477
FXUS65 KPSR 092331
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
431 PM MST Thu May 9 2024

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Just below normal temperatures today will warm to near normal
tomorrow, with a gradual warming trend continuing into next week.
The lower deserts will see increasing chances for triple digit
afternoon high temperatures by the end of the weekend and heading
into next week. Otherwise, typical springtime afternoon breeziness
along with dry conditions will continue.

&&

.DISCUSSION...
Upper-level troughing continues across western CONUS and will help
keep today`s afternoon high temperatures a few degrees shy of normal
for this time of the year. This longwave trough will linger, but
gradually weaken, over the region for the next few days. This will
lead to temperatures going back above normal tomorrow with a gradual
warming trend into next week. A weak jet at the base of the trough
will enforce the typical springtime afternoon and early evening
breeziness through at least the weekend.

As the aforementioned trough weakens this weekend a strong ridge
in the Pacific Northwest will be able to start to make it way into
the Desert Southwest causing heights aloft to rise a little bit.
This will allow for portions of the lower deserts to see triple
digit afternoon high temperatures as soon as Sunday. The NBM gives
portions of the lower deserts in southeast California and
southwest Arizona a 60-80% chance of hitting 100 degrees on
Sunday, which would put these communities in a Moderate HeatRisk.
As for portions of the lower deserts in south-central Arizona,
chances of hitting tripple digits increases by the beginning of
next week. The NBM gives the Phoenix Metro a 30-50% chance of
hitting 100 degrees on Monday. The ensemble guidance does have the
trough linger over our region into early next week, so if it
doesn`t weaken as much as currently forecasted then the triple
digits may hold off until the middle to end of next week.

.PREVIOUS DISCUSSION...
Speaking of the middle to later portions of next week, ensemble
clustering show considerable spread, as the evolution of the
aforementioned trough will determine the magnitude of the warming
trend during this period. However, there is a signal of more robust
ridging building across the region late week, so temperatures
topping the century mark would have a much higher likelihood should
that scenario come to fruition. For now, the NBM deterministic
forecast shows warming through Sunday, with highs hovering right
near 100 degrees for the lower deserts through the early and middle
portions of next week. Rain chances are essentially zero through the
forecast period, but an increase in moisture starting Sunday and
lingering into the middle of next week are expected to result in
increasing clouds in the higher terrain during the daytime hours.

&&

.AVIATION...Updated at 2330Z.

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

Typical Spring diurnal wind tendencies are expected at all
terminals through the next 24 hours, with speeds at or below 10
kts and afternoon gusts into the middle-teens. There will also be
periods of light variability during the overnight/early-morning
hours and during diurnal transitions. Skies will remain mostly
clear.

&&

.FIRE WEATHER...
Slightly below normal temperatures today return to near normal
tomorrow with a gradual warming trend into next week. MinRHs will be
in the 5-10% across the lower deserts and in the 10-15% range across
the higher terrain. Overnight recovery will be poor and in the 20-
40% range. Typical springtime breeziness continues through the
weekend with afternoon and early evening wind gusts of 20-25 mph.
These breezy conditions combined with dry fine fuels, and low RHs
will likely create some elevated fire weather conditions. Dry
conditions persist into next week.

&&

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

$$

DISCUSSION...Berislavich
PREVIOUS DISCUSSION...Young
AVIATION...Benedict
FIRE WEATHER...Berislavich/Young