After heavy rain in parts of the Southwest last week that led to flash flooding in parts of Utah and Arizona as well as record rainfall for areas of California, more tropical moisture is streaming northward into the region. This will likely lead to move heavy rain and the potential of flooding once again in some areas.
Heavy Rain Set Up
While last weeks heavy rain tapped into the remnants of an eastern Pacific tropical system, this heavy rain potential will do the same. As of early Monday morning, Tropical Depression Sixteen-E made landfall on the Baja California peninsula and was expected to continue moving to the northeast over the next few hours before eventually losing tropical characteristics. The track of this system along with a upper level low in the area will help pump in deep moisture into the Southwest and provide enough lift for showers and thunderstorms to form. Precipitable Water (PWAT) values (a measure of moisture within a column of air) will be quite high for this time of year – and could be near record territory. For example, last nights 0z GFS run was outputting a PWAT of 1.91″ for Tucson this evening. If those values were to come true, that would come close to rivaling the September record (1.98″ September 7, 2012 at 12z). What this means is a lot of moisture will be available for storms to work with, and it could lead to very heavy rain at times and the potential of flooding.
Flash Flood Watches In Effect
Already Flash Flood Watches are out for a good chunk of the Southwest, including parts of southern California, the southern two-thirds of Arizona, and western New Mexico. Over the next two days, some areas could easily receive 2-4″ or more of rain – particularly in an area from Caborca, Mexico northeast through Tucson and up toward Show Low, AZ. Phoenix will likely be on the edge of the heaviest, but certainly could still see 1-3″ by Wednesday morning. As we approach the Wednesday time frame, the system bringing the heavy rain will get a boot off to the northeast, bringing drier weather to the Southwest. However, that could lead to heavy rain for parts of the upper Midwest Wednesday and Thursday.
As we can see by the Phoenix seven day forecast, the rain is mainly isolated to the next couple days. A few leftover showers or storms will be possible across the area Wednesday before sunshine and warmer temperatures return for the end of the week.
(CHECK OUT YOUR FORECAST: wx.aerisweather.com)
– Meteorologist D.J. Kayser