Wasatch Weather Weenies

You don't see this every day, but for the 24-hour period ending at 1200 UTC (0600 MDT) Sunday, all of Utah received measurable precipitation, at least as estimated by the National Weather Service's Advanced Hydrologic Prediction Service. Source: http://water.weather.gov/precip/ The Salt Lake City forecast office put together the graphic below summarizing the remarkable increase in river flows during the event. Source: NWS How about that Beaver Dam Wash in Arizona, which went from no flow to 11,800 cubic feet per second! Source: NWS In case you are wondering where Beaver Dam Wash is, it runs along the Utah Nevada border and eventually empties into the Virgin River in NW Arizona (see the BEA in the map below). Source: NWS

A sprinkling of snow in upper Cardiff Fork this morning serves as a teaser for the approaching ski season.   Some aspens are pre-peak, others past peak, so enjoy the fall colors while they last.

It's been impressively wet overnight and thus far today, especially in western Utah.  Twenty-four hour accumulations for the period ending within 1 hour of 1841 UTC (1241 MDT) show several locations in the Dugway area with more than an inch of rain (ignore sites with 0 or very light accumulations as these are almost surely bad).  The 1.22" maximum observed at a couple of sites represents about 15% of their 7.75" annual average.  Accumulations in the Salt Lake Valley and surrounding area are generally around 0.6", with more to come. Source: MesoWest A south–north oriented precipitation band is slowly moving across the Utah and is likely to be bringing periods of rain, possibly heavy at times, this afternoon and during the Ute football game this evening.   The forecast from the High Resolution Rapid Refresh (HRRR, courtesy NOAA's Earth Systems Research Lab), which will become operational in the near future and provide short-range forecasts at 3-km gri...

There's not much change in the forecast from yesterday except that the storm is moving in just a bit slower.  The net result of this slight delay is that the 1200 UTC model runs generally put the heaviest precipitation directly over Rice–Eccles Stadium for tomorrow's football game.  The NAM, for example, is putting out more than 0.5" of rain from 6–9 PM tomorrow.  Kickoff: 6 PM.  Bring the galoshes. If you are interested in tracking the moisture surge, see the NOAA Earth Systems Research Lab's GPS meteorology web site .  They use delays in GPS satellite radio signals to estimate the water vapor content of the atmosphere (sometimes called "precipitable water").  Observations from Needles, CA, for example, show a dramatic increase in precipitable water over the past 24-hours.   Meanwhile in Salt Lake City, we're starting to see things moistening up from the dry air that was in place yesterday (hence the developing cumulus cloud cover this aft...

Although there remain some differences in timing and details between the models, we remain on track for what could be an extremely wet period in northern Utah and other portions of the state.  Given the heat today, I'm officially declaring the start of "Outlier Mode." The record high for today is 92ºF, which is also the latest 92ºF day in the record books at the Salt Lake City International Airport.  As of 1:35 PM, it was 89ºF at the airport.  I'm guessing a 91ºF max is probably most likely, but maybe we can squeeze out a record. Tomorrow there's a chance of showers and thunderstorms as the upper-level trough approaches, afterwhich your ark-construction needs must be complete as the system taps into juicy air over the eastern Pacific and Gulf of California.  The forecasts below show the forecast integrated water vapor transport produced by the GFS (bottom) and the average of all members of the Global Ensemble Forecast System (GEFS) on Saturday morning.  Ther...

Although there has been quite a bit of variation between the models concerning the details, especially timing, things appear to be coming together for what should be an exciting period this weekend. As discussed in the previous post, the precipitation accompanying the Pacific cold front that made landfall along the Pacific coast overnight is expected to die off as the system moves inland.  This is, however, a case of life after death as the cold front will be rejuvenated once the pre-frontal southerly flow begins to move past the Sierra Nevada, enabling juicy air over the eastern Pacific and Gulf of California to push into the Intermountain West. The GFS loop below, which shows the 700-mb (10,000 ft) temperatures, surface winds, and precipitable water (a measure of the total water vapor content of the atmosphere, color fill).  Note as the front pushes across California and Nevada that it eventually draws moist air up the lower Colorado River Valley and into Utah.   ...

