Wasatch Weather Weenies

Two very powerful cyclones, one from the tropics and one from the mid to high latitudes, are going to conspire over the next several days to break the jet stream.  The tropical cyclone is Typhoon Choi-Wan, currently southeast of Japan with maximum sustained winds of 110 knots.  Source: Joint Typhoon Warning Center The mid to high latitude cyclone hasn't formed yet, but is expected to develop over the Sea of Okhotsk on Wednesday.  The ECMWF HRES forecast below from Tropical Tidbits is valid 1800 UTC Wed Oct 7 and includes sea level pressure contours (black lines) and 500-mb height (color fill).  The big circle identifies the mid to high latitude system, the little circle Choi-Wan, which at this point is transitioning into an extratropical system, and the black line the upper level ridge downstream of these two systems.   Source: Tropical Tidbits By 1800 UTC Saturday 10 October, those two cyclones have merged into a massive 976 mb low over the Bering Sea....

Yesterday's high of 93°F at the Salt Lake International Airport was a record for the day but not really all that exceptional when you consider that the record high on the previous day (September 11) is 99°F and a couple days later (September 15) is 97°F.  Somehow September 13 has never gone out-on-the-limb for maximum temperature compared to the surrounding days.  Such are the realities of climate statistics.  That said, yesterday's maximum temperature was out-on-the-limb in terms of what was forecast.  Several days ago, we posted that the forecast for tomorrow (Sunday) was uncertain.  Some models, like the GFS, were bringing in a cold front on Saturday , resulting in much cooler weather for Sunday.  Others, like the ECMWF AIFS brought the front in during the day on Sunday.  I'm not sure if any called for the cold front to come in Sunday evening.     These days one can process the forecast from well over 100 ensemble forecasts to produce...

Watching from a distance, the official start of summer/Memorial Day Outlook is generally looking good for Utah.  For the most part it looks nice, with above average temperatures, although the models are hinting at a chance of some afternoon or evening showers and maybe even a scattered thunderstorm mainly over the high terrain over the weekend.  One example is below, which is the ECMWF forecast for 2100 UTC (3 PM MDT) Sunday 24 May with some showers over the Uintas, Tavaputs Plateau, and high terrain in southern Utah.   Models vary on the where and the when and so it's just worth keeping an eye on the forecasts and the sky when recreating.   Enjoy the long weekend.  

After about 7 weeks in Austria, I feel very detached from the weather in Utah.  I hear rumors and see evidence of an abysmally bad snowpack and have been sent photos from Little Cottonwood that look like late May rather than mid April.  A look at the SNOTEL data shows every site in the Wasatch, Oquirrh, and Stansbury Ranges at a record low water equivalent except the "plucky" Farmington Lower SNOTEL which is in 3rd simply because of what appears to be a spurious reading of 0.1".  Pretty sad.   However, I also noticed that there is a cold front coming through northern Utah tomorrow (Thursday) and it should bring a pretty good drop in temperatures.  The 0000 UTC GFS (I'm 8 hours ahead of  you and writing this in the middle of the night Utah time) shows the cold front draped over northern Utah at 1800 UTC 16 April (1200 MDT Thursday).  Salt Lake City is likely to be post-frontal at that time and seeing colder air moving in.   The front will...

It felt a good deal like spring yesterday with the sun now higher in the sky compared to its winter solstice minimum and mild temperatures from the valleys to the mountains.  Yesterday's high of 55 at the Salt Lake City airport was not exceptional, but combined with the brilliant sunshine, it was a beautiful day to be outside.   We have one storm on tap for the coming week and it's looking like a warm, wet, and juicy one.  It is associated with an inland penetrating atmospheric river.  The ECMWF HRES forecast valid 0000 UTC 25 February (5 PM MST Tuesday) shows the atmospheric river (bottom right panel) over the Bay Area curving clockwise through northern Nevada and Utah.  Integrated vapor transport (IVT) values in our area are > 250 kg/m/s, which puts is in the low end of atmospheric river categories, although that's a fairly high value for the western interior.   It's a relatively slowly evolving pattern. As can be seen above, the ECMWF puts o...

 Pretty good round of snow or should I say graupel overnight and this morning.  Accumulations in the mountains vary substantially and I'm not sure if Alta wiped their interval stake this morning or not as it looks like 4" on it, but the total snow depth is up 5 to 6 inches and the resort is reporting 8" as of 10 AM so I'll go with that.   Gauge measured water total is about 1.2".  I'm hearing rumors that's high, but anyway you cut it, it appears to be a high-density graupelfest up there.  Sounds like a good day of skiing in my book. Forecasts are still on for a colder storm tomorrow that will bring the Greatest Snow on Earth to both the mountains and the valleys.  Timing varies, with the HRRR bringing in a commuter special and the GFS a bit slower.  Strongly recommend that you check forecasts later today if you are commuting in the morning.  Quoting this morning's 5:23 AM issued Area Forecast Discussion from the NWS:  "Locally higher sno...

This post is dedicated to friend and long-time Wasatch Weather Weenies reader Kevin Moore who passed away yesterday after a multiyear battle with pancreatic cancer.   Kevin was a devoted husband and father, avid biker and skier, and lover of life.  He set an example of how to live life to the fullest when facing the greatest of challenges and uncertainties.  

