Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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883 FXUS63 KDTX 041954 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 354 PM EDT Tue Jun 4 2024 .KEY MESSAGES... - Showers and some thunderstorms likely Wednesday as a cold front sweeps across the area. - Some of the storms may be strong to severe in the afternoon and evening with damaging winds and large hail. - Pattern shift for the latter half of the week brings below normal temperatures through at least the end of the week along with periodic chances of rain. && .DISCUSSION... The systems that will be responsible for the upcoming showers and thunderstorms late tonight through Wednesday are clearly defined on satellite this afternoon. A southern stream mid level low is tracking from northern MO this afternoon into WI tonight. Meanwhile the more dominate northern stream trough is cutting through the northern Plains. The latter will absorb the former as they pass through the Great Lakes late Wednesday. We`ve been watching this scenario play out in the models for a couple days now with not too much change, but now as we get closer the small changes have more notable impacts. Since yesterday the trend has been to slow the northern trough which allows the MO low to lift north farther to the west of SE MI which draws the stronger low level jet forcing west as well as it also keeps the trough more neutrally tilts longer vs going negative early in the day. This still draws the warm frontal/theta e gradient up across the MI/OH border early Wed morning and through the Thumb early afternoon which introduces a wealth of moisture into the region. This will be the first chance of showers and storms as it won`t take much to to initiate precip with this sharp of a theta e gradient. But, the greater 850mb forcing looks to hold to our west and the greater 700mb forcing looks to skirt by to the east so overall lack of stronger forcing will keep us with a chance pop. We then get warm sectored with PWATs climbing to near 2 inches with some models and dewpoints in the mid 60s. Forecast soundings are pretty steady with around 1000 J/kg of CAPE and around 30 knots of unidirectional shear, both of which are adequate for strong storms along the cold front as it sweeps through. A few storms may become severe with damaging wind gusts and hail up to 1 inch and the latest SPC day 2 outlook keeps us in a Marginal designation for severe weather. Storms should be tracking to the northeast along the front while the entire line drift east so training of storms will be possible and with the amount of moisture present in the atmosphere, could see some flooding concern. WPC currently has us in a Marginal Risk of Excessive Rainfall in the Day2 outlook. Precip should come to an end for the most part after 02Z, with a slight chance of some lingering activity over the eastern Thumb. A secondary trough will then pivot down through the area late Wednesday night into Thursday morning so there will be additional chances of rain during that time. The strong trough then becomes negatively tilted as it stalls over the region and eventually cuts off for the weekend. The energetic northern stream will pump a series of waves through the weekend and even into next week keeping periodic chances of precipitation in the forecast. A surge of cold air for the latter half of the week will drop temps below normal with highs on Friday about 10 degrees below normal in the mid 60s. Ridging over the Plains then starts pushing back slowing into the region, moderating temps overtime back to near normal next week. && .MARINE... A ridge of high pressure will maintain dry weather for the remainder of the day, outside of northern Lake Huron, where showers and thunderstorms will be possible. This will also maintain light southeast flow through the remainder of the day, outside of the northern thunderstorms activity. A major pattern shift will then take place on Wednesday once a cold front moves over the Great Lakes Wednesday afternoon through evening. Numerous to widespread rain showers and embedded thunderstorms are expected ahead of and along the front. Additionally, there will be a marginal risk for severe weather. The strongest thunderstorms will be capable of producing wind gusts in excess of 30 knots and small hail. Passage of the front will veer wind direction from the southeast to the southwest. A cooler air mass will then gradually setup over the Great Lakes through at least the end of the week while stronger wind set up aloft. The enhanced mixing depths will bring breezy conditions over the nearshore zones on Thursday with gusts on the order of 20-30 knots. Small Craft Advisories will likely be needed. && .HYDROLOGY... A line of showers and thunderstorms is expected to pass through southeast Michigan Wednesday afternoon and evening ahead of a cold front. A very moist airmass will help these storms become efficient rain makers with widespread rainfall amounts between 0.25 to 0.50 inch expected, although localized higher amounts around 1 to 2 inch are not out of the question with any storms training over the same areas. Brief and minor flooding of prone urban and low-lying areas, ponding of water on roadways, and rises in area rivers are possible. && .PREV DISCUSSION... Issued at 122 PM EDT Tue Jun 4 2024 AVIATION... High clouds and light southerly wind conditions will continue through the rest of the day into tonight. Shallow small scale diurnal cumulus has formed in regions away from the influence of the big water and will lift an thin over the new few hours. Southerly flow will increase some Wednesday morning as the incoming cold front approaches from the west. There remains a small chance for an elevated shower or two across the airspace around daybreak Wednesday as richer moisture content air washes in from the southwest. However, much better chances for deep convection will occur starting midday through sunset. For DTW/D21 Convection...while there is a low chance for isolated convection with the elevated warm front Wednesday morning, coverage and intensity of convection will be much greater post 18z. Peak activity across the airspace is expected in the 20z-00z window as the front works through the established deep moisture. DTW THRESHOLD PROBABILITIES... * Low for elevated thunderstorms at DTW between 10-15z, medium for thunderstorms after 18z. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...DRK MARINE.......AM HYDROLOGY....DRK AVIATION.....Mann You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.