Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Mon Aug 25 2014 Valid 12Z Mon Aug 25 2014 - 12Z Wed Aug 27 2014 ...Below normal temperatures are expected across the northern tier on Monday... ...Flash flooding will be possible over the Desert Southwest and Central Plains... The upper pattern across the country will be rather amplified with a pair of troughs affecting the western half of the United States. Meanwhile, the eastern states will remain under the influence of a broad upper ridge which has not very commonplace this summer. Down in the tropics Tropical Storm Cristobal should gradually increase in intensity attaining a hurricane status by early Wednesday. However, the forecast track keeps the system well east of the Eastern Seaboard with the only impacts being some rough surf. A strong upper low over North Dakota is expected to continue lifting north and east carrying the disturbance into southern Hudson Bay by Tuesday afternoon. In the wake of this system, cool temperatures will prevail across the Northern Plains and parts of the Upper Midwest with highs only in the upper 50s to lower 60s. Radiational cooling overnight will allow lows to plummet into the low to mid 40s on Monday night. The air mass does begin to moderate by the following day with readings near 70 degrees by the following day. As this upper low lifts into the higher latitudes of Canada, the associated cold front will slowly begin to lose its eastward push and eventually stall across the center of the country. Ample tropospheric moisture from the Gulf of Mexico will intercept this boundary fueling numerous complexes of thunderstorms. The best combination of lift from the front and moisture appears to be over eastern Nebraska and into western Iowa. This region can expect a threat for flash flooding given this favorable pattern for heavy rainfall. Another area of heavy rainfall is forecast across the Desert Southwest and into the Four Corners. An upper trough slowly moving through the Central Great Basin will help enhance the moisture rising from the tropical Pacific. The combination of lift from trough itself with enhanced moisture and topography will lead to periods of moderate to heavy rainfall, particularly during peak solar heating. Given the complex topography in play, rapid runoff from the steep terrain may enhance the flash flood threat on Tuesday and into the overnight hours. Elsewhere, unsettled conditions will prevail along the Central/Eastern Gulf coasts with showers and thunderstorms developing daily. Further up the coast tranquil weather is expected across much of the eastern third of the nation as a surface ridge anchors the region. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php