Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 442 AM EDT Tue Jul 02 2013 Valid 12Z Tue Jul 02 2013 - 12Z Thu Jul 04 2013 ...Record breaking heat wave continues out West... ...Flash flooding remains a possibility within a muggy airmass in place over the Eastern Seaboard... The atmosphere over the lower 48 will remain on hold during the short range period while an expansive upper ridge stays locked in over the West and a building ridge in the western Atlantic continues to push a deep upper trough back westward over the eastern half of the Nation. Underneath the ridge in the West...excessive heat warnings and heat advisories remain in effect where daytime temperatures will yet again soar past the century mark and overnight lows will struggle to drop into the seventies and eighties. This not only includes much of the Southwest and Great Basin...but triple digit readings will also be possible within the valleys of the Pacific Northwest...Intermountain West...and Northern Rockies. A cold front trying to press southeastward through the Pacific Northwest Tuesday evening should bring some relief from the heat...but temperatures across the rest of the western U.S. will remain well above normal through the middle of the work week. In terms of precipitation across the West...weak impulses dropping down the eastern edge of the upper ridge will continue to trigger scattered convection as they intercept some moisture in place across the Central/Southern Rockies and Southern Great Basin. In between the retrograding upper trough in the East and strong block in the western Atlantic...a rich supply of moisture getting pulled northward will keep muggy conditions in place along the Eastern Seaboard. Widespread showers and thunderstorms containing heavy rains will continue to breakout within the ripe airmass. Localized flash flooding will be a possibility from the Southeast to New England...with the greatest threat expected near the Southern Appalachians. Showers and thunderstorms will also be possible underneath the core of the upper trough spinning over the Ohio Valley on Tuesday. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php