Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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853 FXUS63 KDTX 311104 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 704 AM EDT Fri May 31 2024 .KEY MESSAGES... - Dry weather continues today and most of Saturday with a gradual warming trend through the weekend. - The next chance of rain arrives Saturday evening through Sunday morning. There is potential for heavy rainfall with this system, please refer to the Hydrology section for details. - The weekend finishes dry and warm Sunday with highs near 80. && .AVIATION... A center of deep atmospheric high pressure will remain parked over the central Great Lakes today. Dry air will limit much in the way of cloud development. Weak southerly winds of 5 to 10 mph are anticipated. For DTW/D21 Convection...Thunderstorms are not expected during this forecast period. DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 427 AM EDT Fri May 31 2024 DISCUSSION... Another chilly start to the morning today with current temperatures 10 degrees below normal for late May. Temperatures quickly rebound after sunrise however under full solar insolation and a departing thermal trough. 00z KDTX RAOB recorded a deep layer of static stability, maximized between about 6.0-10.0 kft agl, which will persist through today as ridge amplification builds mid-level heights to 582 dam. This ensures dry conditions that continue through the first half of Saturday. Overnight lows moderate some ten degrees compared to this morning as column winds organize out of the southwest amidst modest warm advection. CONUS-centered satellite imagery highlights two distinct systems that will interact to create the next opportunity for rain late Saturday into Sunday for southeast Michigan. The southern stream wave lifts into the Ohio Valley by mid-Saturday, initiating a period of strong low level theta-e advection on the cusp of a ~30 knot low level jet. Cloud cover thus will be on the increase throughout the day, although rain holds off until 21z (5pm) or later as ambient dry low levels rely on the theta-e push to fully saturate. Moisture quality will be excellent with this system with PWAT forecast to rise above 1.5", which is in the 90th percentile for this time of year. Freezing levels between 10.0-12.0 kft agl accompany deep column moisture, favoring warm rain processes. These favorable thermodynamics raise concern for heavy rainfall Saturday night- Sunday morning. From a forcing perspective, strong theta-e advection and eventual release of the disturbance overhead provide a large footprint of synoptic forcing and thus widespread rainfall across southeast MI. Model QPF from synoptic forcing alone falls around a half inch or less, but the heavy rainfall concern comes from the potential for mesoscale banding to occur as the weakening northern stream trough and southern stream wave interact over the Midwest. 00z guidance struggled to agree on the strength, placement, and duration of any mesoscale forcing mechanisms, likely due to differences in the strength of the northern stream convergence axis and whether the southern stream wave stays closed or opens up before reaching lower MI. More details should become apparent as we get further into the hi-res window today, but the main message at this point is a conditional chance for heavy rainfall to exceed one inch Saturday night-Sunday morning. Rain comes to an end mid-day Sunday as high pressure fills in briefly. Continued southwest flow offers warmer temperatures in the 80s by early next week with the next round of precipitation moving in late Monday-Tuesday. MARINE... High pressure continues to govern local conditions today as it drifts over southern Ontario. Winds shift to the south as a result though hold sub 20kts across the region. High vacates early Saturday as low pressure lifting into northern Ontario drags a cold front into the Great Lakes. A secondary area of low pressure develops along this boundary over the Ohio Valley before tracking into the central/southern Great Lakes latter part of the day Saturday into early Sunday. System brings mainly showers though a thunderstorm or two will be possible over the southern Great Lakes. Weak high pressure then briefly builds in late Sunday and Monday. HYDROLOGY... Showers move into SE Michigan Saturday evening with heavy rainfall possible overnight as a deep supply of Gulf moisture lifts into the region. While the broader footprint of forecast rainfall amounts is around a half inch, there is potential for localized totals to approach 1 inch or greater. There has been a slight slowing trend to the system, but still looks progressive enough to prevent more excessive totals with minor flooding of urban and low-lying areas, ponding of water on roads, and rises in area rivers being the main impacts. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....CB DISCUSSION...MV MARINE.......KDK HYDROLOGY....MV/BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.