606
FXUS65 KPSR 192120
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
220 PM MST Sat Oct 19 2024

.SYNOPSIS...
A deep cutoff low will continue to churn over the region through
tonight, bringing much cooler temperatures and lingering rain to the
higher terrain of south-central AZ. Below normal temperatures are
expected through Sunday before a ridge of high pressure begins to
build back into the Desert Southwest early next week. Temperatures
will gradually rise into the lower 90s on Monday, with highs peaking
in the mid to upper 90s during the middle half of the week. Dry
conditions are expected to persist beginning tomorrow.

&&

.DISCUSSION...
It is noticeably cooler across the region today with temperatures
currently ranging from the upper 60s to lower 70s across the
lower deserts of AZ and southeast CA. This is all thanks to a deep
cutoff low which has been meandering through south-central AZ
since yesterday. Latest mid-lvl wv imagery suggest that the low
center is now centered off to the east of the Phoenix Metro area
which has allowed drier air to begin mixing down to the sfc.
Clouds and light rain from early this morning have now cleared
out, resulting in a very pleasant afternoon. Heading into tonight,
the low pressure system will continue to wobble overhead, but the
best lift will remain north and east of the area, keeping the
better rain chances over N AZ. There may be a few light showers
that try to wrap around the back side of the low circulation early
tomorrow morning, but these showers will likely remain confined
to the higher terrain north and east of Phoenix. Due to skies
remaining mostly clear overnight, low temperatures will cool into
the low to mid 50s in most locations by Sunday morning. Another
round of freezing temperatures can be expected in the highest
elevations of S Gila County where a Freeze Warning remains in
effect.

On Sunday, the low pressure system situated over our region will
continue to weaken and gradually lift into the 4 Corners area. This
will mark the beginning of a warming trend as upper-lvl ridging
begins to build into the Desert Southwest. As hghts aloft increase
over the region Sunday afternoon, high temperatures will rise
around 5 to 7 degrees warmer than this afternoon, reaching the
upper 70s to lower 80s in southcentral AZ and mid 80s west of the
Colorado River valley. The upper level pattern will then
transition to quasi-zonal on Monday before we ridging strengthens
even further Tuesday into Wednesday. During this timeframe, 500 mb
hghts will reach 590-592 dam or above the 90th percentile of
climatology for mid-October. As a result, forecast highs will
reach near 90 degrees on Monday, low to mid 90s Tuesday, and mid
to upper 90s by Wednesday. Ensemble members show the ridging
pattern persisting through the remainder of next week which will
keep the area dry and hot. There is still around a 50% chance of
highs reaching 100 degrees in Phoenix from Wednesday through
Friday. While 100 degree highs are uncommon this late in the year,
they are not out of the question since the latest 100 degree
temperature on record in Phoenix occurred on October 27th, 2016.
Phoenix is currently sitting at 142 days with maximum temperatures
of 100F+ and would need another 3 days to tie the record for most
in a single year.

&&

.AVIATION...Updated at 1752Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Light winds, aob 7 kts, will prevail through the next 24 hours.
There is some uncertainty in wind directions through this evening.
An easterly component is favored, but there will likely be
occasional variability between SE and NE. No additional showers
are expected and FEW to SCT mid level cloud decks will persist
through tonight.

Southeast California/Southwest Arizona including KIPL and KBLH:
Breezy N-NE winds, with gusts to around 20 kts, are expected
through early to mid afternoon at both terminals. Winds will then
subside and tend to veer clockwise this evening. Light variability
is then expected at both terminals tonight. SKC will prevail.

&&

.FIRE WEATHER...
A weather system continues to progress through the region today
which will promote below normal temperatures through this weekend.
Some areas did receive wetting rainfall yesterday, including the
foothills of Maricopa County and Tonto National Forest in S Gila
County. Weak showers will still be possible over the higher terrain
of N AZ through Sunday morning and any new amounts look to be light.
Otherwise, expect the area to dry out tomorrow afternoon with
temperatures slowly rebounding by early next week. MinRHs will range
between 15-25% this weekend before decreasing below 15% from Monday
onwards. Overnight recovery should remain fair over the next few
nights. Winds will be light and follow typical diurnal upslope and
downvalley patterns.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Freeze Warning from midnight tonight to 9 AM MST Sunday for
     AZZ563.

CA...None.
&&

$$

DISCUSSION...Salerno
AVIATION...Benedict
FIRE WEATHER...Salerno