The Spiel on Snow

I-5 by Northgate, Washington on Sunday morning – KOMO News

First off, I’d like to apologize for not posting a blog update yesterday. I was doing tons of math homework and review, because after jumping into Calculus 125 at the University of Washington, I’ve discovered that I have a lot of work to do to get back up to speed (I skipped Calculus 124 with AP credit). I’ll be ok, but I will be spending a lot of time doing calculus. Strong math skills are essential to being a good meteorologist, so I’ll be sure to put a lot of time into my math studies.

Now, I’ve finished my math and I’m ready for some real work: forecasting snow over the next few days.

Yesterday, much of Western Washington saw snow, but only a few places really got any accumulation. Remember how I talked about the shortcomings of the LAWES scale when dealing with local weather phenomena, such as convergence zones? While much of Western Washington escaped with less than one inch of snow, places around Everett got HAMMERED with snow. Take a look at the radar image from yesterday afternoon below, and note the strong convergence zone extending all the way from the northern Kitsap Peninsula through Everett and up into the Cascades.

Meanwhile, places to the north and south got very little snow while this convergence zone was roaring. In fact,  some places saw blue sky. Take a look at the visible satellite shot below.

02:10 pm PST Sat 14 Jan 2012

This shot captures the truest essence of a Puget Sound Convergence Zone. Not only is there a band of clouds where the zone is, but there are clear skies on either side of it. As the air converges and rises in the zone, it descends on either side of the zone, stifling clouds and precipitation. Yesterday’s convergence zone was a textbook example of what a strong one looks like.

Snow totals in the Puget Sound lowlands ranged from 0-1.5 inches outside the zone to up to 4-5 inches in the zone.

Now, let’s talk about today. We are seeing a rather weak low pressure system slide on through to our south, but in the meantime, it is giving us some snow showers. Take a look at the radar and satellite from this morning.

10:51 am PST Sun 15 Jan 2012

10:00 am PST Sun 15 Jan 2012

I know the pictures are out of sync, I’m just trying to write this really quickly. In the radar, you can see some showers around the area, but most importantly, you can see a weak area of convergence getting established over Seattle. There is another convergence zone over the Strait of Juan de Fuca. Neither of these zones are particularly strong, but they will give us precipitation. The National Weather Service is also predicting the northern zone to shift south throughout the day, bring showers along with it! On the satellite picture, you can see the center of the low right off the mouth of the Columbia River. It kind of looks like a tiny hurricane. Needless to say, it isn’t.

The biggest factor in how much snow you will see today is your elevation and distance from the water. Places by the water will likely see snow, but it won’t stick to roads. Places like Capitol Hill, on the other hand, could become quite snowy. If the temperature drops below freezing tonight like it is expected to, ice will be a major problem on the roads tomorrow.

I gotta go soon, but here’s what I am predicting as far as snow goes for the future.

Today:  highly variable snow amounts ranging from 0-4 inches over the lowlands, with higher amounts over the hills and in persistent areas of convergence (LAWES 6.2)

Tomorrow: Snow picking up in the afternoon, LAWES 5.2

Things get interesting Tuesday, as a large system comes in to our south, spreading heavy precipitation over our area while bringing down cool, northerly air. The models are not in agreement on this scenario, as one brings it further north, giving us mostly rain. However, if a strong storm comes to our south on Tuesday, many places could receive up to 6 inches of snow. I don’t feel comfortable forecasting a snowstorm yet, but as the models come into better agreement, I will let you know what’s going on, because we could see a serious snowstorm mid-week.

I have to leave right now to go up to Whidbey Island, but I’ll post more pictures and snow totals from various areas later on today. In the meantime, post your snow totals along with your location and elevation on the comments so that other people can see which areas are getting snow!

Thanks for reading,

Chuck