Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 233 AM EDT Thu Oct 01 2015 Valid 12Z Thu Oct 01 2015 - 12Z Sat Oct 03 2015 ...Wet pattern will persist for portions of the East Coast over the next few days... ...Precipitation expected to increase across the Great Basin and into the Plains... A closed upper level low slowly digging across the Deep South will create a set-up for a very wet period for the Mid-Atlantic and the Southeast. This upper low will force the cold front exiting off the Northeast and Mid-Atlantic coast to stall; meanwhile, deep tropical moisture will be pulled northward across the Southeast and Mid-Atlantic. Consequently, this quasi-stationary front will be the focus for heavy bands of precipitation. The Carolinas will not receive a break in the precipitation as the Mid-Atlantic and will continue to see periods of showers and thunderstorms throughout the short term period. Precipitation will ramp up in the Mid-Atlantic by Friday and will continue well into the weekend. With these areas already soaked from previous rains, flash flooding will be a concern. See WPC's excessive rainfall products for further information. An active period for the western half of the U.S. is expected during the short term period. An upper level low will move toward the West Coast by Thursday afternoon. Consequently, precipitation will increase initially along the Sierra Nevada mountain range and will spread across the central Great Basin and northern Rockies by Thursday night. As the upper level low progresses eastward, moisture from the Gulf of Mexico will aid in firing off convection throughout the Great Basin and Rockies on Friday night. By Saturday morning, showers and thunderstorms can be expected across the western portions of the Plains in addition to the Pacific Northwest and northern Rockies. Fanning Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php