Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 335 PM EST Fri Jan 09 2015 Valid 00Z Sat Jan 10 2015 - 00Z Mon Jan 12 2015 ...Cold temperatures to prevail east of the Rockies... ...Lake effect snows will continue into the weekend... ...Icing is likely from the Big Bend of Texas through the Ozarks and into sections of Illinois/Indiana... A broad vortex anchoring itself near Hudson Bay will allow a series of mid-level disturbances to cross the Great Lakes and New England. This persistent pattern has brought a series of reinforcing shots of Arctic air to most locations east of the Rockies. The forecast temperature anomalies on Saturday are expected to be in the 15 to 25 degrees below average range with the largest departures centered over the Southern Plains and the Mid-Atlantic. This will equate to highs in teens and 20s over the latter location while temperatures in the 30s should prevail across the former. The below normal readings are expected to continue throughout the weekend while the Pacific influence of the air masses out west will keep temperatures at or above normal through Sunday. The cold air aloft tracking above the milder lake surfaces will help invigorate numerous periods of snow showers across the Great Lakes region. This will particularly be the case through Saturday evening while the low-level winds are expected to be the most favorable. Eventually the flow becomes a bit more southwesterly by late in the weekend which will bring milder air into the region along with making trajectories only favorable across Lakes Erie and Ontario. The WPC winter weather desk suggests snowfall amounts around 6 to 12 inches downwind of Lake Ontario while 4 to 6 inches will be more likely east of Lakes Erie and Superior. A slow-moving upper low will finally move off the Gulf of Baja California and migrate eastward through Mexico. Warm advection ahead of this system should continue to pump ample moisture northward into the Western Gulf Coast. The combination of the energy aloft with this upper trough combined with increasing moisture will spread precipitation from Central/Eastern Mexico into the Southern Plains. These impulses are forecast to gradually lift across the Red River of Texas/Oklahoma into the Ozarks where the shield of precipitation will expand into Missouri/Illinois/Indiana. Given the shallow Arctic air lingering at the surface, freezing rain will be likely as milder air overrides the subfreezing air at the ground. This will occur along the northern extent of the precipitation spreading accumulating ice from the Big Bend of Texas through the Ozarks and into Missouri/Illinois/Indiana. Elsewhere, expect an area of light to moderate snow to develop across the Upper Intermountain West/Northern Rockies where an arctic boundary has stalled along the complex terrain. The current forecast suggests 4 to 6 inches of snow will be likely through Sunday. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php