WEEKEND STARTS WITH A BANG...
A major December storm with a split personality will create a wide variety of weather around the region the next 36 hours. For our neighbors to the NW, heavy snow will accumulate 6-10 inches. Further south rain will be the dominate form of precipitation although a switch to light snow or flurries is likely as cold air wraps in on the tail end of the system. Let's break it down.
One of the toughest challenges forecasting any storm is determining its track, especially when there is a wintery component. This one has been fairly well mannered with good consistency among model solutions for several days. Therefore, this is a high confidence forecast regarding the large scale features. Here's the WPC depiction of the surface low heading northeast Friday evening.
For my area, showers are expected to blossom later Friday afternoon as the center of the storm approaches from the SW. These should increase in coverage during the evening as the storms core passes close to the Quad Cities. Despite the strength of the storm, precipitation amounts are expected to remain light (perhaps moderate in a few spots) with the forcing somewhat split and a dry slot limiting its duration. Models show this for rainfall potential.
The EURO (one of the more robust solutions (perhaps too heavy)
The 3k NAM
With the storm moving at a healthy clip, precipitation will also be limited in duration as the dry slot following the center invades the region by midnight. That cuts of moisture and the rain should end or transition to drizzle in all but the far northwest. By late Friday night or early Saturday, wrap around moisture spins back into the area. By then colder air is filtering in on gusty NW winds. Light snow showers or flurries should spread over at least the northwest half of the region. Whether these can make it southeast of the Quad Cities is questionable but some flurries are possible there as well.
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THE SNOWY SIDE OF THE STORM...
As far as the snow potential is concerned, overall there is good consistency regarding the heavy snow band and snow totals. Most certainly the worst of it misses my area to the northwest. Here you can see the winter storm warnings and advisories in effect.
This graphic from the NWS in La Crosse shows the very heavy swath of snow that's expected.
WPC has also upgraded the winter storm severity index to now include major impacts from NW Iowa through southern Minnesota and NW Wisconsin.
These are the odds of at least an inch of snow from WPC
Here's what the actual models are depicting for snow totals, most of this coming Friday night and early Saturday. You'll notice there's excellent agreement among all the various solutions.
The NATIONAL MODEL BLEND
The 3k NAM
The 12K NAM
This will all be nothing more than a bad memory next week when temperatures surge to spring like levels. Wednesday the 15th the GFS has highs near 70 and the EURO is not far behind. Take a look. Records look possible!
The change to colder weather I've been advertising just before Christmas seems on track. The EURO weeklies are in and they show this for 30 day temperature departures December 25-January 24th. Over that 4 week period temperatures came in 5-15 degrees below normal over much the NC United States. I really think that's possible. Time will tell.
As for snow, the weeklies have that too but I'm not nearly as confident in this outlook. It's very hard to define individual storm tracks at this distance. This remains low confidence compared to temperatures but wow, this run of the weeklies really clocks southern Minnesota and NW Wisconsin with 40 to nearly 50 inches of snow. That's at a 10:1 ratio. Most likely they would be higher than that indicating even higher totals than what's indicated. A very interesting trend.
That's enough for this post. Enjoy your day and have a fantastic weekend. 15 days to Christmas and so much to do! Roll weather...TS
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