Wetand News

Most of you will see some snowflakes on Sunday, but for those living near sea level, few will experience accumulating snow. The problem?  The air in British Columbia is too warm and temperatures near sea level will remain marginal for snow to reach the surface. This is the great frustration of Northwest weather forecasters in winter:  marginal temperatures for the white stuff near sea level. Looking now in southern British Columbia, one is underwhelmed  by the tepid temperatures (see below),  Temperatures in the 30sF and 20s.  No strong push of cold, northerly flow. The forecast temperatures don't produce any cold thrills.  The predicted temperatures around 5000 ft (850 hPa pressures)  for Sunday at 10 AM are shown below (red dashes), with difference from normal shown by shading.  Dark blue is much colder than normal.    No sign of primo cold air in British Columbia. And we need cold British Columbia air to displace the mild, marine air that normally floods our region...assuming y

Our region will soon experience colder temperatures and substantial snowfall in the mountains.  The snow level will fall and virtually everyone will see some snowflakes. But the truth is that we will NOT be experiencing the primo Arctic cold air associated with most major lowland snow events, with minimal snow falling around Puget Sound  near sea level . But there is a substantial lowland snow threat and for that one will have to look southward towards Portland and western Oregon. Portland May Get Much More That A Dusting The transition starts on Thursday as a low pressure center moves south of us, pulling cooler air southward from British Columbia (see sea level map below for 1 PM Thursday, with blue colors being colder air). The wind gust forecast for Thursday morning shows northeasterly winds pushing through the Fraser River Valley, across the San Juans, and out the Strait into the Pacific.  Cool, northerly winds will also push southward into the Pacific. But there will be little m

 Earlier this month, stratospheric temperatures warmed by roughly 100F over a period of a few days, in what is known as a Sudden Stratospheric Warming (SSW) .  Should you be concerned?  The stratosphere, by the way, is the layer of the atmosphere from roughly 10 to 50 km above sea level. As we will discuss, such stratospheric warmings are sometimes associated with distortions and alterations of the winds and temperatures in the lower atmosphere, resulting in anomalous weather from heat waves to snow storms .  And major changes in the infamous  polar vortex . There are actually two polar vortices:  one high in the stratosphere  and another in the troposphere Based on this incipient warming, some media has been warning about severe weather for several weeks, including major snowstorms over the eastern U.S. (see below).   The Warming     Early in January, the temperatures high in the polar stratosphere started to warm suddenly and profoundly.    Take are look at this NASA plot of temperat

We have an interesting week ahead (more below).  We start with generally dry conditions for most days through Thursday as high pressure build over the region.   But as the high pressure moves offshore, our region moves into much colder northerly flow.  And embedded in that northerly flow there are some wet disturbances that could bring lowland snow.   Too e arly to have any confidence in the forecast.   And then there was the windstorm on Wednesday morning.  Why did the US model underplay it and the vaunted European Center model get it right?   I talk about all of this on the podcast. Here is my podcast: Click the play button to listen or use your favorite streaming service (see below) But since I know many of you are interest in cold and snow, let me give you a view of the latest forecast for the end of the week. The latest UW WRF pressure and temperature forecast for Friday morning is quite cold, with blue colors showing low-level temperatures cold enough for snow.  But in this forec

It's just after midnight winds are really blowing out there now.....I can hear branches snapping.  Lights are flashing on the horizon and it's not lightning....it is the green colors of transformer fuses blowing. By 1 AM about 67,000 Seattle City Light Customers have lost power and roughly 308000 Puget Sound Energy customers were in the dark.'  A major power outage for the region. Winds are gusting to 50-60 mph last night.  The max winds through 5 AM are shown below.  Lots in the 40-50 mph, some as high as the mid-60s. But if you want to be impressed, the max wind gust hit 121 mph at Alpental Summit (see below).   That is serious wind. The peak winds at Seattle's West Point reached 51 knot (59 mph)...and peak wind on the Evergreen Floating bridge got to 56 mph. Where did the strong winds come from?   A small, but intense, low pressure system passed just to our north, producing a large north-south pressure difference (gradient) over western Washington (see forecast map o

Note: My next blog will be on the sudden stratospheric warming over the Arctic and the implications for the long-term weather forecast. Major changes in the large scale weather circulation in the offering! __________________________________________ As promised, a potent atmospheric river has hit our region, with very heavy precipitation on the upwind (windward) sides of regional terrain. Let be begin by showing you a satellite-based view of total atmospheric moisture from late yesterday.  Purple and red are the highest amounts.   Satellites can sense water vapor content based on the emission of radiation by water vapor.   You can see the plume of moisture heading into us from the southwest.  Amazingly,  our moisture plume can be traced back thousands of miles to the western Pacific near the Philippines and Indonesia: the region of the warmest water on the planet, known as the warm pool.   The map below shows the precipitation for the past 24 h (ending 8 AM).  Some locations on the sout

The most powerful atmospheric river of the season so far is now imminent and will reach our coast later tomorrow (Monday). Atmospheric rivers are fascinating creatures.   Why does the atmosphere concentrate water vapor into fast moving narrow currents?  And why do such currents provide such bountiful precipitation and are so optimal for promoting floods and landslides?    These questions are among those that I and others have researched over the past decades and pretty much understand. Below is a graphic showing the key parameter that characterizes atmosphere rivers, something called Integrated Water Vapor Transport (IVT ),that is forecast for Monday night at 10 PM.  IVT is essentially the magnitude of the water vapor being moved by the atmospheric.  Mathematically, water vapor constant times wind speed. In tis figure, the blue areas are locations with very high values of IVT (over 800 in the units shown) Bringing a lot of water vapor in the area provides a source of water for