Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 430 AM EDT Tue Oct 07 2014 Valid 12Z Tue Oct 07 2014 - 12Z Thu Oct 09 2014 ...Showers and thunderstorms will spread from the Ohio/Tennessee Valley to the Mid-Atlantic/Northeast on Tuesday into Wednesday... ...Tropical Moisture from Simon expected to bring heavy rain to portions of the Southwest beginning on Tuesday... An area of light to moderate rain ahead of an old frontal boundary across the Northeast will move through New England today. Behind this system, showers and thunderstorms developing in the Middle Mississippi Valley ahead of a second boundary will move into the Tennessee/Ohio Valleys this morning, and eventually the Mid-Atlantic region by Tuesday evening. The heaviest and the most organized of the precipitation is expected to develop along and ahead of the front as it makes its way from the Ohio Valley to the Northeast. By Wednesday, this rain will move into New England, bringing another round of showers and thunderstorms to the region. The front should push off the coast Wednesday evening, with high pressure and dry weather following on Thursday for much of the eastern third of the nation. Across the southwest U.S., moisture associated with Tropical Storm Simon should begin streaming into the region by Tuesday morning, reaching the four corners region by Wednesday afternoon. The heaviest of the rainfall is expected across southern Arizona, where WPC will be monitoring the threat for flash flooding over the next few days. Elsewhere, easterly flow off the Atlantic will continue to produce mainly diurnally driven showers and thunderstorms across southern Florida, while light and scattered rain will also possible across portions of the northern High Plains. By Wednesday evening, showers and thunderstorms are also forecast to develop to the north of a warm front lifting through the central Plains and Middle Mississippi Valley. Monarski Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php