Quick Look Towards Early Next Week

November 25, 2014

We tied a record high today, broke a warm record low this morning, and will probably break a record high again tomorrow:

MarkWarm_PortlandRecords

Because of the warm weather, travelling conditions are excellent this weekend

MarkRoadConditions_I84_5_Passes

Enjoy the warmth because it’ll end quickly this coming weekend.

Maps/models have been interesting the past few days; fraught with forecasting peril.  The reason?  A split flow with most jet energy going to our south the next week but some northerly flow in the upper atmosphere too.  Over the past two days the emphasis has been on a shot of colder air Saturday-Monday moving down from the north and into the Pacific Northwest.  It doesn’t last long, because it appears the milder southern portion of the jet will take over again early next week.

There are two reasons the forecast is uncertain in this situation:

1. The interaction between moisture to the south and colder air to the north always raises the possibility of frozen precipitation, mainly in the Gorge, but at times models have shown it almost cold enough in the metro area.

2. Placement and timing of precipitation changes with model runs depending on how much energy from each part of the jet stream affects us most.

As of this evening, it looks like we’ll see a shot of the cold air arrive on Saturday.  This will be drier air so not much rain Saturday.  Then dry offshore flow kicks in for two days (Sunday and Monday).  Get ready for a couple of days of cold east wind.  High temps around 40 instead of 60!  On Sunday we’ll probably be dry, but then models are bringing moisture over the top of the cold air Monday.

Monday is the day I see a good chance for freezing rain and/or snow in the Gorge.  Here in the metro area it remains to be seen if it would be cold enough for freezing rain.  Definitely a marginal event, more so than what we saw a couple of weeks ago.  Plus we’ll see when/where the moisture shows up.  The evening ECMWF doesn’t even give us precipitation Monday!

Another reason to just relax and enjoy Thanksgiving!

I’m working Friday-Sunday and I’ll have a lot more time to see how things are shaping up.

Chief Meteorologist Mark Nelsen


Cascade Meltdown: Bad News in The Mountains

November 25, 2014

As I mentioned in a post late last week, the brand new snowpack was going to have to endure several days of warm temps and rain this week before we get back to cooler weather.

It’s not doing well.  In just 24 hours or so, we’ve seen the nearly 2 feet of snow compress/melt down to 10″ or less.

MarkSnowPack_MeltingQuickly

That’s due to unusually warm weather (45-50 degrees at Gov’t Camp) and heavy rain.  It appears at least 2″ has fallen on Mt. Hood, possibly 3-4″ in spots too.  A 5 foot deep snowpack in midwinter could absorb that much rain and not lose too much depth.  But this rain is falling on fresh snow which can’t handle a deluge.

We have one more warm (but dry) day in the mountains, then another warm/rainy system for Thursday.  So most of the last 10″ will be gone by the time sunrise hits Friday.  At that point all three ski areas on Mt. Hood should only see patches here/there along with any snow harvested from parking lots or created through snow making during that cold weather.  Skibowl tells me they made 3 feet of snow on the tubing run during the cold weather, so that should survive.  Meadows has some new toys that allow them to move all the parking lot snow onto the slopes…that’s pretty clever.  This is not all that unusual to see a miniscule snowpack in late November…check out the numbers for the past 8 years:

MarkSnowPack_MeltingQuickly2

So when DO we get new snow up there?  Possibly some on Friday…maybe.  Then forecast models are all over the place Saturday and beyond.  For now, you can assume there won’t be any big ski area openings through this weekend.  By that I mean 30% or more of the runs open.

Chief Meteorologist Mark Nelsen