938
FXUS65 KPSR 141150
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
450 AM MST Tue May 14 2024

.UPDATE...Updated 12z Aviation Discussion.

&&

.SYNOPSIS...
Above normal temperatures will continue into next week. A slight
cool down of a couple degrees is expected for mid-week, with lower
desert afternoon high temperatures in the mid-to-upper 90s.
Otherwise, the lower deserts will see afternoon high temperatures
in the upper 90s to low 100s. Typical springtime late afternoon
and early evening breeziness along with mainly dry conditions will
continue into next week. Daily afternoon and early evening
isolated shower activity, mainly confined to the High Country,
will be possible through Thursday. These showers could cause some
erratic, gusty winds to make their way into the Valley each
evening.

&&

.DISCUSSION...
The main concern through the forecast period will be some elevated
fire weather concerns due to the hot temperatures, low humidity,
and late afternoon/early evening breezy conditions. Otherwise,
mainly quiet weather will continue into next week. There will be
some daily isolated shower activity in the late afternoon/early
evening through Thursday, however, most, if not all, of this
activity is expected to stay in the High Country.

Upper-level water vapor imagery this morning reveals a closed low
slowly making its way onshore in southern California, with a
shortwave trough diving southeastward out of the Pacific
Northwest. With both of these systems making their way towards our
area, heights aloft will lower slightly today. This will lead to
afternoon temperatures being a few degrees cooler than they were
yesterday. The aforementioned low pressure system will finally
move overhead in SE CA/far SW AZ on Wednesday and then overhead of
south-central AZ on Thursday leading to coolest days of the week
for the respective locations. However, temperatures are still
forecasted to top out in the mid-to-upper 90s across the lower
deserts. This will result in a Minor HeatRisk across the CWA
through at least Thursday, with some portions of SE CA getting
back into the Moderate HeatRisk category on Thursday.

With the low pressure system slowly moving into the Desert Southwest
over the next couple of days, there will be enough moisture and
lift to produce some isolated showers over the higher terrain,
with most activity expected to stay north of our CWA. On Thursday,
when the low pressure system is over Arizona, PWAT values will be
in the 0.6-0.7" range. With the low pressure being directly
overhead and the highest PWAT values being on Thursday, this looks
to be the best day to see activity. Most, if not all, of the
activity is expected to be in he AZ High Country where there is
extra lift provided by the topography. Any isolated showers will
produce very light rainfall amounts, in the range of 0" to only a
few hundredths. With the low moving through on Thursday, the
overall flow pattern will be out of the north. This means that
Thursday will also be the day with the best chance for any of the
higher terrain activity, or any outflows from that activity, to
make their way down into the Valley. Athough at this time we are
not expecting any activity to be able to make it down into the
Valley. Any outflows that make their way Into the Valley would
cause some erratic, gusty winds.

Ensemble members are in fairly good agreement that ridging will
build in on Friday and through the weekend ahead of another trough
developing in the Eastern Pacific Ocean by the end of the weekend
and early next week. With the ridge building in this weekend, we
are forecasted to see the hottest temps of he year so far. The
lower deserts are forecasted to top out in the low 100s and higher
elevations are forecasted to top out in the 90s. This will lead
to a good portion of the lower deserts being in the Moderate
HeatRisk category on Friday and Saturday. The global ensemble
models show the aforementioned trough moving into our region by
the early to middle part of next week, however, they differ on the
exact strength of the trough. A cooling trend is expected with
this trough along with an increase in wind speeds. The exact
strength of the trough will determine just how much we cool along
with just how breezy/windy our area gets, which will have an
impact on fire weather concerns.

&&

.AVIATION...Updated at 0550Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are anticipated through the TAF
period. Widely scattered, high-based cu are expected to develop,
hence the addition of FEW120 for the afternoon and early evening
hours as these cloud fields are expected to be a bit more
widespread across the higher terrain areas. Wind directions will
continue to favor their typical diurnal patterns. Westerly flow
will settle in between 18-20z, with some periodic gustiness 15-20
kts into the evening hours. Otherwise, passing high clouds in the
evening and extending into the overnight hours are expected.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under passing high clouds. Winds at KIPL will favor a
westerly component through most of the period, and confidence is
good in westerly gusts developing this evening and peaking between
20-25 kt. Prior to gusty winds developing, an extended period of
light and variable winds is likely at KIPL this afternoon. Winds
will generally prefer S to SW through the period at KBLH, but
periods of very light and variable winds can be anticipated this
morning.

&&

.FIRE WEATHER...
Localized elevated fire danger will continue into the weekend as
a result of some periodic gusty winds (mainly in the afternoon and
early evening hours), dry fine fuels, and low humidity levels.
MinRH levels will be around 10% across the lower deserts and in
the teens for the higher terrain areas. Overnight recoveries will
range from poor to fair and be in the 20-50% range. Afternoon and
early evening wind gusts will be around 20-25 mph, with some
periodic higher gusts possible in the higher terrain in the
eastern districts due to some high based showers over the
mountains.

&&

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

$$

DISCUSSION...Berislavich
AVIATION...Young/Whittock
FIRE WEATHER...Berislavich/Frieders