Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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568 FXUS63 KDTX 081926 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 326 PM EDT Mon Jul 8 2024 .KEY MESSAGES... - Isolated to widely scattered showers and thunderstorms from Flint to Saginaw/Thumb this evening before shifting south into the rest of the region tonight. - Remnants of Beryl begin to impact Southeast Michigan Tuesday afternoon. Moderate to heavy rain continues through the day Wednesday before it finally departs daytime Thursday. Some flooding is possible dependent on where heaviest rain sets up. - A prolonged period of above average temperatures is expected to start this weekend and continue into early next week. && .DISCUSSION... Diffuse frontal boundary continues sag into southern lower MI this evening with associated weak low level convergence resulting in scattered showers/storms being confined to the Flint/Saginaw Valley/Thumb areas. The parent mid-level trough skirts the region during this time as it tracks over northern lower MI leading to increasing deeper layer shear, pushing into the 30kt range, offering potential for a stronger storm or two. Limiting factor for this outcome however remains the weak convergence along the boundary as well as very modest available instability with latest CAMs struggling to generate more than 500-700J/kg of MLCAPE. Scattered rain chances eventually expand southward across the rest of the region tonight as the boundary pushes further southeast supported by a compact mid-level shortwave riding along it out of the Midwest into the southern Great Lakes. Additionally, this wave brings with it a portion of higher theta-e airmass that is just to our south maintaining some weak elevated instability to support thunder chances throughout the overnight period. Latest model runs are more bullish on frontal progression with most now advertising this front clearing east of the Metro Detroit area by late morning offering a brief end to precip chances before the arrival of the lead edge of Beryl remnants latter half of Tuesday. Focus remains on what would then be Tropical Depression Beryl as it lifts into the Ohio Valley/Great Lakes for the midweek period. Confidence in this system reaching SE MI, rather than taking a more common deflected easterly track to our south, is increasing with the 12Z runs continuing to show its the center tracking somewhere between northern OH and the central portion of the CWA (ie I-69). This is resultant from a faster system speed lending to a delayed interaction with the northern stream shortwave until Wednesday, which is keeping a more westerly track in play (this is especially apparent between the 00Z and new 12Z Euro). This faster arrival leads to the initial deformation arm reaching the southern portions of the area by Tuesday afternoon. Core of tropical moisture then arrives overhead by Tuesday night with PWATs exceeding 2" as the main precip shield likewise overspreads the region with a prolonged period of moderate, to at times heavy, rain persisting throughout the day Wednesday. Another consequence in the later wave interaction, is a slowing of Beryl as it pushes east/northeast likely resulting in a slower departure with the northwest deformation axis lingering over the area, particularly the Thumb, through at least the first half of the day Thursday. In terms of potential amounts, some uncertainty remains due to the westerly trend in track which is making the axis of heaviest rainfall a moving target. That said, an average 1-3" looks likely over all of SE MI from Tuesday afternoon to Thursday morning, with the highest amounts in that range favored south of I-69 currently. Locally higher amounts (near or above 4") are possible dependent on any mesoscale rain banding, though spatial predictability of these features is very low this far out. Upper troughing follows to close out the work week keeping temperatures slightly below average in the upper 70s to lower 80s. Upper flow eventually trends more zonal by this weekend allowing a hotter, humid airmass confined over the Plains to partially spill east into the Great Lakes. Highs during this timeframe likely reach the upper 80s with some 90s being possible especially by early next week. && .MARINE... Southerly wind around 10 knots in place today, allowing for warm moist air to be advected in. This setup brings chances for scattered showers and storms tonight, mainly over northern Lake Huron. Shower chances will continue overnight into early Tuesday morning for southern Lake Huron, Lake St. Clair, and Western Lake Erie. Cold front will pass over the area Tuesday veering winds to the north. Wind speeds will remain around 10 knots, with gusts to 15-20 knots. Remnants of Beryl are then set to move in and bring heavy rain to the area Wednesday and Thursday. The center of the low pressure is forecasted to move overtop the CWA or Lake Erie Wednesday evening. Northeast flow will remain in place over Lake Huron, with wind speeds persisting at 10-15 knots gusting to 20. High winds associated with this system are not a concern at this time. && .HYDROLOGY... The remnants of Beryl will move into the area between a strong ridge of high pressure over the southeast CONUS and a re-expanding upper level wave positioned just to the west. This system will begin to impact the Great Lakes Tuesday afternoon with the remnant low pressure center then tracking over/near the area through Wednesday night into early Thursday morning. Track still carries some uncertainty with a slight westward shift noted in latest model runs, though its center tracking somewhere between I-69 and northern Ohio looks most favored at this time. On average, 1 to 3 inches of rainfall looks likely over all of SE MI in this scenario between Tuesday afternoon to Thursday morning. Highest amounts in this range most favored south of I-69 currently. Locally higher totals, pushing or exceeding 4 inches, will be possible however the exact location of this carries low predictability. Flooding concerns would be likely with amounts of this magnitude with a Flood Watch likely in a coming forecast update when a bit more certainty in track/heavy rain positioning comes into picture. && .PREV DISCUSSION... Issued at 103 PM EDT Mon Jul 8 2024 AVIATION... A stationary front will remain draped across Southeast Michigan through Tuesday. Isolated showers and thunderstorms will be possible along this boundary throughout the forecast period. The greatest likelihood for activity this afternoon and evening will be at MBS and FNT. The focus for new development will shift south overnight into Tuesday across the Detroit airspace. Coverage will be very limited in time and space through midday Tuesday. For DTW/D21 Convection...Thunderstorms are not expected across the airspace this afternoon and evening. A very low potential exists overnight through the daylight hours of Tuesday (peaking at a 20 percent chance - Tuesday midday). DTW THRESHOLD PROBABILITIES... * Low for ceilings at or below 5kft tonight and Tuesday. * Low for thunderstorms overnight and Tuesday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...KDK MARINE.......BC HYDROLOGY....KDK AVIATION.....Mann You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.