302
FXUS65 KPSR 101135
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
Issued by National Weather Service Tucson AZ
435 AM MST Thu Oct 10 2024

.Update...
12Z Aviation Discussion.

&&

.SYNOPSIS...
Unseasonably hot conditions will persist into the weekend with record
or near record highs across the region. A weather disturbance
passing by mainly to the north early next week will eventually
bring some gradual cooling, but temperatures are expected to
remain above normal through most of next week. Dry conditions will
last into next week with only very slight chances for rain over
higher terrain areas toward the end of next week.

&&

.DISCUSSION...
The heat dome that has plagued the region over the past couple of
weeks is finally showing signs of abating, but it is not quite
over. The high pressure ridge responsible for this heat was
temporarily weakened earlier this week from a weak trough that
moved onshore into California, but that system has washed out and
the ridge is expected to rebuild slightly today into Friday. H5
heights will rise to between 588-590dm by Friday, which again puts
our area into the 90th percentile of climatology. This persistent
ridge of high pressure has allowed for the heat dome to build and
persist despite losing roughly two and a half minutes of daylight
per day. As a result, we continue to reach or break daily records
across much of the area.

Forecast high temperatures through Friday will remain fairly
stable with lower desert highs ranging from 102-107 degrees, or
nearly 15 degrees above normal. Starting this weekend, a fairly
compact Pacific trough will move onshore across northern
California before very slowly tracking east southeast through
Nevada into northern Arizona through early next week. This weather
system will gradually knock down our heights aloft over our
region and lead to a cooling trend of roughly two degrees per day
through early next week. Even with this cooling, we could still
see daily records in the Phoenix area through Monday as the NBM
shows probabilities of tying records of at least 75% each day.
Forecast highs look to mostly drop below 100 degrees by Monday and
for sure by the middle of next week as readings are likely to
fall back into the mid 90s. The latest guidance is also indicating
the weak Pacific system may dip far enough south into Arizona
early next week for some very isolated shower chances over higher
terrain areas on Tuesday, but PoPs remain below 10%.

Ensemble guidance for the latter half of next week then suggests
deeper upper level troughing is likely to spread over much of the
Western U.S., including our region by late next week. This would
result in a further decline in temperatures across the region with
NBM forecast highs currently showing highs even dipping just
below 90 degrees around next Friday, or right around normal.
Unfortunately, the trough looks to be fairly progressive, so it is
not likely to bring much in the way of rain chances and the near
normal temperatures are likely to be short-lived.

&&

.AVIATION...Updated at 1130Z.


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


No aviation weather concerns are expected through the forecast
period. Winds will follow their normal diurnal patterns with east
winds continuing through this morning, followed by a W/SW shift at
all terminals by 21Z-22Z this afternoon. Speeds should remain
below 8 kt. Skies will remain mostly clear through this afternoon
with increasing high clouds expected later this evening.


Southeast California/Southwest Arizona including KIPL and KBLH:


No aviation weather issues are anticipated through the forecast
period. Winds will follow typical diurnal patterns with generally
SE winds expected at KIPL and mainly S winds at KBLH. Periods of
variability will be possible. Expect mostly clear skies through
this afternoon followed by increasing high clouds later this
evening.

&&

.FIRE WEATHER...
Strong high pressure will remain dominant over the region through
the weekend allowing for continued unseasonably hot and dry
conditions. Some gradual cooling is eventually expected by early
next week, but temperatures will remain well above normal. Daily
MinRHs between 5-10% can be expected across the lower deserts to
10-15% over higher terrain areas. Winds will continue to be light
over the next several days, following typical diurnal patterns.

&&

.CLIMATE...

Record highs through Sunday:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Oct 10    105 in 1991    107 in 1991    105 in 1996
Oct 11    102 in 1991    107 in 1950    106 in 1995
Oct 12    103 in 1950    109 in 1950    106 in 1965
Oct 13    101 in 1989    105 in 1958    104 in 1999

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...
FIRE WEATHER...Kuhlman
CLIMATE...Young/18