Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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123 FXUS63 KDTX 130357 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1157 PM EDT Wed Jun 12 2024 .KEY MESSAGES... - Warming trend continues through mid-week with high temperatures nearing 90 degrees for Thursday. - Scattered showers and thunderstorms also 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. && .AVIATION... A combination of thunderstorm remnants moving in from the west and new showers developing overhead are expected to affect MBS down toward Flint late tonight and early in the morning. The ongoing activity weakens enough for conditions to remain VFR while any new showers are also high based and light. The plume of mid level moisture tracks east mid to late morning which gives daytime heating a chance to recover for the afternoon. Thunderstorm timing, coverage, and intensity the become the forecast highlights for the afternoon into Thursday evening. There is a wide range of model projections on timing/location of storm initiation, however earlier and/or farther north solutions are favored as the larger scale mid level trough and upper level jet approach from the upper Midwest. Storms are expected to affect all terminals beginning around 20Z at MBS then spreading southeast toward DTW during late afternoon. For DTW/D21 Convection... An approaching low pressure system and cold front bring a chance of thunderstorms later in the afternoon. A general NW to SE progression with increasing coverage is expected across the area, primarily affecting DTW after 22Z. DTW THRESHOLD PROBABILITIES... * Moderate for thunderstorms impacting the terminal after 22z Thursday. && .PREV DISCUSSION... Issued at 957 PM EDT Wed Jun 12 2024 UPDATE... Upstream observational trends this evening suggest the forecast is in good shape calling for a chance of showers and possibly a rumble of thunder late tonight and in the morning. The WI/IL convection has weakened but the parent MCV remains with respectable strength while set to track across Lower MI. The wave has some representation at 500 mb across the spatial range of model data and appears capable of strengthening the low level jet with a corresponding increase in elevated moisture transport and instability late tonight. This forcing has potential for scattered shower production in its own right out ahead of any remnant surface based activity approaching from the upper Midwest. Consensus of hi-res model data carries the bulk of the upstream storms across Upper Mi and northern Lower MI along the instability axis. The latest runs of the RAP and NAM also maintain a couple line segments of convection this far south toward sunrise. This will be monitored as MUCAPE drops to sub 1000 J/kg from west to east into SE MI, however lapse rate in the 700-500 mb layer builds into the 6-7 C/km range toward sunrise, sufficient for late developing elevated/nocturnal convection. The most favored area is north of I-69 and mainly within a few hours of sunrise. Activity dissipates while exiting eastward mid to late morning allowing ample opportunity for recovery of instability for the anticipated afternoon round of storms. PREV DISCUSSION... Issued at 320 PM EDT Wed Jun 12 2024 DISCUSSION... Clear skies have pushed temperatures into the 80s this afternoon ahead of the approaching cold front and associated storms moving in tomorrow. Hi-Res guidance resolves two different chances for rain on Thursday. The first round comes through early Thursday morning, beginning as early as 4am. This threat for storms is focused mainly in the Thumb, where there is potential for the storms to tap in to some MUCAPE of up to 500 J/kg. By the time the rain moves in, shear looks to be scarce and a diurnal temperature inversion will be in place. Currently not expecting any severe storms to develop, although an occasional rumble of thunder is possible. The second round on Thursday boasts a greater potential for storms to develop, but there is still much uncertainty on how everything will play out. Later in the day Thursday a shortwave trough moves overtop Michigan, allowing for a bit more divergence aloft than earlier in the day. That said however, the left exit region of the trough remains to the northeast, meaning that speaking dynamically, the best region for storm development is still not quite lined up with the CWA. Thermodynamics tell a similar story for a different reason, with the better CAPE and moisture environment staying to the southwest. ThetaE values range 10-20K greater to the southwest of Lake Michigan, allowing for the possibility that storms may grow in the direction of greater moisture rather than developing over southeast Michigan. MUCAPE values over Michigan reach 1500 J/kg at their peak, so updrafts still have the possibility to develop with some help from the cold front. Hodographs look decent for the development of supercells with the potential to produce hail, and DCAPE values over 1000 J/kg signify the potential for severe wind gusts. An isolated tornado can also not be ruled out at this time. The cold front then passes over Michigan early Friday morning, ending the severe storms chances. High pressure takes control behind the front, bringing clear skies Friday and Saturday along with slightly cooler, more seasonal temperatures. The next chance for showers comes Sunday evening, when a shortwave embedded within the development of an upper level ridge brings some rain to the Great Lakes area. The timing and extent of these showers is still uncertain, and depends on how the ridge develops over the weekend. Confidence continues to stay high on a significant warmup next week. An upper level high settles in over the Southeast United States on Sunday creating the aforementioned ridge overtop of the CWA. 500mb heights have the potential to hit 590dam at peak, allowing for temperatures 10-15 degrees above climatological normals. Flow is set up in such a way that will allow for warm, moist mT air from the Gulf of Mexico to fill in to the Great Lakes, bringing dew points up into the 70s. Forecasted temperatures currently sit only a few degrees shy of record highs across the area, and has the potential to hit record highs if full insolation can be achieved. Ensemble guidance shows only a handful of runs failing to hit 90 degrees on Monday, with apparent temperatures reaching into the mid-to upper 90s. The same factors remain in place on Tuesday, with temperatures and apparent temperatures once again reaching the low 90s and upper 90s respectively. Overnight temperatures stay in the 70s, offering little relief from the hear. As such, the NWS Heat Risk product identifies a Major Risk (Level 3/4) of heat related impacts on Monday and Tuesday, with local pockets of Extreme Risk (Level 4/4) on Tuesday. Showers are possible for the duration of the event riding up the trough to the west into the Great Lakes region, which could provide some brief relief from the heat. Still, much remains to be resolved on the extent and timing of any rainfall. A slight though not insignificant cooling trend has developed for Wednesday. Previous runs looked to maintain the ridge through the middle of next week, but now look to move it off to the east on Wednesday. Zonal flow is set to take over, but temperatures will remain above normal through the rest of the week. MARINE... Extremely stable over-lake conditions persist through the remainder of the day which will promote light winds leading into tomorrow. Upstream convection west of Lake Michigan will eventually cross the lake and enter, first over northern Lake Huron, which will bring the chance for showers and thunderstorms. Coverage and intensity of activity is expected to wane overnight as it crosses both lakes, but isolated to scattered coverage cannot be ruled out through southern Lake Huron into late tomorrow morning. Southwest flow will become reinforced over the lake through the day tomorrow, veering more northwesterly late tomorrow night into Friday morning. Gusts 20-25 knots will be possible immediately along the nearshore zones, especially through Saginaw Bay with the better fetch, however, have precluded the issuance of any Small Craft Advisories at this time given how stable the over-lake conditions continue to be. The stable marine layer should keep the stronger winds aloft as they flow off the land. Will consider a Small Craft Advisory for the Saginaw Bay tomorrow afternoon and evening if modeled guidance suggests higher probabilities of achieving sporadic gusts aoa 22 knots. Wave heights reach right around the 3 ft mark for the Bay. A cold front and high pressure builds in on Friday, promoting lighter winds speeds. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT UPDATE.......BT DISCUSSION...BC MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.