Pattern change!

Tuesday, September 17, 2013 at 8:32 am

Wednesday AM update:  Cold front has passed through Northern Utah this morning.  Cool today with gradual warming as we head toward the weekend.  A second cold front is timing for Saturday night/early Sunday.  Models have come into more agreement that this will be a mostly dry feature with just winds and clouds and another cool down behind the front on Sunday and Monday.  Models still advertising a deeper, colder system for mid-next week that could bring more precipitation and a bit of snow to the high elevations.


After the hottest summer in much of Utah’s history, it will come as welcome news to most of us that a large scale pattern change is currently taking place. If you remember back to earlier this month, we said there was a good chance of a pattern change beyond mid-month that could bring us more Fall-like weather and maybe even some snow on the high peaks. It’s now past mid-month and that change is on our doorstep. The first in a series of cold fronts will move through Utah tonight, ushering in cooler air and maybe a shower or two. Two more fronts will also affect us over the next ten days, more on those in a bit.

Blustery winds today (Tuesday) will precede frontal passage tonight. As is usually the case, warm air ahead of the front will keep us toasty today with highs in the 80s in the valleys. High temps tomorrow will be up at least 15 degrees cooler than today. The real story will be the low temps, with most locations dipping into the 40s on Wednesday night. Mountains valleys could see 30s, so it might be a good idea to cover up tender vegetation.

We’ll warm up again gradually on Thursday-Saturday back up above normal, before another trough approaches and drags another cold front through the area on Saturday night. Models are having a tough time with the strength of this feature. The GFS brings it through as a dry cold front that would cool us down a bit (similar to tonight’s front), while the EC is much more aggressive and wants to drop temperatures down even further with showers in Northern Utah. If the Euro verifies, we’d likely see a dusting of snowfall above 9K feet in the Wasatch this weekend.

The third front in the next 10 days is timing for the middle of next week. This is far out and therefore details are vague, but there has been a general idea of it being deeper, colder, and stronger than its two predecessors. It will bear watching as we get closer as it could actually have the potential to drop measurable snowfall in the Wasatch. Of course, during a major seasonal transition like we are seeing now, it’s difficult to forecast with any confidence beyond 5 days. So for now let’s just wait and see how the models decide to deal with this system before we get too excited.

Overall, it’s safe to say it will feel more like Fall with a bit of a temperature roller coaster over the next week+. It also seems clear that the Pacific Northwest and the Northern Rockies will be getting their first Winter-like systems. The only question is how much of the action we’ll see this far south. Here is a good illustration from the CFSv2 model showing above normal precip next week for the PacNW and N. Rockies:


It’s been awhile since we’ve really talked about a long-range seasonal forecast. Mostly because nothing has really changed. It still looks like a weak El Nino is developing that could favor California and the southern jet by mid to late winter. Latest CFS seasonal forecast shows an average start to the winter (November-January):


Things get more interesting for the second half of winter as above normal precip is forecasted for much of the west coast, extending inland into the Great Basin:


I wouldn’t put too much stock in these models. Long range seasonal forecasts do little more than just give a general idea of what can be expected, so take this all with a grain of salt. Time to at least start planning your snow dances and ‘pray for snow’ rituals!


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