The Fine Line Between Monsoon And Nonsoon

Short Term

This evening, tomorrow and Monday are going to be the best chances for a few high heat based thunderstorms to pop up, in fact, most afternoons going forward especially the in higher elevations will have a chance at some storms, at times these will drift off the higher elevations into the valleys and plateaus below them.

For the first time this year, I am starting to see some definite signs of the Monsoonal activity getting going in Mexico, then Arizona and New Mexico later this week, however, it looks like it will be suppressed several times over the next two weeks, so while it is very likely you will hear about the Monsoon over the coming week, for us it will still be the Nonsoon. In other words, the rain we get will be directly related to other weather events, cold fronts, frontal boundaries, high heat based convective development, etc.

Using last night’s GFS run I can illustrate what this looks like to demonstrate where Monsoonal activity is occurring and where it isn’t. Keep in mind the GFS could be 100% completely wrong with its forecast, this time it is irrelevant. For the purposes of this discussion, I want to show you what is and what isn’t Monsoonal.

Starting with late afternoon today, none of this activity is Monsoonal.



Sunday late afternoon (every map going forward is late afternoon/early evening), again no Monsoon


Monday, July 1st everything I circled in blue is Monsoon, everything in red is not the Monsoon=Nonsoon


Let’s jump ahead to July 4th, you can see the Monsoonal activity (in blue) building north


Let’s jump further ahead to Sunday, July 7th a fine line when you have to distinguish the source of the moisture and convection. What is in red is due to low pressure over the midwest drawing in moisture from the Gulf of Mexico as it does every summer (which is why the humidity is so oppressive in the Midwest).


Monday, July 8th the battle continues as the Monsoon gets suppressed.


Wednesday, July 10th suppression continues as the old frontal boundary sags south


Thursday, July 11th the Monsoon roars back as the boundary layer has passed to the southeast



Jumping ahead to Saturday July 13th, as you can see below a fairly deep area of low pressure generates upslope flow and showers from Wyoming through the front range and down to New Mexico, if the source of that cold air (shown here in North Dakota) were over Durango it would snow down to 8,000 feet! That is not going to happen, don’t worry.


Sunday, July 14th the surface front digs in further SW suppressing the Monsoonal flow once again. You can see heavy thunderstorms being generated over the San Juans due to a retrograding area of low pressure and cold front, not from the Monsoon.


As I said this whole forecast run of this model could be wrong, but my goal was to show you the difference between the sources of the rain, not all summer rain is the Monsoon, not all snow is a storm(sometimes it just snows), not all wind is a tornado. Going forward hopefully you understand when I refer to any given event as Monsoonal versus Nonsoonal.


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