785
FXUS65 KPSR 061735
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1035 AM MST Thu Jun 6 2024

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Unseasonably strong high pressure positioned over the region will
help promote the hottest temperatures so far this year through
the remainder of the week, resulting in an Excessive Heat Warning
that will be in effect through Friday. Increased cloud cover and
a slight relative cooldown in temperatures are anticipated by this
weekend before another warming trend is expected early next week.

&&

.DISCUSSION...
Excessively hot temperatures will continue across the majority of
the area through Friday as the unseasonably strong high pressure
system sits over the Desert Southwest. H5 heights are currently
analyzed at around 591-592dm over most of Arizona and New Mexico,
or easily into the 90th percentile of climatology, and this will
continue through tonight before gradually lowering into the
weekend. The relative positions of the high center over northeast
Arizona/western New Mexico and the cut-off low a few hundred miles
west of southern Baja are starting to allow for weak
southeasterly flow into Arizona. Current water vapor imagery is
showing some weak moisture advection into Arizona, but guidance is
still pointing at very minimal chances of showers and maybe an
isolated thunderstorm or two well north and east of Phoenix today
and Friday.

Temperatures are likely to reach their peak today with highs
anywhere from 108-113 degrees across the lower deserts. This
should mark the first 110 degree day this year for Phoenix, five
days earlier than the 30 year normal first occurrence. Much of
the lower deserts and even portions of the higher terrain will see
a Major HeatRisk today with the areal coverage shrinking some on
Friday, but still remaining high enough to keep the Excessive Heat
Warning in place. The increasing moisture starting later today,
mostly above 20K feet, will bring some higher level cloudiness
which will hang around into Friday. The clouds along with H5
heights beginning to lower starting Friday should shave a degree
off the highs Friday, but the typically hotter lower desert
locations should still top 110 degrees.

The cut-off low will start to affect our region more starting
Saturday as the low center reaches the northern Gulf of California
later in the day. The increasing proximity of the low should also
bring even more higher level clouds into the region for Saturday,
lasting through Sunday when the weakening low moves through the
area. Some modest cooling will be realized this weekend as NBM
forecast temperatures lower to between 104-109 degrees Saturday
and 103-107 degrees Sunday.

The weather pattern for next week is looking very similar to what
we are currently experiencing as another cut-off low is expected
to develop off the southern California/northern Baja coast by
Monday. Ensemble guidance heavily supports this solution, but
there remains a good deal of uncertainty with the position of the
low and how long it will meander off the coast before swinging
northward later next week. For now, the most likely scenario calls
for a ridge to build back into our region in response to the low
to our west and this should lead to another round of hotter
temperatures, potentially reaching Excessive Heat levels again by
the middle of next week.

&&

.AVIATION...Updated at 1735Z.

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

Winds will follow typical diurnal tendencies for all terminals,
with speeds generally aob 10 kts outside of some occasional gusts
up to 15-20 kts this afternoon through the early evening. High
clouds will start to push into the region from the southeast this
morning and will increase through the TAF period, becoming SCT-BKN
by this evening. Tomorrow will see the same diurnal pattern for
winds. Lingering high clouds will push out of the forecast area by
tomorrow morning/early afternoon.

&&

.FIRE WEATHER...
Hot and dry conditions will continue to support high fire danger
across the area. Well above normal temperatures are forecast
through Friday with highs at or just above 110 degrees for a good
portion of the lower deserts. Winds will continue to be fairly
light much of the time, but occasionally gusting upwards of 20
mph during the afternoon hours. MinRH values will hover around
10%, with poor to fair overnight recoveries as MaxRHs range
between 20-40%. A weak weather system is then expected to move
through the region this weekend allowing temperatures to start to
lower, but remaining 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 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 until 8 PM MST Friday for AZZ530>556-
     559>562.

CA...Excessive Heat Warning until 8 PM PDT Friday for CAZ561-563-566-
     567-569-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...95/Smith
FIRE WEATHER...Kuhlman
CLIMATE...18