Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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018 FXUS63 KDTX 021900 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 300 PM EDT Sun Jun 2 2024 .KEY MESSAGES... - Drizzle to spotty showers chances will continue for portions of Southeast Michigan through the evening. - Temperatures warm up Monday and Tuesday with highs returning to the 80s. Chance for showers or storms Tuesday. - Rain and embedded thunderstorms likely Wednesday as a major weather pattern shift begins. After Wednesday, below normal temperatures are likely through at least the end of the week. && .DISCUSSION... A shallow but saturated boundary layer will continue to promote extensive stratus to strato-cu through the afternoon, where surface based cape values now reside between 250-500 J/kg, outside of the Tri- Cities down into Flint. This diurnally fueled instability in conjunction with multiple weak surface convergence boundaries will support pockets of drizzle to spotty showers activity through the evening. This will not be a supportive environment for thunderstorm development as soundings and water vapor imagery showcase copious amounts of dry air aloft along with an inversion above the start of the dry layer. The weak updrafts and shallow cloud tops will reside well below the freezing level, preventing ice nucleation. Any lingering showers will quickly wane this evening into late tonight with the loss of daytime heating coupled with dry air advection which will scour out low-based cloud cover. Taking into account the widespread light rainfall that fell last evening into this morning and the extensive cloud cover which hampered the drying out of soil moisture, overnight clearing trends will set the stage for fog potential. Calm to light surface winds and condensation pressure deficits dropping to 2mb or less within the hi-res suite will support patchy to areas of fog, dense at times. Visibility restrictions from fog will improve by the late morning hours once daytime heating lift and scours out the surface condensation. SE MI will then reside just east of the Gulf moisture conveyer belt which extends from Texas up through western Lake Superior. A series of shortwaves along this belt, some convectively enhanced, will reinforce shortwave ridging across SE MI tomorrow. The return of sunshine, outside of translucent cirrus, and warm air advection will push highs back into the 80s. Upper-level ridging will sustain into Tuesday once a potent upper-level wave arrives onshore across the Pacific NW tomorrow, before pushing into the upper plains. This will advect in h850 temperatures around 17C and will bring the warmest temperatures of the week with highs in the mid to upper 80s. The constant flux of warm air advection will also make for warm overnight lows leading into Wednesday, with temperatures only dropping into the upper 60s. There will be a couple chances for showers and storms on Tuesday, the first being the low chance for decaying activity upstream to make it into the Tri-Cities/Thumb Tuesday morning. Chances then creep upwards once the Gulf moisture starts to expand into the eastern portion of the state. A major pattern shift will then commence Wednesday, lasting through the end of the weekend and possibly into early next week. The aforementioned Pacific wave will arrive across the Midwest and will possibly get pinched off into a closed upper level low over the Great Lakes Thursday into the end of the week. This pattern has the potential to turn into a blocking pattern with two dipoles of high pressure forming along the flanks of the low, across the central Canadian Provinces and out over Greenland. This will initially result in the Gulf moisture setting up right over SE MI on Wednesday, bringing the likely chance for showers and storms. The meandering influence of the low coupled with an elongated jet stream that develops and holds over the Ohio Valley will then lock in below normal temperatures Thursday into at least the weekend, and will bring the chance for showers and storms every day. This energetic pattern will also maintain stronger winds aloft, bringing breezy conditions (30 mph) during daylight hours Wed-Thu-Fri. Overall this is a high confidence setup, outside of the nuanced details pertaining to the extent of the geopotential height anomaly strength and the staying power of this trough next week. More of the variance surrounds the strength of the trough and extent of cooler air over the Great Lakes, which will impact how far temperatures can drop below the normal averages. At this time highs range between the upper 60s to mid 70s. && .MARINE... Low pressure is currently making its way out of the region, with light showers lingering through the evening. Upper level shortwave ridge brings a brief period of high pressure tonight into Monday. Light northeasterly winds will support the development of patchy fog over the lake early Monday morning, but after sunrise the fog will dissipate. Approaching warm front brings chances for showers and/or storms to develop on Tuesday. Winds remain moderate ahead of the front, but level flow up to 25 knots is expected about 1000 feet above the surface meaning a stray strong gust mixing to the ground is possible. The warm front will then be followed by a strong cold front on Wednesday, sustaining the chances for thunderstorms. && .PREV DISCUSSION... Issued at 1257 PM EDT Sun Jun 2 2024 AVIATION... A small center of low pressure and weak cold front exit SE Mi while supporting clusters of showers this afternoon. A general transition from IFR to MVFR ceiling underway during the morning also continues with afternoon heating and as the pressure systems exit. Light northerly cloud layer wind has weak high pressure/diverging directional influence to help with a decreasing cloud trend as daytime heating/instability diminish this evening. The clear sky and light wind keep a widespread fog scenario in play late tonight and Monday morning. Northerly flow this afternoon and evening is not quite enough to scour out boundary layer moisture and surface Td holds in the 50s as ideal radiational cooling conditions develop. Model soundings capture trends affecting all of the terminal sites and there are convincing fog signals in typically more stubborn GFS MOS/LAMP guidance supporting IFR/LIFR restriction leading into sunrise. Model RH and forecast soundings then suggest fog follows a typical morning dissipation to VFR by late morning through Monday afternoon. For DTW/D21 Convection...Thunderstorms are not expected through this forecast period. DTW THRESHOLD PROBABILITIES... * High for ceiling at or below 5,000 feet this afternoon, low by this evening. * Moderate for cigs/vsby falling below 200 ft and/or 1/2 SM Monday morning. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...AM MARINE.......BC AVIATION.....BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.