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525
FXUS65 KPSR 111738
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1038 AM MST Sat May 11 2024

.UPDATE...
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18z Aviation Discussion.
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&&

.SYNOPSIS...
Temperatures will steadily warm through early next week with many
lower desert communities flirting with the 100 degree mark
throughout much of the week. Seasonably dry conditions with typical
afternoon spring breezes will also be common across the local area
with showers and storms relegated to mountain locations of northern
and eastern Arizona.

&&

.DISCUSSION...
Early morning WV satellite imagery reveals a closed circulation
continuing to spin over the Great Basin comprising the eastern foot
of an expansive omega block. The central portion of this blocking
ridge was covering much of the northeast Pacific basin with
anomalously high heights folded into the Pacific NW. However, this
blocking regime is already showing signs of decay with strong
upstream wave energy breaking into and dampening the high pressure
axis. This upstream kicker wave in combination with an enhancement
in subtropical jet energy will also act to eject the aforementioned
Great Basin circulation, resulting in steady height rises over the
SW Conus through the next 72 hours.

Excellent forecast confidence exists the next several days
characterized by minimal ensemble spread and a very narrow range of
guidance within the NBM. Near normal temperature again today will
warm decidedly early next week as H5 heights increase to around
578dm. With this midlevel height forecast not particularly
anomalous, surface temperatures will warm into an above normal
category, but nothing unusual for mid May. At this time, Monday
appears to be the warmest day with better than a 75% chance of
widespread 100F readings through the lower elevations of western
zones, and greater than a 60% chance of KPHX breaching this
threshold. Otherwise, seasonably deep mixing juxtaposed with jet
energy situated on the southern flank of the circulation center will
support frequent afternoon wind gust 20-30 mph the next couple days.

By the middle of the week, ensemble output remains consistent in
translating the dampened ridge eastward with an extension of the
original upstream kicker wave descending into southern California.
H5 heights should be eroded closer to 572dm allowing temperatures to
recede somewhat closer to the climatological normal. Although NBM
guidance spread remains narrow during this time frame, feel a trend
towards the lower end of the guidance envelop is warranted given the
synoptic pattern. Regardless, this modest cooling will only be
temporary as lower heights should quickly be absorbed into
downstream flow by the end of the week. While dry weather should
persist across the CWA, evidence is growing in support of afternoon
deep convection over the mountains of northern AZ with flow
trajectories favorable towards bringing gusty outflow winds into
lower desert locations (Wednesday and Thursday most supportive of
this outcome).

NAEFS members continue to suggest some form of high pressure ridging
returning to the region towards the end of next week forcing another
distinct warming trend. Some uncertainty regarding the magnitude of
ridging and height rises still exists, however the preponderance of
model output suggests H5 heights rebounding above 582dm next weekend
with some individual members highlighting readings above 585dm.
Based on these trends among ensemble membership, confidence and
probabilities are growing regarding a more pronounced warming event
and expansive 100F+ temperatures next weekend.

&&

.AVIATION...
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Updated at 1740Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds are beginning to shift out of the WSW at all metro
terminals. Gusts will increase by 20Z-21Z, peaking at 20-25 kts
through early this evening. Skies will remain mostly clear,
however there will be a few high-based cu around 10-12 kft this
afternoon across the northern fringe of the Phoenix Metro. Any
showers or convective activity will remain confined to the higher
terrain of northern AZ. The possibility of any storm generated
outflow from the north continues to be very low, thus we will
continue to preclude mention at this time.

Southeast California/Southwest Arizona including KIPL and KBLH:
N to NW winds will continue at both KBLH and KIPL. There will be
an increase in breeziness at KBLH this afternoon with gusts
reaching up to 20 kts. Winds at IPL will eventually shift out of
the W after sunset, but speeds will remain aob 10 kts. Skies will
be mostly clear, with the exception of a few cu at 12 kft this
afternoon.
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&&

.FIRE WEATHER...
Temperatures will continue warming through early next week, reaching
and maintaining an above normal threshold. Seasonably dry weather
should also persist across the districts with minimum afternoon
humidity levels around 10% at lower desert elevations and in the
teens over higher terrain areas. Overnight recovery will range
widely from poor to fair in a 20-50% range. Typical afternoon spring
breezes 20-25 mph will be common over most areas, though it should
be noted there is at least a 25% chance of enhanced gusts and
erratic directions at times during the middle of next week from
outflows resulting from showers and storms over the mountains of
northern AZ. Nevertheless, the combination of periodically gusty
winds, dry fine fuels, and low humidity levels will yield an
occasionally elevated fire danger throughout the week.

&&

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

$$

DISCUSSION...18
AVIATION...Salerno
FIRE WEATHER...18