269 FXUS63 KDTX 030857 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 357 AM EST Sun Dec 3 2017 .DISCUSSION... One more nice day is in store for the area to wrap up the weekend before the weather turns much more active during the first half of the week. High pressure and light wind will allow mild temperatures to continue today as plentiful sunshine helps lift readings into the upper 40s to lower 50s. Monday will actually be the warmest day of this recent stretch as breezy south wind helps lift temperatures well into the 50s, although clouds and rain will take the luster off the mild conditions. A strong cold front is then due to bring sharply colder conditions into the region Tuesday on gusty wind. High temperatures in the 40s will occur during the early morning followed by readings falling through the 30s during the day. The system expected to bring the active weather to the Great Lakes during the week is shown developing over the Pacific NW today. It is responding to the large scale amplification set off by the strong north Pacific wave and associated upper level jet. This process will continue today and tonight as the Pacific NW system moves into the central Rockies with a nearly full latitude trough forming by Monday morning. Lee side surface cyclogenesis will be well underway over the Plains by then with deep southerly flow well established down to the Gulf coast. Strong low level moisture transport into the warm frontal zone will support an expanding area of rain over the Midwest and western Great Lakes through the day. Model trends are just a few hours slower on time of arrival in SE Michigan, however this delay is allowing the bulk of activity to pass by to the west and north before the warm front moves through the region Monday afternoon. The resulting forecast adjustments maintain likely POPs in the Tri Cities region tapering to dry conditions toward the Ohio border. Anticipating less coverage of rain in general will allow temps to make a run into the mid and 50s, especially near the Ohio border. The wing of isentropic lift and associated rain showers will usher in the primary moisture axis/theta-e ridge during Monday night. The low level jet maturing to about 60 kts at 850 mb will continue strong low level moisture transport which will generate enough elevated instability for a chance of thunderstorms. NAM and GFS depictions of 850 mb LI around -2C with 700-500 mb lapse rate around 7 C/km is convincing for this time of year, especially in such a strongly forced large scale environment. There is good model agreement showing the surface low deepening rapidly as it moves across central Lake Superior Monday night as the upper wave gains negative tilt within the long wave trough and as the upper jet max pushes 150 knots by Tuesday morning. In addition to thunderstorm potential, these system characteristics will also support concern for strong wind along and behind the powerful cold front passing through the region early Tuesday morning. Cold advection and subsidence will be top notch immediately behind the front followed by a deepening mixed layer through the day, both of which will potentially direct 40+ kt 850 mb flow toward the surface. There is still time to monitor the strength trends of the low pressure system for potential wind headlines while maintaining a mention of 40 mph wind gusts in the HWO for Tuesday into Tuesday evening. The wind will diminish later Tuesday night into Wednesday but sharply colder temperatures will be in place and last through the remainder of the week. High temperatures barely reaching the freezing mark each day illustrate the staying power of the cold air mass reinforced by westerly flow and scattered to numerous lake effect snow showers. && .MARINE... High pressure will ridge into the region from the south today resulting in light winds gradually becoming more southerly with time by this evening. Low pressure will develop across the northern Plains on Monday and tighten the pressure gradient, resulting in strengthening southerly winds especially over the open Lake Huron waters. The low pressure will rapidly deepen into a powerful storm system Monday night into Tuesday as it tracks northeast across Lake Superior and into central Ontario. Winds will gradually veer southwesterly Monday night and into early Tuesday and continue to remain strong across the entire Lake Huron basin including Saginaw Bay. A powerful cold front will then sweep through the region during the day Tuesday with the flow becoming westerly in its wake. Widespread showers will accompany the frontal passage, along with possible thunderstorms. Colder air rushing in behind the front over the mild waters will continue to support gusty winds well into Wednesday. A long duration, high-end gale event is becoming increasingly likely beginning Monday and continuing through at least Tuesday night, and a Gale Watch remains in effect for the entire Lake Huron basin. Wind gusts during this timeframe may reach 40-45 knots. Lake effect snow showers may also become quite prevalent beginning Wednesday as the cold air continues to get reinforced by a series of troughs through the week. && .HYDROLOGY... Low pressure developing over the northern Plains Monday will rapidly deepen into a powerful storm system as it tracks northeast across Lake Superior and into central Ontario Tuesday. A strong cold front accompanying the system will cross the region Monday night and into Tuesday, bringing widespread showers and possible thunderstorms. Most areas look to see rainfall amounts around a quarter of an inch, with up to a half of an inch possible in the Saginaw Valley. Locally higher amounts will be possible in thunderstorms. No flooding concerns are anticipated due to the progressive nature of the system. && .PREV DISCUSSION... Issued at 1043 PM EST Sat Dec 2 2017 AVIATION... Upper cigs around 20kft will move east of area by the beginning of the forecast period with generally clear skies expected thereafter. Light SW flow of 6 knots or less will back to SE by the end of the forecast period with loss of boundary layer mixing around sunset. //DTW THRESHOLD PROBABILITIES... * None && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Watch from Monday morning through late Tuesday night for LHZ361>363-441>443-462>464. Gale Watch from Monday evening through late Tuesday night for LHZ421-422. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ DISCUSSION...BT MARINE.......IRL HYDROLOGY....IRL AVIATION.....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.