Ice, Then Strong Wind Thursday PM

December 2, 2015

11pm Wednesday…

Another wet system is moving into the region tonight.  The cold airmass is still in place through the Gorge and north-central Oregon below about 3,000′ but that cold air is just about “played out”.  By that I mean the airmass has moderated by 3-4 degrees over the past 24 hours.  So the metro area is remaining ice free and the western Gorge is likely only getting light additional accumulations.   Farther east at the higher elevations of the central/eastern Gorge there should be another glazing of freezing rain during the night.

East winds have ramped up to their highest of the season so far in full ice storm mode.  I can guarantee you it’s gusting to 100+ mph on the Vista House steps with an 11 millibar easterly gradient and warm air less than 1,000′ above that location.  The Troudale profiler shows the cold airmass still about 1,500′ thick, just like last night.

You can see temps around freezing through much of the Gorge so the NWS has re-issued the Ice Storm Warning for additional freezing rain tonight.

PLOT_Temps_Gorge

The wind will back off dramatically late tonight and then…yes…it will actually turn southerly and westerly (through the Gorge) late tomorrow.  Temps at Vista House should jump from 32 to 52 in a short period at some point in the afternoon.  At that point the ice will finally melt quickly.

Now, let’s talk about the warm and mild pattern ahead.  For the next 7-9 days we’ll be in a classic, mild December stormy pattern.  Numerous cold/warm front combinations will pass through our area along with a few strong surface lows.

The first cold front passes overhead tomorrow afternoon, with some sort of surface low zooming up the coastline.  Most models have been giving us just average gusty southerly wind in the afternoon (gusts 25-35 mph) as the low moves north.  Thus 50-60 degree afternoon temps!  But the 00z WRF-GFS has come in much deeper with the low.  This is what it looks like at 3pm:

slp.23.0000

Our RPM is not nearly as strong, neither is the 00z ECMWF or GFS, but it’s still pretty windy showing about 14 millibars southerly gradient from Eugene to Olympia:

ecmwf_apcp_f24_nw

Regardless, we’re going to get a strong push of southerly wind up the coastline and valley tomorrow afternoon.  Right now I’m expecting gusts 30-40 mph in the valley, but that could change if 12z model runs get any stronger.

Beyond tomorrow, several very wet systems arrive:  later Saturday, Monday, and again Tuesday/Wednesday.  We’ll see snow level rise, then fall with each one.  But in general this is a mild pattern.  Check out the snow outlook for the Cascades:

MarkSnow_MtHoodFcst

I’m watching several possibly strong surface low pressure centers next Tuesday/Wednesday too.   Various models have shown solutions that could give us high wind in the valleys

Chief Meteorologist Mark Nelsen