Dec 22: Dangerous California Flood Threat, Record Warmth, and Northeast Snow Chances

The biggest weather story this week will be a series of storms that will bring heavy rain and snow, strong storms, and high winds to California. In fact, most of the state is under some kind of advisory whether it be a flood watch, high wind watch, or Winter Storm Warning. Wind gusts up to 60 mph are possible in the High Wind Watch: 

The flood threat is especially serious and a rare high risk for flash flooding has been issued for Wednesday. Each day this week has the chance for flash flooding but Wednesday appears to be the most dangerous day: 

Tuesday's Flash Flood Risk: 

Wednesday's Flash Flood Risk: 

Thursday's Flash Flood Risk: 

Totals will be impressive across the state with over a foot of precipitation possible in the Sierra and over 5" of rain likely across Southern California:

While snow levels will start relatively high, they will lower as cold air moves in and much needed snow plasters the Sierra. As we mentioned last week, the region is running record low snowpack so far this year: 

A general timing from Mon 4 pm PT to Wed 10 am PT shows when some of the heaviest precipitation will move in. You can also visually see the snow levels lowering as the week progresses: 

Keep an eye on our stations in Ventura County who will be under that high risk for heavy rain and flash flooding on Wednesday not to mention our station in the foothills of the Sierra at Bret Harte High School. Late Tuesday night into early Wed AM will be the worst of the rain for SoCal. Below is a snapshot of the forecast radar for Wed at 4 am PT: 

On to the other active area of the country this week, the Northeast, where a couple of wintry systems are possible this week. You can see both systems starting with the first one on Tuesday and another one late this week into the weekend: 

The first system will bring enough snow to potentially save a White Christmas for parts of the region, with 3-5" for upstate New York and upwards of a foot for Maine: 

The next system will track a little farther south, with the snow footprint potentially making it to New York City and even the Jersey shore: 

This system will also come with the possibility of sleet and freezing rain though. Don't take the below freezing rain totals as an exact forecast just yet but just as the potential for what could happen: 
Why so much freezing rain potential? Warm air aloft over cold air at the surface will allow snow to melt then refreeze at the surface. You can see this in the forecast sounding for State College PA below: 

Finally, the other big story we are tracking is the potential for record warm weather every day, including Christmas Day. Dozens of records are possible from the Central US to the Southeast: 

Tuesday's Record High Potential (30 records possible):

Wednesday's Record High Potential (30 records possible): 

Thursday's (Christmas Day) Record High Potential (59 records possible):

The 5 day anomaly captures this extreme warmth Tue Dec 23 - Sun Dec 28: 

There are now signs of a significant cold front late next weekend that will drop the temperatures back below average for much of the Eastern US by early next week: 

More details on all these stories later this week.