Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 435 AM EDT Mon Jun 17 2013 Valid 12Z Mon Jun 17 2013 - 12Z Wed Jun 19 2013 ...Severe thunderstorms will be possible along the Southern/Central High Plains the next couple of days... ...Below normal temperatures are expected over much of the northeastern states by Tuesday... The upper pattern impacting the country will slowly evolve to a more progressive setup to begin the week. A quasi-stationary closed low which has wobbled offshore of the Pacific Northwest should finally work its way inland by Monday evening which will help shift the upper pattern to the east. The ridge which had been setup over the Intermountain West will gradually shift its focus toward the Great Plains by mid-week. Along the eastern fringe of this ridge, a series of mid-level impulses will continue to work their way off the elevated terrain into the Great Plains and Mississippi River valley. The initiation of the convection along the Southern/Central High Plains will remain a focus for severe thunderstorms where storms should began in a discrete mode. Such is the case the next couple of days as indicated by the Storm Prediction Center outlooks. Beyond sunset, expect the convection to a coalesce into multiple clusters of thunderstorms which are forecast to continue well into the overnight hours. These features are expected to continue marching eastward toward the Ohio/Tennessee valleys although they generally become ill-defined and thus are not a weak focus for convection. A well-defined frontal boundary nosing southward from Canada will bring below normal temperatures to much of the northeastern states by Tuesday. Forecast highs will only be in the low to mid 70s across the Great Lakes eastward into the Upper Ohio Valley and New England. Additionally, this boundary should aid in an increase in the coverage of showers and thunderstorms on Tuesday. Elsewhere, the deep upper trof sliding through the Pacific Northwest and into the Intermountain West will bring rather gusty winds along the frontal zone as the pressure gradient begins to tighten. Moisture will be rather limited so precipitation should remain scattered in nature. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php