Thursday, March 5, 2015

Spring Returns

Normally given the dry sunny weather expected over the next few days I would say that spring has sprung, but since we pretty much didn't have winter this year and had our spring in February, I have to instead say that spring returns.

The forecasts produced by the GFS and the Global Ensemble Forecast System (GEFS) for late Saturday night pretty much tell the story with an upper level ridge once again in full control over the western U.S.  Looks like a great weekend to do whatever you love, be it spring skiing or southern Utah.  For the former, temperatures will likely be just cool enough that upper elevation north facing terrain probably will stay soft.  No promises for lower elevations or other aspects, and anything south or west will get its first cooking today.


Here's our downscaled ensemble precipitation forecast for the next seven days. Pretty much flatlined through the 10th with a few members calling for light precipitation very late in the period.


Take it easy on the BST until it dries out some.  

Park City Readers:

I'll be giving a talk and book signing at Dolly's Bookstore on Main Street in Park City at 6:30 PM tonight (Thursday, March 5th).  Drop by and enjoy a discussion of my book Secrets of the Greatest Snow on Earth including the history of that iconic phrase, avalanches, and other topics of interest to Wasatch Weather Weenies.

Wednesday, March 4, 2015

Bluebird Through the Weekend

Not much to say today except enjoy the next few days.  The GFS time-height section for Salt Lake city pretty much tells the tale: Dry.  We'll have some lingering low clouds this morning, and perhaps a some wispy high clouds at time, but otherwise things look bluebird through the weekend.

Temperatures will be warming up through Friday with the 700-mb (10,000 ft) temperature expected to reach about -2ÂșC late Friday or Saturday.  That means that south and west facing aspects will be going through a melt-freeze cycle later in the week, but high north and northeast should provide great skiing through the weekend.

Park City Readers:

I'll be giving a talk and book signing at Dolly's Bookstore on Main Street in Park City at 6:30 PM this Thursday, March 5th.  Drop by and enjoy a discussion of my book Secrets of the Greatest Snow on Earth including the history of that iconic phrase, avalanches, and other topics of interest to Wasatch Weather Weenies.

Tuesday, March 3, 2015

Storm Update

Looks like Alta picked up about 7 inches since this morning, with 6 inches and about 0.31" of water equivalent falling in a 2 hour period encompassing the frontal passage.  Wish I was there!  

Back to work...

More Radar Potpourri and an Unbelievable Photo

So much cool stuff today.  Here's more from radar and a photo that will BLOW YOUR MIND.

It's quite unusual for a front to blow through the Wasatch like there's nothing there, but that's largely what happened this morning.  The radar image below, for 9:51 AM MST, shows a well formed frontal precipitation band approaching extending from the eastern Uintas southwestward across the Wasatch Range and Utah Valley.  Terrain blockage of the beam prevents analysis of the frontal band further north.


Now, check out the radar loop that ends at the time above and watch the frontal band move through the Wasatch Range and eventually become a distinct feature in the lee.


The other cool thing is the very intense area of precipitation along the front just to the west (or arguably over the western slopes) of the Wastach.  You can see it in the top image as an area of yellow (i.e., radar reflectivity > 35 dBZ) along the front.

And, this from @skitheu showing what I suspect is the front pushing into the mouth of Little Cottonwood.  OMG!

Source; @skitheu

Radar Potpourri

I'd rather be skiing, but if stuck in the office, it's great to have Mother Nature put on a show.

The radar loop this morning is simply fantastic.  There's the strong frontal precipitation band pushing through the Salt Lake Valley.  There are a number of pixels with radar reflectivities < 35 dBZ (yellow), which is quite high for a winter storm.


The orographic effects in the southwesterly flow ahead of the front are also fascinating.  Note the persistent, stationary echoes over the southern Wasatch Mountains.  The radar beam in this area is quite high, which often results in overshooting, as discussed in my book.

Source: Secrets of the Greatest Snow on Earth
As a result, snowfall rates are probably higher than you might infer from the radar echo strength.

Also of interest is a band of precipitation that appeared to form over the high divide between Little Cottonwood and American Fork Canyon (circled).  Note how this band trained off over Deer Valley and even SR-40 between Heber and Park City.  I like to say when looking at radar imagery that there are "a lot of critters in the woods" and I've never seen a critter like that before.

Heavy snow will likely continue on the U of U campus through about 10:30 or 11 before starting to taper off.  Enjoy it while it lasts!


The Final Piece Is Upon Us

A wall of snow in the northwest Salt Lake Valley at 7:40 AM this morning 
Roughly a foot of snow has fallen as of 7 am in the upper Cottonwoods with the final piece of the storm about to move into both the Salt Lake Valley and the central Wasatch.  The analysis below shows the secondary trough and accompanying band of precipitation over the Great Salt Lake at 7 am.  


The radar loop below covers the period from 6:11 AM to 7:34 AM.  The Salt Lake Valley has had a bit of a break during this period.  Notice how the radar echoes tend to persist over the Stansbury, Oquirrh, and Wasatch Mountains, with little happening over the intervening valleys.  That will change once the trough pushes in and the flow shifts to northwesterly.  Expect snow for the latter half of the commute and for a good part of the morning.


In the central Wasatch, the front will bring a burst of heavy snowfall to the entire central Wasatch.  I suspect this will add another 5-8" to the storm totals so far.  Others are going for more and while I can't rule that out, I'm concerned the storm will shutdown fairly quickly after noon.  I'm sure you won't complain if my forecast is conservative.