777
FXUS65 KPSR 270505
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Thu Jun 26 2025

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- Temperatures will gradually heat up into the weekend reaching
above normal levels with widespread Moderate HeatRisk across all
areas by Sunday

- Extreme Heat Watch is in effect for the Phoenix metro Sunday
through Tuesday with areas of Major HeatRisk and high temperatures
topping 110 degrees

- Dry conditions will prevail through at least the weekend, but a
gradual increase in moisture next week is likely to lead to
increasing chances for showers and thunderstorms by the middle to
latter part of the week

&&

.DISCUSSION...
Early afternoon satellite depicts a very dry airmass overhead with
the favored area of convection well removed to the east across
central to eastern New Mexico. General troughing across the region
continues the dry southwesterly flow, but as this feature dissipates
over the coming days, the strong area of high pressure that brought
oppressive heat to the eastern part of the country the last few days
will meander back westward going into this weekend. This will lead
to seasonable temperatures to warm to above normal levels by the end
of this weekend, with widespread Moderate HeatRisk. Temperatures
will be hot enough to reasonably have Extreme Heat products out for
at least the Phoenix metro Sunday-Tuesday as highs warm into the 110-
115 range and lows warm into the mid to upper 80s (probs of KPHX
hitting a low of 90 is around 40-60%). Thus, an Extreme Heat Watch
is in effect, with additional areas of south-central Arizona
included on Monday when Major HeatRisk is the most expansive across
the lower deserts.

The weather pattern evolution becomes much more muddled starting
early next week as a weak trough begins to amplify across the West
Coast. This feature will influence the movement of the subtropical
high overhead the region early next week to retreat near the Four
Corners. This retreat should present the first indication of low
level southeasterly flow with the first significant moisture returns
of the season, a typical feature of the monsoon. However, large
discrepancies are apparent amongst the ensembles on how early and
how quick this moisture will develop across Arizona. The GEFS
remains much quicker than the ECMWF as the latest means depict the
high center north of the Four Corners (GEFS), which would cause the
moisture levels to increase faster than the high center positioned
further south (ECMWF). Thus, GEFS members show an earlier increase
to above normal PWAT`s as early as Monday evening, with the
increasing PWAT signal for the ECMWF delayed more into the Tuesday-
Wednesday timeframe.

Thus, the timing of moisture increases, dictated by the strength of
this troughing and subtropical high positioning, will determine how
soon the region could conceivably see convection potential increase.
The current thinking is convection potential will first increase
across higher terrain areas of south-central Arizona as early as
Tuesday, with gradual increasing chances into the lower deserts
going into mid to late week. Prior to higher potential of
showers/storms into the lower deserts, this transition from dry to
more moist conditions may be preceded by a couple of days of gusty
winds and blowing dust impacts due to outflows stemming from
periphery convective activity in southeastern Arizona and higher
terrain areas during the late afternoon and evening hours. We also
cannot rule out a day or two of a dry lightning threat ahead of more
robust convection.

&&

.PREVIOUS DISCUSSION...
By late next week, we may even be able to see some deeper
tropical moisture seep into portions of our area, but this will be
dependent upon what happens with a potential Tropical Cyclone
south of Baja during the middle part of next week. If we do end up
seeing some tropical moisture at some point late next week, right
now it looks to fall on around next Friday. There are still a lot
of what-ifs, but we can at least point toward the 6-10 day CPC
outlook which shows a 70-80% chance of above normal precipitation
late next week. We will hopefully have a better idea on our
rainfall potential over the next few days.

&&

.AVIATION...Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major weather issues will exist through Friday evening under
occasional, few midlevel cloud - primarily during the afternoon over
mountains east of the terminals. Behavior of wind speeds and
directions will be very similar to the past 24 hours including a
later than usual overnight shift to easterly, then only modest gusts
during the late afternoon/early evening.


Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Friday evening under clear
skies. Wind trends will be very similar to the past 24 hours with
S/SE directions favored during daylight hours and a SW component
during the evening/overnight. While not directly impacting sfc
visibilities, lofted smoke/haze may occasionally affect slantwise
visibilities during the late afternoon/evening hours at KIPL.

&&

.FIRE WEATHER...
High pressure will gradually strengthen across the region through
the weekend leading to a strong warming trend and continued dry
conditions. Temperatures will warm to above normal starting Friday
before peaking early next week. Expect little change in humidity
trends as MinRH values continue to range between 5-15% each day and
overnight recoveries stay between 20-35%. Winds will follow familiar
diurnal trends with typical afternoon breeziness, gusting mainly
between 15-20 mph. Eventually, the weather pattern should become
more favorable for increasing moisture and at least some scattered
high terrain showers and thunderstorms by around next Tuesday. This
may initially result a day or two of dry lightning concerns before
moisture and rainfall chances increases later next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Sunday morning through Tuesday evening
     for AZZ537-540-542>544-546-548-550-551.

     Extreme Heat Watch from Monday morning through Monday evening
     for AZZ534-538-539-552>555-559.

CA...None.

&&

$$

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