The latest GFS forecast shows the remarkable decay of the precipitation band accompanying the Pacific cold front that makes landfall tonight as it pushes eastward across the Cascades. 1200 UTC 23 Sep 2014 GFS forecast valid 1800 UTC 23 Sep – 1200 UTC 26 Sep 2014 Easy come easy go.  It's such a shame to see good rain die like that.  Is there life after death?  We'll find out in the coming days.

Click here for a look inside my forthcoming book Secrets of the Greatest Snow on Earth.  Utah State University Press did a great job putting it together.  It will be released in November, but you can advance purchase it at Utah State University Press  or  Amazon .  I'm hoping to make use of figures and diagrams from the book as we explore mountain weather this winter.  Here's one to get you excited.  Do you remember October 2004, which produced 122 inches at Alta and enabled Brighton to open on October 29?  Many described October 31, 2004, when a major lake-effect snowstorm erupted, as the best day of October skiing ever.  Radar image below. Source: Radar image from 9:24 am 31 October 2004.  Removal of ground clutter causes the "holes" over the high ridges surrounding the Cottonwood Canyons.  Source: Steenburgh (2014).

Few things in life are as satisfying and enjoyable as a fall hike in the rain. Until I moved to Utah, most of my life was spent hiking in the Adirondacks and Cascade Mountains, both of which are well known for wet misery.  I actually rate the Adirondacks higher than the Cascades on the wet misery scale, as the Cascades enjoy a pronounced dry season during the summer.  In contrast, suffering in the Adirondacks is a year round affair.  Nothing hardens you for outdoor pursuits like cross country skiing in freezing rain or forced marches in muggy, driving rain to black fly infested leantos. So, when I woke this morning to the pitter-pat of rain, a smile ran across my face.  There's nothing better than a fall hike in the rain, especially since wet in the Wasatch is typically fairly tolerable. Below is the only patch of mud I ran into the entire morning. And, with the mountains obscured, one's focus tends to turn to the wonderful fall colors.  

The Utah–Michigan game is delayed due to lightning.  It could be a long wait as there is mass of lightning producing storms moving toward Ann Arbor from the west and the west-southwest. Source: http://www.lightningmaps.org/realtime?lang=en I'm guessing is it will be at least an hour, maybe longer, until the teams can take the field.  At least the Utes are winning 26–10 and are poised for another score.

The latest (and some of the previous) GFS forecast is calling for a bonafide fall trough to move into Utah for next weekend.  The coveted 0ºC 700-mb temperature contour is draped across the Great Salt Lake at noon next Saturday. Before waxing the skis, some recognition of the chaotic nature of these long-term forecasts is needed.  We start with the North American Ensemble Forecast System, which consists of 21 forecasts from the US Global Ensemble Forecast System and 21 forecasts from the Canadian Ensemble Forecast system.  The plot below is known as a spaghetti diagram and includes contours of 500-mb geopotential height from all the members, along with a thick red contour for the ensemble mean.  This chart shows that most ensemble members put a trough over the western U.S. but the coverage of spaghetti suggests quite a bit of variability in terms of placement and strength.   Source: NWS Moving to the gold standard ECMWF, I didn't have time to hunt d...

Yesterday was a depressing day to be a meteorologist, with nothing but "cumulus patheticus" developing along the Wasatch Front and all the excitement to our northwest. KMTX radar loop for 0000–0202 UTC 19 Sep (1800–2002 MDT 18 Sep)  The storms shown above developed near a surface trough that was draped across the Intermountain West.  I thought something would bubble up ahead of that trough, but alas, it wasn't to be.  Even the strong outflow boundary that you can see pushing southeastward across the Great Salt Lake in the loop above couldn't get anything going.  What a pity.  The storms above did produce some severe weather, with 1-inch hail reported in Caribou, ID yesterday afternoon.  Mother Nature just seems to have Idaho's number this year. On the other hand, we did have a nice rumbler move through the Salt Lake Valley early this morning and park over the Avenues.  It doesn't look like much on the radar, but the thunder was pretty regular...

