Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 329 AM EDT Sun Sep 20 2015 Valid 12Z Sun Sep 20 2015 - 12Z Tue Sep 22 2015 ...Showers expected for portions of the Pacific Northwest today... ...Showers and thunderstorms expected to increase in coverage across the southwestern U.S. on Monday... A cold front will move off the East Coast this morning, with high pressure building into the Great Lakes, Northeast, and Mid-Atlantic regions behind the front. This area of high pressure will promote dry conditions and below average temperatures today and tomorrow for these areas. On Monday, easterly flow off the Atlantic may spread some moisture back into portions of the Mid-Atlantic, which may bring an increase in clouds and a chance of showers, with temperatures remaining below average. Farther south, the front will become stationary from the southeastern U.S. and Gulf Coast into the southern plains. A weak wave of low pressure along the front will keep scattered showers and thunderstorms in the forecast for the Southeast through the next couple days. A Pacific cold front will move into the northwestern U.S. today, bringing showers to coastal portions of Washington state as well as to the Cascades. As the front moves farther inland, into the Intermountain States, it will remain largely dry. Windy conditions will also accompany the front across the northern Intermountain States The front will move into the northern plains and Midwest Monday afternoon into Tuesday, with the potential for some scattered showers and thunderstorms. An area of low pressure will move northward west of Baja California today. The low is forecast to cross the northern Gulf of California late on Monday before moving into southern Arizona by Tuesday morning. Moisture will increase ahead of this low as it approaches, and will result in the development of scattered to numerous showers and thunderstorms across the southwestern U.S. Monday and Tuesday. Heavy rainfall is possible as the moisture overspreading the Southwest will be originating over the tropical eastern Pacific. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php