Clouds and precipitation are back in the forecast, but unfortunately it's yet another warm event.   Below is the ECMWF HRES forecast for 1800 UTC 11 Feb (1100 MST Wednesday).  A weak, decaying atmospheric river extends across the northern Baja Peninsula and up the lower Colorado River Basin.  Elevated (but atmospheric river level) integrated vapor transport extends into northern Utah with south-southwesterly flow at 700-mb.  The 700-mb temperatures at that time are forecast to be about -3.5°C, which would likely a snow level near or just above the base of Park City (7000 ft).   A look at the HRRR-derived guidance for upper Little Cottonwood shows some dribs and drabs today, but periods of precipitation overnight, tomorrow, and tomorrow night totaling a bit over an inch of water and just under 10 inches of high-density snow through 5 AM Thursday at Alta-Collins.  The middle-left panel shows the wet-bulb zero height and our estimated melting layer i...

Our run of dry weather looks to continue through this coming weekend.  Since January 9, Alta Ski Area has recorded only 2.5 inches of snow.  If we make through Sunday, February 8 without any more snow, that will be 2.5 inches in a month (31 days).   The models are showing some signs of life next week.  The Euro, for example, has a cold front moving into northern Utah Monday night and Tuesday.  That's still a ways away so I'm not betting the farm on it, but a look at the Utah Snow Ensemble shows some signs of life in a number of the members.   If you are a glass half-full type, half the members produce 1.02" of water and 14" of snow by 11 PM Wednesday 11 February  If you are a glass half-empty type, half themembers produce less than that.  More than 90% of the members produce more than 2.5" of snow, so there's a better than 90% chance that we will better what we got over the past month!  So exciting! But for now and through the weeke...

The snow level is a critical variable for mountain weather forecasting, but it is both difficult to define and predict.   In fact, there isn't even an agreed upon definition of snow level amongst meteorologists or the public.  One might say it is the level above which precipitation is snow and below which precipitation is rain, but its just not that simple.  Precipitation doesn't just change from snow to rain at a given altitude.  Snow takes time to melt as it falls.  Different types of snow crystals melt faster than others.  Sometimes it is snowing but not accumulating on the ground due to melt.  What do you do when there is a mixture of snow and rain or drizzle?  Where do you put the snow level?  To begin, perhaps it is easier to begin with a description of the transition zone , the layer in which snow is warming, melting, and turning to rain as it falls.   The schematic below provides a simple conceptual model of the transit...

Sigh...what a start to December. First let's have a look at the northwest storm.  Some bit water totals so far.  For the 3-day period ending at 6 AM PST/1200 UTC today (11 December), more than 10" of liquid precipitation equivalent at many sites in the Washington Cascades including 14.2" at Paradise SNOTEL (agreeing well with the expectations from the previous post) and 18.6" at the Lynn Lake SNOTEL between Paradise and Snoqualmie Pass. Source: https://www.weather.gov/wrh/hazards Crystal Mountain is reporting this morning that WA-410 is closed between Enumclaw and Greenwater, essentially cutting them off given that WA-410 is also closed over Cayuse and Chinook Passes to the south.  Most of their web cams are down but sadly, even at 6800' at the top of the Green Valley Express where a cam is working, it looks like a net loss from this storm. Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams Could be worse.  Below ...

The overnight Utah Snow Ensemble forecast for Alta-Collins may be the crazies I've ever seen.  Most of the European Ensemble (ENS) members are producing little to no precipitation over the next 10 days including during during the period from 10-11 December (more on those dates in a minute).  The wettest ENS member puts out about 0.8" of water and 11" of snow.   Some members of the American Ensemble (GEFS) have very different ideas.  There are 31 GEFS members and 10 of them put out more than 1.5" of water just through 00Z 12 December.  Several more put out between 1 and 1.5" of water.  There are some that track with the ENS (hard to see but they are there), but many GEFS members are much wetter. What gives? I don't plot or attempt to look at forecast plots like our four panel synoptic diagnostic for all 82 members of the Utah Snow Ensemble.  Nobody has time for that.  So I'm going to start here with the ECMWF HRES forecast that serves as the E...

Twenty-four hour totals at the Alta-Collins automated observing site added up to 1.79" of water and 15" of snow, yielding a mean water content of 12%.  Snowbasin-Boardwalk came in with 1.26"/8"/16%.  As evidence of the wet, windy, and rimey nature of the storm, I couldn't verify our 70 mph forecast for Mt. Baldy because the sensor rimed and is no longer spinning.  The Utah Avalanche Center report this morning says that "at 11,000 feet the wind is absolutely ripping, with sustained speeds at 50–60 mph with gusts pushing into the upper 70s."  That's good enough for me.   The Alta-Collins snowstake photo this morning is one of the most comical I've ever seen.  Dense snow apparently carved by wind?  Perhaps with the flow wrapping around the Alta sign?  Who knows.  Come up with your own explanation.   Snowfall at lower elevations is certainly lower and probably a soggy mess between 6000 and 7000 feet (or higher), but that's just a g...

