Mountain West Discussion

[smokeybandit]

It was sunny at 60 at 11:30, now less than 2 hours later, it's 30 with an eerie fog

[Chinook]

On 11/6/2019 at 1:09 PM, smokeybandit said:

It was sunny at 60 at 11:30, now less than 2 hours later, it's 30 with an eerie fog

Temperatures dropped quickly with northeast winds and increasing clouds on Wednesday. Fort Collins had 51.6 and sunny at 10:00 AM and then had 36.5 degrees and cloudy at 1:40 PM. We had some drizzle/ freezing drizzle after 5:00 or 6:00 PM. Thursday was a partly cloudy 45 degrees, and was in the 30's for quite a number of hours. Friday was warmer. Today is now 76 degrees at Denver, which ties a record set in 1927.  Fort Collins has broken a record  high of 70.

Models have some light snow for tomorrow night/ Monday morning. The GFS  predicts 2.0" for my place. After Tuesday, it seems we will be back in the mild air mass, as the colder air with be farther east.

[raindancewx]

Today looks a lot like the November MJO composite for phase six, with the warmth in Billings, Denver, Kansas City, etc, but the East Coast cold, and the heat struggling to push into New Mexico. The push into 7-8-1 later in the month should warm up the East quite a bit - this month probably won't finish anywhere as chilly as it looks right now.

A lot of the US is 6F or more below average in November to date.

[MidlothianWX]

A nice, fluffy snow fell overnight. I just measured 3” on my deck with light snow still falling. This storm should put Boulder right near the 30” mark on the season. 

[raindancewx]

PDO in October 2019 went the most negative it has been in six years. https://oceanview.pfeg.noaa.gov/erddap/tabledap/cciea_OC_PDO.htmlTable?time,PDO

There are no cases of the PDO topping +0.5 from Nov-Apr after a reading of 0 to -1 in October for the 1931-2018 period. PDO was -0.45 in October 2019.

El Nino	October PDO	Nov-Apr
1951	-0.32	-1.02
1963	-0.52	-0.88
1965	-0.36	-0.44
1968	-0.34	-0.81
1977	-0.61	0.50
2004	-0.11	0.47
2006	-0.05	-0.04

Similar SOI matches (-4 to -12 SOI in Sept-Nov) with a similar October PDO -

Year	Oct	SOI SON
1932	-0.29	-5.7
1944	-0.40	-4.0
1946	-0.36	-9.0
1951	-0.32	-10.7
1963	-0.52	-9.9
1977	-0.61	-12.0
1990	-0.69	-4.5
2004	-0.11	-4.6
2006	-0.05	-7.2

[Chinook]

On Wednesday and Thursday, a 500mb low will cut off near San Francisco and will track toward S. California and the Four Corners. The models have been slowly coming into agreement on this. The thing that seems likely is heavy rain for Arizona.  The details of the storm system for Colorado are not as clear.

[raindancewx]

There is a tropical storm in the East Pacific moving North ahead of the system, so I think a pretty widespread precip event is likely. My analogs had several years with a big storm around 11/20 in the SW, so that looks right, at least for now. For NM & Southern Colorado it's probably a rain event initially, even 8,000-9,000 feet up initially, but it would go over to snow later, down to pretty low elevations by Friday. My analogs implied around 0.25"-0.50" for NM with the system - wouldn't be shocked if it came in higher given the dying tropical system plus the other sources for moisture.

[Chinook]

The 00z Euro finally changed its synoptic forecast for the 500mb low. It now has the low moving eastward to the Rockies faster,. QPF values now show 3-5" of snow for the Front Range cities, which the GFS has shown for a number of runs. Note: there is not one single 24-hr period when 3-5" of snow falls. Sometimes I think the Euro can struggle with Southwestern storms. By the way, if you haven't checked Pivotalweather.com in a while, it has the Euro QPF, snowfall, and temperatures, and you are allowed to zoom in on regions of the USA.

If 2" of rain fall at PHX airport in this storm (as the WPC forecast had about 2") then this will be greater than the TOTAL amount of rain that PHX has had since FEBRUARY 22nd. Perhaps Phoenix should be renamed "Atacama."

