638
FXUS65 KPSR 082149
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
249 PM MST Tue Jul 8 2025

.UPDATE...Updated Short Term Discussion.

&&

.KEY MESSAGES...

- Strong high pressure over the region will result in well above
  normal temperatures through midweek with afternoon highs
  forecast to reach and exceed 115 degrees across most of the
  lower desert communities Wednesday

- The heat will result in widespread Major HeatRisk with Extreme
  Warnings in effect for much of the region today through Thursday

- Temperatures lower a few degrees by the end of the week through
  this weekend, but remain above normal

- Thunderstorm activity will continue to be limited to the
  Arizona high terrain and southeast Arizona during the next
  several days

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
High pressure has spread across all of the Southwest and
strengthened considerably since yesterday. Latest mesoanalysis is
showing 597-598dam H5 heights over AZ and SoCal, which is right
around record heights for this time of year. These near record
mid level heights has not fully translated to max PBL heating
quite yet, as indicated by a minimal increase in 850mb
temperatures (+1-2C) on Phoenix aircraft soundings and
mesoanalysis over the last 24 hours. Highs this afternoon are
forecast to be 2-4F warmer than yesterday, with lower deserts
topping out around 108-113F. An Extreme Heat Warning is now in
effect for the South-Central AZ lower deserts and the San Carlos
area, as today`s temperatures push the HeatRisk level up to Major,
meanings everyone is susceptible to heat health impacts without
adequate relief.

The full impact of this strong high pressure over the region will
be felt tomorrow as PBL heat peaks and surface temperatures warm
another ~5 degrees over today`s highs. The Extreme Heat Warning
will expand to nearly all of Southern AZ and SoCal tomorrow, with
widespread Major HeatRisk as afternoon high temperatures are
forecast to reach 114-118F across the lower deserts. A high of
118F is now forecast for Phoenix, from the latest NBM
deterministic, which if it pans out would break the daily record
of 116F set last year and in 1958. Daily records will also be
reachable in Yuma and El Centro tomorrow. Morning lows the next
few days will also be pushing daily record warm lows. The H5
height magnitude and 850mb temps with the current strong high is
comparable to the heights and temperatures with the strong highs
that produced 118H highs in Phoenix in 2024 and 2023.

Aside from the heat, there was a low level moisture flux last
night that pushed surface dew points into the 50s to around 60F.
Despite this, strong subsidence and capping over the lower deserts
will inhibit any convection potential and afternoon storms will
remain focused over the higher terrain north and east of Phoenix
and in Southeast AZ. A weak northerly steering flow over the Rim
this afternoon will be capable of bringing a few showers and
maybe an isolated storm down into parts of southern Gila County
and far eastern Maricopa County. Any storm will be capable
producing strong gusty outflow winds, given high DCAPE (1700-1800
J/kg), with around 30% HREF neighborhood probabilities for >35
mph outflow winds. There is also potential for some gusty outflows
to descend toward the lower deserts this evening. Little to no
rainfall accumulation is expected. HREF shows afternoon convection
tomorrow will be even more isolated and less intense north and
east of Phoenix tomorrow.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The subtropical high is expected to weaken slightly heading into
Thursday as the energy leftover from the cutoff low migrates
eastward into the Great Basin and Intermountain West Regions. This
will result in a slight decrease in the heights aloft and thus
afternoon high temperatures will be slightly cooler but still hot
enough for areas of Major HeatRisk to remain in place with
Extreme Heat Warnings remaining in effect for all of the lower
desert communities. Heading towards the end of the week through
next weekend, the high will continue to very gradually migrate
westward towards the southern CA coastline and as a result heights
aloft will continue to decrease slightly more. This will
translate to slightly cooler temperatures, but still remain a few
degrees above normal as afternoon highs across the lower deserts
will average around 110 degrees, resulting in widespread Moderate
HeatRisk.

With the subtropical high migrating westward into southern CA
towards the end of the week and weekend, the upper-level flow
pattern will remain quite unfavorable for any deep moisture
influx. Thus conditions are expected to remain mostly dry across
much of the region, with any thunderstorm activity limited across
the White Mountains through the southeastern third of AZ. As the
high migrates into the southern CA coastline during the weekend,
the upper-level flow is expected to turn out of the north, which
will bring in even drier air with the latest EPS and GEFS showing
PWATs dropping below one inch. Thus, thunderstorm activity will
likely be more limited, even across the higher terrain areas. This
overall dry pattern will continue into early next week before the
high potentially repositions near the Four Corners by the middle
to latter half of next week, which if it materializes, would be a
more favorable flow pattern to advect deeper moisture into the
region and reintroduce higher thunderstorm chances.

&&

.AVIATION...Updated at 1755Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation weather concerns will exist through the TAF
period under FEW mid and high clouds. Winds will predominantly
favor the W/NW through this evening. Followed by winds going light
and variable during the overnight hours at KSDL and KDVT, KPHX
going light and variable around sunrise, and KIWA going light
southeasterly during the overnight hours. Expect gusts to around
20 kts this afternoon into the early evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under periods of FEW to at times SCT mid and high clouds.
Winds will continue to vary between S/SE and SW, with extended
periods of light and variable winds, particularly at KIPL. Wind
speeds will generally remain AOB 10 kts, though some gusts to
around 15-20 kts are possible, particularly after the switch to a
SW`rly direction this evening.

&&

.FIRE WEATHER...
Regionally dry conditions and above normal temperatures will
persist through the next week as lower deserts highs reach and
exceed 110 degrees nearly every day. MinRH values will range from
10-20% each day, while MaxRH values will be the lowest tonight
and Wednesday night at 20-40% before increasing up to 30-50% the
rest of the week for most of the area. One exception will be
across Imperial and southern Yuma Counties where periodic gulf
surges will result in MaxRH values in excess of 50%. The overall
wind pattern will follow the familiar diurnal trends, with some
afternoon/early evening breeziness (15-25 mph peak gusts). An
uptick in the winds is expected Thursday and Friday afternoons
(25-35 mph peak gusts). This may lead to locally elevated fire
weather conditions, primarily on Thursday due to drier conditions.
Very minimal rain chances will exist during the next several days,
focused north and east of Phoenix and in Southeast AZ, with CWR
<10% through at least next weekend.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Thursday
     for AZZ530>533-535-536.

     Extreme Heat Warning until 8 PM MST Thursday for AZZ534-537>540-
     542>544-546-548-550-551-553>555-559-560.

     Heat Advisory from 10 AM to 8 PM MST Wednesday for AZZ557-558-
     563.

     Extreme Heat Warning from 10 AM to 8 PM MST Wednesday for AZZ541-
     545-547-549-552-556-561-562.

CA...Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday
     for CAZ560>570.

&&

$$

SHORT TERM...Benedict
LONG TERM...Lojero
AVIATION...Berislavich/Whittock
FIRE WEATHER...Benedict/Lojero