Saturday, September 28, 2019

Update - September 28, 2019

Apologies to those faithful followers of this blog.  As many of you know, these posts are done outside of my normal National Weather Service function, i.e., on my own time.  This past month or so has been particularly challenging for me - and my family. 

During this past 30 days, there continued to be ample to excessive rainfall across many areas that had received copious moisture for 2019.  But, unfortunately, there continued to be a region that missed out - again.  Here is a map of rainfall this past 30 days....

The drought monitor has really not changed a whole lot across the western high plains.  Maybe shifted a little west?  But the moderate drought persists across southwest Kansas.

I've done weather and climate presentations lately and I pointed out that signals and the general weather pattern suggested an increase in the opportunity for beneficial rains for the last days of September and going into early October.

Looking at this mornings satellite image....

There was an anomalously cold airmass (for late September) that had slipped south out of western Canada.  A very strong upper level low across the northwest U.S., has set the stage for perhaps record breaking snowfall (for September) across western Montana and adjacent higher terrain.  The fringe of this cold airmass has nudged into the plains this Saturday morning.  The boundary separating the very humid and warm airmass across Oklahoma and the colder air will produce a round of thunderstorms as an upper level disturbance (that red X on the satellite) moves into the central U.S..  Unfortunately, much of the drought area will miss out on that round.  However, it's not done!

The upper level low will continue to strengthen and drop south.  This evolution will tap into a tropical system south of Baja California.  As this all progresses, waves of "energy" and moisture will stream north and east.  It will be a tropical airmass overriding the surface boundary that will waffle north and south across the area.  The following map is the most likely area and amounts of precipitation expected through the end of next week, although the majority will fall by late Tuesday....

Don't take the amounts literally or the exact location. In fact the location of heavier rains is still uncertain as the eventual track of the surface boundary, upper level features and interactions with individual storms is unknown.  Regardless of the area of heaviest rains, there is a very high chance that excessive rainfall will occur at some locations.

BTW, I mentioned that this increased opportunity for beneficial rain was expected.  This notion was tied to the Madden Julian Oscillation and the conditions across the Pacific.  This would also give rise to a drier period by mid-month - and warm again!  At this point I don't see an early end to the growing season across the central plains.  The Northern plains and the upper midwest will most likely see a freeze from this pattern (by the end of next week).    I'm not seeing any indication of a freeze for the central and southern high plains earlier than a climatological normal.

This next week I'll dig into this weather pattern in more detail and go into discussion about the outlook going forward.  I most likely won't get a post done until around October 7 - at least that will be my goal.   It's possible an update will be done Wednesday (2nd).