246
FXUS65 KPSR 031129
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
429 AM MST Thu Apr 3 2025

.UPDATE...Updated 12z Aviation Discussion...

&&

.SYNOPSIS...
A broad trough of low pressure over the western U.S. will keep
temperatures below normal and bring chances for light showers to
the region through Friday. Any shower activity is expected to be
very light with little to no measurable rainfall. High pressure
will gradually build back over the region over the weekend leading
to warmer temperatures and drying conditions. The warming trend
will continue well into next week as temperatures climb to well
above normal by the middle of next week.

&&

.DISCUSSION...
The deep upper level trough that has settled into our region over
the past 24-36 hours will continue to bring near record negative
height anomalies into Friday with high temperatures running 10-15
degrees below normal. A fairly blocked upper level weather pattern
will keep the trough in place for another couple of days resulting
in continued unsettled weather conditions. Early morning isolated
light showers and virga are expected to gradually diminish through
around sunrise, but another round of cold core induced light
shower activity is expected during the afternoon hours favoring
locations mainly north and west of the Phoenix area. Most activity
will only amount to trace to a couple hundredths of an inch of
precipitation due to the lack of any meaningful moisture in place.

As the upper level trough very slowly drifts to the east southeast
through our region Thursday night into Friday, a second cold core
is expected to pass through south-central Arizona during the first
half of Friday. A slight uptick in lapse rates and energy aloft
should help to bring a bit more organized shower activity over the
Arizona higher terrain Friday afternoon. This should bring better
chances for measurable precipitation, albeit still light, and
maybe even a weak thunderstorm.

Temperatures today will again struggle to reach 70 degrees across
the lower deserts, but as the trough begins to slide further
eastward on Friday, the western lower deserts are forecast to
reach back into the mid to upper 70s. As the low finally exits
into New Mexico early Saturday, upper level ridging and drying
conditions will spread west to east across our region. Aside from
a few lingering showers across the eastern Arizona higher terrain
on Saturday, the rest of the area will see sunny skies return and
much warmer conditions as highs likely top 80 degrees over the
western deserts to the upper 70s in Phoenix.

The weather pattern starting Sunday will then shift keeping any
weather systems over the northern Pacific into western Canada
allowing an upper level ridge to gradually build over the
Southwestern U.S. Forecast H5 heights are seen reaching near 580dm
by late Monday, to around 584-586dm on Wednesday, before
potentially peaking near 588dm next Thursday. Ensemble guidance
shows this upper level ridge likely reaching near climatological
record strength for next Wednesday-Friday, potentially pushing
high temperatures to around or just above 100 degrees across the
lower deserts late next week. Temperatures are forecast to warm
about 5 degrees per day from Saturday through Thursday with highs
topping 90 degrees by Tuesday and well into the mid to upper 90s
by next Thursday. Areas of Moderate HeatRisk are likely to develop
during the latter half of next week, with the hottest
temperatures likely focused from Thursday-Saturday. There is still
some model uncertainty with the eventual strength of the ridge
and how hot it will get, but we are nearly assured of seeing highs
reaching 100 degrees for at least some of the lower desert late
next week.

&&

.AVIATION...Updated at 1125Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns are expected throughout the TAF
period. The overall wind pattern for today will be more diurnal
with east winds this morning shifting out of the west by the late
morning/early afternoon hours. Wind speeds overall should remain
under 10 kts throughout the period. Cloud bases for the most part
are anticipated to remain aoa 10 kft. One caveat to this forecast
is that some hi-res model guidance is pointing towards isolated
SHRA development this afternoon, however, the chances of
occurrence and overall coverage are minimal at this time to
include a mention in the TAFs. However, if showers do come to
fruition, some brief gusty winds, reduced visibilities and lower
CIGs will be possible.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected throughout the TAF period.
Westerly winds will persist at KIPL while more variable winds are
anticipated at KBLH throughout the period. Generally clear skies
this morning will give way to FEW to SCT cloud bases generally aoa
8 kft developing this afternoon before clearing skies takes place
once again heading into this evening.

&&

.FIRE WEATHER...
Unsettled weather will continue through at least Friday with well
below normal temperatures and isolated light showers at times.
Chances for wetting rainfall will remain low at less than 10%.
MinRHs will range from 20-30% areawide today before gradually
lowering closer to 10-15% over the weekend. Expect light winds
today before winds increase out of the northwest on Friday with
afternoon gusts of 20-25 mph possible. High pressure will
eventually settle back into the region Sunday into early next week
bringing a rapid warming trend and seasonably dry conditions.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman