842
FXUS65 KPSR 181011
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
311 AM MST Sat May 18 2024

.SYNOPSIS...
High pressure will persist over the region this weekend resulting
in many more lower desert communities exceeding 100 degrees. A
dry weather disturbance will then move north of the region early
next week with temperatures retreating closer to the seasonal
normal. Occasionally breezier conditions are likely during the
afternoon and evenings early next week under mostly clear skies.

&&

.DISCUSSION...
The shortwave ridge is slowly progressing east across the region
with the ridge axis now positioned across eastern Arizona. To the
west of the region, an elongated weak upper level trough is
beginning to edge into southern California while a closed low
hangs back another 800 miles to the west. These features are all
part of the southern branch of a split flow regime with the
stronger northern branch temporarily staying put across the
northern tier states. With H5 heights hovering around 579dm across
southern California to 581-584dm across southern Arizona today,
high temperatures will again top out around or just over 100
degrees for much of the lower deserts, or 5-8 degrees above
normal.

Going into Sunday, the elongated trough to our west along with
increasing influence from the trough to our north will begin to
knock down our heights aloft. Temperatures Sunday will only drop
2-3 degrees from today`s highs, but eventually the current closed
low well off the southern California coast is expected to move
through our region during the daytime hours Monday bringing
further cooling.

The main forecast concern this weekend into Monday will be the
increased winds due to the passing shortwave trough and increased
pressure gradient with the help of the northern stream
trough. Winds will begin to increase already late this afternoon
across southeast California with gusts of 30-35 mph possible in
some locations through this evening. Similar breezy conditions
are likely on Sunday with afternoon gusts commonly reaching 25
mph across the majority of the lower deserts to up to 35 mph
across southeast California. Guidance is calling for the strongest
winds to occur during Monday afternoon with gusts of 30-40 mph
across southeast California to 25-35 mph possible across much of
southern Arizona.

The cooling trend will become more noticeable by Monday as H5
heights fall back to between 572-576dm, or right around
climatological normal for the period. Temperatures are expected
to drop back to around or just below normal starting Monday with
highs in the low to mid 90s. These near normal temperatures will
persist through at least midweek and likely longer as broad
troughing should continue to dominate across the region. NBM
forecast temperatures do show a slight warming trend and a bit
higher temperature spread later next week into next weekend, but
with the bulk of ensemble members keeping at least some troughing
over our region our temperatures should easily stay in the 90s.

&&

.AVIATION...Updated at 0540Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No major weather issues will exist through Saturday night with
only FEW-SCT passing mid/high clouds at times. Wind behavior
across the Phoenix metro will be similar to the past 24 hours,
with afternoon/early evening winds gusting to around 20 kts at
times. At the SE California terminals, breezy W/SW afternoon
winds will resume again tomorrow gusting upwards of around 25-30
kts.

&&

.FIRE WEATHER...
High pressure will hover over the region through the weekend with
dry conditions and temperatures reaching much above normal. Only a
disturbance moving north of the districts early next week will allow
temperatures to cool closer to the seasonal normal. Throughout next
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%.
Breezy afternoon/early evening conditions with gusts around 20 mph
will be common, though somewhat stronger winds will occasionally be
possible in far western districts. The greatest weather concern will
occur Monday afternoon where frequent, widespread wind gusts closer
to 30-35 mph may be common yielding near critical thresholds when
combined with low RH and dry fine fuels.

&&

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

$$

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