Successive Snow Storms, Seattle, WA, February 3 to 12, 2019

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Successive Snowstorms

Seattle, WA

February 3 to 12, 2019

Event summary

An extended period of cold air and a series of storm systems moving onshore from the Pacific Ocean combined to produce multiple snowstorms in the Seattle, WA area. The Seattle-Tacoma International Airport received 20.2 inches of total snowfall from February 3 to February 12, 2019. Data from the Preliminary Local Climatological Data Form F6 produced by the Seattle/Tacoma, WA National Weather Service Forecast Office shows snow was recorded on February 3 and February 4 and for five days in a row from February 8 to February 12.

For reference, the first three columns are day of the month, high temperature (^oF), and low temperature (^oF). The eighth column is liquid precipitation (inches) and the ninth column is snowfall (inches).

F6 for the Seattle-Tacoma International Airport

 1  50  44  47   4  18   0 0.68  0.0    0  7.7 15 210   M    M  10 1      20 200
 2  48  41  45   2  20   0 0.03  0.0    0  7.0 15 190   M    M   9 1      18 190
 3  42  31  37  -6  28   0 0.09  1.0    0 11.2 24 190   M    M   9 1      32 190
 4  32  25  29 -14  36   0 0.13  1.7    1 16.6 30 360   M    M   8 129    39  10
 5  34  20  27 -16  38   0 0.00  0.0    3  3.9 10  20   M    M   3 8      12  20
 6  37  20  29 -14  36   0 0.00  0.0    1  4.7 12 110   M    M   1        15 140
 7  39  25  32 -11  33   0 0.00  0.0    0  5.4 10 110   M    M   6        14 360
 8  37  29  33 -10  32   0 0.46  6.4    6  7.4 16 110   M    M  10 12     22  90
 9  33  25  29 -14  36   0 0.16  1.5    6 13.8 25 360   M    M   8 1      33 350
10  36  21  29 -14  36   0 0.16  3.5    7 12.1 25 190   M    M   6 128    35 190
11  38  29  34  -9  31   0 1.22  6.1    6  7.2 16 110   M    M  10 12     22 170
12  40  34  37  -6  28   0 0.86    T    7  9.2 16 190   M    M  10 1      22 180

Discussion of Atmospheric Features

The first two sets of maps show the movement and evolution of the 500 mb (upper level) and surface components of the storm that produced snow from February 3 to February 4. The third and fourth sets of maps show the movement and evolution of the 500 mb and surface components of the succession of storms which produced snow from February 8 to February 12. The weather pattern was conducive for allowing cold air to get into Seattle and the Puget Sound region. A large and elongated cold surface high pressure system covered the plains of Canada and extended south into the United States. The high pressure system was pushing cold air up against and into the Rocky Mountains. At the same time, in association with the storm on the 3rd and 4th, a deep upper-level low pressure trough at 500 mb moved south to cover southern British Columbia, the Pacific Northwest of the United States, and the adjacent Pacific Oceans waters. Another trough at 500 mb then took a similar track to support a rapid succession of three more storms from the 8th to 12th. The troughs allowed the cold air to move west and at the same time helped guide a series of surface low pressure systems into the coast of Washington State and Oregon. Since the cold air over the high plains was so persistent, it had plenty of time to flow through the mountain valleys toward the coast. Cold air typically gets into Seattle by entering the Strait of Georgia region from the Fraser River Valley at Vancouver, British Columbia, then spreading south into the Puget Sound basin. The article on Puget Sound Cold Air Outbreaks discusses cold air outbreaks in more detail.

Upper air (500 mb) map summary for February 3 and February 4
National Weather Service Storm Prediction Center

00 UTC February 3, 2019 (4 PM PST February 2, 2019)

12 UTC February 3, 2019 (4 AM PST February 3, 2019)

00 UTC February 4, 2019 (4 PM PST February 3, 2019)

12 UTC February 4, 2019 (4 AM PST February 4, 2019)

Surface map summary for February 3 and February 4
National Weather Service Weather Prediction Center

Upper air (500 mb) map summary for February 8 to February 12
National Weather Service Storm Prediction Center

12 UTC February 8, 2019 (4 AM PST February 8, 2019)

00 UTC February 9, 2019 (4 PM PST February 8, 2019)

12 UTC February 9, 2019 (4 AM PST February 9, 2019)

00 UTC February 10, 2019 (4 PM PST February 9, 2019)

12 UTC February 10, 2019 (4 AM PST February 10, 2019)

00 UTC February 11, 2019 (4 PM PST February 10, 2019)

12 UTC February 11, 2019 (4 AM PST February 11, 2019)

00 UTC February 12, 2019 (4 PM PST February 11, 2019)

12 UTC February 12, 2019 (4 AM PST February 12, 2019)

Surface map summary for February 8 to February 12
National Weather Service Weather Prediction Center

Radar images during peaks of precipitation
National Centers for Environmental Information (NCEI)

09 UTC February 4, 2019 (1 AM PST February 4, 2019)

21 UTC February 8, 2019 (1 PM PST February 8, 2019)

02 UTC February 11, 2019 (6 PM PST February 10, 2019)

03 UTC February 11, 2019 (7 PM PST February 10, 2019)

18 UTC February 11, 2019 (10 AM PST February 10, 2019)

21 UTC February 11, 2019 (1 PM PST February 11, 2019)

00 UTC February 12, 2019 (4 PM PST February 11, 2019)

03 UTC February 12, 2019 (7 PM PST February 11, 2019)

06 UTC February 12, 2019 (10 PM PST February 11, 2019)