Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 281036

Area Forecast Discussion
National Weather Service Phoenix AZ
336 AM MST SAT MAY 28 2016

A broad area of low pressure will persist over the western United
States through the beginning of next week yielding somewhat cooler
than normal temperatures and dry conditions. Strengthening high
pressure much of next week will bring a warming trend with high
temperatures in the lower deserts pushing near 100 degrees by the
middle of the week. A stretch of well-above normal temperatures is
likely later in the week.


Dry westerly flow predominates across the desert southwest this
morning. Further upstream, latest streamline analysis indicates the
presence of a weak trough off of the CA coast. Continued increase in
thicknesses is expected today ahead of the trough which will equate
to temperature rises generally between 4 and 6 degrees across south-
central AZ. Despite the warming trend, temperatures will still fall
in the below-normal category.

Operational models remain in good agreement through the short-term,
indicating that the aforementioned mid-level trough will briefly
close off Sunday while moving into southern CA. This system is
moisture-starved and its main impact will be on temperatures, which
will be a degree or two cooler on Sunday. The trough will weaken
slightly Monday while continuing to slide eastward into AZ. An
additional degree of cooling is likely across AZ, however much warmer
conditions are expected across CA as a ridge in the eastern Pacific
moves eastward towards the west coast.

Residual moisture in the wake of the compact low pressure system
should be sufficient for isolated showers and thunderstorms
Tuesday/Wednesday. However, latest hi-res guidance suggests that the
activity will mainly be relegated to the higher terrain north and
east of Phoenix. Pops generally remain less than 5 percent in these

Latest guidance continues to indicate that the ridge will build
across the western CONUS, yielding steady height rises and a
continued warming trend during the mid to late week period. Temperatures
were increased for Thursday and Friday and generally represent the
70th percentile of all available guidance, which is well short of
records. Looking ahead to next weekend, operational GFS and ECMWF
diverge markedly, with the GFS depicting an eastern Pacific trough
fracturing and moving into the intermountain west. This solution is
not supported by other ensemble members and was dismissed, with the
expectation that the dry conditions and above normal temperatures
will persist.


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

Clear skies to persist through Saturday under a light wind regime.
May have some occasional gusts during the afternoon hours Saturday,
but less than 20 kts. Wind directions for the Phoenix terminals will
follow typical diurnal tendencies and generally follow a southerly
component for KIPL and KBLH. No aviation impacts through the period.



Monday through Friday...
A hot and dry weather pattern will dominate the week including a
strong high pressure ridge that will build over the region from
Wednesday through Friday. Hot and near normal daytime high
temperatures reaching as high as the lower triple digits through
Wednesday are expected to increase to 100 to 106 degrees beginning
Thursday. In addition, minimum relative humidities of 8 to 15
percent will dry to the 7 to 11 percent range by Friday.
Breezy southerly to southwesterly winds with gusts of 15 to 20 mph
are forecast for Wednesday afternoon and evening.


Spotter activation is not expected.




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