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A Very Juicy Storm

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I woke up this morning refreshed from an extra hour of sleep and excited to check out the storm.  First thing I did was pull up the radar and saw something that one doesn't see all that often. As full and complete coverage of precipitation as you can observe with the KMTX radar.   It's rare to see situations where there is complete coverage of radar echoes here, but there you have it.  Such a situation also allows you to see all of the places where the radar beam is blocked or partially blocked by the topography.  These produce bands of lower reflectivities or no reflectivity "down radial" or beyond the terrain feature as one moves away from the radar. Below is a schematic of this effect. Source: S ecrets of the Greatest Snow on Earth One can also see a ring around the radar that looks a bit like a donut.  This area of higher radar reflectivities is produced where the beam cuts through the melting layer where falling snow is warming, melting, and becoming r...
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RRFS Operationalization Update

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After many postponements, the Rapid Refresh Forecast System (RRFS) and RRFS Ensemble Forecast System (REFS) are still scheduled to become operational on November 3rd.   The RRFS and REFS are the latest "high resolution" modeling systems developed by NOAA for the National Weather Service.  I have high resolution in quotes because the reality is that many countries are now far ahead of the US National Weather Service in resolution and ensemble design. The RRFS and REFS have 3-km horizontal grid spacing and are based on the Finite-Volume Cubed-Sphere FV3 dynamical core developed by NOAAs Geophysical Fluid Dynamics Laboratory .  A dynamical core is basically the guts of a numerical weather prediction model as it represents the mathematics and numerics used to simulate the motion of the atmosphere on Earth.   In 2016, NOAA decided that the FV3 dynamic core would be the guts of their numerical weather prediction models , starting with the Global Forecast System (...
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It's Time to Pray for Snow

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Early snow often becomes weak snow so the snow-safety cognoscenti often tell me they'd prefer the snow hold off until November and then come in spades.   Right now, the first part of that wish looks like it will come through. Snow in the Wasatch is currently scant and confined to areas near and above 10,000 feet on north aspects.  The 1420 MST Mt. Baldy web cam showing upper Collins Gulch for example show fairly limited snow cover.   Forecasts through Halloween (i.e., the end of October) for the central Wasatch suggest maybe a few periods of precipitation Friday night or Halloween.  Halloween itself is looking warm and windy right now. The GFS forecast for 0000 UTC 1 November (1800 MDT) Saturday shows warm, southerly flow ahead of an approaching upper-level trough with some scattered showers and 700-mb (10,000 ft) free atmosphere temperatures near +1°C.   Thus, I expect to see more snow loss through the end of the month, with snow lingering mainly...
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Lots of October Water But Limited Snow

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For the second year in a row, October has given us above average precipitation, but limited snowpack. Below are the numbers for accumulated precipitation in the Great Salt Basin based on SNOTEL stations.  Median for October (Green line) is 2.5". Last year we got 4.2".  This year, through yesterday (October 24, black line), we are at 4.1".  We'll probably add a bit to that before the month is over.   Sadly, in both months, nearly all of this precipitation ended up in the soil rather than the snowpack, with little snowpack water equivalent at the end of last October and little presently this October.   That isn't to say there isn't any snow.  There are upper-elevation sites with a few hints of snow, but nobody is over an inch of snowpack water equivalent.   If you are wondering, Snowbird is at 0.5".  We're basically near zero in Collins Gulch.   Source: Alta.  Downloaded 1205 MDT 25 Oct 2026 On the positive side, the so...
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The Jet Stream Is Broken

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An upper-level trough is moving through Utah today (Thursday) and tomorrow, bringing with it some convective storms and eventually cooler temperatures.   Snow from the last storm is now almost gone.  The Mount Baldy webcam at Alta this morning shows the snow line has tretreated to nearly 10,000 feet with substantial losses even at upper elevations.  Although the Mt. Baldy summit is obscured, considerable rock and dirt is exposed in the Ballroom at center right of the photo.   Source: Alta.  Photo from about 7:45 AM 22 October 2026 Se, we are essentially starting over from here.  The situation for today and tomorrow is a bit of a crap shoot.  Today, snow levels will be too high for much in the way of accumulations.  Perhaps if we get a thunderstorm or thunderstorm complex today it can lower the snow levels down onto our highest peaks, but the RRFS ensemble shows the wet-bulb 0.5 level sitting over 11,000 feet until later this evening....
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Fall and Winter

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October is a great month in Utah and this weekend has been a beauty.  Fall and winter seasons were in evidence this morning in Big Cottonwood Canyon.  Although past peak, golden aspens were still in abundance.   Then there's the snow on the high north aspects. I'm curious to see how much of that snow can survive this week.  Under clear skies, it can be hard to melt snow this time of year on shady north aspects, but the models are advertising a late-monsoon moisture surge later in the week with mild 700-mb temperatures, cloud cover, and snow levels that could be above 10,000 feet on Thursday.    That's a recipe for rain on snow to at least 10,000 feet so maybe we will lose some of that high north snowpack before the trough swings through and temperatures fall.   We shall see...
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RRFS Operationalization Postponed (Again)

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The operational implementation of the Rapid Refresh Forecast System (RRFS) and RRFS Ensemble Forecast System (REFS) has been postponed again to November 3rd.  That operationalization also includes sunsetting several ancient NCEP forecast systems including the NAM, HREF, SREF, and HiresW.  Those modeling systems will live for a few more days.   Per the NCEP Service Change Notice Update released on October 15, the delay is to include changes to precipitation type products produced during model postprocessing due to overforecasting of freezing rain and underforecasting of ice pellets.  These are issues that have been a thorn in my side for the HRRR and RRFS snow products for some time.   In the case of overforecasting freezing rain, we've seen this frequently in the HRRR and the RRFS.  An example is below.  Apologies for the lack of a map, but the black circle is Alta and the area of pink , purple, and light blue around it denotes an area of fo...
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