Sunday, January 25, 2015

Snow, Warmth, the "Monsoon Surge", and the Storm Killing Rex Block

Here are your four weekend updates from the Wasatch Range.

1. State of the Snow

Much of the snow in the Wasatch has been affected by wind, sun, or humans, but incredibly there is some good settled powder to be had in sheltered areas on the north side of the compass despite it being almost 2 weeks since the last storm.

This time of year you can really see the power of the sun as the south aspects are baking and in some cases have lost their snow, whereas you can find powder on the north aspects.

2. Warmth

I noted a couple of days ago about the building ridge and the potential for very warm temperatures at 700-mb (10,000 feet) today (Sunday) and Monday.  Well, the great warmup is underway and the GFS forecast 700-mb temperature is 3.5ºC for 5 PM this afternoon and 5.8ºC for 2 PM Monday afternoon. You can kiss more of that south aspect snow goodbye.

3. The January "Monsoon Surge"

Tropical moisture will be streaming into northern Utah and giving us some precipitation Tuesday and Wednesday.  It's an odd pattern for January and the model forecasts still lack consistency with regards to potential storm totals.  Brett called it a "refresher" in this morning's Utah Avalanche Center advisory and I'm good with that at this stage.  We'll see how it comes together.

4. The Storm Killing Rex Block

There's no end to the storm-killing Rex Block (a.k.a. high-over-low block).  Although we get a flirtation with tropical moisture Tuesday and Wednesday, it pops right back up at full strength thereafter.  Below is the Euro forecasts for next weekend (ensemble mean left, high-res forecast right) and we're high-and-dry if that forecast verifies.

Source: ECMWF
A fairly similar forecast exists in the GFS.  I've added one of our regional panels below for late Friday night to show the net impact of the Rex Block on precipitation.  High and dry over the northern portion of the western U.S., with precipitation confined to the southwest.

How long could this go on?  Well, let's just say that the overall pattern persists in both the 10-day GFS and ECMWF forecasts.  Of course, there's always hope that the models are off the mark at those long lead times...

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