517
FXUS65 KPSR 050924
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
224 AM MST Wed Jun 5 2024

.SYNOPSIS...
High pressure building over the region through Thursday will push
temperatures higher resulting in the hottest temperatures of the
year through the rest of the week. An Excessive Heat Warning is in
effect across all of the lower deserts today through Friday with
some spots at risk of breaking daily temperature records. A slight
cooling trend will then begin on Saturday with more cloud cover,
but temperatures are expected to remain above normal.

&&

.DISCUSSION...
Over the past 24 hours, the residual higher level moisture from
the atmospheric river that hit the Pacific Northwest earlier this
week has passed through the Desert Southwest. The higher clouds
from this moisture have all since dissipated and/or pushed south
into Mexico leaving clear skies across our region. Current water
vapor imagery shows modestly drier air working in from the north
associated with the building upper level ridge now overtaking much
of the Southwestern U.S. and the Great Basin. As the ridge fully
moves over our region later today, it will push H5 heights from
585dm yesterday to around 592dm which would fall within the 90th
percentile of climatology across the southern half of the region
to as high as the 97th percentile across northern Arizona and much
of the Great Basin. The ridge is forecast to sit over the
Southwestern U.S. through Friday creating a fairly strong heat
dome for early June and pushing surface temperature anomalies to
around 10 degrees above normal.

After a week of temperatures running slightly above normal with
highs between 100-105 degrees across the lower deserts, today will
mark a noticeable jump in temperatures as highs reach to between
105-110 degrees. The full force of the heat dome will then
realized on Thursday and likely into Friday as NBM forecast highs
top out between 109-114 degrees. It`s likely that Phoenix will
break the daily record high temperature on Thursday of 111 degrees,
while Yuma and El Centro fall a few degrees shy of their daily
records. An Excessive Heat Warning goes into effect starting late
this morning and currently lasts through early Friday evening.

While the upper level ridge dominates the region over the next 2-3
days, a weak cut-off low will be spinning off the coast of Baja.
The placement of the low to our southwest and the high center over
New Mexico starting Thursday will result in weak southeasterly
flow into Arizona and some slight moisture advection into the
state. There should be just enough moisture for isolated
afternoon convective showers and maybe a few weak thunderstorms
starting Thursday from the White Mtns northwestward along the
Mogollon Rim. Moisture levels are shown to be quite limited and
these areas should be the extent of the rain chances through the
weekend. A southerly steering flow should keep any of this
limited convective activity well north and east of the Phoenix
area with PoPs only at around 10-15% across eastern Gila Co.

By Saturday, models generally agree the cut-off low will move up
the Gulf of California reaching northern Mexico later in the day.
This should bring increasing clouds to our area throughout the
day on Saturday, while the high pressure ridge weakens and starts
to move east of the region. As a result, forecast highs Saturday
drop back to between 106-110 degrees. The lowering heights aloft
and noticeable cloud cover should then persist through Sunday with
highs lower further to between 104-108 degrees, or back to around
5 degrees above normal. The weather pattern during the first half
of next week may support another cut-off low forming off the
coast of California, but this next one could be stronger. The
positioning of this low and how it will impact our region next
week is still fairly uncertain. If the low stays well to our west,
as the ensemble means currently favor, it would likely present
another warming trend as ridging would be favored to build back
over Arizona and New Mexico. For now, NBM forecast temperatures
show a fairly large spread going into the middle of next week, but
the overall trend should be hotter with more 110 degree
temperatures likely coming as early as next Tuesday.

&&

.AVIATION...Updated at 0530Z.

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

Winds will follow their typical diurnal tendencies with speeds aob
10 kt. There may be some occasional gusts tomorrow afternoon and
early evening up to around 15 kt. Mainly clear skies will prevail
through the TAF period.

&&

.FIRE WEATHER...
Hotter temperatures are expected over the next few days, while
seasonably dry conditions prevail. Lower desert highs are expected
to reach up to 110F today and in into the 110-115F range for
Thursday and Friday. Afternoon minimum RHs of around 10% will
continue through the end of the week, while overnight recoveries
will mainly range from 20-40%. Winds will remain fairly light
across all districts with typical diurnal tendencies and afternoon
gusts up to around 20 mph. A weak weather system is then expected
to move through the region Saturday into Sunday allowing
temperatures to start to lower, but will remain above normal.
Winds will also increase a bit which could push afternoon gusts up
to 25 mph in some locations.

&&

.CLIMATE...

Record high temperatures:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
June 5    113 in 2016    115 in 1957    114 in 2016
June 6    111 in 2016    114 in 1928    113 in 2002
June 7    115 in 1985    116 in 1985    113 in 1985

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM this morning to 8 PM MST
     Friday for AZZ530>556-559>562.

CA...Excessive Heat Warning from 10 AM this morning to 8 PM PDT
     Friday for CAZ561-563-566-567-569-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Berislavich
FIRE WEATHER...Kuhlman
CLIMATE...18