743
FXUS65 KPSR 222331
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
431 PM MST Thu May 22 2025

.UPDATE...Updated 00z Aviation Discussion.

&&

.DISCUSSION...

Key Messages:

1) Slight cooling through the weekend resulting in relaxation of
moderate HeatRisk

2) Enhanced breeziness Friday yielding a locally elevated fire danger

3) Very tranquil weather next week with temperatures hovering
slightly above normal

Early afternoon objective analysis indicates flat ridging settled
over the region with H5 heights near 585dm supporting temperatures
nearly 10F above the daily normals. Meanwhile, hemispheric WV
imagery shows a very progressive upstream flow pattern with several
incoming low amplitude shortwaves poised to slowly erode these
higher midlevel heights over the next 48 hours. In fact, models are
in excellent agreement reducing H5 heights closer to a 578-582dm
range by Saturday with a modest cold core lifting through southern
NV into the Great Basin. As such, guidance spread is extremely
narrow, and forecast confidence very good advertising temperatures
retreating from nearly 10F above normal to 2F-4F above normal.

Although not an optimal setup, sufficient height falls and an
increase pressure gradient will support a period of increased gusty
winds - most notably on Friday afternoon/evening across SE
California. Models are forecasting 25-35kt H9-H8 flow crossing the
San Diego mountains as onshore flow and a deepening marine layer
aids in enhancing the thermal gradient in combination with the
pressure gradient promoting an active downslope event. Some of the
typical locations may experience advisory type wind speeds for a
short duration, but limited areal and temporal extent may preclude
the necessity for headlines. Further east, gusts will not be as
strong, however enough to yield an elevated fire danger given the
antecedent fuel and humidity conditions. Given model agreement and
historical precedent, have slightly increased forecast wind speeds
above the mandated automatic NBM output.

Early next week, the upper level flow pattern will become fairly
stagnant as a retrogressive northern stream block allows pronounced
positive height anomalies to develop over central Canada while deep
negative anomalies become established over the Gulf of Alaska. In
fact, through much of the first half of the week, a general omega
block pattern will characterize the Conus pattern with the forecast
area falling within the southwest cyclonic foot of the block. Even
ensembles with somewhat differing configurations maintain a dry
pattern and H5 heights around a consistent 582dm, resulting in
excellent forecast confidence of a persistence type forecast. Global
ensembles continue to show this general pattern holding throughout
the week with some measure of cyclonic flow maintaining steady state
midtropospheric heights, however with greater uncertainty towards
the end of next week hinging on the blocking evolution.

&&

.AVIATION...Updated at 2330Z.

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

No major aviation weather concerns are expected through the TAF
period. Wilds will favor diurnal tendencies with periods of
variability between transition periods outside of
afternoon/evening breeziness. Periodic afternoon breeziness is
anticipated, with gusts upwards of 15-20 kts across the Phoenix
area as well as afternoon/evening gusts up to 20-25 kts possible
at KIPL and KBLH this evening and tomorrow afternoon. Confidence
in VIS restrictions at KBLH due to a nearby wildfire is low, but
recent smoke production appears to be minimal at this time, thus
no VIS restrictions are currently reflected in the TAF at this
time. Otherwise, expect FEW-SCT passing high clouds throughout the
period.

&&

.FIRE WEATHER...
Temperatures will steadily cool into the weekend, though still
remaining around 5F above normal through the middle of next week.
Very dry conditions will also prevail with minimum humidity levels
around 10% following poor to fair overnight recovery of 20-45%.
Typical afternoon upslope breeziness will be common through the
period, however enhanced gustiness Friday will result in an elevated
fire danger. Gusts 20-25 mph should be expected on most days,
however localized gusts 30-35 mph will be more prevalent Friday.

&&

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

$$

DISCUSSION...18/Berislavich
AVIATION...Young/Smith
FIRE WEATHER...18