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Mountain West Discussion


Chinook

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Chance of snow on wed followed by a strong wind event. NWS is saying 70+mph winds possible. It will be interesting to see.

What? 70mph winds in Utah? Is this a downsloping wind for you? This event won't be a downsloping 70mph wind for us. We could get a north wind at 30mph. I read the recent Boulder/Denver discussion on this, and it is a fairly in-depth discussion.

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What? 70mph winds in Utah? Is this a downsloping wind for you? This event won't be a downsloping 70mph wind for us. We could get a north wind at 30mph. I read the recent Boulder/Denver discussion on this, and it is a fairly in-depth discussion.

Yes, looks like a strong downslope event. They call these mountain wave events right? At any rate looks like a huge pressure gradient builds up against the mountains with easterly flow at 700mb veering towards the north at 500mb. Pretty classic set up. I won't see the worst of it but I may head a couple miles north to the mouth of provo canyon where its normally quite a bit stronger wednesday night.

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Yes, they call the downslope events mountain wave events. Technically it is a mountain-induced gravity wave. The stable layer near the mountaintop level helps reflect some of the wave energy down instead of letting it escape to other areas of the atmosphere. We see this sometimes when the sounding at DNR has a stable layer at 12000-14000 ft. above sea level and a dry adiabatic layer below that. Then 40-50 knot westerly winds at mountaintop level (12000-14000 ft.) sometimes make for 60 knot wind gusts at Boulder or other locations.

http://en.wikipedia.org/wiki/Lee_wave

http://en.wikipedia.org/wiki/Chinook_wind

http://www.ucar.edu/communications/factsheets/winds.html

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I've always heard that the Fraser Valley area near Winter Park is situated in a way that promotes cold and clouds. Fraser is kind of at the end of a valley. There are high mountains to the west, south, east, AND north of it. It is almost entirely surrounded. To get out of Fraser without going over a huge mountain, there is only about a 2 mile gap toward the NW, where US 40 runs. I believe this makes it much easier for cold air to get dammed in this area without wind coming in to mix it out. A NW wind would conceivably mix out the dammed cold air more readily, but this would already likely be a cold wind, since it is from the NW. Also, any cold air drainage from the surrounding mountains is coming from nearly all directions and from very high areas over 13,000 feet. A lot of this is just based on my reasoning right now so feel free to correct any deficiencies.

Great, thanks! Nice reasoning (to my untrained eye!!) Have to use that quote: "the dammed cold air is making my nose freeze!"

And it will be whiter soon as well as cold, if luck would have it.

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Great, thanks! Nice reasoning (to my untrained eye!!) Have to use that quote: "the dammed cold air is making my nose freeze!"

And it will be whiter soon as well as cold, if luck would have it.

My girlfriend and I are actually heading up that way this weekend so we'll get some firsthand experience of the frigidness! We're planning to go to Hot Sulphur Springs Saturday, stay in Grand Lake that evening, then cut down a Christmas tree from the National Forest on Sunday on the way back toward Berthoud Pass. Will definitely pack the warm clothes and snowshoes!

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GFS temperatures for Fort Collins. This shows 3 mornings below 20 degrees. The 9.7mm total precipitation is the 18z GFS precip value for both storms. That is 0.38". This could end up being 5 or more inches of snow including both storms. That doesn't sound too extreme.

post-1182-0-19259000-1322610655.png

post-1182-0-18018500-1322610691.gif

MEX MOS (starting wednesday, going to next wednesday morning)

N/X 25 57| 25 31| 10 36| 16 27| 7 32| 12 34| 14 44| 16

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GFS temperatures for Fort Collins. This shows 3 mornings below 20 degrees. The 9.7mm total precipitation is the 18z GFS precip value for both storms. That is 0.38". This could end up being 5 or more inches of snow including both storms. That doesn't sound too extreme.

MEX MOS (starting wednesday, going to next wednesday morning)

N/X 25 57| 25 31| 10 36| 16 27| 7 32| 12 34| 14 44| 16

Any such stats like this for Denver or more specifically Littleton/Englewood?

Thanks!

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Wow, things really ramped up quick with this thing! Already the third winter storm watch of the season.

...WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY EVENING

THROUGH THURSDAY AFTERNOON...

A WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY EVENING

THROUGH THURSDAY AFTERNOON.

* TIMING...FROM 11 PM MST WEDNESDAY NIGHT UNTIL 5 PM THURSDAY.

* ACCUMULATION/WIND...4 TO 8 INCHES OF SNOW ACCUMULATION IS

POSSIBLE WITH THE HIGHER AMOUNTS IN AREAS SOUTH OF INTERSTATE

70. NORTH TO NORTHEAST WINDS OF 20 TO 30 MPH LATE WEDNESDAY

NIGHT AND THURSDAY MORNING MAY PRODUCE CONSIDERABLE BLOWING

AND DRIFTING SNOW MAINLY EAST OF I-25 WHERE GUSTS WILL REACH

40 MPH.

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Wow, things really ramped up quick with this thing! Already the third winter storm watch of the season.

...WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY EVENING

THROUGH THURSDAY AFTERNOON...

A WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY EVENING

THROUGH THURSDAY AFTERNOON.

* TIMING...FROM 11 PM MST WEDNESDAY NIGHT UNTIL 5 PM THURSDAY.

* ACCUMULATION/WIND...4 TO 8 INCHES OF SNOW ACCUMULATION IS

POSSIBLE WITH THE HIGHER AMOUNTS IN AREAS SOUTH OF INTERSTATE

70. NORTH TO NORTHEAST WINDS OF 20 TO 30 MPH LATE WEDNESDAY

NIGHT AND THURSDAY MORNING MAY PRODUCE CONSIDERABLE BLOWING

AND DRIFTING SNOW MAINLY EAST OF I-25 WHERE GUSTS WILL REACH

40 MPH.

And yet here I am with 1.5 for the season and I don't really expect more than flurries tomorrow. No big snow storms in sight either. Wind will still be interesting but unfortuntely Provo as it turns out doesn't do very well with these type of events either. SLC north should get hammered though. At least I will be up there next fall

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I really don't like this screw zone type thing. I hope the NAM is wrong for my backyard. I was hoping to maybe get more than 1 or 2".

post-1182-0-16506800-1322696728.png

13 in for the Palmer Divide and 10 for me? Nahhhhh. NAM's out to lunch. Its accumulations look like they'd need a mega N-NE upslope wind which is not forecast. I'm starting to learn about this place.

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Winding up for the big blow now. NWS is saying 40-60mph sustained winds with gusts to 80mph are possible. It lists my city but I would have to assume it wont be that strong, I am thinking 60mph gusts at this time.

Centerville UT just north of SLC has been gusting to 100 MPH. Incredible downslope windstorm for portions of the Wasatch Front.

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I think I had 4 to 5". I guess I will have to try a couple more measurements in the yard. The winds were much less than 30mph here.

Looks like I'll end up with about 4-5" here as well. Another shot of snow Saturday, and then another good chance Sunday night/Monday. And temps look to remain well below normal through next week.

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I will have to revise my earlier estimation of 4-5". It looks like we have 6" in the front yard.

CoCoRAHS shows variation from 2 to 10" across Fort Collins.

I was looking at the ECMWF 2-meter temperatures on Wunderground. the 12z run has Fort Collins at about -20C for Monday morning. That's actually quite close to the MEX MOS (2 degrees F)

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