Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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124 FXUS63 KDTX 120000 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 800 PM EDT Sat May 11 2024 .KEY MESSAGES... - Above normal temperautures are expected Sunday into Monday. - Showers and thunderstorms return late Sunday night and Monday as a cold front drops through the region. This front will then stall overhead leading to persistent rain chances into early Tuesday. - The potential for heavy rainfall will exist for a portion of Southeast Michigan Monday and Tuesday. - Cooler than average temperatures are expected Tuesday and Wednesday. && .AVIATION... Scattered rain showers decrease in coverage this evening as a low pressure system exits toward the east. MVFR clouds have scattered out while several residual VFR cloud layers linger above 5 kft AGL. Ceilings should thin with time as current satellite trends depict the decay of diurnal cumulus upstream, over western Lower Michigan. The western edge of the system could result in a slower exit for KDET given the closer proximity to the system, but VFR conditions are still expected. Winds will hold from the northwest tonight with decreasing speeds as a ridge of high pressure briefly crosses through the region. This helps to reinforce column stability and a clearing trend into Sunday. Winds flip toward the south-southwest Sunday afternoon upon arrival of a northern Great Lakes low pressure system`s warm front. Can`t completely rule out a few showers as the elevated portion of the front encroaches, but this scenario is more likely for FNT/MBS than the southern terminals. Minimal impact to ceilings/visibility anticipated, thus VFR conditions likely persist through the TAF period. For DTW/D21 Convection...Thunderstorms are not expected through the forecast period. DTW THRESHOLD PROBABILITIES... * Low for ceiling at or below 5000 feet tonight. && .PREV DISCUSSION... Issued at 239 PM EDT Sat May 11 2024 DISCUSSION... Cold core aloft has extensive cumulus/stratocumulus deck in place across Southeast Michigan this afternoon. Spokes of absolute vorticity and corresponding axes of convergence have provided for waves of ascent to result in loosely organized, scattered to numerous rain showers over Southeast Michigan. Satellite imagery and radar reflectivity trends support a very shallow convective response with a struggle to get much above 8.0-11.0 kft agl where dry air and a slightly stable environmental temperature lapse rate profile exists. Given the absolute vorticity center and support for cyclonic flow, expectations are for a persistence of rain showers for the remainder of the afternoon. There is a potential for the showers to wane for some areas while focusing more across the Thumb. There still remains a potential for some thunder particularly if a few breaks can develop due to increasing convective depths and convective scale subsidence. No strong or severe weather with CAPES of only 100-200 J/kg. For tonight, the popular question again centers on whether or not the Aurora Borealis will be visible across Southeast Michigan with a G5 Severe Geomagnetic Storm Watch in effect from the NWS Space Weather Prediction Center. A difference scenario today with the extensive lower tropospheric cloud due to the vorticity maximum. Will most likely see some thinning out of the cloud as the boundary layer cools, however, cannot not envision a total clearing out. Therefore, sky coverage is expected to vary on a local basis, particularly earlier in the evening. It behooves one to err on a more pessimistic/cloudier outlook this evening/tonight for two reasons. The forecast area will be in a zone conducive for persistent weak stretching deformation and a lowering subsidence inversion could hold/trap saturation at its base. Possible for some clearing, but will be carrying a mostly cloudy forecast early. Rising geopotential heights and confluence aloft will allow for another shortwave ridge feature for the Central Great Lakes on Sunday. A sharp, distinct absolute anticyclonic vorticity maximum is progged to to push directly through the cwa between 12-18Z. Forecast soundings depict active subsidence occuring in the midlevels by the mid morning hours, then lowering down in the column around midday. Pleasant and comfortable conditions are anticipated for much of the day. By afternoon, its only natural Southeast Michigan will be influenced by differential cyclonic vorticity advection as the AVA moves eastward away from the region. Therefore, increasing clouds are expected as warm advection precipitation spreads across the U.P. and northern Lower Michigan. Temperatures are expected to be near 70 Sunday afternoon, but have kept it lower by a degree or two. Two PV anomalies are then forecasted to move eastward over portions of North America in tandem from Sunday night through Tuesday. Locally, the first wave is expected to drop a cold front into Southeast Michigan on Monday while it stalls and becomes stationary. Difficult to pinpoint duration of rain shower and/or thunderstorm activity. High confidence in an unsettled period with relatively higher certainty there will be showers and thunderstorms Monday afternoon. Will need to monitor model trends as very weak flow will bring the potential for slow moving convection and heavy rain. Potential for severe weather is on the low side with 0-6km bulk shear of 20 knots and Mixed Layer Cape of less than 1000 J/kg. Wet weather to continue on Tuesday with Southeast Michigan possibly getting clipped by the northern periphery of the southern wave as it passes through. Concern there is if the same area could get heavy rainfall both days. Way too early to try and hammer out details on convection. MARINE... Northwesterly gusts to 25 knots in the wake of cold frontal passage will subside late this evening into the overnight. Until then, will maintain current Small Craft Advisories for Saginaw Bay and Lake St Clair/Western Lake Erie. While an isolated thunderstorm cannot be ruled out into early evening, generally just expect rain showers (which will taper off quickly this evening). High pressure briefly builds into the area Sunday morning providing favorable marine conditions before a secondary low approaches later on Sunday. This second system offers potential for enhanced southwest flow over Saginaw Bay, and possibly Small Craft Advisory criteria gusts. Showers and storms arrive late Sunday evening and overnight. A stationary front then settles over the Great Lake early next week offering additional opportunities for thunderstorms. HYDROLOGY... A cold front will settle southward into Southeast Michigan Monday night before stalling across the area on Tuesday. Showers and thunderstorms will be possible along this boundary. Rainfall may exceed 0.50 inch for portions of Southeast Michigan. Forecast confidence is low at this time and impacts to rivers next week is unknown. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....KGK DISCUSSION...CB MARINE.......DG HYDROLOGY....CB You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.