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Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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829 FXUS63 KDTX 081703 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 103 PM EDT Mon Jul 8 2024 .KEY MESSAGES... - Isolated showers and thunderstorms will linger into Tuesday. - Remnants of Beryl begin to impact Southeast Michigan Tuesday night and Wednesday with the potential for excessive rainfall. - A prolonged period of above average temperatures is expected to start Friday and continue into early next week. && .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. && .PREV DISCUSSION... Issued at 307 AM EDT Mon Jul 8 2024 DISCUSSION... As shortwave ridging over the area flattens and edges east today, expect a weak frontal boundary to sag southeast into parts of the forecast area. In advance of this front, temperatures will warm nicely into the mid to upper 80s in many locations with a notable increase in humidity as well as surface dew points climb into the mid to upper 60s. This will yield modest instability with SBCAPE readings around 1000 J/kg. Increasing west-southwesterly mid level flow will also bring an increase in deep layer shear to 30 knots or so by late in the day. So, scattered convection within area of low level convergence along/near this front is expected with a strong storm or two possible. Activity late this afternoon into evening will focus over the Saginaw Valley into parts of the Thumb and will be of the scattered variety. This frontal boundary becomes very diffuse as it settles southeast into the forecast area tonight into Tuesday as the mid level wave driving it weakens considerably as it crosses the lower Great Lakes. A bit of a sub-tropical air mass shifts into the area along this stalled front with PWATs to near 1.75" by Tuesday morning along and south of the mean frontal position (somewhere in the middle of the forecast area). Periodic scattered showers/thundestorms will remain possible, but with weak forcing and dubious instability within this higher moisture environment, activity should remain disorganized with only locally heavy downpours possible. The attention turns to the remnants of Beryl late Tuesday night into Wednesday and Wednesday night. 00z models have continued to converge on a solution that will bring an extended period of rainfall, some quite heavy, to the area. First, a significant surge of tropical air will work into the region late Tuesday night into early Wednesday in advance of this remnant low with PWATs increase to 2.00" or more. This will promote an expanding area of rainfall into the region which will lift from southwest to northeast across the area early Wednesday. This will be followed by a shield of deformation rainfall as what is left of the center of Beryl tracks through the northern Ohio Valley to near western Lake Erie by Wednesday night. Additional heavy rainfall will occur within this area closer to the core of the system as PWATs remain on the order of 2.00". At this time, it appears that the risk of a fairly wide swath of 2+ inches of rain looks increasingly likely over parts of the region given the consensus track of Beryl this package. It will be very interesting to see what the 12z model suite does as the system will be better sampled as it is making landfall along the TX coast. If this basic forecast track does not change too much, headlines to highlight the flooding potential will most likely be required. It should be noted that tropical systems often (but not always) have some difficulty tracking this far north into the Great Lakes as they re-curve around dominant ridging over the SE Conus and take a more easterly trajectory once they encroach on this part of the country. At this time, it appears that a northern stream shortwave dropping fairly sharply southeast through the upper midwest will help steer this system a bit farther north than usual as it helps re-establish the lingering positive tilt trough positioned just west of the area (hence a stronger consensus for heavy rain making it north into the area). This northern system, now topping upper ridging over western Canada, will also be better sampled today as it begins to translate towards south central Canada. Today`s model solutions should give a pretty decent indication of what will transpire with this system by midweek. Later this week into the weekend, general upper level troughing will initially linger with temperatures in the 70s to around 80 slowly building back into the 80s. By the weekend, this trough axis shifts east with a more or less zonal upper level flow bringing very warm temperatures back into the upper 80s to around 90. Rain chances may linger into Thursday, but a fairly dry pattern seems to set up late week into the weekend (although confidence by the weekend is pretty low as an increasingly hot/humid air mass shifts back east into the region. MARINE... Southerly wind around 10 to 15 knots today ushers in a warmer and more unstable air mass ahead of a frontal boundary moving in from the west. This system will bring a pattern of scattered showers and storms mainly to Lake Huron today before coverage expands southward to Lake St. Clair and Lake Erie tonight into Tuesday. Frontal passage on Tuesday will veer wind to west/southwesterly with speed remaining on the order of 10 knots or below. The mid-week period remains a focus for more active weather as the remnant low pressure of Beryl tracks northeast across the area. The forecast remains sensitive to the eventual track and strength of the system, but latest information continues to suggest gusty northeast winds and heavy rain will be possible Wednesday into Thursday. 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 night into Wednesday with the remnant low pressure center then tracking over/near the area Wednesday night into early Thursday morning. At this time, the exact details on the track of this system remain a bit tricky to determine. That said, the risk for heavy rainfall still looks to be elevated as the system encroaches on the area. Most of southeast Michigan is set to receive at least an inch of rain, and if impacted directly, rainfall will most likely reach or exceed 2 inches in some areas. If this scenario unfolds, flooding will become a concern for Southeast Lower Michigan. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....Mann DISCUSSION...DG MARINE.......TF HYDROLOGY....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.