It's Snowing!

It's snowing, not in Utah, but in the Alps.  And probably enough to ski in some areas.

Today's snow depth analysis for western Austria shows significant snow depths for September at mid and upper elevations.  

Source: https://avalanche.report/weather/map/snow-height

There are a few questionable observations, mainly due to the need to recalibrate (i.e., some stations strated with no snow but a measured snow depth of say 10 cm) but here's one that looks legit:  76 cm (30 inches) at Seegrube (1921 m) above Innsbruck.  

Source: https://avalanche.report

Here's a corresponding web cam view confirming that it looks legit.

Source: https://www.foto-webcam.eu/

The GFS forecast for 0600 UTC 14 September shows a great setup for heavy precipitation in the northern Alps of Austria and the Alpine Foreland (i.e., the upstream plains) of Austria and Germany with a deep closed low centered over the Balkan States and strong integrated vapor transport wrapping cyclonically (counter-clocwise) from the western Mediterranean and across the Black Sea Basin, Ukraine, Poland, and Germany.  That is a favored moisture-transport corridor for the northern and western Alps.   

The situation though in eastern Austria is quite serious as heavy precipitation in that area is expected to continue for some time.  Below is the GFS forecast valid 1200 UTC tomorrow showing continued precipitation in the Lower and Upper Austrian States.  

Todays Tirol Daily News in western Austria highlights the flooding in the east as well as the heavy snowfall and avalanche situation in Tirol in western Austria.  

I took a look at the Avalanche danger article and if my translation is accurate, it was a 70 year old hiker who was buried on Saturday and is still not recovered.  The second person was on the rescue team and was partially buried and with a right leg injury.  The rescue was called of that afternoon.  

Enjoy the Lake Stink and Clean Air While They Last

Smoke primarily from fires in southern California invaded northern Utah yesterday resulting in hazardous air quality for the Salt Lake Valley.  

Modis imagery from yesterday afternoon showed a corridor of smoke extending from multiple fires in the mountains around the Los Angeles Basin, across the Las Vegas area, and through western Utah to northern Utah. 

Source:  https://worldview.earthdata.nasa.gov/

PM2.5 at our mountain meteorology lab on the University of Utah campus crested at 120 ug/m3, at the upper end of what is considered to be unhealthy levels.  

Source: https://mesowest.utah.edu

Thankfully, those values have dropped into the single digits this morning, so all you notice as you inhale might be the lake stink, which I noticed in the avenues as I rode to work.

Breath easy for now because we're in a gap between the smoke from SoCal and smoke from OreIda (Oregon and Idaho).  The latest HRRR smoke forecast has smoke from the latter moving into the area later this morning and afternoon.  The forecast valid 2100 UTC (3 PM MDT) this afternoon shows near-surface concentrations in the Salt Lake City area near 60 ug/m3, not as high as yesterday's peak, but still at unheathy levels.  

By 0000 UTC (6 PM MDT), concnetrations > 60 ug/m3 have spread over the entire Salt Lake Valley and extend in a narrow region into southwest Wyoming.  

There are areas, however, where concentrations are > 100 ug/m3, so this has the potential to be another bad round of unhealthy air quality depending on your location and how this plays out.  Exercise this morning if you can.  

It's a Front!

Exciting news in the weather department this week with a bonafide cold front coming late Wednesday.  The 0600 UTC GFS has the cold front draped over northern Utah at 0300 UTC 12 Sep (9 PM MDT Wednesday), so right now the frontal passage looks to happen in the evening in the Salt Lake Valley, although give that a +/- 3h window given the inherent uncertainties.  

The pre-frontal airmass is fairly dry, so the models aren't going for much in the way of precipitation prior to or during the frontal passage, although there may be some high-based convective clouds and wind.  Perhaps the biggest concern will be fire-weather conditions.  The National Weather Service has issued a red flag warning for most of the lowland regions of Utah for 11 AM Wednesday to midnight Wednesday night given the wind and low humidity.  

