Unusual Early Season Lightning But Few Fires

There has been an extraordinary amount of lighting during the last week or so....far more than usual this early in the season.  Let me show you with a series of maps showing 24-h lightning totals over the region.  These are from the NLDN lightning detection network.

May 23:  Over and east of the Cascades

May 24th:  Lots over the Cascades as cumulonimbus clouds developed over and east of the crest.

 May 25th:  NE Washington and Idaho

 May 26th:  Eastern WA and Idaho

 May 27th:  Ditto

 May 28th

 May 29:  Cascades and NE Washington

 May 30th:  Eastern WA and Oregon

May 31st

 

 June 1

 June 2:  WOW.

The Cascades and eastern Washington have had huge number of lightning hits.  How many major lightning induced fires have resulted?  The Northwest Interagency Coordination Center (NWCC) gives the answer:  none.

How could this be?  Because the ground is too moist.   The Standardized Precipitation Index from the National Drought Mitigation Center for the last month shows the story:  wetter than normal east of the Cascade crest due to all the rain from incessant convection in that region.  Southwest of our region it has been crazy wet.

The Pacific Northwest Significant Fire Potential (from the NWCC) indicates low potential (mainly green) ahead.

The latest NOAA Climate Forecast System (CFSv2) runs for the summer indicates wetter than normal conditions expected for the interior.

Why has the region east of the Cascades been so wet?  Because the large scale atmospheric circulation has been anomalous.   To illustrate this, here is difference from normal (climatology) of the heights of the 500 hPa pressure surface (you can think of it like the pressure pattern at around 18,000 ft).  There was anomalously low pressure over the SW U.S. and nigh pressure over the Gulf of Alaska.  This pattern brought enhanced easterly flow over region, with moisture circulating westward. This pattern has brought unusually heavy precipitation over the SW US, including Texas.

All of this shows why one has to be very careful in predicting a disastrous early wildfire season based on low snowpack:  temperature and moisture are much more important.  But eventually, the ground will dry out and wildfires will return.    The models are predicting warmer than normal conditions for the summer, which would enhance wildfire potential.  But they are also wetter than normal.  That works against wildfires.   But if much of that rain is from thunderstorms, that might enhance wildfire potential.  To put it another way, there is a lot of uncertainty in the wildfire outlook.  We need to be prepared.