Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 251011 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 611 AM EDT TUE OCT 25 2016 .AVIATION... Prevailing cold northwest flow prompting some downstream expansion in stratus over northern and central lower MI early this morning. Recent model guidance indicates this moisture will make some inroads southward and into the SE Michigan airspace today. This would potentially support a greater coverage of stratus by afternoon locally as diurnal heating strengthens. Favor a trend toward a BKN VFR coverage, with greatest coverage and longevity across MBS/FNT. Modest northwest wind today, becoming northeasterly this evening. For DTW...a mostly clear sky this morning, with a sct/bkn coverage of sub-5000 ft VFR cigs for the afternoon. Winds at a 320-330 direction today, peaking around 7-8 kts. //DTW Threshold Probabilities... * Medium confidence in cigs aob 5000 ft this afternoon. && .PREV DISCUSSION... Issued at 313 AM EDT Tue OCT 25 2016 DISCUSSION... A cold start to the day, as temperatures currently reside in the 30s under mostly clear skies. Surface High/Ridge axis over Western Great Lakes this morning to slide East today as upper level ridge builds through Tonight. A back door cold front attempts to sink south from northern Lake Huron this morning as strong high (1037 MB) builds over northwest Ontario, and looking at more low clouds across northern half of the cwa, underneath/closer to the cold pool (-4 to -5 c at 850 mb), as just about every model (rap/nam/gfs/hrrr) indicating saturation at 850 mb sinking south during the day before mixing out. 925 mb temps ranging from 1.5 C north to 4 C toward the southern Michigan border suggestive of highs in the upper 40s to lower 50s, in line with latest MAV guidance. Upper level energy working through the Rockies this morning, and there has emerged some differences for Wednesday, as bulk of the upper level energy/pv drops into the southern Mississippi River Valley. Subsequently, the surface low over the Midwest is not forecasted to be as strong. Still plenty of trailing upper level support and moisture advection to support developing rain Wednesday evening/night, but 00z nam draws into question the daytime hours of Wednesday, as the 700 mb front becomes active just over the north third of the cwa, with no precipitation associated with the 850 mb fgen indicated for southern two thirds of the cwa. The NAM Looks to be an outlier compared to Canadian/GFS/Euro, as those solution also show an active 700 mb zone with about 5.5 g/kg of specific humidity, but slicing right through the center of southeast Michigan, supportive of widespread rainfall by the afternoon hours. Also, with the weaker low, less of a surge of warm air, and a low track south of the Michigan border, potential precipitation type issues still lurking along/north of I-69. With that said, still will favor all rain with easterly flow coming off the mild waters of southern Lake Huron, as raw surface temps (per colder euro/gfs solutions) forecasted to reside predominately in the upper 30s to lower 40s. As the low passes east Wednesday Night, more of a northerly drainage wind (less influence from Saginaw Bay) setting up across Tri-Cities Region could make for a close call with respect to wet snow mixing in before rain tapers off. Even during the day on Thursday, cold cyclonic flow with 850 mb temps of -4 C could support convective showers of graupel with the steep low level lapse rates as highs reside in the 45 to 50 degree range. For the weekend, model consensus splits the upper level energy, and looking at two weaker low pressures sliding through the Great Lakes Region, which is a significant deviation from last night`s single stronger low tracking through. With the energetic Pacific flow still well offshore, still time for additional model adjustments, as Canadian solution is much faster and weaker compared to Euro/GFS. Also, Hurricane Seymour in Pacific could have a modest influence as it interacts with the strong upper wave/trough approaching California Thursday night. MARINE... Cold northwest flow will maintain unstable conditions across area waterways today. Small craft advisory conditions will persist during this time for all near shore waters of Lake Huron including outer Saginaw Bay. Gusts of 25 to 30 knots will be common across the open waters, but winds are expected to remain below gale force. Winds and subsequently waves will gradually diminish late today and tonight as high pressure builds into the region. Winds will increase out of the east Wednesday and Wednesday night as low pressure lifts toward the region. Strongest winds expected Wednesday night and early Thursday, where gusts of 25 to 30 knots are again expected. While the potential for a period of near gale force is still possible over portions of the open waters, the current forecast maintains gusts below gales at this time. HYDROLOGY... A low pressure system tracking from the central Plains through the northern Ohio Valley will result in a widespread rainfall event locally Wednesday through Thursday. The heaviest rainfall will occur late Wednesday into Wednesday night. Rainfall will taper off in both intensity and coverage on Thursday. The current forecast calls for a broad area of rainfall amounts around three quarters of an inch. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory until 8 PM EDT this evening FOR LHZ421-441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....MR DISCUSSION...SF MARINE.......MR HYDROLOGY....MR You can obtain your latest National Weather Service forecasts online at is the U.S. government's official web portal to all federal, state and local government web resources and services.