Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 244 PM EST Mon Nov 19 2018 Valid 00Z Tue Nov 20 2018 - 00Z Thu Nov 22 2018 ...Light to moderate snow accumulations for portions of the Great Lakes and Northeast tonight into Tuesday... ...Improving air quality expected across the West Coast through the middle of the week... ...Moderate rain to impact central/northern California by Wednesday bringing both relief and potential problems... ...Bitter cold temperatures for the Great Lakes to Northeast mid-week... A storm system currently approaching Pennsylvania and New York will continue to bring a mixture of rain and snow to the northern Mid-Atlantic and Northeast tonight through Tuesday. Light to moderate snowfall accumulations are expected for Upstate New York into New England with the highest totals (3-6 inches) forecast from the Catskills into the Berkshires, Green Mountains into southern New Hampshire and coastal Maine. All rain is expected from Boston to Philadelphia given warm temperatures in place. This will all occur as an area of low pressure strengthens offshore of New England Tuesday. A shot of colder air will follow behind the system's cold front but a second and stronger cold front will reach the region from the northwest on Wednesday bringing accumulating snow to the upper Great Lakes and some of the coldest air of the season to the Northeast for Thanksgiving. Average high temperature departures across the lower Ohio Valley into the Great Lakes will range 10 to 20 degrees below normal on Wednesday with similar anomalies spreading to the northern Mid-Atlantic and Northeast for Wednesday. For Thanksgiving, high temperatures near 30 degrees below late November average highs are expected to impact most of the Northeast. The middle of the nation will be fairly quiet into mid-week as upper level ridging slides eastward from the western U.S. bringing generally fair weather from the Rockies to the Mississippi River Valley. Out West, the departure of upper level ridging and the approach of upper level troughing will bring the first in a series of cold fronts as the large scale weather pattern undergoes a shift. The first cold front should arrive into California late in the day on Wednesday, preceded by rain and higher elevation snow into the Sierra Nevada. The departure of stagnant high pressure and the onset of precipitation will bring welcome relief to poor air quality which has been plaguing portions of the West for weeks, as well as to help get the ongoing Camp Fire in northern California under control. The rain may be moderate at times which could cause debris flows given fresh burn scars in portions of northern California. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php