The Third Act in the Snow Drama. Plus Freezing Rain Around Portland

 This snow drama was always going to to be in three acts.    The first was a teaser, the second was the main act, and the third will be the transition from snow to rain.

The second act brought substantial snow to the region, particularly from 11 PM Friday through 9 AM this morning.  Here are a few reports from this morning…and keep in mind that many had another inch or two after these reports.

Around 15 inches near Olympia.  12 inches at Ocean shores.    Seattle reaches 8 to 11 inches.

Public Information Statement

National Weather Service Seattle WA

1236 PM PST Sat Feb 13 2021

..SNOWFALL REPORTS…

Location                     Amount    Time/Date       Lat/Lon/Elev (ft.)

Carbonado                    18.0 in   1041 AM 02/13   47.08N/122.05W

9 WNW Alder                  16.0 in   1016 AM 02/13   46.83N/122.47W

3 N Olympia                  15.5 in   1135 AM 02/13   47.09N/122.89W

2 N Tanglewilde-Thomps       15.0 in   1118 AM 02/13   47.08N/122.77W

2 NNE Melbourne              15.0 in   1027 AM 02/13   46.98N/123.61W

Olympia                      14.0 in   0950 AM 02/13   47.04N/122.89W

2 ESE Graham                 14.0 in   1119 AM 02/13   47.05N/122.26W

5 SE Roy                     14.0 in   0932 AM 02/13   46.94N/122.47W

4 SSE Rainier                13.0 in   1042 AM 02/13   46.84N/122.64W

2 SE Tanglewilde-Thomps      13.0 in   0855 AM 02/13   47.03N/122.75W

6 N Tanglewilde-Thomps       12.5 in   1000 AM 02/13   47.14N/122.80W

7 NW Dupont                  12.5 in   1117 AM 02/13   47.18N/122.76W

5 S Vaughn                   12.5 in   0909 AM 02/13   47.28N/122.77W

6 S Port Orchard             12.5 in   1206 PM 02/13   47.45N/122.66W

9 W Alder                    12.0 in   1037 AM 02/13   46.82N/122.48W

1 SSE Lacey                  12.0 in   1001 AM 02/13   47.03N/122.80W

1 NNE Stanwood               12.0 in   1110 AM 02/13   48.26N/122.34W

1 NE Bellevue                12.0 in   0745 AM 02/13   47.62N/122.19W

Ocean Shores                 12.0 in   0930 AM 02/13   46.97N/124.16W

A snowfall map for the last 24 hr from the National Weather Service shows the heaviest amounts between Portland and Olympia (as much as 15-20 inches), with 8-12 inches extending to the central Sound.  Lighter amounts (4-6 inches) over Northwest WA.  

The forecast models were not bad, but overplayed the east-west differences.  I will be looking into this deficiency during the next few weeks (one of my projects is to improve precipitation prediction by numerical models).    

Now about the third act!

Tomorrow morning, a trough of low pressure associated with a weak front will approaching our coast (see surface weather map for 10 AM below, the solid lines indicate pressure, the color shading show low-level temperatures, and I put a dashed oval around the feature of interest).

We will have some residual cold air at low levels and the initial precipitation will be snow, but it will slowly transition to a rain/snow mix during the late morning and afternoon.

This mixed situation is indicated by the forecast precipitation fro 10AM Sunday, with colors indicating snow and gray shades showing rain.

By the evening tomorrow it will be all rain in the lowlands below 1500 ft and snow above.  And Monday, we will see all rain and temperatures zooming up into the lower 40s.

Finally, I should note that Portland and NW Oregon had a significant freezing rain even overnight, as warming temperatures aloft allowed rain above the surface that fell into subfreezing air near the surface.   As a result, the rain became supercooled (still liquid water but below freezing) and then froze on contact with the cold surface.

Portland and vicinity are particularly susceptible to ice storms because of the ready supply of cold air coming out of the Columbia River Gorge.  Seattle has no such cold air source, so ice storms are rare.

Here are some images from Oregon DOT:

The freezing rain weighed down branches and powerlines and resulted in over a quarter-million PGE customers loosing power (that is probably around 3/4 million people). Here is the power outage map this morning.

Enjoy the snow….it is beautiful.   And will probably be the last lowland snow event this season.