May Is Often Flood Month

Some of our worse flooding events occur during May as the Jet Stream lifts to the north and cold fronts run out of steam as they try to move across the northern Gulf.  We talk about "training" of cells along the slow moving boundary that can see many inches, sometimes feet of rainfall in only a few hours.  Here's two examples.

The May 1978 event was my first experience with "100 year floods", but by far the 1995 flood was the greatest for both sides of the Lake, including the Mississippi Gulf Coast.  So what's going on?  Look to the upper air pattern, especially off the West Coast.

There is a large low south of Alaska with the hints of a ridge west of California & a deep trough over the Rockies.   This is called a "Rex Blocking Pattern" that results in little or slow movement.  I'll focus on the trough over the Rockies.

The main upper low is in Colorado with spokes of energy rotating around it.  Zoomed in, I find 3 distinct swirls.  Note the bottom radar view shows not everybody is getting drenched as we stayed mostly dry today. Yesterday's swirl has moved into Arkansas with another swirl to our SW that will bring us some showers over night with Thursday being mostly dry until later in the afternoon.   These are all upper disturbances as we have no surface fronts around.

All the clouds & showers are helping keep temperatures in check while we are humid, but it's not August-like heat.

IF the radar returns to our SW hold up, look for some showers after midnight ending before daybreak.  With the upper trough staying over the Rockies, a weak upper ridge might lower our rain chances for this weekend.

I have mentioned before, the 60% chance for rain does NOT mean it will rain 60% of the time.  In fact, it might be dry most of the day.  I have a 8:52 tee time tomorrow.  Will I be surprised if I'm rained out?  Nope, but I'm going with the thinking the 60% rain chance happens after the noon hour.  Stay tuned!