Wasatch Weather Weenies

Things came together nicely yesterday and continue this morning in the form of lake effect to give us a pretty good storm for the central Wasatch.  The Utah Avalanche Center reports totals in the central Wasatch of 10-15" of cold smoke (5-6% water content) through 5 am.  Through 6 am, the Alta-Collins automated snow-depth sensor has recorded 14", Canyons-Daybreak 15", and Deer Valley-Ontario 10".  To the north, Snowbasin-Boardwalk is clicking in with 11".  Perhaps Mountain Dell has gotten enough that with some effort the Nordic track can be set.  I'm always amazed at what the groomers can do there.   At around 11 UTC (4 AM MST), precipitation features began to form over the Great Salt Lake (apologies for the old lake outline in the loop below) and began to train off into the north Salt Lake/east Salt Lake Valley area.  The lake effect continues through the end of this loop at 1356 UTC (0656 AM MST).   My expectation is that these lake-ef...

I've felt quite conflicted the past week as we have a robust snowpack for late November, but ski conditions at the resorts have been scratchy, whereas a multitude of crusts and other less-than-desirable snow surface have predominated in the backcountry.  Touring on Saturday, I had 3 good turns and 97 bad ones (that's an estimate).  Far be it from me to complain given the healthy snowpack, but we need snow.  The good news is we are going to get it with an upper-level trough and associated frontal system moving through the area today and tonight.  The 0600 UTC initialized GFS forecast valid 2100 UTC 28 Nov (2 PM MST Monday) shows the upper-level trough axis over Nevada, the 700-mb trough over northern Utah, and a mixture of orographic (i.e., mountain induced) and frontal precipitation over northern Utah and extending upstream across Nevada, Idaho, and Oregon.   The corresponding GFS time height section shows moisture aloft this morning with dry (lower relativ...

 By popular demand, output from the the European Center for Medium Range Weather Forecasting (ECMWF) High Resolution Forecast (HRES) is now available on weather.utah.edu. The HRES goes by many names.  It is sometimes called the ECMWF, the EC, the Euro, or even one of those with "Deterministic" added to the end (e.g., the EC Deterministic).  On weather.utah.edu I am labeling it the HRES because that is what the ECMWF calls it. The HRES is a global forecast produced using ECMWFs Integrated Forecast System (IFS) with an effective grid spacing of approximately 9 km.  It is the highest-resolution and on average the most accurate global forecast produced by any forecast center. Much is made about the rankings of the various forecast models, but it is a bit like the NFL standings.  Some teams are better than others, but on any given Sunday, upsets happen.  One metric of model performance is the 5-day forecast 500-mb geopotential height anomaly correlation coeffic...

I've been watching the models over the past few days hoping of a clear sign of a major storm during the Thanksgiving weekend, but one does not exist.  Most of the models and ensemble members say we will see little to no precipitation, but there are a small number that give us a bit more love.   The GFS is one of the models that gives us a bit more love.  Below is the 0600 UTC initialized GFS forecast valid 1200 UTC (5 AM) Wednesday (Thanksgiving Eve).  It brings a short-wave trough that most of the models and ensemble members keep to our north a bit farther south and across northern Utah.   As a result, the GFS does generate some snowfall for northern Utah, especially in the northern Mountains, on Thanksgiving Eve including about 0.49" of water equivalent at Snowbasin and 0.47" at Powder Mountain.  Amounts are lower in the central Wasatch.    That would translate into about 7 inches in the northern mountains and 4 inches in the central W...

Sure Alta, Snowbird, and Snowbasin are opening today, but it is the Great Lakes snowbelts that are getting the goods today.  It's always a "good" sign when Jim Cantore comes to town and he measured 32" south of Buffalo in Hamburg, NY this morning.   32” and counting in Hamburg, NY pic.twitter.com/WEcO8teIWs — Jim Cantore (@JimCantore) November 18, 2022 Satellite and radar imagery at 1445 UTC (945 AM EST) showed an intense long-lake-axis-parallel (LLAP) snowband extending along nearly the entire length of Lake Erie and across the southern portion of the Buffalo Metro Area.  Another LLAP snowband extended downstream of Lake Ontario into the western Adirondacks.  LLAP snowbands can develop during flow along the long axis of elongated lakes like Lakes Erie and Ontario.  They tend to produce intense snowfall rates, sometimes exceeding 4 inches an hour (we measured up to 5.5" in an hour once on the Tug Hill Plateau east of Lake Ontario and I have seen unofficial...

