Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 444 PM EDT Fri May 03 2013 Valid 00Z Sat May 04 2013 - 00Z Mon May 06 2013 ...Heavy rainfall with potential flooding is possible along much of the Mississippi River Valley and across the southeastern U.S... ...Another day of warm/dry conditions accompanied by gusty winds is expected across California... The upper pattern will continue to be rather blocked across the nation with the prevailing westerlies displaced well to the north. The primary feature of interest is a closed low currently spiraling counterclockwise across the Ozarks. Throughout the next 48-60 hours, this circulation is forecast to remain nearly quasi-stationary at times although a general east to east-southeastward movement is expected. An anomalously cold air mass in response to this vortex has brought early May snowfall to the Upper Midwest and Middle Mississippi Valley today. While the snows will continue to wind down with the mid-Spring solar angle overhead, low-level vertical temperatures profiles still suggest a threat for freezing rain/sleet will be possible through tonight. The other aspect of this storm is the heavy rainfall occurring along a very deep moisture plume emanating from the Tropics. Moderate to heavy rains are forecast to continue from the Central Gulf Coast up through the Tennessee Valley and into the Middle Mississippi Valley. As time proceeds onward, the better activity should be confined to the lower latitudes of the U.S. with primary impacts across the Tennessee Valley and into the Southeastern U.S. In particular, the Southern Appalachians may see an increase in activity later in the weekend given the upslope flow in place. However, in the near term, Northeastern Florida continues to be intercepted by a well-defined moisture plume which has continued to bring steady rains throughout the day. As a result, the Weather Prediction Center has highlighted this location in a risk for flash flooding through Saturday afternoon/evening. Yet another day of offshore flow across the state of California will again raise temperatures into the 90s, particularly across the valley/desert locales. The persistent downsloping flow will lead to strong compressional heating and very low relative humidities. The offshore pressure gradient is forecast to also bring locally gusty winds, thereby enhancing the fire danger over this region. Fortunately, by the weekend, an upper low retrograding westward from the Central Great Basin will help bring a return to onshore flow to California along with a small threat for showers. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php