Tempe, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

685
FXUS65 KPSR 220504
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1004 PM MST Wed May 21 2025

.UPDATE...Updated 06z Aviation Discussion.

&&

.KEY MESSAGES...

1) Afternoon high temperatures will reach the triple digits across
much of the lower deserts through the end of the workweek, with some
of the typically warmer communities topping 105 degrees today and
Thursday.

2) These hot temperatures will result in Moderate HeatRisk (Level 2)
particularly today and Thursday, posing an increased risk to
vulnerable populations.

3) Afternoon breeziness is expected Thursday and Friday, with the
strongest winds on Friday resulting in locally elevated fire weather
conditions.

&&

.DISCUSSION...

Weather Pattern Overview:

Current mid-level wv imagery shows dry, quasi-zonal flow over the
Desert Southwest, with RAP analyzed H5 heights around 585 dam
overhead. Based on observed temperatures thus far today at Phoenix
Sky Harbor, we are on track to hit our forecast high of 104F and
have already reached the century mark early this afternoon.
Ensembles still advertise heights aloft peaking tomorrow around 586-
588 dam (approaching but just under the 90th percentile of CFSR
climatology), which should yield temperatures around 5-10 degrees
above daily normals. As such, expect afternoon highs to peak
tomorrow with readings between 102-106F. Despite temperatures
exceeding 5F in some places, NBM probabilities for tying or breaking
any daily record highs remain below 10% through the end of the
workweek.

A decaying upper level trough is advertised to move onshore along
the CA Coast Friday and pass through the Great Basin early this
weekend. This will tighten gradients aloft, though this is not a
particularly potent system, which will allow higher momentum air to
be mixed down to the surface during the daytime thanks to the deep
mixing heights this time of year. Sensible weather impacts from this
system will include increased breeziness Thursday and particularly
Friday focused over the AZ high terrain and portions of SE CA, where
gusts upwards of 25-30 mph are likely (60-70%), and a cooldown to
near normal temperatures (upper 90s) by Saturday.

Over the weekend a stagnant upper level pattern takes shape at the
higher latitudes, with positive height anomalies centered over
Canada and a broad area of strong negative height anomalies over the
Gulf of Alaska. This pattern looks to be maintained, with WPC
clusters all depicting some slight variation of this pattern through
Wednesday-Thursday this upcoming workweek. Meanwhile, over our area,
weak ridging looks to take shape during the Sunday-Monday timeframe,
resulting in temperatures inching back to a slightly above normal
category (NBM highs in the upper 90s to lower 100s for the lower
deserts). The main forecast uncertainty seems to be the strength,
exact positioning, and timing of any relatively weak upper lows that
attempt to undercut the Northern CONUS/Canada ridge and influence
our region as we head into the upcoming workweek. Regardless, the
forecast area should remain dry through at least the middle of
next week, with some day to day variations in temperature but
generally remaining near to slightly above daily normals.

Forecast Confidence & Deviations:

In keeping consistent with the previous forecast package, have
increased winds over Imperial County on Friday evening by around
15%. The only area that may (30-60% chance) reach wind advisory
criteria with gusts to 40+ mph would be the southwest corner of
Imperial County on Friday evening. Otherwise, did not make further
edits to NBM grids. Forecast confidence is quite good through the
weekend but decreases gradually heading into the upcoming workweek.

&&

.AVIATION...Updated at 0505Z.

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

No major weather issues will exist through Thursday evening under
clear skies. Trends in wind speeds and timing of typical wind
shifts will be similar to the past 24 hours. Periods of
variability and nearly calm conditions during these transitional
periods will be common.

&&

.FIRE WEATHER...
High pressure will continue to prevail through the rest of the week
with warming through Thursday. Above normal temperatures are
expected, with afternoon highs reaching the lower 100s across the
lower deserts starting today and lasting through Friday. Very dry
conditions are expected each day, with widespread MinRHs down to 5-
12% and overnight recoveries to 15-30%. Light winds will continue
today before winds increase Thursday with gusts to around 20 mph and
even higher gusts of 20-30 mph possible on Friday. This could bring
another period of elevated fire weather conditions on Friday. The
dry conditions will continue over the upcoming holiday weekend, but
with diminishing winds and temperatures running a few degrees above
normal.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Whittock
AVIATION...Young/18
FIRE WEATHER...Whittock/Kuhlman