Wasatch Weather Weenies

Snowfall in the central Wasatch has been scant in recent days with a ridge in charge, but that will be changing tomorrow.   Currently a monster cyclone lurks over the eastern Pacific with clouds along the accompanying cold front pushing into California.  Hooray! This is, however, a splitting storm so the GFS forecasts the primary 500-mb trough and so called "synoptic forcing" associated with the system (also referred to as large-scale lift as indicated by the red upward vertical velocity contours in the upper left-hand panel below) to be over northern Mexico, SoCal, and Arizona at 1200 UTC 2 Feb (5 AM MST Friday).   However enough of the frontal remnants and instability move through northern Utah that the GFS does give us periods of snow showers, including Friday night as the remnants of the front have moved downstream and we are in unstable northwesterly flow.   A look at the GFS-derived guidance for Little Cottonwood shows mild conditions today, but ...

Following up on the prior post looking at record temperatures globally, let's zoom down to the state level. The first half of 2023 was actually fairly cool statewide.  In fact, the January–June mean temperature for the state was only 41.6F, making it the coldest January–June since 1984.  Source: NCEI By midsummer, I was thinking we might be able to finish the year below the 20th century average temperature, which is something that hasn't been done statewide since 1993.  However, the latter half of 2023 was quite warm.  In fact, for July–December the statewide average temperature was 55.3F, which ties for the 3rd highest on record just behind 2020 and 2021. Source: NCEI As a result, 1993 remains the last year that Utah's statewide average temperature has been below the 20th century average (note that 2011 tied the 20th century average but was not below).   Source: NCEI As can be readily seen from the graph above, we simply do not live in the climate of the 2...

Updating graphs for talks and classes now that the numbers are in and processed from 2023.  This is no surprise given what has been observed throughout the year, but 2023 was the warmest year on record.  Expect more records in the future.  Every year might not top the previous given that there is some variability from year to year, but the long-term trend is not our friend.

We have a weak storm moving through northern Utah today, after which we will have to hope that the advertised Groundhog Day pattern change comes through.   Today's storm is associated with a weak 700-mb trough that at 1200 UTC was located along the Utah–Nevada border.  As I type this at 7:50 AM, it is producing some valley rain here at the University of Utah, but so far not much at upper elevations.  The passage of the trough and then the unstable postfrontal period looks to produce some snow though for the mountains.  The GFS is going in for 0.45" of water and 6.2" of snow for Alta-Collins.  The HRRR is pretty unenthusiastic producing only 0.17" of water and just under 2" of snow.  Looking at the local radar, I was quite discouraged as the band ahead of the trough is nearly through with little accumulation in the central Wasatch (the southern Wasatch is doing better), but there are some instability showers behind the trough over Nevada, so maybe we ca...

This has been a ski season characterized by dramatic boom and bust cycles that are very clear in the snowpack water equivalent trace for Snowbird below.  Evident are two major storm periods from December 1 to 10 and from Jan 3 to 22 that added 6.4 inches and 8.6 inches of water, respectively.  Together, these two periods account for 15 inches of the total water equivalent in the Snowbird snowpack, or about 75% of the 20.1" total.   Source: NRCS During the January storm period, it is likely that we eclipsed the 100 inch mark on the Alta-Collins total snow depth stake, but due to some erratic reports, it was difficult to know with confidence if that was the case.  The time series of total snow depth at that site over the past two weeks is below and it shows 100" first being eclipsed late in the evening on January 13.  Shortly after that though, the measurements drop abruptly back down to 94 inches and then bounce around from the high 90s to 118 inches until t...

I spent the last week in Steamboat attending a meeting known as the Weather Summit and helping out a bit at Storm Peak Lab, a major meteorological observing facility at the top of the ski resort that is now operated by the University of Utah after it was transferred over from the Desert Research Institute.  We arrived late Tuesday, which turned out to be the only day we saw the sun.   The meeting was structured to allow for morning turns, which featured dust on crust Wednesday morning and cream on crust Thursday morning.  On Wednesday morning, as the airmass warmed, there was a transition in snow crystals from lightly rimed dendrites to rimed crystals. Steamboat has trademarked the phrase Champagne Powder (don't tell the French about this) and the morning snow was of such quality (although not deep).  By mid morning though, the dendrites were heavily rimed, as illustrated by the snow crystals on my shell. A lot of work has been done using data from Storm Peak La...

