Wasatch Weather Weenies

State epidemiologist Dr. Angela Dunn lives a few blocks from us.  Earlier this week, her address was released on social media and groups gathered at her house yesterday in protest .  This is a diabolical act of harassment and intimidation that cannot stand.  Picketing of this type at someone's residence is also likely illegal.  I am not sure what codes apply within the Salt Lake City limits, but Salt Lake County has an entire section of code dedicated to this issue and classifies it as a Class B misdemeanor.   Dr. Dunn is not an elected official.  She is a civil servant who has had to do a  very difficult job.  In the tweet below, her neighbor, Mark Cronin, shares views that are similar to mine.   Here's what neighbor, Mark Cronin said to the group. Full story, including response from the medical community, and Dr. Dunn on @KSL5TV at 5&6pm. pic.twitter.com/UpZ4s4DHwA — Mike Anderson (@mikeandersonKSL) October 29, 2020   ...

Although inversion "season" doesn't begin until November 1, the reality is that we're in a pretty good inversion right now in late October. Here are a couple cherry-picked observed temperatures at 7 am this morning: Salt Lake City Airport (4226 ft): 30˚F Snowbird SNOTEL (9177 ft): 40˚F This morning's sounding from the airport shows a surface temperature of 32˚F.  You have to go all the way up to 13,397 feet (about 600 mb) to find a colder temperature.   Source: SPC That's where the free-atmosphere freezing level is.  You can find pockets of sub 32˚F air at the surface across northern Utah where overnight cold pools developed or cold air from the weekend cold surge persists in valleys, basins, and canyons, but beyond that, there's a mild airmass now in place.  On Monday, Alta was making snow.  Look closely and you can see the guns running in Collins Gulch.   Source: Alta.com This morning?  It looks like they've either given up are are doing it...

Bit of a late post for me today due to other pressing concerns.   Portions of the western United States are in the grips of an impressive cold surge for late October.  For Salt Lake City, it's not as far out there as last year's, when we had minimum temperatures of 17˚F and 14˚F on October 29 and 30, but it's still cold.  Last night's minimum was 19˚F, a record for the day and the 2nd earliest 19 on record (the earliest was recorded on October 25th).   For those of you on the Wasatch Back, valley temps dropped to below zero near Park City including -5˚F at Silver Creek Junction and -4˚F along SR-244 at Meadows.  It also got down to -5˚F at the top of the Snowbird Tram.   Alta-Collins' snow-depth sensors were pretty finicky overnight and today.  There could be a couple of inches of snow there, or maybe a 115" base.  I'll let you decide if you want to go up and check it out. Peter Sinks normally brings the goods in patterns like these...

This weekends storm looks to be "meh" like the last, although we might see a few flakes in Salt Lake City.   The models agree on a cold frontal passage through northern Utah on Saturday with some precipitation in it's wake eventually moving in late Saturday or Saturday night, but there are differences in the timing and amount of precipitation depending on the track and intensity of the upper-level trough.  As things stand now, this looks to be a "central Wasatch skipper" with the odds and amount of precipitation greater in the mountains to the north, south, and east, as illustrated by our downscaled SREF product below, covering the period ending 0000 UTC 27 November (6 PM Monday).       I'd be perfectly fine with this storm skipping us and going to Colorado as they could use the fire-fighting assistance and a small storm will do us no good for skiing at this stage.   In terms of snowfall, odds of more than an inch are about 50-60% in the uppe...

 It's October 22nd.  I repeat October 22nd.   Yesterday, the East Troublesome Fire in Grand County Colorado exploded.  It's worth taking a look at a couple of fire maps to illustrate the explosive growth. At 2055 on the evening of October 20th, the fire perimiter covered 19,086 acres.   At 0030 hrs on the evening of October 22nd, it was 125,602 acres.    I am now seeing reports that the fire has jumped the Continental Divide to the east slope of the Front Range. Radar imagery from yesterday shows no echoes associated with the fire at 1911 UTC (1311 MDT). Source: NCAR/RAL By 2057 UTC (1457 MDT), echoes extended from the fire area near Granby (GNB on the map below across the Continental Divide, an indication of both explosive growth and strong flow.   Observations from Kremmling, just upstream of the fire, over the past five days show that yesterday was the warmest day of the period, with the lowest relative dewpoints and relative hum...

With the end times near, today would be a good day to get out and enjoy the mild fall weather.  It should be sunny and warm by seasonal standards.  Tomorrow will be colder, a harbinger of things to come.   The first blow to mild fall weather comes this evening in the form of a cold front that the HRRR forecasts to be moving through Salt Lake City at around 0400 UTC (10 PM MDT).   The front will spread across Utah tonight and tomorrow, with strong northerly to northwesterly flow and colder air in its wake.   The National Weather Service forecast highs for the Salt Lake City International Airport today and tomorrow are 72˚F and 52˚F, respectively.  A bit of a breeze will make the change feel even more dramatic.  Then the weekend is "interesting."  First, we have a brushby system on Saturday.  The GFS forecast keeps most of the precipitation to our north and northeast, with just a few light valley showers and high-elevation snow s...

I frequently see people on social media talking about a medium- or extended-range forecast produced by the GFS.  Alternatively, they might talk about a forecast produced by the ECMWF Integrated Forecast System, the so called "gold standard" of medium- and extended-range forecasting and commonly referred to as the "Euro" or ECMWF. Don't take the bait.   It's not that those forecasts aren't useful.  They can be, but only when viewed with the range of possibilities produced by an ensemble forecast system.   The reality is that a GFS forecast (or a "Euro" forecast) is only one solution.  It represents one of many possible outcomes based on what we know about the state of the atmosphere, ocean, land-surface, and ice cover when we start the model.   As a result, the GFS produces a credible forecast, one that is physically realistic and believable.  It just might not verify with great veracity. Let's take a look at the GFS forecast initialized ...

