With skies turning cloudy, expect a daytime high around 53, with a south wind of 5-10 mph, along with potential gusts up to 25 mph.
Expect rain to develop well after sunset and continue overnight; with heavy rain at times, flooding is possible in urban and low-lying areas, as well as smaller streams, especially considering that significant snowmelt is expected. For this reason, the National Weather Service has posted a Flood Watch for the area. Make sure your drains are clear of snow! Over 2 inches of rain may fall overnight tonight and into tomorrow. Rain will end during the evening tomorrow. Additionally, a few strong to severe thunderstorms are possible during the morning tomorrow, which would only enhance the wind damage threat (more below); a line of thunderstorms appears possible.
Additionally, high winds are also a significant hazard with this system. A High Wind Warning is in effect as southeast to south winds of 10-20 mph, with peak gusts over 60 mph, are expected tomorrow morning. Expect the most likely time for the strongest gusts to be just after sunrise into mid-morning, although strong gusts are expected throughout the night as well. The wind will calm down during the afternoon tomorrow. Power outages are likely for some folks; take care to make sure devices are charged and the like.
As for the snowpack, most or all of it will be gone by tomorrow. The definition of a “White Christmas”, as per the National Weather Service, as having 1″ or more of snow cover on the ground Christmas Day. It’ll be a race against the clock. It used to be said that it had to be 1″ at 7 am, but the National Weather Service does not reference this any longer. 7 am is a good marker of “Christmas morning” though. Whether we have 1″ left on the ground at 7 am is an open question, especially because fog is possible which could further eat away at the snowpack, but we should have more than enough to have a White Christmas if you use midnight as the definition. Either way, I’ll follow up on how much snow I have left tomorrow morning.
Temperatures will rise through the 50s overnight, with the Christmas daytime high being around 60 during the morning. It won’t be nearly as warm as 2014 (when a Christmas Eve/Day storm brought heavy rain and temperatures in the low 60s) and 2015 (when an abnormally warm pattern brought the Christmas Eve and Day that most of us probably want after putting up with this nonsense of a year – a high of 71 Christmas Eve and 64 Christmas Day with dry conditions throughout).
Temperatures fall back into the 50s during the afternoon tomorrow. Friday night will be mostly cloudy, with a low around 29, and a south wind at 5-10 mph, with gusts up to 25 mph possible.
Saturday will be mostly sunny and much colder, with a daytime high around 35 (although for technical purposes, the official high will be somewhere in the 40s at midnight Saturday morning). Saturday night will be mostly clear and 21. Sunday will be mostly sunny and 38; Sunday night will be mostly clear and 24; and Monday will be mostly cloudy and 46.
I will have an update later today if changes in the forecast warrant. Otherwise, Merry Christmas Eve to those who celebrate, and enjoy your day!