An active pattern finally comes to a close.

Sunday, December 30, 2012 at 6:34 am

Sunday, December 30:

There are a lot of clouds and a few very light snow showers currently passing through northwestern Utah right now. Don’t expect much more than a few flurries over the next 24 hours. After that, we fall under the influence of dominant high pressure for at least 7 to 10 days. GFS has been consistent in the last few runs in wanting to retrograde the ridge enough to allow systems to affect the area around January 10. Still too far out to put much faith in this but it’s worth noting.

Temps on the mountain will continue to warm up this week while lower valleys will stay in the cold pools, aka inversions, and see air quality worsen throughout the week.

Saturday, December 29:

Calmer weather and cold temperatures abound today. A splitting system is moving ashore along the west coast currently. The northern half of the system will move into the Great Basin tonight. This system is very weak and at best will only give Northern Utah a couple light snow showers tonight and tomorrow with little to no accumulation. Southern Utah might do a bit better with a few inches for the mountains down there on Sunday/Sunday night. San Juans of Colorado could also see several inches of snow.

Next week we’ll start to see what is looking more and more like an extended period of dry, cool weather. Expect mostly sunny skies almost every day with valley inversions becoming increasingly troublesome as time wears on. Ridge will gradually move west during the first week of 2013 and become more of a blocking Eastern Pacific ridge (sound familiar?) by the second week of January. Our next chance for decent snow likely won’t come until we can retrograde this ridge far enough west again for systems to start dropping into the area. As of right now, it doesn’t look like this will happen until at least 10 days or so into the new year. CFSv2 is not looking good as of now . . .

(Click to enlarge)


As you can see, the CFS is forecasting this ridge in the Eastern Pacific to keep the west coast dry through most of the month of January. This type of pattern certainly isn’t uncommon during the mid-winter months and often times is referred to as a January Thaw. Again, our best hope is that the ridge retrogrades west and allows the storm door to open again sooner than currently expected. Yesterday, I outlined some good signs in the teleconnections that might help us do this. We just have to wait and hope that these show up in the long-range forecast models as well.

At the very least, the temperatures should remain fairly cool which will keep the snow in good shape and even allow resorts to make snow if they need to. Stay tuned . . . WSF

Friday AM update:

Weak lift and moisture associated with the last little impulse of this storm is firing up some orographic snow showers in the mountains and even a few in the valley.  There is a tiny bit of lake-enhancement going on as well.  A couple inches have accumulated in the Cottonwoods and an inch more is possible… freshen up the already soft snow!  This snow should end by mid-day today and we should start to clear out but continued cold through the weekend.  Not much else has changed since last night’s discussion.  Next update tomorrow or sooner if warranted.


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Previous . . .

Snow showers have continued all day in orographically favored areas like the Cottonwoods where several more inches accumulated today.  Storm totals ranged significantly due to most of the snow being heavily dependent on topography.  Overall the Wasatch has seen 8-24″ of snow.  A reinforcing wave of moisture will move in overnight and could fire up snow showers a bit in these same areas.  An additional 1-3″ is possible in the Cottonwoods and other west-facing slopes.  Friday should see clearing and should be a great day.

The month of December has been an active one with frequent snowfall all month. Most of these storms were small to medium in size so we didn’t see epic amounts of snow, but it has added up pretty quickly.  It has also created about a dozen very good powder days so far this month. Snowpack numbers in the Wasatch are generally in the 100-120% of normal range so we are looking good heading into 2013. If you’d like to see exact numbers as to the current SNOTEL snowpack numbers in Utah, you can do that here.

Looking forward, we definitely should see a break from the action. The next week or so should be cool which will keep the snow in good shape.  A splitting pattern is developing–systems that move into the west coast will shear apart as they hit a ridge of high pressure over the intermountain west.  This sends some energy shooting north into the Pac NW and British Columbia, and other energy sliding down the west coast and moving inland into the desert Southwest and Northern Mexico.  The first of these splitting systems should affect Utah on Sunday, Dec 30.  At best we’ll only see a bit of light snow with an inch or two in the high elevations.  The next system is timing for about the 3rd of January, but again it looks like it will weaken significantly as it moves inland.

The most telling sign as far as teleconnections go is the PNA which is going positive for the first time in a couple months.  +PNA usually favors ridging along the west coast, so a break in the action is typical for this pattern. The good news is that there is very little blocking upstream or downstream of us right now so the Jet should remain progressive and it’s unlikely we’ll get stuck under a ridge for too long.  The PNA is also currently forecasted to start heading back negative during the second week of January which would also favor a return to snow.  The MJO, which has not been a factor all winter is now forecasted to strengthen and move into Phase 3 and 4 — these are good phases for west coast troughing.  Overall we think that this break from significant storms will last for the next 10 days or so but a return to more snow is also a good bet before the middle of January.  Time will tell!

Lots of fresh snow to be had out there!  Good ski conditions should last well into the new year.  We’ll keep you updated when big storms are once again in the forecast.


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