Wasatch Weather Weenies

November is almost in the record books and it looks like we're going to be pretty close to average for temperature and below average for precipitation. At the Salt Lake City airport, the trough-a-week pattern dominated the month, yielding fairly typical late fall ups and downs in temperature.  The last trough decided to hang around for a few extra days, yielding our current cold stretch. Source: NWS With one day left to go (today), the average temperature for the month is 40.15ºF compared to a long-term average (1981–2010) of 40.0ºF.  We'll probably end up just a hair below that long-term average after today is factored in. For precipitation, the airport received 0.40", well below the average of 1.45".  Overall it was a decent month for artificial snowmaking, but Mother Nature had her struggles.  The thin natural snowpack is now quite weak and will be a prime concern for backcountry travel if it ever starts to snow again.

Ah, freshies were had in the Avenues Foothills.  Not today, but five years ago today.  I just wanted to share that memory as that was the start of the epic 2010–11 ski season that we all remember so well. The 2015-16 ski season is getting off to a slower start.  SNOTEL stations in the central Wasatch sit at 60–71% of average.  Average this time of year is not huge, so we're basically one good storm short of average.  If only we could get that one good storm! Unfortunately the pickings are pretty slim in the medium-range forecasts.  The European ensemble shows very little outside of some snow showers today and tonight through at least December 4th.  Similarly, the North American Ensemble Forecast System (NAEFS) plume for Alta-Collins produces some snow showers through tonight, followed by a flat line until December 4th.  At that point, a few of the ensemble members bring a storm in, but others keep us mainly dry. Thus, the upcoming work ...

There is not always a direct relationship between the amount of new snow and road-weather impacts.  Sometimes a little is enough to create problems. The snow that fell late last night didn't come fast and furious.  It started at the Salt Lake City airport at around 4:50 AM MST and has added up to a whopping .03" of water equivalent through 8:40 am this morning.  That's probably pretty close to what I got in the Avenues foothills. However, after the cold weather the past couple of days, the road surfaces are cold and the snow is sticking.  In addition, I suspect the road crews were caught off guard and nothing was plowed when I woke up this morning in my neighborhood.  Further, Commuterlink at 8:48 AM MST showed fairly slow going for a Saturday along much of I-15 and I-215 through the Salt Lake Valley. Source: UDOT Traffic cameras showed the light snow covering all but the busier lanes. Source: UDOT An inch at Alta so far.  It's not much, ...

Black Friday is here.  Despite the thin snowpack, I'm going skiing.  I don't recommend shopping, but if you must, my book Secrets of the Greatest Snow on Earth  makes a great gift. The first print run is almost sold out.  A second is in process, but if you have to have it for the holidays, get it now to be sure.  Options are direct from University Press of Colorado , Amazon , Barnes and Noble , and great local bookstores like King's English at 15th and 15th, Weller Book Works in Trolley Square, and Dolly's on Main Street in Park City.  If you by direct from University Press of Colorado, enter 50for50 at checkout for 50% off.

Although I'd rather talk about snow, Mother Nature just keeps giving interesting weather and I experienced the full force of it on my pre-Turkey hike this morning. While hiking in the Avenues Foothills, I experienced increasingly strong, cold easterly flow as I hiked eastward and upward to the top of the Avenues Twin.  It was absolutely frigid on top, with screaming easterlies of perhaps 25–30 mph.  I wasn't dressed for that! Observations from the University of Utah show the development of the easterlies this morning with gusts reaching about 40 mph around 11 am. Source: MesoWest As is often the case, there was a well developed "Sandy Eddy" with the easterly flow turning cyclonically (counterclockwise) and becoming northwesterly or westerly flow over the Salt Lake Valley and upslope flow over the Wasatch Range near the Cottonwood Canyons. Source: MesoWest The Sandy Eddy has a very apparent signature when viewed from the Avenues foothills.  There is typ...

Ah, it's a beautiful morning in Salt Lake.  The sun is shining.  Temperatures are around 50ºF.  Gorgeous. The loop below shows very nicely the situation that has proven to be the bane of forecasters for so long.  As mentioned in earlier posts on this event, we have a situation of large-scale Rossby-wave breaking, with the upper-level trough forming rapidly over the Pacific States overnight last night. All the action right now is to our north and west, although it's less impressive than I hoped it would be prior to moving into the Wasatch Front (thinking from a skier's perspective here, not a commuter's).  Each successive model run slows the system down a bit more and that continued to be the case through this morning.  Here's yesterday's NAM time-height for Salt Lake City showing frontal passage around 2100 UTC (2 PM MST) this afternoon, as well as a slug moisture in the pre-frontal southerly flow for this morning and the early afternoon. Now her...

