Thursday, August 22, 2013

Juicy Air Coming to Southwest

Yeah, it's a dry heat, but that won't be the case on Sunday and Monday in the lower Colorado River Basin.  As shown by the GFS loop below, a major surge of moisture will push into the lower Colorado River Basin ahead of and with the remnants of a tropical cyclone that is currently forming in the tropical eastern Pacific.

GFS sea level pressure (solid contours), 10-m wind, and integrated water vapor (color fill with warm
colors indicating higher values) forecast loop valid 1200 UTC 22 Aug through 0000 UTC 26 Aug 2013.
The water vapor content of the atmosphere is indicated by the color fill in the loop below, with warmer colors indicating higher values.  Note that the initial surge of moisture into the lower Colorado River Basin from the Gulf of California that occurs in response to enhanced south-southeasterly flow associated with a tropical cyclone currently called tropical depression NINE-E (hopefully it gets strong enough to get a better name than that!).

In response to the moisture surge, the latest GFS forecast for the 48-hour period ending at 0000 UTC 27 August (6 PM MDT Monday 26 August) shows a narrow band of heavy accumulated precipitation extending from northern Baja up the Colorado River, and into southern and eastern Utah.  Model generated precipitation exceeds 6 inches in that grey strip just south of the southern tip of Nevada.

Model forecasts always look relatively smooth and simple, so ultimately much will depend on the track of the moisture and the triggering and organization of thunderstorms and related precipitation systems.  The devil may be in the details, but in general, Sunday and Monday look extremely active in the lower Colorado River Basin as this juicy air moves into the region.  

It looks like Utah will also get in on the action.  This is not a good time to be going slot canyoneering.  The latest forecasts keep the juiciest air to the southeast of Salt Lake, but we still have a threat of thunderstorms.  We'll see how this all comes together in the coming days.  

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