The mild first-half of November is now in the books.  The Salt Lake City International Airport came in with the warmest on record with an average temperature of 53.0°F. Source: https://xmacis.rcc-acis.org/ Last night's storm dropped about 4" on Alta Collins.  Not much to get excited about.  I haven't looked carefully, but the big winner appearred to be Ben Lomond Peak which got about 2.3" of water and had a total snow depth of 10" at 5 AM this morning.   The pattern continues to look splitty for the next few days.  Just an an example, below is the GFS 500-mb height (contours) and wind speed (color fill) forecast valid 2100 UTC 20 Nov (2 PM MST Thursday).  The Pacific Jet is forecast to be well consolidated near 150 W but split upstream of the North American coast into two branches, one moving through western Canada and the other over northern Mexico.   The various ensemble forecasts either keep us dry or give us some light amounts as sys...

A few days ago we discussed how the GFS was an outlier of the many forecasts for the storm that will come through northern Utah tonight (see Some Thoughts on Using Long-Range Forecasts ).  Specifically, it was producing a good deal more precipitation than most members of the Utah Snow Ensemble, which is derived from the US Global Ensemble Forecast System (GEFS) and ECMWF Ensemble (ENS).   Sadly, the latest forecasts continue to produce light precipitation and just a frosting of snow for Alta-Collins.  As an example, the six members of the Rapid Refresh Forecast System (RRFS) ensemble produce 0.25" of water equivalent or less and 3" of snow or less for Alta-Collins.   The latest HRRR and GFS are also below those thresholds.  The 0600 UTC GFS is down to 0.08" of water and about an inch of snow.  Dust on dirt if it verifies, although the snow might be somewhat wet and not cold smoke.   Sometimes an outlier forecast like the one from the GFS...

It's a rarity here in the Great Salt Lake rainforest, but it looks like we have a dry spell settling in that will last through the weekend.   The trough that brought us rain over the past few days is exiting the area today.  On Saturday, a low-amplitude upper-level ridge looks to be moving in, with no monsoon moisture or Pacific storms to be found in our area.   There is a brush-by system that flirts with northern Utah late Sunday but right now the precipitation from that looks not push into Utah through 0000 UTC 20 Oct (1800 MDT Sunday). That system could bring a bit of precipitation to northern Utah, mainly in the mountains, on Sunday night. For Alta Collins, for example, a bit over half of the Utah Snow Ensemble members produce no precipitation Sunday night, but a fee give us some light amounts Sunday Night, with a couple doing a bit better than that.  That's the main threat for precipitation over the next few days if you are hoping to add to aour alread...

Spring powder has been limited this season with April and early May coming in relatively dry, warm, and at times windy and dusty.   In April, Alta recorded 53.5" of snow, but 37.5" of that was on the first three days of April.  Automated obs suggest about 10" on the 6th of May and we gotten perhaps 4" yesterday.   So if you are still looking for a late-season powder fix, Sunday has some potential.  The models are hinting at a digging trough and front to be moving through Sunday morning.  The GFS, for example, puts the front right over nothern Utah at 1500 UTC 18 May (9 AM MDT Sunday).   Some of the models then call for unstable northwesterly flow thereafter, although the moisture, wind direction, and instability do vary some.   For Alta-Collins, the GFS puts out 0.94" of water and 9" of snow from Saturday evening through Sunday evening, most of which falls with the frontal passage Sunday morning.   The median forecast from...

It's been a dry start to April with only 0.16" of precipitation at the Salt Lake City International Airport, 0.15" of which fell on April 1st.  We won't see precipitation today, so that will be the tally through the half-way point of April, which will tie it for the 9th driest first half of April on record.  If you are wondering, there are five Aprils in which we had no measurable precipitation in the first half of the month, most recently in 1992.   The April Fools storm was a bigger producer in the Avenues Foothills than the airport, but my full-sun gardens are now starting to dry out.  We could use some April showers soon.   The likelihood of valley precipitation will finally be on the increase late Wednesday into Thursday as an upper-level trough digs into Utah from the Pacific Northwest.  The GFS shows the trough over central Idaho at 1200 UTC 17 April (6 AM Thursday) with some showers across northern Utah with the accompanying cold front....

Pickin's are slim this week for weather entertainment, although I'm hoping you are getting out for some time in the sun. On tap for tomorrow is the passage of what looks to be a mainly dry cold front, which is due to arrive tomorrow morning.  The overnight GFS forecast shows the front at 700-mb (10,000 ft or crest level) pretty much right over northern Utah at 1500 UTC 12 April (0900 MDT Saturday).    By 0000 UTC 13 April (1800 MDT Saturday), the flow has finally come around to west-northwesterly and 700-mb temperatures have dropped to about +4C over the Salt Lake Valley from +9C today.  So tomorrow will be cooler, but still mild, with valley highs in the low 70s and 9500 foot highs in the mid to high 40s.  Sunday the 700-mb temps will be down even lower and our machine-learned forecast for Little Cottonwood is calling for temps at Alta-Collins  and on Mt. Baldy to be near or just above 20°F.   Thus, although there may be some clouds around, it lo...