First Day of Winter (Meteorological Winter)

No that is not a typo. Today is Dec 1st, the first day of Meteorological winter. I know the calendar goes with Dec 21st, but when we compare records of past winters it is from Dec 1 - Feb 28/29 not Dec 21- Mar 21. So today is the first day of winter (statiscally you might say.) 

Today’s Discussion:

We certainly made a dent in the precipitation deficit of the last 6 weeks. Lots of great rain. Good for the ground water and for the stream flow. Plus, we are not done yet, as at least one more heavy rainstorm looks to impact us next week. There could be two, depending on how that SW system ejects out of extreme northern Mexico this weekend or early next week.

Today through Sunday look decent. More clouds than sun today, but more sun Friday – Sunday with seasonal temperatures. It will be breezy at times today and Friday as well. A flurry or even a very light snow shower may occur Fri into Sat morning, but that is unlikely.

The forecast challenge for this period occurs Sunday night through Tuesday. And it all revolves around that SW 500 mb low. It will come out, but the timing it tricky.  Here are the differing thoughts:

1. Upper low comes out Sunday and joins forces with some other energy to the north and produces a heavy rainstorm for our area as it lifts to our NW on Monday.
2. Upper low comes out Monday, but beforehand some moisture gets handed off to the northern energy and produces some light snow for us Sunday night. Then the main storm follows Tuesday as a significant rainstorm.  
3. Same as #2, but the storm is blocked from lifting north, and it redevelops off the SC/NS coastline and moves east. With a big high to our north, we run the risk of some light snow/sleet/rain for Tue.
4. Upper low comes out Monday night and stays to our south missing us entirely.

The forecast is all about timing. And the problem is that most of the computer models are notorious for being too slow with these storms. So, a forecaster must try and figure out with is most likely.  And for me, the most likely is 2 or 3 because they are so similar.  Since there is nothing coming in behind the upper low, it will not move out quickly, yet it will come out due to the active pattern. The question then becomes, does it head northeast over our area or redevelop off the coast? 

Looking at what has been happening, a redevelopment seems likely. And being several days from one storm to another, there should be enough time for yesterday’s storm to get out of the way … but, the weak system for Sunday night is the fly in that thinking.

I suspect Sundays system will force Monday’s system to be further SE, so a colder, and possibly somewhat more wintery outlook may exist for Tue than is now forecast in many areas.

Once past next Tuesday, a warm-up will occur with a major storm moving through the central states. This storm will have a blizzard on one side with true arctic air, and mild to warm conditions with heavy rain and some severe storms along the very strong cold front.

Yes, winter weather is coming and coming soon …