599
FXUS65 KPSR 262020
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
120 PM MST Sat Apr 26 2025

.SYNOPSIS...
Dry conditions with below normal temperatures will prevail during
the first part of next week as a weather disturbance moves through
the region. However, a return of high pressure will result in a
steady warming trend during the second half of the week with
temperatures rebounding into a slightly above normal range.

&&

.DISCUSSION...
A cyclonic circulation center was moving across the southern
California coastline early this afternoon as the cold core and
negative PV anomaly rotate through the trough base. While the bulk
of this system will be lifting northeast through NV/UT over the next
24 hours, lingering height falls and cooling tropospheric
temperatures within the southern extension of the trough structure
will continue to progress inland across the forecast area. This
configuration will support another round of strong, gusty winds with
deep mixing partially tapping a robust midlevel jet. The most
significant gusts should reside over ridgetops and downstream of
high terrain features. Once again this evening, enhanced downsloping
winds off the San Diego mountains will result in advisory levels
winds near and west of the Imperial Valley. Enough evidence among
modeling and observational data substantiates a small areal
expansion of the ongoing advisory with the primary impacts focused
on issues for motorists with strong gusts and localized blowing
dust.

As the core of the upper level trough migrates northeast tomorrow,
the pressure gradient will begin to relax resulting in weakening
winds and only modest afternoon/evening gusts. Dampened H5 heights
below 570dm will hover over the region as the overall large scale
synoptic trough elongates in a positive tilt fashion leaving
lingering cooler temperatures across the SW Conus. In fact,
temperatures Sunday will languish some 10F below the seasonal
normal, and the delayed forward propagation of the southern
extension of the trough will only allow a steady warming trend.
Despite heights aloft remaining fairly steady, thermal modification
of the lower troposphere with the higher late spring sun angle will
support about 5F/day of warming through the first part of the week
such that near normal readings should become reestablished by
Tuesday.

While heights aloft and thermal profiles will certainly increase
during the middle and end of next week, models indicate only modest
ridging developing as a blocking pattern shifts eastward from the
Pacific forming a temporary Rex block over the western Conus.
Guidance spread remains rather narrow during much of this time
frame adding confidence of temperatures settling in a slightly above
normal range. Towards the end of the week, large ensemble spread
becomes evident owing to model difficultly resolving whether
blocking is resolved, or actually expands and intensifies over the
entire western hemisphere. Recent GEFS output has trended more
towards a more pronounced blocking regime with a deep cutoff feature
hovering somewhere near the SW Conus, which is fundamentally
different than the operational member. The growing percentage of
these cutoff GEFS solutions far more resemble the majority CMC
ensembles and operational ECMWF output from the past couple days
yielding marginally better confidence of this type of solution (not
to mention this type of high amplified blocking becomes notorious in
May). Nevertheless, given the wide range of ensemble possibilities,
guidance temperatures spreads continue to be unusually large (10-15
degrees within the NBM interquartile ranges). The aforementioned
ensemble trends may eventually result in some of the cooler
temperature forecasts to come to fruition by next weekend.

&&

.AVIATION...Updated at 1740Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No significant aviation weather concerns are anticipated through the
TAF period. Winds will continue to veer toward the WSW heading into
this afternoon as winds increase. Breezy afternoon conditions are
expected today with gusts climbing upwards of 20-25 kts at the
terminals. Breezy conditions decrease this evening but expect a
westerly component to persist well into the overnight hours.
Confidence in a diurnal switch to the east overnight is low with
perhaps more light and variable conditions favored early Sunday
morning. Otherwise, mostly clear skies will continue with a few
passing high clouds Sunday.


Southeast California/Southwest Arizona including KIPL and KBLH:
The primary aviation weather concern through the next 24 hours will
be strong, gusty winds at the TAF sites, particularly at KIPL.
Westerly gusts generally around 25-30 kts can be expected at KIPL
through the afternoon with an uptick to around 35 kts at times this
evening. With these strong winds, blowing dust may result in some
surface/slantwise visibility restrictions. Strong gusts look to
subside around midnight but speeds will remain elevated out of the
west through the overnight period. At KBLH, S-SW winds will persist
through the period with gusts upwards of 25-30 kts this afternoon
and evening. Otherwise, mostly clear skies will persist with perhaps
a few afternoon CU and a few passing high clouds.

&&

.FIRE WEATHER...
Temperatures cooling below normal will allow an increase in humidity
levels early next week, however warming conditions during the latter
half of the week will return conditions back to more typical for
early May. Winds will maintain a seasonally typical upslope
gustiness through the entire period with the strongest gusts
occurring Sunday afternoon. With dry weather prevailing, afternoon
minRHs will generally fall into a 15-25% range during the first part
of next week before returning to a 10-15% range by the middle of the
week. Fair to good overnight recovery of 30-60% will retreat towards
poor to fair (20-40%) levels.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 5 AM PDT Sunday for CAZ562.

     Wind Advisory until 10 PM PDT this evening for CAZ566.

&&

$$


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