Flood Watch issued September 20 at 11:18PM MDT until September 23 at

* WHAT...Flooding caused by excessive rainfall is possible.

* WHERE...Much of south-central New Mexico and Far West Texas,
including El Paso, Las Cruces, and the Mesilla Valley.

* WHEN...From Tuesday afternoon through Wednesday evening.

* IMPACTS...Excessive runoff may result in flooding of arroyos,
rivers, streams, and other low-lying and flood-prone locations.
Flooding may occur in poor drainage and urban areas. Low-water
crossings may be flooded, resulting in road closures.

* ADDITIONAL DETAILS...
- An early season back door cold front will interact with a late
season plume of deep monsoonal moisture, bringing several rounds
of thunderstorms with torrential downpours to the region Tuesday
afternoon through Wednesday evening. Repeated thunderstorms may
tend to focus in one or two areas, resulting in higher end
precipitation totals. The most critical period with the heaviest
rain potential will likely be Tuesday night into Wednesday
morning.
- A broad swath of moderate to locally heavy rainfall is likely to
affect most of the Watch area between late Tuesday afternoon and
Wednesday evening, with typical, scattered monsoon season flood
impacts. However, there is increasing potential for a narrow band
of repeated thunderstorms which will result in particularly heavy
rainfall amounts, possibly exceeding 3 inches in a 6 to 12 hour
period, resulting in higher-end impacts. Forecast models
currently favor placing the focus for heaviest rainfall over the
Mesilla Valley and El Paso. But forecasts this far out,
especially when dealing with thunderstorms, are simply not
accurate enough to precisely tell yet where exactly this area of
heaviest rainfall will set up. It could just as easily shift west
or east and avoid the more populated corridor.
- http://www.weather.gov/ElPaso