Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 434 PM EDT Wed Apr 29 2015 Valid 00Z Thu Apr 30 2015 - 00Z Sat May 2 2015 ***Amplified pattern transitioning to a more zonal pattern*** ***Low pressure areas to provide rain to eastern U.S.*** ***Mainly warm and dry elsewhere across the U.S.*** The beginning of the forecast period on Wednesday night and Thursday will be featured with an upper level trough over the eastern U.S., and a ridge over the Great Plains. This trough will allow an upper level low from Canada to move southeastward and interact with a coastal low pressure system on Thursday and Thursday night. The majority of the bad weather that will be associated with this developing low will be over the offshore waters. However, there will be enough moisture and lift available with the upper level low to result in scattered areas of rain and a few thunderstorms from the Ohio Valley to the southeast coast. It will also be cooler than average for Thursday and Friday for the East Coast as widespread clouds and onshore wind keep temperatures in check. By Friday afternoon, a weather pattern change will be in the works as the atmosphere transitions from an amplified flow pattern to more of a zonal one. In other words, the steering winds aloft will be more west to east. This will allow for a gradual warm-up across much of the eastern U.S. as we head into the weekend as the colder weather remains over Canada. Highs are expected to reach the 70s and low 80s for many areas by Saturday. Elsewhere across the continental U.S., a cold front crossing the Rockies and High Plains will likely have a narrow swath of showers and thunderstorms with it, along with some snow showers for the highest elevations of the Rockies. This frontal boundary is expected to dissipate later in the period as the thermal contrast weakens considerably. Most areas from California to the Deep South will enjoy warm days with very little rain. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php