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Chinook

Mountain West Discussion

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On ‎9‎/‎30‎/‎2017 at 0:31 AM, Dakota said:

The Canadian model brings some snow into western SD and even far western Nebraska late Monday.  The Black Hills could see their first accumulating snow of the season. 

Nothing out of the ordinary as Lead (elev. 5347') has a mean October snowfall of 10.7" and Rapid City (elev. 3379') with a mean of 2.3".

Going through some of the snow data for Lead reveals some pretty amazing numbers...including 64.6" of snow in October 2013 (the record for October was 70.2" in 1995)...and a 364.7" total for the 1993-94 winter as a whole. 

In sharp contrast, the NWS WFO Rapid City had "only" 25.5" of snow in October 2013.

 

 

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11 hours ago, Dakota said:

Going through some of the snow data for Lead reveals some pretty amazing numbers...including 64.6" of snow in October 2013 (the record for October was 70.2" in 1995)...and a 364.7" total for the 1993-94 winter as a whole. 

In sharp contrast, the NWS WFO Rapid City had "only" 25.5" of snow in October 2013.

 

 

Lead, S.D. / 10 Snowiest Winters:

1/ 364.7" / 1993-94
2/ 324.0" / 1996-97
3/ 287.9" / 1995-96
4/ 280.5" / 2008-09
5/ 265.4" / 2007-08
6/ 262.6" / 1982-83
7/ 258.2" / 1976-77
8/ 253.1" / 2005-06
9/ 242.1" / 1983-84
10/ 233.2" / 1997-98

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Big difference down at the Rapid City NWS WFO 1968' lower and about 32 miles to the SE of Lead: 

Rapid City, S.D. NWS WFO / 10 Snowiest Winters

1/ 90.2" / 2008-09
2/ 80.3" / 1969-70
3/ 79.3" / 1949-50
4/ 73.5" / 2013-14
5/ 73.0" / 2012-13
6/ 67.1" / 1970-71
7/ 66.6" / 1919-20
8/ 66.5" / 1926-27
9/ 66.4" / 1928-29
10/ 64.1" / 2000-01

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The three better long range models (ECMWF, Canadian, and GFS) are not too anxious to bring down any substantial cold air anywhere in the Lower 48 over the next 240 hours or so.

There is actually some cold air up north; as some places well above the tundra and taiga of Nunavut have temperatures of less than -20 C @ 850 MB.

I just found out yesterday that Nunavut was a Canadian Territory; as the Northwest Territories were divided back in 1999...with Nunavut now comprising the eastern sector.  The Yukon is, of course, the 3rd Canadian Territory.

But overall, the next 10 days do not look terribly winterish anywhere in the Lower 48.

 

 

 

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I guess Rapid City, snow-wise, is kind of a mix between the very snowy northern Black Hills (north wind blizzards,) and normally dry western Dakotas. And when I say normally dry, I mean the western half of the Dakotas, (Black Hills excluded) have relatively low amounts of snow and rain, although the snow could last a long time.

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12 minutes ago, Chinook said:

I guess Rapid City, snow-wise, is kind of a mix between the very snowy northern Black Hills (north wind blizzards,) and normally dry western Dakotas. And when I say normally dry, I mean the western half of the Dakotas, (Black Hills excluded) have relatively low amounts of snow and rain, although the snow could last a long time.

Outside of the Black Hills and in Rapid City proper, bare ground is not uncommon from December through February.  Most of the snow falls in March and April here anyway.  With the chinook winds coming down the eastern slopes of the Rockies and many arctic anticyclones passing too far to the east; (and the cold, dense air is sometimes too shallow to make its way up into the higher spots) its pretty easy to see why, in many ways, Rapid City experiences some of the mildest winter temperatures in the Dakotas.

You are right; most of the western third of the Dakotas outside the Black Hills would be considered semi-arid; Rapid City right on the cusp.

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38 minutes ago, Dakota said:

Outside of the Black Hills and in Rapid City proper, bare ground is not uncommon from December through February.  Most of the snow falls in March and April here anyway.  With the chinook winds coming down the eastern slopes of the Rockies and many arctic anticyclones passing too far to the east; (and the cold, dense air is sometimes too shallow to make its way up into the higher spots) its pretty easy to see why, in many ways, Rapid City experiences some of the mildest winter temperatures in the Dakotas.