Thursday will seem fall like. High temperatures at KSLC are likely to be around 72F. Somewhat elevated areas like the east bench will struggle to hit 70.  Think of it as a fast-forward to the wonderful temperatures of early October.  

Mountain snow?  It's a possibility, but the moisture-starved nature of this system means that nothing to a skiff is probably most likely and that will be on Thursday when the coldest air arrives rather than with the cold frontal passage. Below is our downscaled and combined EPS+GEFS ensemble forecast of the total snowfall through 0000 UTC 13 Sep (6 PM Thursday) showing a mean from the 82 ensemble members of about a half an inch and a maximum of 3.4 inches at at Alta-Collins. 

We don't have plumes working for this product yet, but I suspect that most ensemble members are not going for snow. I won't be surprised to see a little of the white stuff, but I also won't be surprised if we see some flakes with little to no accumulation.  

I'm hoping to do a deeper dive into this newer ensemble product soon, but I'll share a few details here, with the caveat that we're still testing and tweaking:

• The ensemble will replace our current NAEFS product and is based on all 51 members of the ECMWF Ensemble Prediction System (EPS) and all 31 members of the NCEP (US) Global Ensemble Forecast System (GEFS).
• Model forecasts are downloaded on a 0.25 degree latitude-longitude grid and downscaled to 800 meter grid spacing.  
• Snow-to-liquid ratio is based on a new algorithm that we have developed using data from 14 snow-study stations in the western United States, including at least 3 sites in northern Utah.  This should be a big improvement over what was in the NAEFS.
• Due to the use of the EPS, which is not available (for free) until 8 hours and 40 minutes after the EPS initialization time, this product will be available a couple of hours later than the NAEFS, but that's a tradeoff I'm willing to make as the EPS is the best ensemble product out there.  
• We are anticipating providing more and better graphics, although we're still trying to figure out what we can provide in a reasonable amount of time.

First Snow?

For a couple of days now the models have been suggesting that the coldest trough of the season so far will push into the Pacific Northwest during the middle of next week.  Below is the GFS forecast valid 0000 UTC 13 September (6 PM MDT Thursday) with the 500-mb low center over central Colordo and northwest Utah in the cold air behind the accompanying cold front.  

Precipitation chances for northern Utah vary depending on the model run.  We've been working on a new ensemble for snowfall forecasting over Utah based on the European Ensemble Prediction System (EPS) and the American Global Ensemble Forecast System.  It will have 82 members, downscaling to 800-m grid spacing, and a new snow-to-liquid algorithm based on machine learning with observations from 14 western U.S. snow study stations.  The run from 0000 UTC shows that the EPS control is producing a bit under an inch of snow at the highest elevations in the central Wasatch, a mean of up to 0.4", and a max of 5.7 inches for the 24-h period ending 0000 UTC 13 September.  

So, chances are probably more likely than not that we won't get much, but it's something worth keeping an eye on and a welcome change from summer weather.  

Meteorological Summer is Over

Meteorological summer, consisting of the months of June, July, and August, is thankfully over.  

In case you haven't noticed, temperatures have been climbing in the Salt Lake area in recent decades.  This summer at KSLC featured an average temparture of 80.3F, good for the 5th warmest on record.  The top 9 years are all in the 21st century.  

Yes, I know some of you don't like the KSLC site, but these trends do also reflect global warming and urbanization.  Both of those are real, and they are reducing the comfort and livability of Salt Lake City and probably a good portion of the Wasatch Front.  

To that point, there are continuous records from the Bountiful Bench site since 1975 and this summer looks like it will squeak in as the warmest on record (there are still 2 days that haven't yet been received, but the current average temperature is 76.8F, 0.4F warmer than the next warmest summer (2021).  

If you are wondering, the year so far rates as the 2nd warmest on record at KSLC, behind only 2018.