30
Day

Noticeable warming observed across the Eastern half of the U.S. this past weekend to above average temperatures (mainly 60s-70s) marks start of mild pattern change of increased confidence to effectively end prolonged periods of below average temperatures through most or all of November. The source region for warmer air flooding the central and Eastern U.S. is the unseasonably hot Desert Southwest where the recent extended period of 90s is forecast to peak early this coming week (Nov 3-4) before moderating to less extreme warmth (mid-upper 80s). This does not preclude briefer surges of Canadian air from periodically draining southward through the Great Lakes and Northeast cooling temperatures 7°-10° below average (highs mainly 40s-50s). However, unlike October moderate Eastern cooling will remain both transient and less frequent (the 1^st forecast Nov 9-10), while most of the U.S. west of the Appalachians remains above average. Between less frequent Eastern cool intervals all extended range models forecast longer several day periods of 50s-low 60s across the Great Lakes and Northeast at a time climatological high temperatures are plummeting into the low 40s. This mild late fall pattern driven by well established La Niña conditions favors wettest conditions in the Pacific Northwest along with near seasonal temperatures. Longer range modeling indicates no sign of effective end to relatively mild temperatures everywhere else from the Southwest to the East and Gulf Coasts into the start of December. Model trends indicative of a mild start to winter include latest runs of the 30-day MWA ensemble which backed off prior forecasts transporting arctic air into northwestern Canada in late November.  Subsequent runs may shift colder again in high latitudes, but snowcover is likely to remain well below average across most of Canada limiting intensity of cold air reaching the U.S. prior to mid or late December.