490
FXUS65 KPSR 260000
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
500 PM MST Fri Apr 25 2025

.UPDATE...
00Z Aviation Discussion.

&&

.SYNOPSIS...
A weather system will traverse the Great Basin this weekend
resulting in frequently breezy conditions with wind gusts peaking
Saturday afternoon and evening. This system will also cause
temperatures to fall nearly 10 degrees below normal by the end of
the weekend. However, readings are likely to quickly rebound to near
seasonal normals by Tuesday as weak high pressure builds back over
the western United States.

&&

.DISCUSSION...
Afternoon WV imagery and objective analysis depicts mean longwave
troughing over western North America with several vorticity centers
rotating through the cyclonic flow acting to further carve out
deeper negative height anomalies across the SW Conus during the next
72 hours. As is typical for this time of year, shallow moisture will
remain trapped on the windward side of the coastal range in the form
of a persistent marine layer. However, modest height falls combined
with an increasing pressure and thermal gradient crossing into
southern California will support periods of strong, gusty winds this
evening through Saturday night. While not the most optimal setup,
there is sufficient ingredients and model support for hydraulic
jumps and mountain rotors navigating well inland off the higher
terrain this evening, and have made minor areal expansion of the
ongoing Wind Advisory. In addition to creating difficult driving
conditions for high profile vehicles, areas of blowing dust
emanating from the usual areas around Borrego Springs, as well as
recently disturbed agricultural fields across the Imperial Valley
and northern Mexico will be possible.

Models are in excellent agreement pushing the cold core and
deepening vorticity center onto the southern California coast
Saturday afternoon with renewed height falls and cooling
tropospheric temperatures entering the forecast area. While the main
brunt of the system will lift into southern NV and the Great Basin
the remainder of the weekend, inland height falls and deep
mechanical mixing depth will partially tap a strengthening jet core
forming downwind of the central circulation. As such, widespread
breezy conditions Saturday with gusts 25-35 mph will become common
during the afternoon and early evening. While HREF membership is not
completely supportive, especially given the reduced thermal gradient
through southern California, will need to monitor the potential for
another advisory expansion inland for Saturday evening. Otherwise,
this system will funnel unseasonably cool air into the Southwest
dropping temperatures nearly 10F below normal Sunday. By this time,
heights falls and jet energy will have largely lifted away from the
CWA such that only lingering muted gustiness more typical for mid
spring will remain.

During the first half of next week, the forecast area will fall
under the influence of the trailing end of a positively tilted full
latitudinal trough with H5 heights generally rising, but still
sequestered near 570dm under cyclonic flow. While this pattern will
yield little to no weather impacts for the region, temperatures
will respond by quickly rebounding to near normal levels. Ensemble
spread begin to grow markedly towards the end of next week as the
influence of a central Pacific blocking pattern migrates into the
western Conus. The range of possible outcomes varies widely from
predominant ridging and much above normal temperatures, to some
form of a Rex block becoming established over the region yielding
weaker height fields and fairly normal temperatures, to incoming
deep negative height anomalies and another brief period of breezy
conditions and cooler temperatures. Not surprisingly, ensemble
forecast temperature spreads are in excess of 20F given these
possibilities resulting in low forecast confidence beyond the end
of next week.

&&

.AVIATION...Updated at 2350Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
The main aviation concern will continue to be afternoon/early
evening breeziness across the region. Occasional gusts into the
teens to 20 kts will be possible until speeds diminish below 10
kts after sunset. The typical diurnal return to easterly flow is
expected to occur between 07Z-09Z. A very similar wind pattern is
expected again on Saturday with a few hours of southerly winds in
the morning followed by a slow transition to the southwest with
gusts increasing to around 20 kts by the afternoon. Clear skies
will prevail through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
The main aviation concern over the next 24 hours will be breezy to
locally windy conditions, particularly at KIPL. Gusts are expected
to range from 25-30 kts over the next several hours, however high-
res model guidance continues to indicate a period of higher gusts
likely reaching 35+ kts at times after sunset. These enhanced
winds will have the potential to generate areas of blowing dust
which could translate to windows of reduced visibilities. Winds at
KBLH will remain breezy out of the S-SW overnight. Clear skies
will prevail during the forecast timeframe.

&&

.FIRE WEATHER...
An approaching low pressure system will increase southwest winds
through the weekend with widespread gusts to between 20-35 mph, and
the strongest gusts likely occurring Saturday afternoon and evening.
This will result in an elevated fire danger, particularly for higher
elevation of eastern districts. Temperatures cooling below normal
will allow an increase in humidity levels, and in combination with
some fuels not quite fully cured should preclude critical fire
weather conditions. Otherwise, afternoon minRHs will generally fall
into a 15-25% range through the first part of next week before
return 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%) during the middle of next week as temperatures warm back
towards the seasonal normal.

&&

.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 CAZ566-567.

&&

$$


DISCUSSION...18/Whittock
AVIATION...Salerno
FIRE WEATHER...18/Whittock