I'm up early and looking at the overnight numbers.  It was quite windy last night, so there is more uncertainty in the automated observations than usual, but from 5 PM yesterday to 5 AM this morning, the Collins gauge measured 1.91" (48 mm) of water and probably about 20 inches of snow (the 33 below is spurious).  The drop in total snow depth is odd, and that is one reason why I mention the uncertainty.   Assuming it came in around 48 mm in 12 hours, that's somewhat unusual.  Below is a histogram of twice-daily 12-h snowfall and water equivalent (called liquid precipitation equivalent in the chart) over a 22 year period at Alta.  48 mm or more happened 10 times in that period, so about once every 2 years.   Source: Wasserstein and Steenburgh (2024) Since those are twice daily measurements, we would probably expect a few more events than that for any 12-hour period, but still, it appears we were in unusual territory.  Combined with wind and a ...

Snow continues to stack up in the Wasatch and the red flag continues to fly for the backcountry avalanche danger. Utah Avalanche Center Forecast Summary Issued 13 January 2024 From 5 AM MST Wednesday to 5 AM MST Saturday, the Alta-Collins automated snow-depth sensor has ticked off 30" of snow, putting us half way to the over-under that I set at that time for the remainder of the storm cycle through Monday (see Shall We Set the Over Under for This Storm Cycle ?).  It also lifts us up to about 43" since Jan 9 and 68.5" since Jan 4.  These numbers are based on a mixture of data from the Alta Snowfall history and the automated snow stake so they may differ slightly from other estimates, especially given yesterday's wind.  I notice that the Alta web page is listing the storm total as 44", so they must be using Jan 9 as the start date.  As I write this at 7:20 AM, we are in a bit of a lull, but I say that with a caveat. There are still some snow showers around, includ...

I thought for today we could talk about how much snow we might get from this storm cycle. A storm cycle is a series of storms that occur in succession.  One has to decide when to start or end such a cycle.  There are two options for this one.  One is to start on January 4th, which is when we first started seeing snow after the holiday drought.  The other is to start yesterday, January 9, as there was nearly a 24-hour break in the snow.   I'll use both here. Jan 4 start: 38.5" so far (per Alta Snowfall History) Jan 9 start: 13" so far (per Collins automated measurements) These are a little inconsistent because the Collins automated measurements don't perfectly correspond to the snowfall history, but this is only for fun and we're not running a professional gambling house here, so I'll go with it.   How much will we add to these totals?  For the purposes of defining and end, I'm going to use 1200 UTC 15 January (5 AM MST Monday) as most models ...

Today is probably going to be the quietist of this work week.  For the most part, it is dry, although if you peer to the west from the University of Utah, you can still see some of our dendritic friends are still falling over the Oquirrhs.   Cams from the central Wasatch also show some flakes falling, although it's not adding up to much.   Source: Alta Ski Area This is what constitutes a break in our current storm cycle.  It will persist through tomorrow morning, and then Mother Nature will release the hounds.  It doesn't matter what elevation you live at in northern Utah, you are going to be experiencing significant snows through the weekend.   Let's get to it.  First, the GFS forecast calls for a frontal system to be moving across northern Utah by 0000 UTC 10 January (5 PM Tuesday.   It is likely that this will bring all-elevation snow to northern Utah for the evening rush hour and significant snows overnight for the mountain...

All caps seem appropriate given the overnight snowfall and the forecasts for the coming week, which can be summarized in two beautiful words: Cold and Snowy.   Based on the Alta-Collins automated observations, Alta has picked up 21" since the holiday snow drought ended on Thursday through 10 AM this morning.  This is all of the low-density variety with a water content of about 6%.  I might have preferred some higher density snow to start and help bury the old snow surfaces, but beggars can't be choosers given the lack of snow through the holiday period.   Additionally, the forecasts are spectacular.  More snow showers today, then a bit of a break before the next system drops in late Tuesday.  The GFS forecast valid 0600 UTC 10 January (11 PM MST Tuesday) shows a large-scale pattern with an upper-level risge well off the west coast and strong northwesterly flow moving over the northeast Pacific and into the interior western United States. ...

The stoke is high here at the Government Weather Control Office as we have finally been allowed to pull the "winter" lever for Utah and we are starting to see results.   First, we got a skiff of snow overnight at the University of Utah.  Very exciting! This snow is being produced by a closed low that is tracking to our south and is expected to be over western New Mexico by 1800 UTC (11 AM) this afternoon.   Normally I would just say today is no game changer but any snow right now seems like a game changer .  For Alta, the HRRR generates little to no snow with this system today, but the GFS produces about 4" of low density fluff.  I'll go for 1–3" for Alta by 5 PM. Be grateful if we get that.   But there's more coming.  Another weak upper-level trough moves into Utah tomorrow. Although it is weak, there's enough moisture and orographics in northwesterly flow that we continue to see periods of snow in the mountains tomorrow. That snow tape...