If At First You Don’t Succeed…. Repeat The Forecast.

3 AM Snowfall
Snowfall Eugene South Hills 600 Ft. Elevation 3AM 2.22.18 | Photo by Michelle Chuey

I’ve been in the weather forecasting business since 1972 and like most of us in this line of work the struggle has always been to produce the most accurate forecast possible. The problem arises when the forecast doesn’t verify. That’s a meteorologists term for when the weather doesn’t cooperate and goes against what I said would happen. This is particularly frustrating here in the Southern Willamette Valley when a Winter storm is moving down from the north. All indications are that we will get at least a dusting of snow on the valley floor and possibly a couple of inches could pile up. The storm hits Washington and sweeps into Portland dumping at least a couple of inches of snow producing dangerous driving conditions. That storm was expected to push into the Eugene-Springfield area complicating our daily commute.

Trough Monday 2.19.18
Upper Level Low Pressure Trough Over Pacific Northwest Monday 2.19.18 | Image by NOAA through sfsu.edu

As luck would have it the snowfall stopped just to our north. That made all of us in the forecasting field look like we got it wrong. Well, I think it is a good idea to show you what actually happened. An upper level low pressure trough (shaded “U” shape with blue arrows) was positioned over the Pacific Northwest in such a way as to give us a north-northwest airflow bringing cold Arctic air down through Canada.

Surface Storm
Surface Low (L) Sliding Southward Along Oregon And California Coasts | Image by NOAA Weather Prediction Center

A surface low with its associated cold front was moving southward along that upper level airflow aiming the cold air right at us. This is why the storm was forecast to push all the way south into the South Willamette Valley. The perfect scenario was set up for all of the Willamette Valley to receive a significant snowfall right down to the valley floor.

Snowfall Prediction
National Weather Service Forecast Office Portland Snowfall Predictions | Image by NWSFO Portland

The National Weather Service Forecast Office in Portland issued their snowfall forecast for Tuesday evening 2.20.18 which included a 2-4 inch amount southward down to the Eugene-Springfield area. Portland received a record 4.2 inches of snow on Tuesday and a record 0.50 inch of snow on Wednesday. You don’t have to guess how that turned out for us. The storms energy hit north, but died out before reaching us and the result was just a trace of rain and no snow for Eugene. You might say, and many probably did, that we blew that forecast. You might be correct, or did the situation change just enough for the storm to miss us?

Trough Thursday
Upper Level Low Pressure Trough Position Thursday 2.22.18 | Image by NOAA through sfsu.edu

An Upper Level Low Pressure Trough sets up again Wednesday night into Thursday in the same position as Monday into Tuesday. Another surface storm is expected to ride down the backside of the trough giving us the chance for another possible snow storm. Imagine you are the forecaster. There is an old saying “Fool me once shame on you, fool me twice shame on me.” Do we forecast the snowfall knowing the last time it missed us or do we assume the same scenario will repeat itself and downplay the storm? The thing I learned years ago is that you can’t let the previous forecast effect the next one. I’d much rather warn you that a storm looks likely and have you prepared rather than be gun-shy and assume no snow will fall. That brings up another one of my favorite sayings ” When you assume you make an ass out of you and me.”

Hourly Observations
Observations For Eugene Maylon-Sweet Airport | Image by NWSFSO Portland

The NWSFO  observations for Eugene shows snow falling from 1:54 AM through 9:09 AM Thursday. There’s absolutely no problem verifying the forecast this time. Some snowfall totals reported for Thursday 2.22.18 include 2.00 inches at the Eugene Airport, public reports 4 inches in Marcola and 3-4 inches of snow in the Oakway area. At 600 ft. elevation in South Eugene I measured only 0.75 inch to 1.00 inch of snow in my driveway Thursday morning. Portland saw 1.7 inches of snow Thursday beating their old record of 1 inch of snow back in 1957.

3 AM Snowfall
Snowfall Eugene South Hills 600 Ft. Elevation 3 AM 2.22.18 | Photo by Michelle Chuey

My Daughter Michelle took a picture out of a window looking to the east from our house at about 3:00 am Thursday showing how beautiful the snowfall looked. That’s of course before you have to go out your door and drive or walk on it.

Snowfall 9:00 AM 2.22.18
Snowfall Eugene South Hills 9:00 AM Thursday 2.22.18 | Photo by Tim Chuey

Here’s what it looked like at about 9:00 am Thursday from my driveway. The snow was beginning to compact and later in the afternoon would be nearly gone. To sum this all up, yes one forecast was a bust. The second one, however, was spot on accurate. We did receive significant snow accumulation down to the valley floor. The roads were a bit slippery, but for the most part driving conditions were more of a nuisance than a hazard because it melted away rather quickly.

Snowstorm 24 Hours Later
South Hills About 24 Hours After Snowstorm Picture Taken 2 AM 2.23.18 | Photo by Michelle Chuey

One last picture shows just how long this particular storm lasted. I convinced my daughter to attempt a recreation of her nighttime snowstorm scene abut 24 hours later and, as you can see, the snow is just about gone.

To wrap this up I can give you my philosophy of weather forecasting. I would much rather give you a forecast for a storm that doesn’t materialize than to give you a rosy forecast and have you caught unaware in a bad weather situation. Too may lives and livelihoods depend on knowing what to expect from the weather to be flippant or careless when letting you know what kind of weather we can expect at any given time.

By the time you read this we very well might be in the throes of another snowstorm or maybe not. Just remember Winter is not over yet. Spring officially begins with the Vernal Equinox at 9:15 AM PDT Tuesday March 20th, but that doesn’t mean that Winter weather will be over at that time. Historically we have seen Winter storms reach into the month of April. The Boy Scouts of America have the right idea. You must always “Be Prepared.”

Let me know what you would like me to talk about or explain. You can comment below or email me at: [email protected].

Tim Chuey is a Member of the American Meteorological Society and the National Weather Association and has been Awarded Seals of Approval for television weathercasting from both organizations.

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