Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 442 PM EDT Thu Sep 19 2013 Valid 00Z Fri Sep 20 2013 - 00Z Sun Sep 22 2013 ...Showers and thunderstorms along the frontal system moving into the Great Lakes and the Ohio Valley... ...Heavy rains will affect the southern Plains... ...Stormy weather expected in the Pacific Northwest... A robust frontal boundary is beginning to make its way into the Great Lakes and will continue its journey eastward towards the Ohio Valley and eventually the Mid-Atlantic. This system has a nicely defined upper level low along with warm, moist low level air filtering in from the Gulf of Mexico. These conditions are favorable for showers and thunderstorms to develop along and ahead of the cold front. Some of these thunderstorms could be strong to severe in nature. The frontal boundary should arrive in the Ohio Valley by Friday night and into Saturday with a cold front draping over the southern Plains and into Mexico. Once the front departs the Great Lakes and Ohio Valley, surface high pressure will quickly follow its footsteps. With drier air and northwesterly flow, these regions should have a good quality airmass. The drought-stricken areas of the southern Plains can expect showers and thunderstorms throughout the short term period. The cold front dropping through will interact with tropical Pacific moisture will promote locally heavy rainfalls throughout the Big Bend and south Texas regions. However, the front will slowly sag south toward the coast which will continue to fuel moderate to locally heavy rainfall throughout the weekend. A cold front will approach the Pacific Northwest by Thursday night and into Friday morning. Showers with moderate rainfall will begin by Thursday night and continue through Saturday morning. The heaviest activity will occur on Friday. By Saturday, showers will become more scattered. Fanning Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php