Hi everybody! I apologize for the delay in posts over the past several days – I have been working very hard on my Grads scripts and have been trying to figure out how to get them online! For those who don’t know, Grads is a programming language used to plotted gridded datasets such as those output by weather models. Although I still have a lot to learn, I’ve been making good progress and hope to have some of these charts online in the next few months!
We are coming off a record-wet February for Portland, and March has not proven to be much drier for us. As of 3/27, the Portland NWS office in Parkrose (where official measurements are taken) has recorded exactly 7.00 inches of rain, making this March the 5th wettest march since measurements began in 1940. And with more rain in the forecast, we have a decent chance of breaking the March record of 7.89 inches set in 2012.
Retrieved from NASA Worldview MODIS Viewer
Today’s MODIS image from the TERRA satellite shows a classic pattern we see during the springtime: diurnal showers and sunbreaks over land, with little precipitation over the ocean. The reason we see these showers over land and not the ocean is because the land heats up far more quickly than the ocean, warming the air at the surface. Since warm air is less dense than cold air, the air over land has an easier time rising through the atmosphere, forming clouds and precipitation.
During days when the atmosphere is very unstable (i.e. a large decrease in temperature with height), these showers can grow into thunderstorms. This morning’s sounding at Salem showed an average decrease of 6.76 degrees C per km for the first 3 kilometers above ground, which is slightly unstable but nothing remarkable. This number should be higher for this evening’s sounding as the ground warms up. And as you can see in the climatology below, we are approaching the time of the year with the highest lapse rates (decrease in temperature with height) and most the unstable atmosphere.
Credit: Storm Prediction Center
The atmosphere will stabilize on Tuesday, resulting in decreasing showers, but another frontal system should make landfall along the coast Tuesday evening, giving us a wet start to our Wednesday. This system could be relatively strong for this time of year, and should deliver gusty SW winds to the coast. The GFS model shows sustained winds of 30 knots early Wednesday morning along the coast, and there are currently high-end small craft advisories over the coastal waters of Oregon and Washington for this feature.
This system will also direct a good slug of moisture into the area Tuesday afternoon into Wednesday morning. Right now, the bulk of the moisture appears to be headed north towards Washington, but Portland could still pick up close to an inch with this system. If it did, Portland would set consecutive monthly rainfall records!
Thankfully for those tired of the rain, we should finish March on a sunnier note as a ridge of high pressure moves over the area for Friday.
I wish I could say I was joking, but it looks like light rain may once again move into the area on April Fools day. And unfortunately, long-range forecasts keep us wetter than normal, with near-normal temperatures. Talk about no rest for the weary!
Thanks for reading, and enjoy the sun this Friday!
Charlie