Although we've seen a substantial decrease in smoke in recent days, a look at the sky sometimes shows a bit of smog due to pollution along the Wasatch Front.  Here's an example from yesterday afternoon. Inversion season is coming, and while it isn't here yet, on some days we're starting to see that the decrease in daytime heating due to the shorter days and lower angle sun is resulting in decreased mixing of the lower atmosphere and a bit more particular matter buildup.  During the day, energy from the sun warms the ground and in turn the lower atmosphere, leading to turbulence and mixing.  The layer in which this occurs is known as the convective boundary layer , which I'll abbreviate as CBL.  The maximum depth of the CBL, typically achieved in the afternoon, depends on many factors, one of which is the amount of incoming energy from the sun.   During the summer, the CBL in Utah can be very deep, sometimes extending to more than 10,000 feet above the ...

After days of anticipation, yesterday's valley rain and skiff of mountain snow was a nice change, but pretty meh.  Water equivalent precipitation observations reported to the National Weather Service in the Salt Lake Valley maximized at 0.39" at the City Creek Water Plant and included 0.29" in the upper Avenues, 0.19" at the Salt Lake Airport, and 0.14" at Olympus Cove.  Pretty paltry amounts and enough to wet the upper soil layers, but it remains parched below.   In the central Wasatch, Alta reported 1.3" of snow with 0.23" of water equivalent and Brighton 2" of snow with 0.35" of water.  Dust on dirt and probably for the best as below-average precipitation looks to persist as the storm track remains to our north the next couple of days and the western ridge redevelops thereafter.  Hopefully Mother Nature is saving it for November.   Although it would have been nice to get a better soaker, yesterday afternoon was spectacular. Smoke-free fall...

You'll be hard pressed to find a nicer Saturday than today.  Low humidity.  High temps in the 80s.  Low angle sun.  Fall colors at low elevation.  Spectacular.   Just the pick me up I needed!  Get out and enjoy.  

There's a saying amongst meteorologists that the severity of a storm is inversely proportional to the hype preceding it.   I've seen tweets about this weekend's storm and a possible pattern shift going back about 10 days.  However, at that time, and as recently as a couple of days ago, the ensembles produced a wide range of possible outcomes from very little snow to quite a bit in the central Wasatch.   The latest forecasts lean not toward a bit storm, but instead toward a solution with the heaviest heaviest precipitation going to our friends to the north including the Central Idaho Mountains and Teton Range.  We get a frontal passage and cooler air, but less precipitation.  For the 24-hour period ending 0000 UTC 12 Oct (1800 MDT Sunday), the ECMWF IFS gives valley locations in northern Utah only 0.2 to 0.3 inches of precipitation, which would fall as rain.   Source: Pivotal Weather That's one of the wetter models.  The GFS is between 0....

Chances are you've been hearing about the pattern change we are going to experience this weekend for about two weeks.  Chances are you've been dreaming of it for at least two months.  It's going to happen, but for mountain snowfall, there are some flies in the ointment.   As discussed in the previous post, the medium range forecasts from a couple of days ago exhibited a good deal of spread for precipitation and snowfall at Alta.  The North American Ensemble Forecast System (NAEFS) exhibited three solution clusters, one that produced light accumulations (two inches or less), a second that produced moderate accumulations (about 6-12 inches), and a few others that produced considerably more.  This reflected uncertainty in the speed and depth of the upper-level trough as it moved through the western United States. There has been some convergence of the large-scale solutions produced by the models since then.  As shown by the thumbnails of the 32 members of...

In late September, the National Weather Service upgraded its Global Ensemble Forecast System, GEFS, which should lead to improved medium range forecasts for ski season.   The upgrades include the following: GEFS is now based on the new "FV3" dynamical core Horizontal grid spacing decreased from 33 to 25 km Members increased from 21 to 31 members Use of new techniques to produce initial conditions for the members For more details, see this NOAA Press Release or this Service Change Announcement .   Time will tell if these upgrades lead to significant improvements, but I'm optimistic they will help some.  The increase in membership and new techniques they are using to initialize those members should help improve the spread of the ensemble, providing better probabilities of precipitation thresholds.   What we don't know is how these changes are going to affect GEFS biases at individual locations and, in turn, how those biases will affect our downscaled fo...

Here are a couple of items to distract you from pandemic-fueled political coverage today.   Storm Alex Rakes Northwest France A powerful midlatitude cyclone named Alex (such storms are named in Europe) moved across northwest France overnight, bringing damaging winds.  Below is a Meteosat loop showing the development of the system and its movement Bretagne and Normandy.   Source: CIRA The UK MetOffice analysis for 0000 UTC 2 October shows the low centered over nothwest france with a central pressure of 969 mb.  Source: UK MetOffice Peak wind gusts relayed through some of my channels by Tim Hewson of the ECMWF include 186 km/h (116 mph) on Belle-Île, and island just off the south coast of Bretagne, 157 km/h (98 mph) in Groix, 142 km/h (88 mph) in Granville, and 135 km/h (84 mph) in Sarzeau.  These are sites on or very near the Atlantic or English Channel coasts.  However, even inland, Cholet had a gust of 129 km/h (80 mph). Northern Utah Radar Upgra...