It was a great run over the past couple of weeks with some of the best early season skiing seen around here in the past 30 years.   Coverage after last week's storm was quite impressive and for November 12, likely the 2nd best since 1990 based on long-term observations from the Snowbird SNOTEL.  Pent up desire was apparent in both the backcountry and at the resort with hoards of skiers ascending into the Cottonwood Canyons backcountry and resorts.   OPENING DAY PART TWO!! @Reilly_kb93 pic.twitter.com/YzPToy7PDe — UteParodyDaddy 🥃 (@utedaddy) November 12, 2022 Sadly, the powder party is over for now as the pattern is shifting fairly dramatically.   Call it "Fall Break."  The GFS forecast below shows a high amplitude ridge developing along the west coast of North America early this coming work week (forecast below for 5 PM MST Tuesday).   This ridge will dominate the upper-level flow and the relatively dry, cold northerly flow downstream...

This is a reproduction of a report prepared and presented to the Great Salt Lake Advisory Council at their 14 September 2022 meeting.  It has been modified for formatting, to remove personal information, and to correct a few typos.  I thank students and colleagues whose research or comments contributed to and improved the manuscript. Contributions of Lake-Effect Periods to Precipitation and Streamflow in Northern Utah W. James Steenburgh Professor of Atmospheric Sciences University of Utah Executive Summary Lake-effect periods are sometimes produced during cold-air outbreaks over the Great Salt Lake, contributing to snowfall and streamflow in the surrounding mountains. Prior research indicates that precipitation produced by lake-effect periods is greatest south and southeast of the Great Salt Lake and contributed 5.1-8.4% of the cool-season (16 September – 15 May) precipitation at observing sites in the Cottonwood Canyons and Oquirrh Mountains from 1998–2009. During this study...

So much talk about a red or blue wave last night, when it was really a great white wave that won.  The numbers from Alta are very impressive and means a climatologically deep early season snowpack will control upper elevations of the central Wasatch for the next few weeks. Let's talk some numbers.  The storm-total SWE and snowfall at Alta-Collins (so far) are 3.38" and 24" respectively.  The 24-hour and 12-hour SWE for the period ending at 6 AM this morning was 3.06" and the 12-h total for the period ending at 6 AM were 3.06" and 1.99".  These are big water totals at the upper ends of what happens at Alta during the winter.   Observations from the last 24 hours also show a peak hourly SWE of 0.40" (I consider anything above 0.30" to be exceptionally heavy snowfall), which was accompanied by a 4" increase in snow depth on the interval board, and .86" in 3 hours.   Source: MesoWest This snow was mostly high-density base builder.  The mean ...

Mother Nature is serving appetizers this morning before the main course tonight and tomorrow in the form that I can only describe as an Early November Storm of Our Dreams .   The surface cold front moved into the Salt Lake Valley last night, passing over the University of Utah at about 0530 MST this morning and producing a rapid drop in temperature.  Temperatures have subsequently fallen into the high 30s.   As of 1441 UTC (0741 MST) this morning the front was very near Point of the Mountain with north winds and temps near 40 in Bluffdale and Draper, but southerly flow and temps near 50 around Point of the Mountain and Saratoga Springs.  Crest-level winds in the central Wasatch remain southerly or southwesterly on Hidden Peak, Mt. Baldy, Cardiff Peak, and Reynolds Peak.  The front has not arrived in the central Wasatch, so snow levels remain high.  It is 32–35˚F at observing sites near the base of Alta for example.  Radar imagery at 1440 UTC ...

 Red sky at morning sailors take warning? Actually, the sky looked sort of purple today, as if I woke up in Mordor.  I knew something was up when I woke in the night and the house was shaking.  Indeed it was an impressively windy night in the lowlands with several sites reporting gusts of 60 mph or more including 68 mph near Point of the Mountain and 65 at the intersection of I-80 and SR-201 in the Salt Lake Valley.   The instigator of this big blow is a deep upper-level trough that is amplifying off the Pacific coast.  The interaction of this feature with the Sierra Nevada is resulting in the development of low pressure over the Great Basin and a strong pressure gradient over western Utah.   I'm a little surprised it blew so hard last night based solely on the large-scale analyses, suggesting something else is happening, but my time is limited for proper sleuthing and I'm more interested in the potential for snow.   The upper-level trou...