You are right; most of the western third of the Dakotas outside the Black Hills would be considered semi-arid; Rapid City right on the cusp.

I actually e-mailed the NWS office out here today to see if they could find some additional records; the stuff on the NOAA site has huge gaps in the snowfall records for most of the stations around here.  The gentleman was very courteous and indicated that he would see what he could dig up.

Here's the Rapid City snowfall monthly averages at the NWS office downtown; but again, its a record....dating back to 1888...just after the town was incorporated...with quite a bit of missing data; it pretty much follows a Denver pattern; though Denver about 10 inches snowier per average year...and Denver likewise with plenty of intervals with bare ground during the winter.  Even with frigid temperatures at 44 N; it doesn't take a lot to melt snow with such typically low water equivalents; and of course the area sees quite a bit of sunshine.  It was a chilly and overcast day today; clearing late and temps have dropped back into the upper 20's and lower 30's just before 10:00 PM MDT...the coldest day of the season so far.

 

September: 0.1"

October: 2.9"

November: 6.5"

December: 6.3"

January: 5.4"

February: 7.8"

March: 10.2"

April: 9.0"

May: 2.0"

June: T

Annual Average: 50.2"

  

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12 hours ago, Dakota said:

The three better long range models (ECMWF, Canadian, and GFS) are not too anxious to bring down any substantial cold air anywhere in the Lower 48 over the next 240 hours or so.

There is actually some cold air up north; as some places well above the tundra and taiga of Nunavut have temperatures of less than -20 C @ 850 MB.

I just found out yesterday that Nunavut was a Canadian Territory; as the Northwest Territories were divided back in 1999...with Nunavut now comprising the eastern sector.  The Yukon is, of course, the 3rd Canadian Territory.

But overall, the next 10 days do not look terribly winterish anywhere in the Lower 48.

 

 

 

Taking another look at the mid-range models over the next two weeks; really a general consensus remains...most of the nation mild and not too unsettled; most of the active weather over Canada...British Columbia should see some extraordinary snow totals through the end of the month...and it will be snowy over the northern Prairie Provinces (especially Manitoba)...and the northern half of Quebec.  There might be a couple of shots of cooler air coming down in the Great Lakes and New England (really just restoring seasonable temperatures)...but most of the wintry weather should remain (well) north of the border. 

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Just a bit of amplification in the pattern this month. The look so far is actually not super far off from what I put out what for winter, but I think it relaxes/reverses at times, and its further south as the cold air builds. We shall see. Pretty sure Nov is going to be quite warm for much of the West though.

 

DMN8Sn-VoAA5NHD.jpg:large

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1 hour ago, Chinook said:

We'll start the winter thread whenever my point&click forecast doesn't say 70 degrees, which should be within the next 7 days.

Obviously a long ways out, but the GFS is sniffing around a broad cold air intrusion for the 26th and 27th.  

 

plt03.gif

 

plt03.gif

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Yep, the 26th-28th could be a turning point to wintry weather, say, for example, high temp of 45, chance of snow (for 5000-5200 ft). Let's see if the GFS ensembles and ECMWF ensembles trend this way in the next couple of forecasts.

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This probably made some neat lenticular clouds near Denver. I got a pic of some thin lenticular clouds about 1 hr after this (satellite image is from 18:02z)

Xvkk88o.jpg

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Last year, the La Nina was starting to peak about this time. With cold Neutral conditions for the moment, Nino 3.4 is way warmer than last year. The changes y/y resemble a Modoki El Nino, although the tropical Pacific is cold overall in absolute sense.

Atlantic is colder near the US - always a good sign for wetness/moisture out here.

hI7YOOT.png

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Moderate to strong La Nina years:  (see list of years.) If you composite these temperatures vs. the 1981-2010 normal temperatures, you find below normal to normal temps from Los Angeles to Denver. That does not mean that all these Southwestern areas have above normal precip; they do not. North Central and West Colorado climate divisions average above normal precip, but most of the Southwest is below normal. The upcoming winter is not necessarily a strong La Nina-- it hasn't even formed into a La Nina yet.

bPgF0Wd.png

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^^  I went with the following for my winter analogs:

