106
FXUS65 KPSR 011139
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
439 AM MST Sat Jun 1 2024

.UPDATE...Updated 12z Aviation Discussion.

&&

.SYNOPSIS...
Seasonably hot and dry weather conditions will persist through early
next week with temperatures running 3 to 5 degrees above normal. By
the middle of next week, high pressure is forecast to strengthen
across much of the western United States, resulting in hotter
temperatures as high get closer to 110 degrees across much of the
lower deserts.

&&

.DISCUSSION...
The month of June will start off hot and dry across southern
California and Arizona with clear skies persisting this weekend.
The dry westerly flow aloft is set to continue for at least
another few days with stable H5 heights between 583-586dm and
daily high temperatures topping out between 100-105 degrees across
the lower deserts.

Starting late Monday into Tuesday, the upper level pattern will
begin to shift as the sub-tropical ridge which currently extends
from off the California coast through northern Mexico begins to
build over much of the Western U.S. At the same time, a weak cut-
off low is forecast to develop just west of Baja and sit nearly
stationary to our southwest through the middle of next week. The
main forecast concern is still the expected hotter temperatures
for the latter half of next week as H5 heights are likely to rise
to between 589-593dm by Wednesday.

Ensemble guidance seems to be settling on the cut-off low staying
far enough to our south and west that it will have little to no
impact on our weather for at least Wednesday and Thursday as the
ridge becomes the dominant weather feature. The latest NBM
temperatures are nearly in line with the past several runs with
the exception of boosting temperatures a couple degrees on
Thursday. Given the expected higher heights, highs by Wednesday
should top 105 degrees across the majority of the lower deserts
with the warmest spots getting close to 110 degrees. Thursday`s
forecast highs are now between 107-111 degrees with a good portion
of the Phoenix metro and the Lower CO River Valley forecast to
see 110 degrees for the first time this season. The current
forecast temperatures would result in localized areas of Major
HeatRisk mainly on Thursday.

Eventually, most likely late Thursday into Friday, ensemble
guidance indicates the cut-off low tracking northward through
southern California and possibly western Arizona. Depending on the
timing and the track of the low, it should lower temperatures
away from 110 degrees by around next Friday or at the latest
Saturday. There should also be another larger scale trough coming
off the Pacific from the northwest tracking through our region or
at least through the Great Basin at some point later next
weekend. Moisture levels are also shown to increase across the
region late next week, but it is doubtful it would bring anything
other than low end rain chances across portions of the Arizona
high country.

&&

.AVIATION...Updated at 0535Z.

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

No major weather issues will exist through tonight under clear
skies. Wind trends across the region should be nearly identical to
the past 24 hours. Across the Phoenix metro, this will include
directions switching to an overnight easterly drainage component,
then shifting back to westerly early Saturday afternoon.
Probabilities of gusts 15-20 mph at the Phoenix area terminals are
greater Saturday afternoon than previous days. SE California
terminals will experience winds oscillating between SE and SW with
extended periods of variable directions, until the late afternoon
and evening where there could be periods of gustiness 20-25 kts.

&&

.FIRE WEATHER...
Little to no change in the weather pattern will keep seasonably
dry and hot conditions in place through early next week. Expect
lower desert highs between 100 and 105 degrees, or 3-5 degrees
above average each day. MinRH values will continue to run between
5-10% across the majority of the area each day, while overnight
recoveries will continue to range from poor to fair at around
25-40%. Winds will overall be fairly light following diurnal
tendencies with periodic afternoon gusts of 15-20 mph.

&&

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

$$

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