Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sat Sep 29 2018 Valid 12Z Sat Sep 29 2018 - 12Z Mon Oct 01 2018 ...Hurricane Rosa in the eastern Pacific is expected to become a heavy rain threat to the Desert Southwest by Monday... ...A cool air mass from Canada will provide much below normal temperatures from the northern Rockies into the upper Midwest... ...Snow over the higher elevations of the northern Rockies expected to spread east along the northern border of North Dakota... Hurricane Rosa, currently in the eastern Pacific to the southwest of Baja California, is expected to take the center stage as a heavy rain producer for the Desert Southwest by early next week. Rosa is in the process of recurving into the mid-latitudes ahead of a developing upper-level trough/cut-off low pattern. The current forecast track from the National Hurricane Center indicates that Rosa will approach the northern portion of Baja California on Monday as a tropical storm. Although the winds associated with Rosa are expected to weaken, copious amounts of tropical moisture will be drawn northward toward the Desert Southwest starting on Monday. In addition, a developing front will help focus the heavy rain along an axis from central Arizona northward. Residents in the Desert Southwest should keep abreast of the latest watches and warnings issued by the National Weather Service as Rosa approaches early next week. Elsewhere across the country, a cool air mass from Canada will continue to provide much below normal temperatures across the northern Rockies into the northern Plains. A zonal upper-level pattern means that the cool air mass will spread eastward toward the Great Lakes through the weekend into Monday. Higher elevation snows aided by upslope flow over the northern Rockies will likewise spread eastward along the northern border of North Dakota on Monday. Rain will be the primary precipitation type farther south across the northern Plains on Monday to the north of a cold front. Lingering showers and thunderstorms can be expected for the Gulf Coast as a result of a quasi-stationary front. The rain should slowly become more scattered in nature during the next few days as the front gradually dissipates, although day-time heating will tend to reinvigorate showers in the afternoon into early evening. Meanwhile, weather across the Mid-Atlantic should remain fine for the next few days. New England will begin to see moisture arriving from the west on Monday as a stationary front begins to form in the vicinity of the lower Great Lakes. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php