Area forecast discussion 
National Weather Service Phoenix Arizona 
845 PM MST Sat Aug 1 2015 


lingering storm chances the rest of today will mainly affect areas 
across higher terrain areas of central and eastern Arizona with a 
slight chance of a few storms over the lower deserts. Considerable 
drying occurs starting Sunday and into the middle of next week with 
storm chances confined to the higher terrain east of Phoenix. 
Temperatures will hover near normal or slightly above through next 


Discussion... a much quieter afternoon/evening today than what we 
saw yesterday...especially across the lower elevations of south- 
central Arizona. Dry air that is being pulled northward ahead of an upper 
trough that is approaching the West Coast has now moved into southeast California and 
the western 1/2 of Arizona. This dry air has pretty much shut 
convective activity down and pushed surface dewpoints down into the 
50s across the western 3/4 of our County Warning Area this afternoon. 

Ahead of this dry surge...thunderstorms have once again developed 
this afternoon across souther Gila County...where dewpoints are 
still well up in the 60s under the main monsoon moisture plume and 
continued diffluence aloft. This ts activity is now beginning to 
slowly diminish and shift off to the north this evening as the 
moisture plume continues to shift off slowly to the east...with the 
latest hrrr high-res model run indicating that any remaining 
convective activity to end by midnight tonight. Tomorrow still looks 
like it will be the 1st in a series of very quiet days as dry air 
makes its way across all of Arizona. As far as the short-term gridded and 
zone forecasts are concerned...have lowered probability of precipitation for the rest of 
this evening and tonight into the single-digit range across the 
lower deserts of south-central Arizona and have made some minor edits to 
the short-term temperature/dewpoint grids to better reflect current 


so far this afternoon we have little shower or thunderstorm activity 
as the atmosphere just has not recovered. Skies have remained mostly 
clear so sunshine has not been an issue...but surface temperatures 
are still somewhat cool for this time of day and generally 5-8 
degrees cooler than yesterday. Mesoscale analysis does show ample 
mixed layer cape across south-central and Southeast Arizona along 
with broad diffluence over much of Arizona. Still expecting more 
thunderstorm development through the rest of this afternoon...but 
coverage will likely be limited to mostly higher terrain areas. Have 
lowered probability of precipitation over the lower deserts into the slight chance category 
due to the poor convective start to the afternoon...but we should 
still get a few storms in the deserts by the end of the day. There is 
some potential for some strong downdraft winds with any stronger 
storms...but with more moist air in the boundary layer...outflow 
interactions should be less active than yesterday. 

Water vapor imagery shows dry air quickly moving northward through 
the Baja California area into northern Mexico and models show this dry air 
working across Arizona starting tonight and overtaking all of the 
state by Sunday night. Lingering lower level moisture will allow for 
some higher terrain showers and thunderstorms...but little to no 
chance of any activity over the lower deserts. This dry air will 
basically end our storm chances for a few days early this 
week...while temperatures start to warm up. Highs across our 
southeast California and southwest Arizona deserts will likely break 
110 degrees Sunday through Wednesday. South-central Arizona desert 
temperatures will peak on Monday or Tuesday...but fall short of 
hitting 110 degrees. 

The subtropical high positioned over the Desert Southwest for Monday 
and Tuesday is forecast to shift eastward into New Mexico sometime 
Wednesday and Thursday and redirecting our flow out of the southeast. 
This will bring a return to at least some limited monsoonal moisture 
and chances for showers and thunderstorms over mainly the eastern 
half of Arizona. 


south-central Arizona including kphx...kiwa...and ksdl... 

Through 18z sun...scattered clouds at or above 10 thousand feet above ground level. Light mostly 
southwest wind under 8 kts. However...thunderstorms over mountains 50 miles east of 
phx through 06z sun. 

Southeast California and southwest Arizona including kipl and 

Through 18z sun...scattered clouds at or above 12 thousand above ground level. Light wind under 8 knots. 

Aviation discussion not updated for amended tafs. 


Fire weather... 

Tuesday through Saturday...drier and stable westerly flow aloft will 
produce partly cloudy skies Tuesday and Wednesday...with lower 
minimum relative humidity generally in the 10 to 15 percent range. 
Moisture will gradually increase over southwest and south central 
Arizona Thursday through Saturday...into the 15 to 25 percent 
range...with a slight chance of afternoon and evening showers and 
thunderstorms in southern Gila County. Afternoon southwest winds 10 
to 15 miles per hour. Fair recovery at night. 


Spotter information statement... 
spotters are encouraged to report conditions according to Standard 
operating procedures. 


Psr watches/warnings/advisories... 


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fire weather...vasquez 

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