Monday, March 14, 2011

Spring Climate Transition and Storm

There are important changes that occur in the precipitation climate of northern Utah during the spring, with implications for skiers, flora, and fauna.

It is often said that April is the wettest month in northern Utah, but this observation depends on elevation.  At the Salt Lake International Airport, April is indeed the wettest month of the year, with March and May following in a close second and third, respectively.

In the mountains, however, January is the wettest month, with February (if you adjust for the relatively small number of days), March, and December not far behind.  Thus, in the northern Utah mountains, winter is the wet season, whereas in the northern Utah valleys, spring is.

Note also that the contrast between mountain and lowland precipitation is largest in the winter, decreases during the spring, and reaches a minimum in the summer.  In winter, it's not unusual for the mountains to get hammered with snow when there's little happening down in the valleys, but that occurs less frequently in the spring.

To my knowledge, this aspect of the Utah climatology has not been carefully described or explained, although it is likely related to the increased importance of deep convection, including thunderstorms, during the spring and summer.

Today, we have a spring storm approaching northern Utah with considerable shower activity over western Utah and Nevada this morning.

Thus, showers and possibly a thunderstorm are on tap for today, providing a nice example of the spring climatology of northern Utah.


  1. The April precipitation maximum seems be confined mostly to the Wasatch Front and south along the I-15 corridor, although it shows up in a few other spots around the region. I also find it curious the much of eastern Utah has an October maximum, which also shows up as a secondary maximum in some other (mostly central) portions of the state. I think the October maximum in these areas is related to interaction of frontal passages or closed lows with late-season monsoon moisture, but still seems a little odd.

  2. The spatial variability that you note is quite interesting. Climate studies frequently lump stations together by geographic region or use gridded data that might fail to capture the true signal observed at climate stations. It would be very interesting to look at some of these issues on the mesoscale. I'll put it on the to do list.

  3. Of course there is also a July/August maximum in some areas, mostly southern mountains where summer monsoon rains are the most frequent, but it seems that the October maximum is by far the most widespread in the eastern half of the state (stations such as Vernal, Moab, Blanding etc). I guess Utah really is all over the map with regards to the seasonal precipitation cycle.