Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 417 AM EDT Wed Oct 30 2019 Valid 12Z Wed Oct 30 2019 - 12Z Fri Nov 01 2019 ...Extremely critical and life threatening fire weather conditions will continue for portions of northern and southern California... ...Huge temperature contrasts expected across the nation with numerous record cold and warmth likely... ..Snow spreading from the central Rockies into the central Plains today and into the Upper Midwest tonight... ...Large low pressure system will potentially bring major disruptions to trick-or-treaters on Halloween over the eastern U.S.... An anomalously amplified upper level pattern across the nation will support very active and impactful weather for much of the nation over the next two days. An expansive area of high pressure that is bringing record cold temperatures for much of the interior western to central U.S. will also lead to winds gusting as high as 80 mph into parts of California. These winds, together with extremely low relative humidities, will produce extremely critical and life threatening fire weather conditions through today across northern California and through Thursday across southern California. In addition to the record cold, snow has been impacting much of Colorado today as the forward motion of the arctic front is impeded by the complex terrain. The snow is expected to start moving into the central Plains today, into the upper Midwest tonight, and across the Great Lakes on Thursday. In contrast to this, much above average temperatures continue to persist for the entire Eastern Seaboard where record high minimum temperatures are common. This huge contrast in temperatures across the country, when combined with the anomalously amplified upper trough, will spawn a large-scale low pressure system along the frontal boundaries over the Deep South. The storm will then intensify rapidly and head toward the eastern U.S. on Halloween. This storm has the potential to bring flooding rains from the interior Southeast through the Appalachians and New England on Halloween and into Friday morning. In addition, severe thunderstorms will be possible for the entire Mid-Atlantic region Thursday night into early on Friday ahead of a strong cold front. Overall, the atmosphere will be giving tricks to large portions of the nation over the next two days, with calmer weather likely by the weekend. Kong/Oravec Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php