Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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326 FXUS63 KDTX 061814 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 214 PM EDT Sat Jul 6 2024 .KEY MESSAGES... - Isolated to widely scattered showers will be possible this afternoon and evening, generally north of I-94. Some rumbles of thunder cannot be ruled out. - The holiday weekend closes out with dry weather Sunday under partly sunny sky. - Hot Monday with highs in the upper 80s. Shower and thunderstorm chances return Monday and Tuesday. && .AVIATION... Early day stratus lifted and mixed out leaving mostly VFR cu around for the afternoon. Could see a few cigs still dipping to 2500- 3000ft for a bit before finally mixing out for good here in the next hour or two. We then look to this afternoon into the evening hours where the trough draped across Mid MI tries to initiate showers and thunderstorms. There have been some very small isolated showers popping up already but all very short lived as the upper levels of the atmosphere are not favorable for longer lived cells. I left any mention of showers/thunderstorms out of the tafs as there isn`t a clear signal for any taf site to make a mention. Best chances appear to be PTK and FNT due to the current activity, when models showing MBS having better chances this evening. We`ll monitor and amend when necessary. Chances of thunderstorms appear low due to short duration of the showers and unfavorable upper levels of the atmosphere. Dewpoints hanging around 60 degrees and any rain that occurs will make fog possible again tonight. For DTW/D21 Convection...Widely scattered showers and a thunderstorm or two will be possible this afternoon/evening, but best chance will hold north of KPTK. DTW THRESHOLD PROBABILITIES... * Low for thunderstorms this afternoon. * Medium for ceilings at or below 5000 ft this afternoon. && .PREV DISCUSSION... Issued at 1102 AM EDT Sat Jul 6 2024 UPDATE... Low level stratus this morning has been keeping temperatures down in the low 70s and limiting the potential for convective activity thus far today. Temperatures into the upper 70s are still expected to materialize today, creating chances for convective showers this afternoon and evening. Multiple embedded shortwaves are forecast to move across the northern Lower Peninsula this afternoon and evening and will assist in shower development. The best chances for showers will be north of I-69, while south of I-94 expected to see little to no shower development. Once sufficient surface heating has taken place, convection will be able to initiate, but conditions remain unfavorable for stronger storms to develop. SBCAPE of 500 J/kg and 0-6km bulk shear of 20-25 knots do not suggest that any developing showers will be sustained for long. Steep 0-3km lapse rates up to 7 C/km this afternoon do suggest potential for development at the lower levels. Warmer air at the 600mb level will move in this evening and bring lapse rates of around 5 to 5.5 C/km, below the moist adiabatic lapse rate and in turn cutting off convective access to the upper levels. An isolated thunderstorm is possible in areas that may see enough breaks in cloud cover to overachieve on temperatures. However, the updraft is not expected to be able to reach high enough to allow for lightning to develop. Once surface temperatures cool down after sunset, convective development is expected to drop off and any remaining showers will die out soon after. The area is expected to be clear of any showers around midnight tonight. PREV DISCUSSION... Issued at 336 AM EDT Sat Jul 6 2024 DISCUSSION... A cold front has cleared the state as of early this morning, where dry weather now prevails in the wake of the front with temperatures presently in the mid-60s. Residual moisture and humidity will hold on today across SE MI, which will aid in the production of isolated to widely scattered shower activity. The inherited forecast looks reasonable, holding PoP chances north of I-94, with highest PoP chances (30-35%) located along and north of I-69, tied to the greater moisture and subsequently better instability. Instability and bulk shear are not favorable for sustainable activity today, holding at 500 J/kg and around 15-20 knots respectively. Additionally, a cap just under h600 will limit convective depth and coverage. However, steep low level lapse rates with the passage of multiple upper-level waves do justify the PoP potential. Cannot rule out some embedded thunderstorms, but LI values of 0 to 1 and very poor mid-level lapse rates favor rain showers. Shower and storm potential will wane with the loss of daytime heating, with lingering potential lasting through 10PM- Midnight. Highs hold in the upper 70s in the wake of the front. A weak shortwave ridge will fill in behind the departing shortwave and will bring a day of dry weather tomorrow with temperatures returning into the mid 80s for a high. The return of warmer weather is a result of multiple upper-level waves that fill in over the Plains with trough amplification taking place across the greater Plains through the early week period. Initially, this directs heat and moisture from central US downstream into the Great Lakes noted by h850 temperatures increasing from 16C Sunday evening to 18C by Monday evening. This brings daytime highs in the upper 80s, possibly reaching 90 across urban areas on Monday. Rain and thunderstorm chances are also possible Monday with the improved moisture and support from glancing shortwaves ahead of the main trough axis. The better chances for numerous to widespread showers with embedded thunderstorms will enter late Monday into Tuesday tied to the better connection with the trough, with the axis swinging over Michigan late Tuesday night. Medium range models are more muddled through the midweek period given subtleties with shortwave passages and interactions. One major consideration that models are struggling with this far out will be the upstream impacts of Tropical Storm Beryl. The latest ECMWF is much less progressive relative to the 12Z model run and pushes the system into the Ohio Valley, clipping portions of SE MI. Even less progressive is the ICON (and ICON-EPS), which pushes the center of the low right over Michigan. Regardless, not much credence is given into any one particular model solution at this time factoring in limited sampling from the upper-air network, but it is worth noting as several deterministic runs display a much less progressive solution for the 00 cycle. Closer attention will be given to the path of the system as it makes landfall somewhere over southeast TX by early Monday. MARINE... Low pressure departs to the eastern Great Lakes this morning but leaves a trailing trough that lingers over the local area much of the day. This feature and enough moisture wrapping around the departing system will keep scattered showers in the forecast with potential for a few thunderstorms as well. Light northwest winds develop today at generally 10 knots or below. The trough exits tonight with weak high pressure moving back in through Sunday bringing continued light winds. Southerly wind of 10 to 15 knots then develops on Monday ahead of the next frontal system moving in from the Midwest. This system will bring showers and storms late Monday into Tuesday as it tracks through. Slightly cooler northerly flow follows for the mid-week. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....DRK UPDATE.......BC DISCUSSION...AM MARINE.......TF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.