Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 337 AM EDT Tue Oct 27 2015 Valid 12Z Tue Oct 27 2015 - 12Z Thu Oct 29 2015 ...Wet weather in store across the eastern third of the country... ...Light snow accumulations expected over areas of the Upper Midwest... ...Persistent onshore flow will bring unsettled weather to the Pacific Northwest... The upper pattern anchoring the nation will be rather complex to begin the period as a series of smaller scale features traverse the country. Gradually the elements will become better organized on a larger scale allowing a well defined upper trough to slide eastward through the Great Lakes region by Wednesday evening. The associated cold front which continues migrating eastward will eventually bring an end to the wet conditions affecting the eastern third of the United States. Early in the forecast, an upper trough will continue to weaken as it lifts from the eastern Gulf Coast up the Appalachians. However, enough moisture intercepting the system combined with orographic effects should at least support a moderate to occasionally heavy rainfall threat. Given the weakening nature of the system, expect the shield of precipitation to be less organized than previous days with general amounts of 1 to 2 inches expected from the Ohio Valley eastward to the Eastern Seaboard. Some of the convection could be locally severe depending on how much warm and unstable air can work its way up the I-95 corridor. The pattern farther west is expected to become much better organized as a potent upper low drops down from southern Saskatchewan. This feature is forecast to combine forces with additional energy downstream to bring a shot of much cooler air to the Nation's mid-section and a potential for wintry precipitation along the northern tier. While the better moisture will remain confined to locations farther east, enough lift underneath the upper low should spread precipitation across the Upper Midwest and Great Lakes region. Temperatures should be cold enough to support some light snowfall accumulations over northern Minnesota/Wisconsin. The WPC winter weather desk expects amounts generally under 4 inches through Thursday morning. Elsewhere, a strengthening Pacific system will approach the northwestern states bringing an increase in the low-level onshore flow. This enhanced Pacific moisture in conjunction with a favorable west-to-east flow regime will support orographically driven precipitation over Washington and Oregon. The heaviest amounts should focus along the coastal ranges with lower forecast totals farther east given diminishing moisture due to downsloping effects. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php