The forecast for tomorrow morning provides a good example of one of the problems we have as meteorologists using higher resolution models. For the 3-hour period ending at 1800 UTC (1100 MST) tomorrow, the NAM is generating just a bit of light precipitation over the northern Wasatch. In contrast, the high-resolution 4-km NAM goes for considerably more precipitation, amounting to 0.16" of water in three hours at Alta-Collins.  Those aren't huge numbers, but they add up. I'm seeing similar behavior in the NCAR ensemble for tomorrow.  The largest precipitation rates are being produced in the southerly flow ahead of the front at Alta-Collins. High resolution forecasts like these are alluring as we know the central Wasatch can have strong effects on precipitation.  The problem, however, is that these models produce heavy mountain precipitation far more frequently than Mother Nature does, so the issue in a situation like this is how much to believe such a forecas...

Predictability describes the extent to which the weather or an aspect of the weather can be predicted with existing tools and knowledge.  Its close partner is uncertainty, a measure of the ambiguity or lack of precision in a forecast. In any given forecast, some aspects can be relatively predictable, while  others are less predictable.  A good example is the forecast for this Thanksgiving week. Over the next few days, a Rossby wave breaking event will occur over the north Pacific and western North America, as can be seen in the GFS dynamic tropopause (jet-stream level) loop below.  The wave breaking features the amplification of the high-amplitude ridge over the Gulf of Alaska and northwest North America and the near simultaneous amplification of the upper level trough over the western United States. There is very strong agreement amongst the models and ensembles on this large-scale evolution.  Below are forecasts from several members of the Global Ensemb...

We have been in quite a cycle the past month with a trough passing through northern Utah early in the work week each of the past four weeks.  Each trough is similar in that it brings a temperature drop, followed by a recovery.  Check out the temperature ranges below for each day in October and November.  After a long stretch of quiescent weather in October, we had a trough passage and associated temperature drop around Oct 29, Nov 4, Nov 10, and Nov 16. Source: NWS The trough of the week club will continue to deliver this week, bringing the warm before the storm through Tuesday, and then a return to more winter-like temperatures on Wednesday. As was the case with the previous storms, we're dealing with a crap shoot for what will happen for mountain and possibly valley snow.  Contrasts in the track, strength, and shape of the trough can make a big difference for precipitation around here, so I'm still taking a wait and see approach until we get a big c...

There are some numbers coming out of the high elevations of the central Wasatch that I really like.  How about 3 inches of snow with 0.6 inches of water at Alta-Collins through 7 am.  That's 20% water content, nasty by even Cascadian standards, but the sort of stuff we need to build up a base.  I'll take it gladly over cold smoke at this stage. Less encouraging are the outrageously high global mean temperatures for October.  Talk about off the charts.  Thank you El Nino and global warming. Source: NCEI And for those keeping score at home for the year to date, it's still 2015 1, the rest of the instrumented record 0. Source: NCEI Two predictions for the future.  2015 will be the warmest year on record by a wide margin (an easy forecast).  When there is an inevitable temporary drop in global temperatures following this El Nino, such as occurred following the last Uber El Nino in 1997, you will hear people claiming a global warming hiatus onc...

There was a beautiful cloud display this morning as the altostratus covered the sky like a wavy blanket.  The morning sunrise tickled its soft white underbelly. Here's another view later.  Pity my cell phone camera is such a piece of junk. Clouds that cover the sky like a blanket and have large wave-like undulations are now called undulatus asperatus , the first cloud type to be officially recognized in many years.  I'm not sure if the amplitude of the waves this morning was sufficient for to qualify as that cloud type, but it was a pretty scene. We are very close to having forecasts from the National Center for Atmospheric Research 3-km ensemble available on our web site.  It's based on the Weather Research and Forecast model and has 10 members.  We have no idea how well it will work, so I'm interested in seeing how it does over the next several storms, including tonights, which looks to be a windy, orographic affair with strong crest-level flow shi...

