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Forecast Discussion for Phoenix, AZ

FXUS65 KPSR 250437

Area Forecast Discussion
National Weather Service Phoenix AZ
937 PM MST Wed May 24 2017

The high pressure system over the region that produced above normal
afternoon temperatures will weaken tonight as several weather
systems move into the western states. Although dry weather is
forecast, gusty afternoon southwest winds can be expected through
Saturday. Also, afternoon temperatures on the lower deserts will
cool into the 90s, or below normal temperatures. Dry weather with
warmer temperatures are expected beginning Sunday and continuing
through next week.


Complex flow pattern over western North America and the northeast
Pacific. In general there is troughing centered near the coast
but with 3 distinct systems embedded. Offshore is a narrow high
amplitude ridge with significant undercutting flow making it`s way
into the Southwest states. The ridge that was over us has been
pushed eastward but the cooler air in the lower levels lags behind
and will be slowly moving into our area tonight through Friday
for a cooling trend. This will be quite welcome as we had another
hot day today (at or near records at some locations including
Phoenix and Yuma) - even hotter than expected for portions of SE
CA and SW AZ which didn`t see any cooling (contrary to model
depictions). Breeziness (mainly afternoon and evenings) will
continue as well. A wind prone location in western Imperial County
will continue to have locally strong winds and thus a Wind
Advisory remains in effect there. Aloft, an upper low centered
off the California coast will weaken as it moves inland and merges
with the main system moving through the western CONUS. Too dry
for any precip unfortunately. Early next week, the ridge moves
inland and we see triple digit highs on the deserts again.



Tonight through Saturday...

The high pressure system over the region which resulted in
anomalously hot afternoons will break down this evening, as a series
of weather systems move into the western states.  Although dry
weather is forecast through Friday, cooler and windy afternoons are

Gusty winds are slated for this evening, blowing strongest in
Imperial County where advisories continue tonight. Nearly the same
magnitude winds are expected Thursday afternoon and evening, but
less strong Friday. The coolest days will be Thursday, Friday and
Saturday when temperatures drop below 100 on the deserts, and below

Sunday and Monday...

Dry westerly flow aloft with warmer days are forecast. Desert
temperatures will warm back to slightly above 100 degrees. Much
lighter afternoon southwest winds are also expected.

Tuesday and Wednesday...

This is an uncertain period with regards a northward flow of Mexican
moisture across eastern AZ, and the potential for afternoon/evening
thunderstorms. Both the GFS and European solutions this far suggest
a weak Pacific upper low developing along the northern Baja Tuesday
and Wednesday to circulate the moisture north. At this point we
introduced a slight chance of afternoon and evening thunderstorms
over the highest terrain in eastern southern Gila County bordering
the white mountains on Tuesday. Breezy south to southwest winds are
also expected to reappear Tuesday and Wednesday afternoons.


South-Central Arizona including KPHX, KIWA, and KSDL:
Southeast California/Southwest Arizona including KIPL and KBLH:

Moderate to strong southwesterly flow aloft will continue through
Thursday. Southwest and west breeziness will continue to weaken
tonight (more slowly over the Imperial Valley). Breeziness returns
Thursday afternoon. In between, for metro Phoenix, anticipate a
period of relatively light southeasterly surface winds (roughly
09Z-17Z). Otherwise, expect the mid-high high clouds to continue
decreasing from west to east.



Saturday through Wednesday:
Wind speeds will weaken by Saturday, compared to earlier in the
week, as a pronounced area of high pressure builds over the Great
Basin. Temperatures will also be near or slightly below seasonal
normals on Saturday, with highs in the low-mid 90s. Warmer
temperatures will occur by Sunday, with highs near 100 degrees,
and will remain similar each day through the middle of the week.
Winds will also be generally light during this period.

A weak Pacific low pressure system will develop and move eastward
towards the Southwest, and could result in a slight chance for
thunderstorms across the higher terrain of east-central Arizona,
including southern Gila County. However, confidence in any rain or
lightning potential is still low this far out.


Spotter reports should not be needed.


CA...Wind Advisory until 5 AM PDT Friday for CAZ562.

     Wind Advisory from 2 PM Thursday to 5 AM PDT Friday for CAZ566.



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NWS Phoenix, AZ (PSR) Office Area Forecast Discussion

Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather