002
FXUS65 KPSR 190955
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
255 AM MST Sun May 19 2024

.SYNOPSIS...
A weather disturbance will slide primarily north of the region
early this week, but it will allow temperatures to retreat closer
to the seasonal normal. This system will also bring an increase in
winds, especially during the afternoon and evening hours with
Monday having the strongest winds and greatest impacts. Very
tranquil weather with near normal temperatures will prevail during
the second half of the week.

&&

.DISCUSSION...
A Pacific upper level trough is gradually shifting southward
across Pacific Northwest into the Great Basin with a much weaker
southern branch shortwave trough now tracking through the Desert
Southwest. The disturbance moving across our region will help to
lower temperatures today several degrees from yesterday`s highs
in the lower 100s, while winds will become breezier over much of
the area. The main forecast concern over the next couple days will
be the increased winds combining with low humidities to create
elevated to near critical fire weather conditions. Wind gusts this
afternoon and early evening are expected to easily reach into the
mid 20s areawide to 30-35 mph across portions of southeast
California. As the trough to our north continues to shift farther
south, the gradient over our region will increase into Monday
while another shortwave trough currently well west of southern
California tracks through our region. Both of these features will
enhance winds further with wind gusts Monday afternoon and early
evening likely reaching 25-35 mph across south-central Arizona to
30-45 mph across the western deserts of southeast California
through the the Lower CO River Valley. Near critical fire weather
conditions are expected over much of the area Monday afternoon.

Temperatures will continue to trend downward on Monday with
afternoon highs mostly in the lower 90s, or a couple degrees
below normal. The broad troughing over the Western U.S.,including
our region, should then persist through the rest of the week as
several progressive shortwaves are forecast to track across the
Northwestern U.S before sliding just to the north of our region.
This should keep upper level heights fairly stable over our region
at between 574-578dm, or right around climatological normal for
this time of year. This will keep seasonably dry conditions in
place through the coming week with temperatures right around
normal. Guidance is still suggesting we will eventually see a
warming trend, but as of now that should hold off until around
Memorial Day.

&&

.AVIATION...Updated at 0550Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns will exist through the TAF
period under clear skies. Wind directions will exhibit their
typical diurnal tendencies, with afternoon and early evening
breeziness out of the SW-W. The SE switch will take hold between
08-10Z at KPHX, with sustained speeds overnight remaining mostly
aob 8 kt across all the terminals. Confidence is low in a weak
surge of SW winds reaching the terminals over the next few hours,
which would act to temporarily increase speeds and slightly delay
the SE switch. Speeds are expected to be slightly lower (i.e.,
gusts peaking around 20 kt) tomorrow afternoon than what was
observed today.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns, aside from gusty winds, are
anticipated over the next 24 hours under clear skies. Wind
directions will remain WSW at KIPL through the period, whereas
directions will favor SW to S at KBLH through much of the period.
Gusts to around 20 kt will persist through the early morning at
KIPL before calming to aob 12 kt sustained, and winds will soon
establish out of the south at KBLH and remain aob 8 kt through
tomorrow morning, albeit with some periods of very light speeds
and variability. Gusts are expected to redevelop tomorrow
afternoon at both terminals, again peaking around 25-30 kt at KIPL
and slightly lower at KBLH.

&&

.FIRE WEATHER...
A disturbance moving mostly north of the districts early this
week will force temperatures to cool closer to the seasonal normal
while also producing a period of strong, gusty winds. Throughout
the week, minimum afternoon humidity levels will fall into the
single digits at lower elevations and the teens across higher
terrain areas. This will follow poor to fair overnight recovery of
20-40%. Widespread wind gusts as high as 30-35 mph may be common
Monday afternoon yielding an extended period of near critical
thresholds when combined with low RH and dry fine fuels. Land
managers should be cautious for rapid, uncontrolled spread of any
ongoing fires or new starts Monday. Otherwise, afternoon gusts of
20-25 mph should be more representative the remainder of the week
resulting in a slightly elevated fire danger.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Whittock
FIRE WEATHER...Kuhlman