Tuesday, October 27, 2009

Brrrrrrrrr....

Anyone who has walked outside today can feel the cold front that came thru last night. Normally these inside slider storms are dry & what does cause snow is the cold unstable air being lifted by the mountains. As the cold front came thru last night a thin band of precip formed right around Truckee and then grew as it moved Southward. Snow levels were still high & the ground warm as it started at Northstar so there was at most frozen rain drops on the mountain.  It will remain cold & unstable today so a snowshower is not out of the question. It will stay cold thru Thursday so snowmaking is possible the next couple of nights.

Ok, enough about dustings, when is the next or should I say First big dump coming. The Northern jet stream is definitely strengthening and storms will begin taking aim at the West coast this weekend. The ridge off the coast of CA was thought earlier this week to retrograde back westward in the Pacific allowing storms to dive down the coast into CA starting this weekend. It now appears that the ridge will stay where it is and will be able to keep the moisture from the storms just to the North or barely touching Tahoe. We may be in for one more week of nice weather starting Friday. Wouldn't matter anyway because in that position any precip here would be rain.

I believe that the retrogression or "destruction" of the ridge off the CA coast is inevitable & is only being slightly delayed. Maybe because of some prayers or wishes by some that were caught off guard by the report of a possible big snowstorm this weekend & you have been procrastinating getting ready for winter. I think a few of you were in front of me in line for tires yesterday. For you this is your gift of an extra week to get ready.

I believe that there will be a retrogression of the ridge, possibly by the weekend of the 6th, opening the storm door. This is not only supported by unreliable fantasy charts on the models, but by the more reliable teleconnection forecasts that show the PNA & AO teleconnections heading negative for the month of Nov. This would help support a cold wet pattern for the West Coast. Only thing missing is some help from the MJO that is off on the other side of the globe, but forecasted to head East towards the Pacific the next couple of weeks. The negative SOI should be helping to get convective activity going in the tropical Pacific to help feed the jet stream as well.

The NWS 3 month outlook that shows us above average precip is based more on the months of Dec. & Jan., but I think we can get going a little early. BA

4 comments:

Anonymous said...

"by the more reliable teleconnection forecasts that show the PNA & AO teleconnections heading negative for the month of Nov. This would help support a cold wet pattern for the West Coast. Only thing missing is some help from the MJO that is off on the other side of the globe, but forecasted to head East towards the Pacific the next couple of weeks. The negative SOI should be helping to get convective activity going in the tropical Pacific"

I have no idea what that means. But I love that you are so into it that you do. Keep it up!

BA said...

haha, on the main site there is a "tools" page where you can see these teleconnection predictions.

Negative PNA mean a flatter jetstream across the Pacific & supports more storms.

AO is the Arctic Oscillation. When it's negative it is warm in the arctic & the cold is displaced South into the Continent. This usually supports cold & wet in the West.

The MJO is an area of convective moisture that drifts back & Forth from Africa to the Pacific. When it's in the Pacific it normally feeds the jetstream & causes it to crash into the west coast.

The SOI is the difference in pressure between Tahiti & Darwin in the Pacific. When it's negative it usually causes weaker trade winds or reversed from West to East instead of East to West. This would help strengthen ElNino and feed the jet stream.

That is a simple explanation.

Anonymous said...

This is nasty La Nina deja vu... I just heard some resorts on Mt Hood already have over 2 ft of snow!

BA said...

that can be the problem with an overall cold Pacific cycle that we have started. El Nino can have less of an affect unless it's strong.

Not all that uncommon though during El Nino for the fall to be wet in the Pac NW & then wet in CA once winter starts.