Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 AM EDT Sun Apr 23 2017 Valid 12Z Sun Apr 23 2017 - 12Z Tue Apr 25 2017 ...Heavy rain possible over parts of the Southern Mid-Atlantic and the Southeast... ...Heavy rain possible over parts of the Pacific Northwest... The upper-level pattern over the next few days will feature a fast onshore flow with multiple disturbances moving through the western U.S. while a trough is forecast to deepen near the Southeast U.S. coast. This will continue the cool and unsettled weather across the northwestern U.S. through the weekend, with rain/snow in the lower/higher elevations. By Monday, another Pacific cyclone is forecast to move onshore. This will invigorate a new round of precipitation from northern California northward through the Pacific Northwest, which will spread further inland on Monday. Upper-level dynamics will then surge eastward across the northern Rockies and interact with a cold front across the northern Plains, where a new low pressure system is expected to develop on Monday. Temperatures will be cold enough to support wintry precipitation near the U.S.-Canadian border from the northern Plains eastward into the upper Great Lakes on Monday. Meanwhile, much below normal temperatures from the central and southern Plains into the Midwest this weekend will be replaced by much warmer temperatures by Monday afternoon ahead of the developing low pressure system in the northern Plains. Farther to the east, a low pressure wave developing along a frontal boundary is bringing rain across the mid-Atlantic and showers and thunderstorms into the Deep South. This system is forecast to gradually deepen as moisture associated with a weak tropical low moving up from Florida begins to interact with the associated upper-level trough. This will keep wet weather in place across the southeastern U.S. as well as Florida for the rest of the weekend. The rain should begin to head northward up the East Coast on Monday as the low pressure system centered near the southeast U.S. coast deepens. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php