Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 208 AM EST Mon Dec 23 2024 Valid 12Z Mon Dec 23 2024 - 12Z Wed Dec 25 2024 ...Heavy rain and mountain snow returns to the West Coast region Monday night... ...Showers and thunderstorms developing over portions of the south-central states... ...Relatively mild conditions across the majority of the country leading up to Christmas... An active weather pattern is expected to continue across the West Coast region as an energetic storm track across the eastern Pacific brings in multiple rounds of precipitation. After a brief respite Monday, the next atmospheric river event arrives across northern California and western Oregon late Monday night and into Tuesday. Although the storm system will be progressive overall, there will be a deep surge of moisture ahead of the cold front that will intersect the coastal terrain and the western slopes of the northern Sierra Nevada. Rainfall totals on the order of 2-4 inches, and locally higher, are likely across this region through Tuesday evening. Snow levels will be initially high, but should fall some once the front passes. The heaviest snow from this event should affect the highest terrain of the central and northern Sierra Nevada, with up to a foot of accumulation possible. A low pressure system crossing the Great Lakes region on Monday will produce a corridor of mixed wintry precipitation from southern Minnesota to southern Lower Michigan, and mainly light to moderate snow to the north across northern Wisconsin and into northern Michigan. Winter weather advisories are currently in effect for those areas. This low reaches the Northeast U.S. Christmas Eve, with light snow mainly for interior portions. Farther to the south across Texas, a separate surface low develops, and increasing southerly flow from the western Gulf of Mexico ahead of that system will fuel the development of scattered to numerous showers and some thunderstorms from eastern Texas northward across much of Arkansas and into southern Missouri through Tuesday. Much of the East Coast region will have a very cold start to the holiday week on Monday, with an arctic surface high slowly moving east across the region. The coldest morning of the season thus far is expected for most of the Mid-Atlantic and Northeast states, followed by another chilly day on Monday, albeit slightly milder compared to what was observed on Sunday. A further moderation trend is expected going into Christmas Eve as the surface high moves offshore and milder air from the Ohio Valley advects eastward across the region. The remainder of the country should enjoy generally above average temperatures by late December standards, particularly across the central and southern Plains where daytime highs could be 15-20 degrees above average. This would equate to highs well into the 60s and 70s for much of Texas. Hamrick Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php