The big storm for the east coast that we discussed last Wednesday and Friday certainly did a marvelous job! The snows we discussed for the deep south through the northeast fell with vigor causing hundreds of thousands to be without power with New York City having its first snow day in five years. So what’s next?
Well to begin with let’s take a look at our Medium Range Forecast Precipitation Type Animation. Recall that each frame in the animation represents a 6 hour period, and that each frame represents that if precipitation were to fall within the 6 our window preceding each valid time (timestamp on bottom), what form might the precipitation take. Most users find it best to stop the animation via the controls on the bottom, and advance each frame individually.
Our first frame valid 1pm EST today (Monday March 2, 2009), shows the remnants of the big east coast storm with the greater plains free of precipitation with a respectable area of higher pressure centered generally over the Great Lakes region. However, what is going on in the Pacific Northwest?
We briefly mentioned this system last week. This very expansive closed upper low has been sitting and spinning off the PNW for quite some time, which is really not overly unusual, especially this time of year. When this occurs disturbances tend to shoot out of the system and propagate onshore and into the Northern Rockies. However this week the low seems to be in the mood to make the big move! Click the “forward one” button a few times and watch what happens. She starts to spin inland doesn’t she? In reality what will happen in this instance is a solid shortwave will move through, and cause the closed low to do what we call “shear out” as it moves into the mountainous regions of northern California.
Normally when we have a closed low off the PNW little disturbances will shoot in and cause the usual rain along the coastal regions of Washington and Oregon, no big deal, that’s the story there. As the disturbance moves inland snows of course will occur in higher elevations. However, now that the main system will shoot inland, we are going to have some more monster snows.
For the next few days we will have areas of at least two feet of snow, and quite likely three feet in the Sierras of California and then more snow, but less impressive in most of the northern Rockies as the system moves inland.
Now since we have two areas of lower pressure centered on each coast, how will that affect our temperatures? Well take a look at both our Forecast Minimum and Maximum Temperature Animations. Recall that each of these animations are at 6 hour intervals, similar to our Precipitation Type (ptype) animation above. Each represents either the minimum or maximum temperature that is forecast to occur for the 6 hours prior to, and ending at the valid time (timestamp on bottom).
Notice on the first frame of the Forecast Minimum Temperature animation, valid 1pm EST today (Monday March 2, 2009), that the freezing line (red line, toi = temperature of interest) covers a large swath all the way to the deep south, and if you advance a few frames, it tries to hang on, but some warmth is shown in the deep south.
Now compare that animation to our Forecast Maximum Temperature animation, valid 1pm EST today (Monday March 2, 2009), and let her fly! What happens? Well notice as the days progress that warm air just screams into the southern plains. This is because a large upper ridge is setting itself up in the central U.S. so that warmth will punch their way through all the way to western Nebraska. Noted Forecast Hour 36 for example, valid tomorrow / tuesday at 7pm. Very strong warm air advection just screams up from southwestern Texas through the Panhandle and up into Western Nebraska. The blue line (Temperature of Interest = TOI = 72ºF) representing 72 degrees is a nice indication of the warm air tongue and the extent of the advection.
As you advance through the next few days, notice that by the time Friday rolls around most of the south, and even portions of the midwest will begin to see respectably warm temperatures. Let’s hope it holds true for all our sakes!
Now looking more into the future we return to our Medium Range Precipitation Type Forecast Animation and advance a few frames to oh, let’s say the Forecast Hour of 102, valid Friday March 6, at 1pm.
Notice the area of lower pressure centered between northern Colorado and Southern Wyoming. What is going to happen there? If we advance a few frames through Saturday and Sunday, it is a little difficult to tell quite yet how it will choose to develop. Not an unusual scenari this far out, but we will have to keep an eye on it. So far it looks like it might try to swing up to the east, and we can see the associated rains in the midwest and snows in the northern tier from it, but quite often this far out things will vary just a tad from initial runs. The good news is we now know to keep an eye on the development!
As always stay tuned to your favorite weather outlet, stay informed, and stay safe!