Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 414 PM EDT Sat Apr 04 2015 Valid 00Z Sun Apr 05 2015 - 00Z Tue Apr 07 2015 ...Low elevation rains and mountains snows expected to move across the northwestern U.S.... ...Showers and thunderstorms expected to spread from Texas northeastward across the lower Mississippi valley and Southeast over the next couple days... A frontal boundary, the dividing line between cold polar air and warmer air, will linger across the northern tier of the contiguous U.S. through the short range forecast period. A low pressure system will cross the Northeast tonight, bringing a chance of scattered snow showers. The surface frontal boundary will linger from the northern plains to the Northeast and will continue to act as a focus for periods of rain and snow Sunday into Monday as weak upper-level disturbances move across the region. Below average temperatures will persist due to the colder air north of the front as well as expected periods of precipitation. A frontal boundary extending from northeastern Mexico into the Gulf of Mexico this afternoon will drift northward as a warm front over the next couple days. Moist southerly flow off the Gulf of Mexico will be in place across the southern U.S. and the warm front will assist in the development of showers and thunderstorms across Texas and the lower Mississippi valley on Sunday. Showers and thunderstorms will spread northeastward into the Southeast and Tennessee valley Sunday night into Monday. A Pacific upper-level disturbance will move into the northwestern states tonight into Sunday, bringing an increase in rain and snow from the Northwest to the northern Intermountain West. Whether precipitation falls as rain or snow will be elevation dependent. Snow levels will gradually lower on Sunday as colder air associated with the upper-level disturbance moves in. Another upper-level disturbance and surface low pressure system will approach the West Coast on Monday, bringing another round of rain and snow. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php