A Last Gasp Of Winter? A Snowy Gorge Likely Monday

February 20, 2014

10pm Thursday…

The next 3 days look very nice weatherwise…partly cloudy skies with just a few sprinkles likely on Friday morning.  There will be rain and snow to our north in much of Washington later Saturday and Sunday, but at this point it appears it’ll all stay to our north.

I had a grand plan for this evening since I’ll be on vacation tomorrow through Wednesday.  I was hoping to put the chance of snow/freezing rain in the Gorge and north central Oregon to rest this evening for the first part of next week and then (see previous post) tell the viewers that winter is pretty much wrapped up in the lowlands of Western Oregon/Washington.  But then the 00z GFS came in even a little colder with some “backdoor arctic seepage” Monday and Tuesday.  Ewww…what is that?  It’s cold air that gradually works its way down from Canada, into Eastern Washington, and then through the Columbia River Gorge and into the Portland metro area. That’s as opposed to an arctic blast that brings cold air across the entire region.

As a result there will be no “Winter is Over” proclamation for now.

Our RPM clearly shows rain approaching the coast quickly on Sunday evening, as does the GFS and ECMWF.  At the same time pressures are lowering to our west with an approaching “warm front like”  system, high pressure and cold air is building east of the mountains.  The result is a very strong east wind (8-10 millibars) through the Gorge.  850mb temps are below zero eastside and just a few degrees above zero westside.  It will be a very shallow cold air mass west of the Cascades as a result.  My current forecast even assumes the GFS/WRF-GFS is bringing down too much cold air eastside.  In fact take a look at the snow forecast from the WRF from late Sunday night through early Tuesday morning:

or_snow48.108.0000

I think the snow west of the Cascades probably won’t happen as I mentioned, but look at the healthy totals in the Gorge!  A good 6-10″ from Bonneville to Hood River!  And snow all the way down into central Oregon too as the cold air pushes south.  You can also see with the east wind the WRF is trying to create the same heavier snow up against the Coast Range and in Columbia county that we’ve seen a couple of times this winter.   Again, I’m assuming it’s bringing too much cold air down at that time.  Note the 2 day rain totals from the same model:

or_pcp48.108.0000

IF the air is cold enough in the Gorge, which it appears to be, that’s plenty to support those snow totals.  The reason is that moist and mild westerly flow is undercutting the upper level ridge over us.

So it boils down to this:

MONDAY IN METRO AREA:  A cold and rainy day in the Portland metro area, instead of high temps around 50 or so on Sunday, temps will hover in the upper 30s to around 40 all day.  A gusty east wind 20-30 mph will make it feel colder!  Could see freezing rain as close as Corbett and the hills above Washougal in the Gorge.

TUESDAY IN METRO AREA:  Still chilly and breezy eastside.  Showers taper off, temps creep into the mid 40s.

MONDAY/TUESDAY  IN THE GORGE:  Some sort of snowfall is looking more likely this evening.  Depending on how cold the air mass is, could be just 2-3″ or if it’s as cold as these models show and with plenty of moisture, could be two days of snow with 6-10″ with freezing rain at the western end.  Extremely slow warmup Tuesday/Wednesday with cold easterly flow continuing.

Now keep in mind if models warm Monday/Tuesday significantly, none of this will happen.  Keep on top of the latest forecasts!  And the 00z ECMWF was significantly drier than the GFS.  The 00z GEM would be just barely cold enough for that snow too.  So still up in the air for sure.  Maybe LIKELY is too strong of a word.  We’ll see.

Chief Meteorologist Mark Nelsen


Long Range Outlook

February 20, 2014

Just checked out all the maps/models and made the 7 Day forecast.  Not a whole lot going on the next few days.  Friday should be dry!

It appears some sort of upper level ridging is going to be near/along the West Coast for the next 10 days or so.  This time it won’t be totally dry though because it doesn’t appear to be a big blocking ridge that shunts storms well away from our area.  Note the ECMWF ensemble forecast of upper level heights for this coming Tuesday.

ecm_tues

You see the above average heights over us.  Then by next Friday a nice cold trough runs right into California…good news for  them!

ecm_fri

Beyond that, ridging builds along the coast again during the first full week in March.  Here’s one week later on March 7th:

ecm_fri_7th

These maps tell me we are done with the stormy weather for now, and it’s on to a more “March-like” pattern with wet periods mixed with drier weather at times.   Not a real warm pattern, but we should see our first 60-65 degree temp at some point between day 7-14.   With a chilly and wet February, one thing we did miss out on was any sort of “false spring” type weather.  In many Februarys we have at least a day or two in the lower 60s…not this year!

Here are the ensemble charts from the 12z ECMWF and 12z GFS, showing no sign of real cold air, but no huge ridges either.  Interesting to note that these would say no “lower Cascades & foothill ” snow in the next two weeks either.  I’m talking the 1,000-2,500′ elevations where some people live west of the Cascades.  This is an area that has seen an unusually low snow total this season.  It’s been arctic air with snow in the lowlands, or good snow higher up in the Cascades.   Almost none of the cold/wet shower pattern with snow levels around 1,000′ to 2,000′ the whole winter.  I’ve only had 7.5″ the whole winter at my home east of Corbett at 1,000′.

tseries_850t_000-360_Portland

tseries_850t_000-384_Portland

And some more maps, the ECMWF monthly run from last night, showing average 500mb heights.  Each map covers a whole week.  You see the ridging, and then by the 4th week just a jumbled mess.

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

Chief Meteorologist Mark Nelsen