Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 317 PM EST Sat Dec 28 2024 Valid 00Z Sun Dec 29 2024 - 00Z Tue Dec 31 2024 ...Atmospheric river to produce heavy rain/snow across much of the Northwest... ...Severe Thunderstorm outbreak and Excessive Rainfall potential from the South to the Northeast... ... Heavy Mountain West Snow Possible ... ...Above average temperatures across the South and East... The wet Pacific Northwest will continue this weekend as another low pressure system moves through the region. Some heavier rainfall is likely overnight and into Sunday day with this surge in moisture across northern California and southern Oregon. A Slight Risk for Excessive Rainfall is in effect for Saturday and Sunday to account for the possibility of flooding. In addition to the flooding threat, there are surf hazards, wind hazards (power outages are possible with gusts near 60 mph), and there is a river flooding threat beyond this weekend as some rivers crest pass its capacity. However, there is hope on the way; a cold front is expected to clear the area. High temperatures will drop behind the front into the 40s and most of the heavy rainfall potential should subside, but a few lingering showers remain possible with moisture still streaming in from the Pacific. A major severe weather event is unfolding across the South this afternoon. A line of thunderstorms is moving across the region with strong gusty winds and large hail. Additionally, discrete supercells are forming ahead of the main convective line with possible tornadoes. The conditions are highly favorable for severe weather and the Storm Prediction Center has issued a Moderate Risk (level 4/5). The severe weather threat should continue across the Southeast on Sunday in the form of a combination of discrete supercells and a linear line of storms called a QLCS (Quasi-Linear Convective System). Damaging wind gusts, large hail, and tornadoes will be most likely from north Florida to the Carolinas. The Ohio Valley may also see strong wind gusts in thunderstorms that develop as a surface low deepens and moves over the region. A flooding threat will also ensue with the severe weather threat in the South and Ohio Valley. For the remainder of today, a Slight Risk for Excessive Rainfall is active across much of the South. Training thunderstorms may dump 3-6 inches in the heaviest spots. On Sunday, there is a Marginal Risk for Excessive Rainfall for the Appalachains as a shield of rain moves northward with the low pressure and gets enhanced lift with upslope flow along the terrain. The last big weather story will be the heavy snow in the Mountain West. In the next 3 days, the northern Rockies and the Cascades may see 1-2 feet of snow accumulations as moisture from the Pacific continues to funnel into the region. The snowfall will be enhanced by a stationary boundary draped across the area and followed by a cold front passage on Sunday. Blowing and drifting snow may be possible as winds near 40 mph and a few Winter Storm Warnings are active. Elsewhere across the rest of the country, the Southwest, South-Central, and East Coast will be more than seasonably warm as all these regions may see temperatures more than 20 degrees above average. The desert Southwest will see highs in the middle 70s, central Texas may approach 90 and threaten record daily highs, and the east sees highs in the 60s and 70s. Wilder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php