783
FXUS65 KPSR 171205
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
505 AM MST Sat May 17 2025

.UPDATE...
12Z Aviation Discussion.

&&

.KEY MESSAGES...

1) Gusty winds today resulting targeted advisories and locally
elevated fire danger, and a return of gusty winds on Monday

2) Substantial warming trend next week resulting in widespread
Moderate HeatRisk during the latter half of the week

&&

.DISCUSSION...

Weather Pattern Overview:
Little has changed with the pattern across the Southwestern U.S.
since yesterday, but within the broad troughing a stronger
shortwave is now approaching from the northwest. As this
disturbance quickly tracks southeastward through northern
California into Nevada this morning, it will eventually reach
northern Arizona later this afternoon and evening. Strong height
falls later today across our region will lead to increasingly
gusty winds this afternoon with gusts as high as 30 mph across
Arizona and likely in excess of 30 mph across a good portion of
southeast California. The strongest winds today should be focused
across the western half of Imperial Co. during the evening hours
with gusts between 40-50 mph expected.

As the shortwave trough passes through northern Arizona this
evening and tonight, a dry cold front will also traverse our area
leading to modestly cooler temperatures Sunday. Sunday looks to
be the best weather day over the next week with clear skies,
temperatures around five degrees below normal, and some breeziness
with gusts of 20-25 mph in the afternoon. The broad trough will
still be in place across the western U.S. with another even
stronger shortwave set to dive southward through the Great Basin
Sunday night before likely passing through northeast Arizona
during the daytime hours Monday. This second disturbance looks to
be a bit farther east and north compared to today`s system with
the main expected impacts again being winds. Winds Monday are
expected to be more out of the north northwest with the strongest
afternoon gusts of 25-35 mph likely focused across the Lower CO
River Valley and over the Arizona higher terrain. We should also
begin to feel the affects of a strong Pacific ridge nearing the
California coast as it should bring our daily highs back into the
normal range.

Once the shortwave trough exits well to the northeast, the
Pacific ridge will begin to spread over the region boosting H5
heights to between 582-584dm on Tuesday. Heights are forecast to
continue to rise through the middle of next week before H5 heights
peak somewhere between 588-590dm, or into the 90th percentile of
climatology on Thursday and/or Friday. NBM forecast temperatures
remain quite consistent showing highs warming to 100-104 degrees
already by Wednesday before peaking between 102-107 degrees on
Thursday and/or Friday. These highs would be around 10 degrees
above normal and roughly 3-5 degrees below daily records. Moderate
HeatRisk will develop as early as Wednesday and for sure for
Thursday and Friday across all but the highest elevations. Model
uncertainty rises for Memorial Day weekend, but ensemble guidance
somewhat favors a flattening of the ridge and a modest cooldown.
NBM temperatures currently show readings dipping back closer to
100 degrees next weekend, but this may be a little optimistic.

Forecast Confidence & Deviations:
Confidence in temperature forecasts remains very good this
weekend, while we see improving confidence early next week as
models are likely settling on keeping the shortwave trough further
to the north. Forecast confidence for the hotter temperatures
next week remains quite good, but some adjustments to these
readings (maybe a 1F-3F higher) may still occur, especially over
the Memorial Day weekend depending on the pattern evolution.

&&

.AVIATION...Updated at 1150Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
The main aviation concerns this period will be elevated southerly
crosswinds this morning followed by gusty SW winds through much of
the afternoon and early evening. Winds are currently light out of
the ESE, but are expected to veer out of a southerly direction and
increasing to 8-11 kts late this morning. This will create a 3-4
hour period of a southerly crosswind component at KPHX and KDVT
through mid morning. By this afternoon (21-22Z), anticipate winds
to establish a prevailing southwesterly direction, with gusts up
to 20-25 kts becoming common through much of this evening. It is
still likely that gusts will linger well after sunset at all
terminals until subsiding by 06Z-07Z. There will be periods of
passing high clouds, however coverage will remain FEW-SCT.

Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty winds and potential for lower vsbys due to BLDU will be the
primary aviation concerns through the TAF period under occasional
FEW-SCT high clouds. Winds are expected to maintain a westerly
direction at KIPL while winds at KBLH will favor S-SW through much
of the period. Expect winds to become elevated at both terminals
by 15Z-16Z this morning with gusts around 25-30 kts materializing
by early this afternoon. There is a high likelihood (>75% chance)
that gusts will reach 35 kts or greater especially at KIPL during
the late afternoon into the evening which could produce temporary
surface visibility restrictions due to blowing dust/haze.

&&

.FIRE WEATHER...
Wind speeds will increase substantially beginning this afternoon
with gusts 25-35 mph becoming common. For the eastern districts
into portions of southwest Arizona, the combination of the gusty
winds and humidity values falling into a 10-15% range will yield
an elevated fire danger. While wind speeds will only be slightly
weaker Sunday, humidity values only falling into a 20-25% range
will preclude a greater threat. Correspondingly, poor to fair
overnight recovery of 20-50% will improve closer to a 40-60% range
Sunday. Drier conditions will again move back into the region
starting Monday with another breezy day potentially bringing
elevated fire danger later in the day. By the middle of next week,
very warm temperatures will return with MinRHs in the single
digits following poor overnight recovery, however wind speeds
will be much weaker as high pressure starts building into the
region.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory from 2 PM this afternoon to 7 AM PDT Sunday for
     CAZ562.

     Wind Advisory from 4 PM this afternoon to 2 AM PDT Sunday for
     CAZ563-566-567.

&&

$$

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