Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 182333 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 633 PM EST Thu Jan 18 2018 .AVIATION...
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Quiet aviation period during the next 24 hours for middle of January standards. VFR conditions are anticipated throughout with dry air in place. Vigorous shortwave maximum will push dig east of the central Great Lakes this evening which will open the door for a greater southwest trajectory to winds in the lower troposphere. This will advect any residual higher theta e content from Lake Michigan northward. Southeastern Michigan will remain in relatively close proximity to the jet stream axis aloft, which will keep high cloud over the region. For this reason, went fairly bullish on opaque high cloud. /DTW THRESHOLD PROBABILITIES... * None.
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Issued at 348 PM EST Thu Jan 18 2018 DISCUSSION... Steady southwest wind will continue to lift temperatures through another stage of the warming trend that will carry into the weekend. Conditions will also remain dry through Saturday leaving cloud trends as the main variable in the forecast to go along with temperature refinement. Afternoon observations indicate a mix of lake effect stratocu and high clouds associated with the upper circulation moving across the northern Great Lakes. The high clouds will move eastward with the system during early evening only to be replaced by the cirrus expanding across the Plains today. Meanwhile, southwest low level flow will maintain a favorable fetch across Lake Michigan for stratocu production mainly into the Tri Cities region but also possibly redeveloping toward the I-69 corridor. The main question is how long boundary layer temperatures will be cold enough for cloud production. There is usually a decrease as low level warm advection lifts 925 mb temps above 0C over top of relatively cold water this late in the season. However, at least partly cloudy conditions will be required in the forecast due to the high clouds through Friday morning, possibly trending toward mostly cloudy during the afternoon. After morning lows around 20, these clouds will likely cap high temperatures to the mid and upper 30s Friday afternoon. Moderate southwest low level flow and associated warm advection will continue Friday night through Saturday, augmented by enhanced surface gradient as low pressure across James Bay. Gulf modified air off high pressure over the SE states will enter the picture by then, moving northward across melting snow cover. Daytime satellite imagery today indicates snow on the ground as far south as Arkansas which will add to boundary layer moisture while melting off. Model and MOS dewpoint projections take surface readings into the lower and mid 30s by Saturday afternoon as stratus coverage expands over the region which look like reasonable solutions. The difficult aspect of this portion of the forecast will be temperature trends Saturday night into Sunday morning. Continued southwest flow and warm/moist advection will battle the diurnal cooling trend for dominance and potential for temperatures to drop below freezing. It will be a close call for the possibility of freezing drizzle, especially in the typically colder locations of the Thumb region. Significant increase in upper mass gradient will get underway Friday into Saturday as east Pac jet energy releases into the northern tier of the US against the southern periphery of the tropospheric polar vortex Hudson Bay/northern Quebec. Trailing energy will dig into the southwest United States Saturday through Sunday, prompting a lee cyclogenesis episode as strong right entrance support steadily matures through the weekend and becomes increasingly focused over the Great Lakes region. Light warm advection/overrunning type precip will be possible as early as Sunday morning as the low-level jet responds and moves up the developing frontal slope. Surface cyclone is then progged to lift from the Lower Missouri River Valley to The Straits by Monday into early Tuesday. Strong model support that SE Michigan will remain on the warm side of this system, supporting temps on the milder side for late January. There is potential for pre-fropa temps on Monday to make a run toward 50 degrees over the southern portion of the area before showers and possibly t-storms along the front shift through the area. Cold lake temps/ice on Lake Erie suggest usual caveats with northward progression of the surface portion of the warm front. Will leave out t-storms and remain more conservative, low to possibly mid 40s, with temps for now. Per the norm, a brief snow-fzra-rain transition is possible as the warm front lifts through Sunday. MARINE... Persistent southwest flow will continue into the weekend. Winds look to top out around 30 knots over central Lake Huron Friday evening, but will diminish as we head into the Weekend as warm air leads to stable profiles. A deepening low moving into the western Great Lakes on Sunday will cause winds to become easterly and increase, but still probably holding around 30 knots Sunday night into Monday, with rain during this period as well.
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....CB DISCUSSION...BT/JVC MARINE.......SF 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.