Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 431 AM EDT Thu Oct 29 2015 Valid 12Z Thu Oct 29 2015 - 12Z Sat Oct 31 2015 ...Another heavy rainfall event expected for the Southern Plains... ...Persistent onshore flow will support heavy rain over the Pacific Northwest... ...Cool and breezy conditions in store for northeastern corridor of the U.S... An active weather pattern to continue across the nation as a deep upper low traverses the Great Lakes region. Cold and unstable air in association with this feature will support a mixture of rain and snow showers across the Upper Midwest/Great Lakes. Any accumulations should remain minimal at best. In addition to the threat for wintry precipitation, a strengthening pressure gradient will bring cool and breezy conditions over much of the northeastern U.S. However, the passage of the cold front will bring much drier air toward the Eastern Seaboard as the shield of heavy rainfall exists the coastline. A myriad of disturbances currently advancing through the Desert Southwest should continue to become better organized during the next 12 to 24 hours. During this gradual intensification process, rainfall will spread across the Four Corners region. The mid-latitude flow is expected to become a more meridional in nature which will help transport a tremendous amount of Gulf moisture poleward. The slow-moving nature of the amplifying upper trough combined with sufficient moisture advection will support a concentrated axis of showers and thunderstorms over the Southern Plains by early Friday. Given areas of Texas just saw extremely heavy rainfall during the past week, some regions will be susceptible to flash flooding issues. Given that, a slight risk for excessive rainfall has been placed over the region per the latest WPC outlook. Elsewhere, a west-to-east oriented upper ridge stretching from the Eastern Pacific into the southwestern states will allow zonal flow to prevail to the north. This particular set up is forecast to allow a persistent feed of Pacific air into the Pacific Northwest coast. Moist onshore flow perpendicular to the north-south oriented terrain will aid in tremendous upslope flow across the Olympics and Cascades. In particular, the WPC precipitation forecast suggests 4 to 7 inches are likely across the Washington Cascades through Saturday morning. Given how dry the region has been recently, flash flooding is not anticipated. In spite of the wet conditions in place, the dominance of Pacific air into the western U.S. will support above normal temperature readings possibly approaching 10 to 15 degrees above climatology. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php