[raindancewx]

This is what the European had earlier today through Friday at 6 am. It should be a great event for SW Colorado snow.

A tropical system in late-October 2018 also came into the SW last year too. In some ways, the pattern nationally seems like last year, but delayed by 25-30 days. We had 1-3" widespread rains and some snow around 10/23 last year.

[smokeybandit]

Hopefully a bit more of that moisture finds it way into the Denver area.

[Chinook]

18z GFS and 12z Euro today are still not going too big with snow amounts, with some decent values over 9000 ft.  Of course, there should be higher snow values for SW Colorado (San Juan Mountain Range.) Also, around 6" for Raton NM, with potential of 6" - 18" in the Sangre De Cristo near Raton. The 18z GFS shows the highest 12-hr amount of snow for Denver is 2.9" from 18z Thursday to 06z Friday. I am actually hoping that this won't produce much slippery roads on Thursday night.

[raindancewx]

1953, 1983, and 1992 all had a major SW storm around Nov 20 when I did my analogs - I think those might be good precip analogs for Utah, Colorado, New Mexico and Arizona. I don't think they'll work for the Northwest or California as well. A blend of 1953/1992 has been a pretty decent match to precipitation totals and timing in Albuquerque for close to six months now.

The idea with 1983 in there is that occasionally some kind of Blue Norther level cold front will run into moisture coming in from the subtropical jet, and someone will get smoked for snow in New Mexico or Colorado or Texas. I had 2009/2018 in there too, and then 1995 because we should have some extended dry/warm periods in the SW too. 

There was another big SOI crash 11/16-11/17, so have to watch for something around 11/27. The models are already hinting at it actually.

[Chinook]

Not too much has changed with this storm. The GFS now has the most of the snow hitting the Front Range cities with the 500mb shortwave on Wednesday, that is 00z Thu to 06z Thu. Then the second pulse, associated with the closed 500mb low, will produce additional snowfall across central and southern Colorado and New Mexico, with some lower snow possibilities up north near me. The weakening 500mb low will also be likely to bring some snow to Kansas. 

Interesting stat: 

At Fort Collins,  Nov. 9th had a high of 73 and a low of 30, with a temperature departure of +10.0F. This is the first 10.0F positive temperature departure since September 16th, which had a high of 89, low of 57. 

At Fort Collins, Nov. 16th had a temperature departure of +12.6F, which is the largest positive temperature departure since April 8th, which had a high of 75, low of 44, departure of +12.8F.

Models may indeed be hinting at something around 11/27. This 00z GFS run produces a very very strange storm. I don't think this is possible. Other GFS runs had something different. It's so strange that I'll post it.

[smokeybandit]

GFS pummels eastern Colorado with that storm

[smokeybandit]

Unsurprisingly the 12z backs off mega storm totals but still gives a nice storm. Definitely something to keep an eye on

[Chinook]

Yeah, the 06z GFS has 38"  within 24 hours for Limon to almost DIA at hour 204 (snow total of hours 180-204). So I think that's a little bit unlikely, but fun to look at.

[smokeybandit]

GFS keeps going back and forth with what it wants to do with next week's system.

[Chinook]

Models have a somewhat better agreement on Monday-Tuesday, as a mostly westerly feature at 500mb could produce some moderate snow amounts in Colorado.

[raindancewx]

On 10/11/2019 at 5:34 PM, raindancewx said:

I have a fairly warm November for the West, but I think we may sneak in a big snow storm for WY/CO/maybe NM too during that month.

This looks pretty good right now. Denver is warmer than normal through 11/20 after a cold start, and we're getting a big snow storm 11/21 in New Mexico. Albuquerque is probably just above normal now through 11/20, but will fall below again by the end of the month.

For December, I had the center of the US pretty cold, including Colorado and New Mexico, with temperatures trending to slightly above average on both coasts. There is a pretty strong tendency in El Ninos for whatever the US pattern in the second half of October is to shift East, and become the December pattern. That matches my analogs. Last year, you had tremendous heat centered in Montana in the second half of October, and that shifted East keeping the North/East warm. The H2 Oct, but East thing has worked for all El Nino Decembers since 2009 - will be curious to see how it does this year. 

