Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 432 PM EDT Mon Oct 21 2013 Valid 00Z Tue Oct 22 2013 - 00Z Thu Oct 24 2013 ...The northeastern quarter of the U.S. can expect below normal temperatures throughout the week... ...A clipper-like system will bring light snowfall accumulations to sections of the Mid-Mississippi Valley... ...Persistent ridging from the Rockies westward should maintain quiet weather over the West... The pattern aloft will remain very blocked during the short range period with a deep upper trof anchoring the eastern half of the country. This should allow a series of disturbances to drop from Central Canada eventually moving through the Great Lakes/Ohio Valley, and into the northeastern states. Such a pattern will continually reinforce the colder air in place resulting in below normal temperatures over much of the region. In fact, a slew of frost advisories and freeze watches/warnings are in place over much of Illinois, Indiana, and Ohio. The coverage of such issuances should translate eastward in time as the modified arctic air works its way into the Eastern U.S. by mid-week. Current forecasts suggest this air mass will feature highs generally in the 40s while lows plummet to near the freezing mark. One of the stronger impulses tracking from Southern Saskatchewan will race through the Mid-Mississippi Valley and eventually into the Ohio Valley in the form of a clipper system. This progressive upper trof should have enough cold air to work with at the surface to produce a few inches of snow from Northwestern Iowa eastward into Northern Illinois. Temperatures are forecast to be marginal at times so a mixture of rain/snow will be possible at times while precipitation falls. Other areas of unsettled weather include the Great Lakes and Gulf Coast region. With the Great Lakes, persistent west-to-northwesterly flow over the still mild lake surfaces should initiate rain/snow showers downwind of the lakes. The cold air should be enough to drop a few inches of snow along the shores of Lake Superior. Such a pattern will remain in place given the deep upper trof holding strong overhead. Elsewhere, a frontal boundary lingering in the Gulf of Mexico should bring a threat for showers and thunderstorms along the Gulf Coast region. The activity should gradually wind down by the middle of the week as the strong cold front ushers in drier air from the north. And finally, the western states will remain quiet given the strong ridge aloft. Little change in this pattern is expected through Wednesday. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php