Flood Watch

* WHAT...Flash flooding caused by excessive rainfall is possible.

* WHERE...A portion of Southeast Arizona, including the following areas, Baboquivari Mountains, Dragoon and Mule and Huachuca and Santa Rita Mountains, Upper San Pedro River Valley and Upper Santa Cruz River Valley/Altar Valley.

* WHEN...Until 5 AM MST Tuesday.

* IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations.

* ADDITIONAL DETAILS... - An organized cluster of storms or mesoscale convective system (MCS) in northeast Sonora Mexico is expected to slowly drift northwest across portions of south-central Arizona late this evening and overnight tonight. This storm system will be capable of producing moderate rainfall with pockets of very heavy rainfall. Although widespread rainfall amounts between 0.50 and 1.00 inches are anticipated, localized rainfall amounts between 1 and 3 inches will be possible resulting in localized flash flooding. The heaviest rainfall is expected over the southwest half of Santa Cruz county and extreme south-central Pima county and may have significant impact on the Nogales Wash overnight. Heavy rainfall Monday evening along Highway 286 and along and Arivaca Road have made portions of south central Pima county vulnerable to flash flooding with additional rainfall overnight. - http://www.weather.gov/safety/flood