Yesterday's maximum temperature of 94ºF at the Salt Lake City International Airport set a new record for the day.  In addition, the only higher maximum temperature record later in the year is 97ºF, set on Sep 19, 1956.  Thus, we were in rare but not unprecedented territory for so late in the year. On a global scale, data released by the National Climatic Data Center shows that August 2014 was the hottest in the instrumented record. Source: NCDC You might recall that August was relatively cool here in Utah and this shows up well below. Source: NCDC Globally for the year to date, 2014 is now the 3rd warmest behind 1998 and 2010. Source: NCDC It will be interesting to see how things play out in the home stretch.

As a forecaster this time of year, one needs to be alert when midlatitude troughs interact with monsoon moisture.  For much of the summer, monsoon thunderstorms in Utah form in an environment of weak to moderate instability and weak flow.  The primary forecast concerns are flash flooding and, in some instances, strong winds from microbursts.   Add a midlatitude trough to the mix, and you have stronger synoptic forcing, stronger instability, and stronger flow.  If the instability, moisture, and shear are right, strong or severe thunderstorms can develop. I'm not sure if we have the necessary mix of instability, moisture and shear for strong or severe thunderstorms tomorrow in parts of Nevada and Utah tomorrow (and tomorrow night), but the pattern warrants attention.  The forecast for tomorrow afternoon (6 PM MDT) shows a midlatitude trough extending across northern California with large-scale southwesterly flow over Nevada and Utah.   Although...

Ski Utah has put together a nice piece on my book Secrets of the Greatest Snow on Earth .  The videos of snow and powder skiing should help stoke you for the coming season. Secrets will be released in November, just in time for the ski season.  You can preorder it from Utah State University Press or Amazon.com .  I'm hoping we'll have a preview available soon, but until then, here's the intro photo for chapter one.  

Over the past two days, Hurricane Odile has been rumbling northeastward and crossed the southern tip of the Baja Peninsula overnight.  High integrated precipitable water values (contours below) are rumbling up the Gulf of California with and in advance of Odile, posing the potential for another major monsoon surge and related convection over the next couple of days.    IR and GFS precipitable water analyses from 1500 UTC 13 Sep – 1500 UTC 15 Sep 2014 As with Hurricane Norbert , the long-range forecasts of Odile by the GFS have been super wacky (a technical term).  The forecast from Saturday morning (13 Sep) called for Odile to move westward and be located well off the Baja coast (near the bottom of the plot below) at 1200 UTC Friday 19 Sep. The forecast from Sunday morning called for Odile to weaken with just some remnants over the northern Baja Peninsula by 1200 UTC Friday 19 Sep. And now the forecast from this morning calls for Odile to curve ha...

Our first canyon wind event of the season is underway this morning.  Unlike big downslope wind events that typically roar along much of the northern Wasatch Front, this morning stronger winds are confined to a few locals including near Weber Canyon (currently gusting to 36 mph in the canyon) and near Centerville (25 mph). Wind and wind gust observations within one hour of 14:47 UTC (8:47 MDT).  Source: MesoWest. There are also east winds on the University of Utah Campus and Parley's Canyon. Wind and wind gust observations within one hour of 14:47 UTC (8:47 MDT).  Source: MesoWest. The winds at Parley's Canyon increased at a very gradual rate overnight.  The peak gust of 49 mph occurred early this morning. The cause of these canyons winds is an area of high pressure that slid down the east side of the Rockies and is currently centered in northwest Nebraska.  The resulting pressure gradient is driving easterly flow into northern Utah. This eas...