397
FXUS65 KPSR 160003
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
503 PM MST Wed May 15 2024

.UPDATE...
Updated Aviation section.

&&

.SYNOPSIS...
Above normal temperatures will continue through at least the
weekend with lower desert highs warming from the mid to upper 90s
Thursday to just over 100 degrees on Saturday. Typical
late afternoon and early evening breeziness along with mainly dry
conditions will persist. Isolated afternoon shower and
thunderstorm activity will occur over the high country through
Thursday, which could cause some erratic, gusty winds that could
make their way into portions of the lower deserts each evening.

&&

.DISCUSSION...
The main concern through the forecast period will be the continued
elevated fire weather concerns due to the hot temperatures, low
humidity, and late afternoon/early evening breezy conditions.

Ensembles in overall agreement with lowering heights through
Thursday as a weak upper low moves across the region. This system
will induce isolated showers and thunderstorms across the high
country to the north. Not seeing any rainfall across the Phoenix
valley, but some virga and a few sprinkles are possible overnight
tonight and in eastern areas late Thursday. With steering flow
from the north, a bit higher outflow winds from the north could
penetrate south this evening and again late Thursday. The best
chance for this would be for La Paz and northern Maricopa Counties
this evening and then eastern Maricopa County and over Gila
County late on Thursday. There could be some local gusts upwards
of 30 mph, especially in eastern areas on Thursday. This system
will keep temperatures in check, but still hot, mainly into the
middle to upper 90s for Thursday.

For Friday and through the weekend, heights again build across
the area ahead of troughiness developing along the west coast into
early next week. This will push temperatures up several degrees.
Lower deserts will see more widespread 100 to 105 degree readings.
The minor HeatRisk will increase into the moderate category
beginning Friday and into Saturday. This higher heat will be short
lived with temperatures coming down a few degrees and closer to
normal levels by next week.

For next week, a southwesterly flow will dominate with the trough
across the western CONUS. This will keep the daily risk for
afternoon breezy to windy conditions with temperatures closer to
normal levels in the mid 90s. This along with relative humidities
in the single digits, will maintain an elevated fire weather risk.

&&

.AVIATION...Updated at 0002Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Scattered showers and isolated thunderstorms over Yavapai County
have produced and area of outflow that is propagating southward
and nearing the Maricopa County border. That outflow is expected
to weaken with time but it is anticipated there will be a shift
from westerly directions to northwest and northerly directions
early in the TAF period - more noticeably at KDVT and KSDL than
KPHX and KIWA. A follow-on weather disturbance may initiate
renewed northerly winds roughly in the 04Z-07Z time frame before
light (less than 8kts) and variable winds develop (favoring
east/southeast at KPHX and KIWA). Probabilities of strong winds
(gusts AOA 30kts) are around 10-20%. Cloudiness from the higher
terrain will waft over the lower deserts this evening. In fact,
there will be isolated showers/sprinkles amongst the cloudiness
(More so west of the Phoenix area). Ceilings get as low as
10-12kft ASL. For now, held off on inserting VCSH in the TAFs due
to modest coverage/likelihood on the Valley floor.

Cloudiness thins out Thursday before increasing again later in the
afternoon due to shower and thunderstorm activity over east-
central AZ. Probability of outflow winds reaching the TAF site
increases to 30-50% in the 21Z-02Z time frame.


Southeast California/Southwest Arizona including KIPL and KBLH:

An upper trough over the Intermountain West will lead to an
increase in mid and high clouds tonight. KBLH is may see a weak
outflow late tonight from the northeast in the 06Z-10Z time frame.
Isolated showers and sprinkles may stray over eastern Riverside
County as well but likelihood at KBLH too low to reflect in the
TAF. Before that for this evening, winds will favor southwest and
west directions - especially at KIPL with some gustiness up to
20kts. Winds will be light and variable during the day at KIPL
but favor northerly directions at KBLH.


&&

.FIRE WEATHER...
Elevated fire weather conditions will remain across the area
through the forecast period as dry fine fuels combine with
localized gusty winds, hot temperatures and low relative
humidity. Late day gusty winds of 20 to 25 mph will be common each
day. Although, into Thursday, the higher terrain will also see
isolated high based shower and thunderstorm activity which could
result a few higher gusts and erratic winds dropping south into
the valley. These stronger winds will be most likely across
northern portions of Maricopa and La Paz counties this evening and
over Maricopa and Gila counties Thursday afternoon/early evening.
Minimum humidity values will mainly be in the 10 to 15 percent
range into Friday, before dropping back into the single digits for
Saturday and beyond. Temperatures will top out about 5 to 10
degrees normal through the weekend before coming down closer to
normal for next week.

&&

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

$$

DISCUSSION...Frieders
AVIATION...AJ
FIRE WEATHER...Frieders