Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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977 FXUS63 KDTX 120018 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 818 PM EDT Thu Jul 11 2024 .KEY MESSAGES... - Showers and storms hold west and north of the Tri-cities this evening. Chances for isolated showers and storms expand across Southeastern Michigan tomorrow. - The next chances for storms comes Sunday and Monday evening. Severe weather is possible with this system. - A period of hot and humid conditions are forecasted for Sunday and Monday. && .AVIATION... Broad and weak high pressure will maintain VFR conditions through tonight with scattered showers and thunderstorms holding to the west of TAF sites. Light winds will gradually settle out of the east- southeast by tomorrow morning. Diurnal cumulus field develops again tomorrow and a chance for scattered showers and thunderstorms return. Models point towards the metro terminals as the favored area for any activity that develops tomorrow, but coverage and and exact location is too uncertain to mention in TAFs at this time. For DTW/D21 Convection...Scattered showers and thunderstorms will be possible around the D21 airspace tomorrow. Confidence in location, coverage, and timing is too low to mention in TAFs at this time. DTW THRESHOLD PROBABILITIES... * Low for thunderstorms tomorrow. && .PREV DISCUSSION... Issued at 339 PM EDT Thu Jul 11 2024 DISCUSSION... Weak high pressure has built into the region today as the remnants of Beryl continue to move off to the east. Light cumulus deck in place has not deterred heating today, as overachieving temperatures have pushed into the mid 80s this afternoon. Pop up showers are a possibility tonight in the Tri-city area, but hi-res guidance has trended away from bringing rain that far east and resolves developing showers raining themselves out on the west side of the state. Friday shows a bit better chances for shower potential over the CWA. Daytime heating will push temperatures into the mid-80s and allow for SBCAPE values to reach up to 1000 J/kg. Shear up to 30 knots will be more prevalent over the southern part of the CWA, so expecting any popup showers or storms to have the best chances to sustain themselves in that environment. Warm air advection at the 700-600 hPa layer is set to move in Friday evening, potentially shutting off convection depending on how warm the profile gets. Early timing of the warm air or underperforming surface temperatures may also limit the convective ability of these storms. Severe weather is not currently expected out of this setup. Weak ridging on Saturday maintains support of high pressure and keeps relatively clear skies and dry conditions in place. Temperatures will increase into the upper 80s, with some urban areas having the potential to touch 90 degrees on Saturday. A weak warm front has to potential to develop and move in Sunday followed by a cold front from the same low pressure system on Monday. Moisture will build with the passage of the warm front Sunday as PWATs between 1.5 and 2 inches will take hold and dew points will rise into the low to mid 70s. There is some concern for heat as a hazard for these two days, especially due to the lack of overnight relief. Highs on Sunday are expected to reach the upper 80s to low 90s, and overnight temperatures on Sunday are not expected to drop below 70 degrees before rebounding back up to 90 degrees on Monday. The NWS HeatRisk product gives a Moderate to Major risk of heat-related impacts across the CWA on Monday for those without an effective way to cool off. Urban areas in and around Metro Detroit have the highest risk. In terms of severe weather potential, early looks for Sunday/Monday show CAPE values around 2000 J/kg. Directional shear will be present for the event and creates clockwise hodographs, although shear conditions are far from perfect. Wind speeds at the upper levels on Sunday in particular will be outpaced by lower-level winds, creating favorable conditions for storm development in the lower few thousand feet of the atmosphere but providing a potential obstacle for storms to develop further up. Another obstacle for any convection looks to be a small temperature inversion around 800 hPa present both days. Updrafts will likely be able to overcome this either by eroding the cap or by using forcing from the front. Despite these obstacles, convection is expected for these periods at this time, with Monday looking to be the best shot at severe weather. Conditions will dry out and cool down after frontal passage on Tuesday as high pressure moves into the Great Lakes once again and upper level ridge to the west remains stagnant for the foreseeable future. Dew points will drop back down into the low 60s-upper 50s and seasonal to below-seasonal temperatures are expected. MARINE... An area of weakly organized high pressure provides a diminished wind field across the central Great Lakes this afternoon and evening, evidenced by single digit marine anemometer readings (as of 19Z). A weak area of convergence could drift east this evening and sustain some isolated thunderstorms, mainly over Saginaw Bay. Otherwise, light winds organize out of the south-southeast Friday as diffuse surface ridging drifts toward the Eastern Lakes. Winds/waves generally hold below criteria through Saturday and likely into next week. Main caveat associated with the potential for marginal Small Craft Advisory wind gusts amidst veered southwest flow over Saginaw Bay as peak afternoon winds approach 25 knots. Chance exists for isolated showers/storms Friday afternoon before coverage expands for Sunday and Monday with some stronger storms. Late weekend and early next week storms should pose a higher risk for locally higher winds/waves and hail. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....AA DISCUSSION...BC MARINE.......KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.