794
FXUS65 KPSR 141228
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
528 AM MST Fri Jun 14 2024

.UPDATE...Updated 12z Aviation Discussion.

&&

.SYNOPSIS...
Very hot and dry conditions will persist through the weekend,
with Excessive Heat Warnings in effect for various parts of the
region through Sunday. The hottest day is expected to be Saturday
with highs topping 110 degrees over the majority of the lower
deserts. Temperatures will eventually cool back to normal levels
during by the early part of next week before heating back up late
next week.

&&

.DISCUSSION...
The upper level low that brought considerable cloudiness and some
light shower activity yesterday is currently centered just
northwest of Phoenix. Dry air has swept in from the southwest
since the evening hours with any residual clouds and showers now
confined to the north and east of Phoenix. By sunrise, skies
should be clear across all but far eastern Arizona. The low is
forecast to become an open wave before exiting into New Mexico
this afternoon as strong ridging begins to quickly build in from
the southwest. By late afternoon, forecast H5 heights reach to
around 590-591dm before peaking at 592-593dm tonight across
southern Arizona and southeast California.

Given the increasing heights today and sunny skies, temperatures
will heat up quickly with highs topping out between 109-112
degrees across the western deserts to 105-109 degrees across the
south-central Arizona lower deserts. The hottest temperatures are
still expected to occur on Saturday with highs between 110-114
degrees across the lower deserts and areas of Major HeatRisk.
Excessive Heat Warnings are in place for portions of southeast
California today and Saturday and through Sunday for much of
south-central Arizona. Starting Sunday, lowering heights aloft
from an incoming Pacific trough moving through the Pacific
Northwest will begin to lower temperatures, but some locations in
the Phoenix area could still top 110 degrees.

Relief from the excessive heat is expected by Monday as H5 heights
lower down to 582-585dm and highs drop well below 110 degrees.
Near normal temperatures are expected Monday through Wednesday as
the region stays under the influence of the Pacific trough,
despite the core of the trough only brushing across the northern
portion of the Great Basin. Unfortunately the "cooler" but still
near normal temperatures will be short-lived as the unseasonably
strong ridge that impacts the eastern U.S. early next week is
forecast to shift westward starting next Wednesday. Temperatures
should quickly heat up starting next Thursday with highs likely
topping 110 degrees over the south-central Arizona lower deserts.
Ensembles generally agree the core of the ridge with H5 heights
around 592-594dm is likely to move back over the Desert Southwest
by next Friday into the following weekend. The latest NBM
temperatures show highs peaking during this time between 112-116
degrees, or roughly 8-10 degrees above normal. Granted this is
still a week out, but models are fairly certain we will see
another excessive heat event later next week. Guidance is also
showing the flow turning out of the east southeast later next week
potentially allowing for some modest moisture advection into
Arizona. For now, forecast ensemble mean PWATs increase to around
or just over 1" by next weekend. This could present our first
real chance for some monsoon activity in Arizona, albeit still
minimal.

&&

.AVIATION...Updated at 1220Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation impacts are expected for the valid forecast period.
Winds will generally favor light diurnal trends for today. Winds
have shifted out of the southeast over the last hour or so, but
this recent development is expected to be short-lived this
morning. Winds will predominantly become light and variable
through the morning hours, with exception of KIWA, which may see a
more definitive westerly shift late this morning. Focusing on
KPHX, light and variable winds could extend past 00z, before a
W-NW component develops through the evening and early overnight
hours. Otherwise, expect the westerly winds to lighten late this
evening and into the overnight period, with either light and
variable or a southeasterly component winds to develop. Otherwise,
clear skies are expected through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation impacts are expected for the valid forecast period.
Winds at KIPL will favor a westerly component aob 10 kt through
the TAF period. At KBLH, light and variable winds will go
southeasterly this afternoon and then back southwesterly tonight.
Wind speeds will be aob 10 kt through the TAF period. Skies will
be clear through the period as well.

&&

.FIRE WEATHER...
Hot and dry conditions will continue to bring elevated fire danger
to much of the region into next week. Lower desert high
temperatures will approach 110 degrees today and likely exceed
110 degrees on Saturday. After light winds today, winds will
become breezy over the weekend with gusts oftentimes reaching
20-25 mph during the afternoon and early evening hours. MinRH
values will range between 5-10%, while poor overnight recoveries
can be expected with MaxRHs only reaching towards 15-35%. A
gradual cool down will bring temperatures back to near normal
early next week with breezy conditions persisting through Tuesday.
High pressure is then expected to build back over the region later
next week leading to another period of very hot temperatures while
RHs stay quite low. There are signs of some moisture seeping into
the eastern half of Arizona by next weekend and this could bring
some chances for showers and thunderstorms over higher terrain
areas.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Sunday for AZZ534-537>555-
     559-560-562.

CA...Excessive Heat Warning from 10 AM this morning to 8 PM PDT
     Saturday for CAZ562-563-566-567-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Young/Berislavich
FIRE WEATHER...Kuhlman