While Southern California, Nevada and western Arizona trend toward drier conditions Wednesday, the risk of flash flooding will increase in Colorado and New Mexico.
Cities at risk for disruptive downpours and urban flooding include Colorado Springs, Pueblo, Vail, Aspen, Durango, Montrose and Alamosa in Colorado and Sante Fe, Albuquerque and Las Vegas, N.M.
Flash flooding will also be a threat into parts of southeastern Utah and eastern Arizona.
A moist and unsettled air mass will bubble into dangerous, slow-moving thunderstorms during the afternoon and evening hours.
In some areas, rainfall will exceed one inch or more in a couple of hours. Places that receive rainfall of this magnitude will have rapid flooding of small streams and normally dry washes.
Along steep canyons, ravines and mountainsides, dangerous mudflows and rockslides are possible.
If you will be driving though mountain and back country roads, hiking wilderness trails, camping or sightseeing, be prepared for flooding.
Be sure to have a plan of action and to let someone know which trails or roads you will be taking.
Keep a keen eye to the sky. Rapidly building clouds and thunder may be your only hint of what may soon follow.
Flood waters can travel a long distance from the origin of the rainfall through dry wash channels and stream/creek/river beds.
Aside from the dangers of flash flooding, the rainfall is greatly needed over the region. Downpours will shift toward Texas and Oklahoma to end the week, where rain is in tremendous need.
The same storm system will bring the first snow of the season to the Colorado high country.
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Strong thunderstorms are impacting areas from Texas to Louisiana with large hail, damaging winds and a risk of tornadoes.
Severe storms, some capable of producing tornadoes, will threaten communities across northeastern Texas, northwestern Louisiana and Arkansas into Tuesday night.
The same storm system responsible for producing violent thunderstorms in Oklahoma recently will reach the Atlantic Seaboard Thursday.
While additional strong thunderstorms will roll through through portions of tornado-ravaged Oklahoma Tuesday, the risk of tornadoes has diminished.
The atmospheric severe weather engine began firing on all cylinders this past weekend and reached full speed Monday over Oklahoma.
Preliminary reports are calling it an EF-4 tornado that has caused numerous fatalities and injuries in Moore, Okla.
San Antonio, TX (1998)
Very dry since April 1st - only 0.05 of rain.
Sichuan Province China (1986)
More than 35,000 homes and 7,700 acres of crops were destroyed by a devastating hailstorm. Reports indicated that 100 people were killed and 9,000 injured. (Reports vary as to the exact date of the hailstorm.)
Waterville, ME (1832)
Kennebec Flood discharged 140,000 cubic feet of water per second -- high stage not equalled until 1901, and not exceeded until 1936.