The hottest year on record in Utah remains 1934, a black-swan year if ever there was one. Source: NCDC However, we are making a run at it this year.  For the year-to-date through the end of October, 1934 and 2015 are in a near dead heat with statewide average temperatures of 54.8ºF and 54.9ºF, respectively.   Source: NCDC November and December 1934 brought temperatures that were 2.6ºF above average, so that's the number for November and December 2015 to aim for.  Lots can happen in November and December, so I'm not making any predictions.  I do suspect that unless we get really cold in December, something in the top 5 is virtually assured.

If I had my choice, I'd take a dry October followed by a really big storm cycle in November to kick off the ski season.  We had the former, but we've yet to really get walloped this November.  Instead, we've had three storms that collectively have given us about as close to a run-of-the-mill snowpack as we can have, and given what we dealt with last year, I ain't complaining. Here's the latest from three SNOTEL sites in the central Wasatch (I skip Brighton, which I've always considered problematic).  Thaynes Canyon is running at 80% of median (median being the value that splits the upper and lower halves of past snowpacks), Mill-D North is right on median, and Snowbird is just a shade behind.  At Snowbird, the data does not include yesterday, however, which would probably push it pretty close to median. Source: NRCS What will the winter bring?  Jason Samenow posted a nice article on Capital Weather Gang yesterday discussing how El Nino is now in u...

We're currently post-frontal, but the depth of the northwesterly flow is quite shallow.  I'm not sure if this explains the radar distribution seen below, but there does appear to be enhancement on the west side of the Stansburys, Oquirrhs, and central Wasatch with more limited penetration into the high terrain.  The enhancement on the Oquirrhs also wraps around the NE side for reasons I can't explain. On the other hand, the flow is weak and it's a complicated pattern, so other ideas welcomed.

Interesting radar loop this morning.  Note how the echoes are coming from the east across the central Wasatch. The upper-level low has closed off sufficiently that the flow has an easterly component.  Nobody is happier than than those in the Park City area who are getting some of the white stuff this morning. Source: UDOT The overnight phase of the storm didn't exactly play fair.  Precipitation spread just far enough north for the southern and central Wasatch to do well, but the northern Wasatch largely got skunked.  An example radar image is below.   Source: NCAR/Ral Alta-Collins had an 8" storm total on the stake as of 8 am, from only .54" of water.  Upper portions of PCMR may have done a bit better.  The Thaynes Canyon SNOTEL has 0.6" of water through 8 am and an increase in total snow depth of 7" (typically that underestimates the new snow depth due to compaction of the underlying snow).   A few hours of easterlies can do...

To paraphrase The Who, "meet the new trough, same as the old trough."  Yes, we have another storm rolling in.  Yes, on the large scale, it is remarkably similar to the other storms we've had this month. The loop below begins yesterday morning and goes through early morning on the 19th when the storm is exiting Utah.  We've seen this movie before.  An amplifying upper-level trough digs off the California coast and continues to strengthen as it moves inland.  Central and southern Utah and Colorado once again appear to be favored by the storm track. How similar is the large scale in these events?  The loop below shows analyses of the previous two storms and the forecast for the one moving through the west this week.  Identical?  Nope, but quite similar.   Thus, many characteristics of this storm will be similar to the previous two.  Today we will have the warm before the storm, with warm, windy conditions,  Then a transitio...

The natural snowpack remains a bit thin for my backcountry interests, but we got out for our first day today, taking advantage of the man-made-enhanced snowpack in Collins Gulch.  Alta plans to open on Thursday, so kudos to them for keeping the mountain open for uphill skiing today. My back has limited my ski adventuring the past couple of years, so days like this skiing with my son are priceless, even if the snow is scratchy instead of bottomless. Of course, my tours always involve some snow science.  Since nothing was falling from the sky, we investigated the dreaded man-made crust.  Nasty stuff! Hopefully it will be buried by the real stuff soon.

This is a continuation of the previous post ( DIY Forecast Tools, Part I ) and examines some additional products available from the Utah Weather Center ( http://weather.utah.edu ) that are useful for DIY weather forecasting. 1. Time-Height Sections To my knowledge, we are the only group providing access to model time-height sections.  I've always found this surprising because they are a wonderful tool for forecasting. Most of the time-height sections on our site are produced with BUFR sounding data from either the NAM or GFS model.  BUFR sounding data pulled directly from each model at very high vertical resolution, enabling highly detailed time-height sections. Time-height sections show the evolution of the atmosphere with time over point.  We plot ours so that time increases to the left .  This sounds strange, but it results in the winds appearing to curve cyclonically with a trough passage, which is easier to visualize if time increases to the right and th...