity that rolls through. && .MARINE... Tranquil weather will continue through the mid week as a ridge of high pressure continues to shift eastward. Southerly winds will slowly shift to the southwest as the gradient becomes more established for the second half of the week. A low pressure system is projected to arrive on Thursday into Friday which could support a period of Small Craft Advisory conditions with several opportunities for showers and thunderstorms. && .PREV DISCUSSION... Issued at 1203 AM EDT Wed Jun 12 2024 AVIATION... Broken to overcast mid and high clouds precede the Midwest frontal system as a plume of elevated moisture moves across Lower Mi late tonight. Upstream observations support lower ceiling but still above 5000 ft while also presenting some virga indications from radar and possibly a stray sprinkle reaching the ground through early morning. The cold front weakens but still remains the focus of cumulus enhancement while moving west to east across Lower Mi during the afternoon. The cumulus component contributes to broken ceiling around 5000 ft into Wednesday evening. For DTW/D21 Convection...Thunderstorms are not expected late tonight through Wednesday evening. DTW THRESHOLD PROBABILITIES... * Moderate for ceiling 5000 feet or less in the afternoon. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...TF MARINE.......SS AVIATION.....BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.