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Forecast Discussion for Phoenix, AZ

FXUS65 KPSR 262158

Area Forecast Discussion
National Weather Service Phoenix AZ
300 PM MST Wed Apr 26 2017

A series of mainly dry Pacific weather disturbances will move across
the western states through early next week. These systems will keep
afternoon temperatures near or slightly below normal, along breezy
afternoons and evenings. One stronger disturbance expected to move
across northern Arizona on Friday will bring windy conditions, and
the potential for showers over the eastern Arizona Mountains.



Tonight and Thursday...

Dry northwest flow aloft will continue to provide mostly clear skies
and warmer temperatures through Thursday. Afternoon westerly breezes
in the 10 to 20 mph are also forecast.

Friday and Friday Night...

Another but stronger disturbance, under northwesterly flow aloft, is
forecast to deepen across AZ Friday afternoon and night. Strong
height falls sweeping in from northwest AZ Friday afternoon, then
into east central AZ Friday evening portend another windy episode.
A Fire Weather Watch has also been posted Friday for the Colorado
River Valley east to Phoenix and points east over our southern Gila
County Mountains.

Additionally, models have been forecasting a moderate surge of low
level moisture from Mexico Friday afternoon into south central and
southeast AZ. However the lack of morning weather balloon data from
northwest Mexico may have caused the 12z models to forecast more
moisture than previous model runs. None the less, an increasingly
strong dynamical pattern with enhanced vertical motion fields over
east central AZ Friday, including parts of our zone 24, still
warrant a slight chance showers or thunderstorms.

Clearing skies with a drier airmass is expected later Friday night
along with diminishing breezes.

Saturday and Saturday night...

Saturday will be the coolest day after Fridays frontal passage.
Breezy to windy conditions are also expected. The windiest areas
Saturday afternoon will occur down the Colorado River Valley where
northerly gusts to 40 mph are possible.

Sunday through Wednesday...

Dry northwest flow aloft along with near normal temperatures are
forecast. Normal high temperatures for the lower deserts are in the
lower 90s for the first week of May. Mostly clear skies are also
forecast this period.


South-Central Arizona Including KPHX, KIWA, and KSDL:

Another breezy day is expected this afternoon, however speeds
will be lower compared to yesterday. Westerly winds will start to
pick up near 21Z, with sustained speeds near 10 to 15 kts and
gusts up to 20 kts. Speeds will gradually weaken after sunset and
remain out of the west until around 10Z. However, confidence is a
little low on the exact time of the downslope wind initiation.
SCT to BKN decks primarily aoa 25 kft will persist through the TAF

Southeast California/Southwest Arizona Including KIPL and KBLH:

Less wind is expected today as compared to yesterday with speeds
mostly below 12 kts over the next 24 hours at both TAF sites. At
KIPL, light and variable winds will persist until about 20Z when
the winds will then shift to southeast. After sunset, near 02Z,
winds will shift back to the west-northwest. At KBLH, light and
variable winds will continue this morning before shifting to the
west early this afternoon near 20Z. SCT to BKN decks primarily aoa
25 kft will persist through the TAF period.

Aviation discussion not updated for amended TAFs.


Saturday through Wednesday:

A sharp cooling trend will settle into the region as a mostly dry
storm system sweeps through the Great Basin and down through the
Southwest Friday into Saturday. On Saturday, breezy conditions from
the north will persist over the western deserts and with minimum RH
values to stay mostly below 10 percent area-wide, we can expect
continued dangerous fire weather conditions out west during the
afternoon hours.

Dry and warmer conditions are expected Sunday into Monday as high
pressure builds into the area from the west. By Monday high
temperatures over the deserts will climb into the mid 90s for the
most part with minimum RH values to stay mostly in the single
digits. Less wind is expected although we should see continued
afternoon and early evening breezes across much of the area,
favoring the west. Another weather system will push across the
region Tuesday/Wednesday, bringing breezy conditions back to the
area and a very very slight chance of rain on Wednesday to the
higher terrain of southern Gila county.


Spotter activation will not be needed through the middle of next



AZ...Fire Weather Watch from Friday afternoon through Friday evening
     for AZZ132-133

     Fire Weather Watch from Friday morning through Friday afternoon
     for AZZ131.

CA...Fire Weather Watch from Friday morning through Friday afternoon
     for CAZ231



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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