H2 October Shifted East

My Raw Analogs, but +2F for a warmer Nino 4, looks damn close to the spatially adjusted Oct 16-31 observations:

[Chinook]

My place got about 1.5" to 2" last night, with temps around 32.

The GFS has this for Monday-Tuesday. The 00z Euro is  similar but a little weaker with 2.3"-3.9" at our cities (10:1 ratio).  The 12z Canadian has this snowfall in Wyoming. I suppose the Canadian might be disregarded at this point. The new 12z Euro isn't done yet. The other storm from next week continues to undergo large changes in the models.

[smokeybandit]

GFS has had it for the most part the last 8 runs or so, but still varying widely each time, which isn't surprising this far out

[Chinook]

2nd piece of our snow storm is coming in right now.

The 12z Euro has 6-7" of snow all around Denver metro, up to my area, for Monday-Tuesday.

[raindancewx]

We're at 1.25" precipitation in November through 5 pm 11/21 in Albuquerque. The storm that times up with the big SOI drop around 11/18 is still shown for 11/28 or so. The 1.25" is already near record November precipitation, wettest November here since 2004. Since 1931, the record wettest November here is 1991, around 1.9" - we may beat that actually, as it may rain or snow a bit tomorrow before the 11/28 system.

In the past 90 years, November is correlated pretty well to January for precipitation - typically the wetter November is, the wetter January is. Last big wet November here was in 2016, and then January 2017 was very wet too.

[Chinook]

22 hours ago, Chinook said:

2nd piece of our snow storm is coming in right now.

The 12z Euro has 6-7" of snow all around Denver metro, up to my area, for Monday-Tuesday.

Much later than I posted this, the snowfall really started. Apparently it snowed 2.5" to 3.5" in Denver overnight. My area got about 1" overnight.

[mayjawintastawm]

We got a surprise 2.5" at least, maybe a hair more. Not expected! Good moisture and the commute home will be fine, just as we like it.  23" on the season to date. I think this is the most pre-Thanksgiving snow we've had since we moved here in 2010.

[Chinook]

Tuesday: The GFS and Canadian continue to have 7.9" - 14.1" for Fort Collins-Longmont-Denver stations on the maps. The 00z and 12z Euro went north to Scottsbluff Nebraska with a large amount of snow, and the Front Range cities are mostly dry. I think the Euro has the surface front farther north.

[raindancewx]

So far, the Northwest mountains have been getting screwed on precipitation, while the Southwest has been doing OK to well.

[Chinook]

As I mentioned in October (I believe,) there are above normal water temps in the North Pacific, south of Anchorage, by 2 degrees C. I think this has, in this 30-day time period, helped larger ridges to form in the NE Pacific, leading to troughs in the central US. I think the warmer water temps in many recent years have led to larger 500mb-ridges in Alaska, helping to send down arctic air, like during "the blob" of 2013 or 2014 or something like that. So, too much ridge action near Seattle means that little precipitation has fallen. Now, of course, our synoptic systems are also linked to other things, most notably the MJO and east Asian jet streams.

 

 

[Chinook]

We will get a winter storm watch for the northern half of Colorado.

[raindancewx]

I'd really like to see another 0.7"+ precipitation here by the end of the month. We haven't had a record wet-month for the 1931-now era in Albuquerque since September 2013 when 3.97" fell.

The GFS and European are really struggling with the storms for NM & CO this week again. I think they'll start to have a unified message by Sunday Night though. Weather.com currently has a snowy Wednesday Night for Albuquerque, which would be a mess for travel. 

There are some striking similarities to the Fall pattern so far, both in the US and for global ocean patterns/oscillations. One thing that would really cement last year as a good analog is the CFS depiction of a positive SOI burst (La Nina) in December, at basically the same magnitude as last December. I don't think the once-in-a-century cold places like Billings experienced last February would necessary repeat, but you'd probably see another warm month in the SE US with cold displaced somewhere to the NW of that zone if the SOI verified at +10 in December. It'd be a huge change from November if nothing else, since we are running around -9 so far.