Tuesday, October 4, 2016

Wasatch Snow, Eastern Apprehension

A beautiful fall sunrise over Salt Lake City
Salt Lakers were treated to a beautiful fall sunrise and crystal clear skies.  Days like this you just have to take a deep breath and suck it all in.  

A quick look at the mountains reveals a new white frosting.  Data from Alta-Collins is AWOL this morning, but the NWS reports about 5 inches fell yesterday in the Town of Alta.  I'm not sure it looks like that much in weather cams, but I did notice that Alta is making snow or at least testing their snow gun near the Albion base.  Get up there now for first scratches.  

Source: Alta.com
Overnight forecasts for the rest of the week are a bit disappointing if you want more snow, but encouraging if you are in the snow-safety industry.  The latest NAM, for example, keeps us cool, but even with the next trough pushing through, brings us just some scattered snow showers and little in the way of well-organized precipitation.  

Now that fall is upon us, I'm starting to look at the downscaled Short Range Ensemble Forecast system products that we put together this summer.  We have no idea if these are good or reliable, but this is a blog, so I'll go with them anyway.  There are 26 members in this ensemble, which is run at 16-km grid spacing, but we downscale that to higher resolution.  All but 3 downscaled members produce 0.4 inches of water equivalent or less for the rest of the week at Alta.  There are a couple that go bigger than this, so one can't rule out a larger storm, but the odds are low.  
As I mentioned above, this is good news if you are in the snow-safety industry.  If we're not going to go huge and start building up a snowpack, early snow almost always turns to weak snow when the inevitable ridge returns during the fall.  Better for us to have just a little snow this week and melt or sublimate most if it away rather than have a couple of feet of snow facet and rot before the next storm.  Let's stay dry until the end of the month and then open the spigot.

Meanwhile to the East, Hurricane Matthew is currently an extremely dangerous storm that will likely impact the entire eastern seaboard of the U.S.

As of 6 AM MDT, Matthew had just made landfall over Haiti as Category 4 hurricane with maximum sustained winds of 145 mph.  Wind, storm surge, and rain, which is expected to be in the 15-25 inch range with isolated amounts of 40 inches, will unfortunately make this a catastrophic storm for Haiti.
Hurricane warnings are now posted for Cuba and the Bahamas.  Nothing yet for Florida, but the latest forecasts have moved the storm tracks ever closer to the east coast.

The latest GFS forecasts suggests that Matthew will have some impact along the southeast coast in the form of waves, beach erosion, precipitation, and/or wind, and possibly the entire eastern seaboard all the way to Maine.

Details will, however, depend on track, timing, intensity, etc. that can't be nailed down this far in advance.  Pay attention to official forecasts from the National Hurricane Center and National Weather Service.  

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