682
FXUS65 KPSR 310529
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1030 PM MST Thu May 30 2024

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
Expect high temperatures to remain above normal through the rest
of the work week, into the weekend, and into next week.

&&

.DISCUSSION...
The hot, dry, and clear skies weather pattern persists across the
Southwest as dry zonal flow prevails with upper ridging now shifting
east across the central CONUS. Ensemble guidance indicates 500 mb
heights will remain steady around 583-585 dm through the remainder
of this week and into the start of next week. This will keep
afternoon temperatures each day several degrees (3-5) above normal
as lower desert highs top out in the 100-106 degree range for most
places. With these temperatures will come widespread Minor and
pockets of Moderate HeatRisk, so the necessary heat safety
precautions should be exercised. Winds through the rest of the work
week will overall remain light, outside of periodic afternoon wind
gusts to around 20 mph. A very weak shortwave pushing through the
Southwest this weekend may slightly enhance winds and also lead to a
degree or two dip in temperatures.

By next Monday and Tuesday, guidance continues to favor a weak
cyclonic circulation forming just off the southern California and
northern Baja coast. Eventually, this feature is likely to become
fully or partially cut off from the main flow during the middle part
of next week as it should strengthen a bit more and wobbles just to
our west for several days. For now, guidance highly favors this
disturbance staying over the Pacific or at most reaching into
portions of southern California later next week, but either way it
should have little impact on our sensible weather conditions.
Moisture levels are likely to increase across the Southwestern U.S.
next week, but much of the moisture will stay to our west and north
leaving near to slightly above normal PWATs for our area. As of now,
the most we can hope for is some higher level cloudiness and maybe
some low end rain chances across the Arizona high country at some
point late next week into the following weekend.

The main forecast concern is the potential for even hotter
temperatures during the latter half of next week as the sub-tropical
ridge currently to our south is expected to strengthen and shift
northward through the Southern Plains and likely northwestward
through much of the Desert Southwest into the Great Basin by around
next Wednesday. Both the GEFS and EPS mean H5 heights are shown
increasing to between 588-594dm over at least much of Arizona and
New Mexico during the middle of next week. Model guidance is nearly
certain of this ridge building over our region, but there are still
differences on how strong it will be and how far west it can build
due to the expected presence of the cut-off low. For now, guidance
is definitely leaning toward hotter temperatures by next Wednesday
through the rest of next week with the latest NBM forecast highs
between 105-109 degrees over much of the lower deserts. If the cut-
off low ends up closer to our region, temperatures are not expected
to be that hot, but so far that is the less likely solution.
Starting next Wednesday, the NBM shows up to a 20-30% probability of
reaching 110 degrees for the warmest lower desert locations. Hot
temperatures of this magnitude are not unusual for the first week of
June as daily records for Phoenix range from 111-115 degrees and
records for Yuma and El Centro are a degree or two higher. As
temperatures reach near 110 degrees, this would put the majority of
the area well within a Moderate HeatRisk.

&&

.AVIATION...Updated at 0530Z.

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

No major weather concerns will exist through Friday night under
clear skies. Wind patterns across the Phoenix metro will again be
nearly identical to the past 24 hours with the typical easterly
drainage wind developing overnight, then shifting back to westerly
early Friday afternoon. For the SE California terminals, a SW wind
direction late this evening should generally back to a SE direction
Friday with extended periods of nearly calm conditions common.

&&

.FIRE WEATHER...
Hot and dry conditions will persist through the remainder of this
week with daily highs remaining 3-5 degrees above average. Daily
highs will reach the 105 mark in most lower desert locations with
widespread readings between 100-108 persisting through the remainder
of the week into the weekend. MinRH values will be 10% or less
across the central and western deserts each afternoon and overnight
recoveries will continue to range from poor to fair at around 25-
40%. Winds are expected to generally remain below 15 mph.

&&

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

&&

$$

DISCUSSION...95/Kuhlman
AVIATION...18
FIRE WEATHER...95