Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 302 AM EDT Wed Oct 02 2013 Valid 12Z Wed Oct 02 2013 - 12Z Fri Oct 04 2013 ...The first significant snows are expected across the Northern Rockies this week... ...A slow-moving boundary will focus convection over the Middle Mississippi Valley and Upper Midwest... During the next couple of days, a pattern change will begin to take place as a deep upper trof crosses the Central Great Basin and into the Central/Northern Rockies. This amplification process will transport much cooler air into the Intermountain West region. While temperatures in the valley locations will be too mild for wintry precipitation, higher elevations across the Northern Rockies can expect decent snowfall accumulations. The latest WPC winter weather desk forecast suggests amounts exceeding a foot extending from the Tetons and Absaroka Range eastward into the Big Horn Mountains. It appears locally possible that some of these ranges may see up to two feet of snow through Friday morning. The system will be rather potent given the strong nature of the mid-level low combined with persistent upslope flow. This particular setup will strengthen the vertical lift along the topography bringing bursts of heavy snowfall with even the potential of some thundersnow given the dynamic nature of the storm. As this system carves out a well developed upper trof across the western states, a highly meridional pattern is forecast to set up as an expansive ridge sets up over the Mississippi River Valley. This trof/ridge interface will be the site for persistent showers and thunderstorms where a frontal zone should be nearly quasi-stationary. While flash flooding is not anticipated, a period of heavy rainfall can be expected anywhere from the Middle Mississippi Valley into the Upper Midwest the next couple of days. Some of the storms may become locally severe on Thursday across sections of Nebraska/Iowa per the latest Storm Prediction Center outlook. Elsewhere, persistent east to northeasterly flow along the Gulf Coast will foster areas of thunderstorm activity. As time proceeds onward, low to mid-level moisture will be on the increase as a disturbance currently near the Yucatan Peninsula lifts northward. This should gradually increase the coverage of rainfall along the Gulf Coast although the heaviest activity should remain offshore during this period of time. Looking north of this region, a warm front lifting northward into the Great Lakes will bring mild weather across much of the eastern half of the U.S. Highs in the low/mid 80s should be commonplace although it will be somewhat cooler in New England where a backdoor cold front will lower temperatures into the 70s. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php