Wasatch Weather Weenies

We are excited to share that the Utah Snow Ensemble is now available on  https://weather.utah.edu and has replaced the old NAEFS product. The Utah Snow Ensemble is an 82-member ensemble for predicting snow over the contiguous western United States based on the ECMWF ensemble (ENS) and the US National Centers for Environmental Prediction Global Ensemble Forecast System (GEFS), with 51 members coming from the ENS and 31 from the GEFS.  The forecasts are provided in 6-h intervals out to 240 hours (10 days).  A summary of the data and methods and graphics is provided below.  Precipitation Downscaling Precipitation from all ENS and GEFS members is downloaded on a 0.25°x0.25° grid and downscaled to 800-m grid spacing to provide higher resolution guidance.  The downscaling assumes seasonally varying climatological precipitation-altitude relationships.  See Lewis et al. (2017) for more information.  Such a technique produces improved forecasts, but it does n...

Just outside my window I hear the late September dogs And I understand their warning I understand their song Since you left I feel the change in the air And night after night I'm searching for mercy everywhere So I wake in the street and I call out your name I shout to the sky please Come on let it rain Let it rain down on me Let the rain touch my hands Let the rain set me free - Melissa Etheridge Plenty of insanity in the weather world currently with Hurricane Helene providing a sad reminder that it is water, not wind, that causes most tropical cyclone impacts.  That said, there is insanity here as well.  Yesterday, KSLC reached 96°F.  Not only is that a record for the day, but it is the highest temperature ever observed after 19 September.  Below is a listing of the 10 highest maximum temperature observed at KSLC from 16 September to 15 October.  The record is 97, but that was on September 19th, 1956, a full 10 days earlier in the calendar.   About t...

 Ron Perla, an pioneering avalanche researcher and Little Cottonwood legend, was recently named a distinguished alumnus of the University of Utah Department of Atmospheric Sciences. As described in this College of Science online article , Ron was an Alta Ski Patroller and US Forest Service Snow Ranger in the 1950s and early 1970s who researched slab properties, avalanche rescue methods, etc.  He commuted back and forth from Alta to the U to complete his classes in meteorology and conduct his research.  Ron was also a mountaineer who established first routes on Mt. Robson (Canadian Rockies), Grand Teton, and our own Lone Peak in the Wasatch.   Ron Perla, US Forest Service, 1968 Alta skiers may be familiar with a run called "Perla's" on Mt. Baldy, which is named for Ron.  Ron tells the story of how he survived an avalanche on Mt. Baldy in 1967: “In 1967, I was working as a USFS Snow Ranger near the top of Mt. Baldy,” Perla says. “The cornice broke off prematu...

 We're getting closer to having a replacement for the NAEFS with a lot of big upgrades including replacing the Canadian with the ECMWF ensemble, a new snow-to-liquid ratio algorithm, more and better graphics, etc.  We're thinking of calling it the Utah SnowCast Experimental Ensemble (USCEE, or "You Ski").  If you have other ideas, let me know.  Naming rights available for a large enough donation.   Below is our new time-series layout.  I'm plotting Berthoud Pass, CO since they hve a shot at some snow in the near future.  There's a huge amount of information in these plots.  Probably more than most people want to see, but this is an experimental product and we're trying to understand the capabilities and limitations.   More soon.  This is one reason why blogging has been light lately.  

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 c...

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 in...

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 hi...

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 ma...

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...