Rain threat continues through Saturday, then drier and warmer before Fall arrives late next week.

Thursday, September 12, 2013 at 8:11 am

Friday AM update:

Not too much new to speak of… We will see off and on rain showers today and tomorrow in Northern Utah before we start to dry out on Sunday. A weak cold front will cool us off from the 80s to the 70s on about Wednesday of next week. We’ll warm back up again before what is looking like a much strong trough dives into the Great Basin next weekend (September 21-22). This trough is a long ways out, but both the GFS and the Euro models are currently forecasting a dramatic drop in temperatures and a chance for snow in the high elevations (above 8K feet). We’ll have to keep an eye on this over the coming days . . .

Previous discussion:

Low pressure system responsible for bringing days of rain to the area, especially Southern Utah, is slowly moving north roughly along the Nevada-Utah border. This low will spin just to our west through Saturday before finally lifting north and east. Expect periods of rain throughout the next few days, some of it heavy. Afternoons will be the most likely candidate for heavy rain with the combination of heating and moisture.

This low has caused widespread flooding in Southern Utah over the past few days. Normally dry slot canyons are now running with water throughout canyonland with rivers near or above flood stage. Last night, an upslope flow along Colorado’s Front Range brought up to 7″ of rain from Denver north to the Wyoming border, with extensive flooding reported. Northern Utah likely won’t see quite that much rain, but we will see more showers on top of already damp soil. Burn scars may be susceptible to flooding issues through the weekend.

We will finally dry out on Sunday into next week with warmer weather for the early week. Things get a little more interesting later next week as a large scale trough, our first of the Fall season is expected to develop and drop into the Pacific Northwest and Northern Rockies. We mentioned a few days ago that this should bring us at the very least some clouds, breezes, and more Autumn-like temperatures. That still holds. However, yesterday’s 12z run of the ECMWF (Euro) showed an unseasonably deep and cold trough digging into the west around the 21st of September, coincidentally the astronomical and official beginning of Autumn. This is what the EC looked like:


You can see how cold and deep this trough is over the West. Unfortunately, this morning’s 00z model backed off on the idea a bit. Essentially, if the cold, deeper version were to verify, we’d likely see much colder weather with our first measurable snowfall in the Wasatch. However, if today’s run or the GFS verify, we’d likely see cooler, breezy weather with a chance for a dusting on the highest peaks. The smart money is on this morning’s run. But still, it is our first real chance to see a little white stuff up high. Of course, snow in September is useless except as a teaser for winter. Perhaps for the fishers, hunters and mountain bikers out there — it’s best if we wait just a few more weeks for winter to arrive anyway.

Main message is we are at least guaranteed to see more Fall-like weather as we head into the second half of September. This is obviously very typical as we are now approaching Fall (go figure, right?). For you strange warm weather lovers out there, we normally see an Indian Summer in October, so don’t say goodbye to the 80s quite yet.

More on this developing pattern as we get closer and the models reach some kind of consensus . . .


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