Wasatch Weather Weenies

It's not time to panic yet, but I've been looking at the forecast for the next couple of weeks and it is bad news for the spring runoff.  Much can happen in late March and April, but it appears we will need to make up a lot of ground if we are to have anything close to a decent runoff this spring in the Great Salt Lake Basin. First, let's have a look at the current snowpack situation.  The Bear, Weber, Ogden, and Provo/Jordan river basins are all sitting at about 75% of average snowpack. Source: NRCS This week, we have a high-amplitude ridge building in.  The 700-mb temperatures are forecast to climb to about +5ºC over Salt Lake City by Thursday afternoon. Thursday will easily be the warmest day of the year.   Portions of the Salt Lake Valley will see maximum temperatures in the low 70s .  I think 70ºF will be broken at the Salt Lake Airport if the lake breeze is kept at bay. All of this means that we will be chipping away at the mountain sno...

During spring break, I'm upgrading some of the products available on http://weather.utah.edu .  The latest addition is output from the North American Mesoscale (NAM) model high-resolution nest, which covers the continental U.S. at 4-km grid spacing and produces forecasts out 60 hours.  Below is the surface wind and 3-hour accumulated precipitation forecast valid for 1800 UTC (1200 MDT) this afternoon. We'll have to keep an eye on these forecasts and see if the resolution is a help or a hindrance.  During the 2002 Olympic Winter Games, we found that the accuracy of 4-km precipitation forecasts was greater than that of those produced at 12-km, but also that the utility of the 4-km forecasts was reduced by an increase in "false alarms" (i.e., large forecast precipitation events that didn't verify).  Proceed with caution. Stay tuned for more.

Spring break has arrived at the U and students have scattered in search of adventure.  The beauty of March in Utah is that you can have it all.  Great skiing, rock climbing, mountain biking, or whatever your heart craves.  Sometimes you can have it all on the same day. This week, March is going to serve up what will undoubtably be the nicest weather of the year so far.  Every member of the GEFS calls for a ridge to be parked over Utah by mid week. Source: Penn State E-wall Perhaps more importantly, so does the ECMWF Ensemble Prediction System.  So, no deep powder, but beautiful weather for everything from spring skiing to canyoneering.  Enjoy.

Toast the end of inversion season as I did a couple of nights ago with an Inversion IPA from the Deschutes Brewery.  I'm thinking the worst is finally over.  It certainly felt great to have a beautiful day of skiing today in the mountains and then return to the warmth of the Salt Lake Valley this afternoon.  Ain't March grand.

No deep powder this morning, but we did get a few inches last night and we'll be happy to take it.   We've had a number of upside down storms this year, but last night gave us a good backwards storm, one in which the Wasatch Back gets more snow than the Cottonwoods.  According to the UAC, we got 7–9 inches on the Park City ridgeline and 3–6 in the Cottonwoods.  I suspect that if you are skiing Alta-Bird today, you'll notice a clear decrease in snowfall from Supreme to Gad-II. Why the backwards storm?  It was an event with large-scale southeasterly to easterly flow, as can be seen in the movement of precipitation features in the radar loop below, which covers most of the event. The backwards storm isn't all that uncommon.  They happen a few times each winter.  Given the meager snowpack, I'm sure the Park City folks are glad to get it. Addendum @ 10:00 AM The NWS has posted some snow totals and those from the central Wasatch show the east-west snow...

All models are wrong, but some are useful - George Box But not today - Wasatch Weather Weenies Numerical weather prediction models form the backbone of modern weather forecasting and will play an increasingly important role in the future. Most of the time they are extremely helpful, but there are times when they seem to make the crystal ball even cloudier, and this is one such situation.  We've already seen situations this week where the NAM and GFS have produced dramatically different forecasts (e.g., Which Model Will Win ), and we have another one tonight.   In particular, compare the 6-hour accumulated precipitation in the 0600 UTC GFS forecast with that from the 1200 UTC NAM (sorry about the different initialization times, which is an artifact of availability as I write this, but this is still a reasonable comparison).   0600 8 March 2013 GFS forecast of sea level pressure,  surface wind, and 6-h accumulated precipitation valid 0600 UTC ...

Yup, things are coming together nicely, if you live in Arizona.  The front and accompanying precipitation band sagged into northern Utah last night.   Looks like the most snow fell in the northern Wasatch, with Snowbasin and Powder Mountain reporting 3 and 5 inches respectively.  Chalk this one up to the NAM and the SREF, which didn't push the front as far south and gave the greatest odds of .25" of precipitation in the Wasatch north of Big Cottonwood.  As was forecast by both models, however, the precipitation band is moving back to the north this morning.  C'est la vie. My view of the forecast for the next couple of days is that this remains a pattern that is ripe for disappointing Wasatch skiers.  It is not impossible that we pick up several inches of snow somewhere, but we are simply outside of the good dynamics, orographics, and moisture.  I'm going to once again emphasize the forecast produced by the Short Range Ensemble Forecast system (SRE...