1932: x2, 1943: x3, 1944: x3, 1996: x3, 2005: x3, 2007: x3, 2008: x2, 2012: x1

1932 Atlantic hurricane season is very similar to 2017: Irma=Fl/AL Hurricane, Nate= Tropical Storm 11, Maria = San Ciprian, Harvey = Freeport, similar attempt at an El Nino in Summer before cooling, had a big time volcanic eruption (Agung as a VEI 5 in 2017?) before winter, similar PDO values, two years after a big El Nino in 1930-31, which itself followed an El Nino like 2014-2015 (1929-30). Winter 1931-32 temperature anomalies were similar to 2016-17 as well. I pray to god the similarities break - this is not a good time globally for a dust-bowl pattern (1933-34) to re-emerge. I have 2007 in there to cancel out the Neutral years, and 2012 is in there because of how warm it was in the SW.

All analog years (except 2012) had low solar activity. Mean of the analogs is a La Nina following a La Nina. PDO is near 0 in the mean. Structure of the La Nina mean is Modoki-ish, but less so than last year, with Nino 1.2 expected much colder. The blend of the years also matches well to observed Monsoon rainfall totals, as a sanity check on the weighting. Globally, I was pretty pleased with the look of the oceans v. what the models have for winter. Atlantic has warm anomalies north of the cooler anomalies in the tropics, which is what we have now and what we should see in winter. Pacific looks OK in the La Nina zone, with similar PDO features. 

Main issue is the Indian Ocean is cold now, unusual for a La Nina, and the analogs don't have that. So the MJO will probably screw up the timing of the cold shots and heat waves in the winter, but overall it looks close to me. The relatively huge cold shots in the West in late Sept & Oct (valleys in Western NM were in the mid-20s in Sept) are consistent with some of the big time cold shots in the analogs. Not expecting a cold winter here, but much colder than last year. The structure of Summer heat here corresponds well to winter cold - we had 96 days at 87F or hotter here, but only 21 at 95F or hotter. Last year, 83 days at 87F or hotter, but 33(!) at 95 or hotter. To me, implies the warm days this winter are less warm, even though there will be still be a lot of them. July was nearly 4F colder for highs v. 2016, and July corresponds fairly well to Dec here as well. I see people like 1999-00 for this winter, but that was a super cold Summer in the West and then a super hot winter nationally, it was a strong La Nina following a strong La Nina, 1999 had very high solar activity, which we don't have at all, and the PDO was super negative.

Some years I considered for analogs but didn't use: 1933, 1954, 1962, 1984, 1985, 1995, 2011. 

I have an analog system that automatically selects best years to a wide variety of independent conditions. It had 1984 as the best match to the winter pattern, but I threw it out because the AMO was so cold that year. If you use super-warm AMO years though, you can blend in 1984 with it:

1932: x1, 1933: x1, 1943: x3, 1944: x4, 1984: x1, 1996: x1, 2005: x1, 2007: x1, 2008: x1, 2012: x1

I went with the first blend ultimately, because I don't think the cold AMO years really have any place in helping with the current pattern. Blends aren't super different though -

 

kvkpQXB.png

eit0jgu.png

I put out my winter forecast a week ago if anyone is curious - https://t.co/ZnvyQletct

 

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That's kind of what happened last year though (decent match to 1942) - pretty dry for a La Nina in Washington, and Montana didn't really see a huge year either.

EEIyLRj.png

I think the blend has a pretty big Spring in parts of the NW though.

To me, there are 27 La Ninas (July-June basis) since 1930: 1933, 1938, 1942, 1949, 1950, 1954, 1955, 1956, 1964, 1970, 1971, 1973, 1974, 1975, 1983, 1984, 1988, 1995, 1998, 1999, 2000, 2005, 2007, 2008, 2010, 2011, 2016. You had substantial dryness in parts or all of the NW in 1938, 1942, 1954, 1956, 1975, 1983, 1984, 1988, 2000, 2008, 2011, 2016

The NW seems to be drier in La Ninas after La Ninas - that's factored in the analog system I have - since I use ENSO order as a variable.

3B0THk4.png

 

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Also, for what it's worth, this is the latest CFS run. We're close enough to winter that it probably isn't completely out to lunch for the season. I'm not a huge fan of the models for temps/precip, but I do try to look at them. I think they are much better at forecasting ocean temps v. anything else.

jFZcomq.png

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