Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/13/23
Area Forecast Discussion
National Weather Service Phoenix AZ
437 PM MST Wed Jul 12 2023
.SYNOPSIS...
Strong high pressure will continue to dominate the overall weather
pattern, allowing very hot temperatures to prevail. As the high
shifts northwestward, temperatures are expected to increase this
weekend leading to areas of Major and Extreme HeatRisk. Increased
moisture will lead to shower and thunderstorm chances over high
terrain areas the next few days.
&&
.DISCUSSION...
Shortly after daybreak this morning a few convective mid-level
showers developed in Maricopa County. An uncommon sight so far
this monsoon. The 12Z sounding sampled a ~8K ft layer of saturated
air between 700-500mb, but the moisture was sitting below a strong
subsidence layer. So the showers did not amount to anything
consequential. We did receive a report of drops reaching the
surface at least. The dry streak (# of days with <0.01") for
Phoenix Sky Harbor currently sits at 111 days, 6 days off the top
10 longest stretches. The morning clouds have all but evaporated
now and the sun is beating down. The morning clouds and dew points
in the 50s did help Phoenix set a new daily record warm low of
94F. Similar weather to the past 24 hours is expected for the
next 24.
The lower troposphere, below 850mb, has warmed slightly from
yesterday, based on aircraft soundings out of Phoenix. This
conceptually should yield slightly warmer surface temperatures
this afternoon. As of 230 PM MST, Phoenix Sky Harbor has reached
110F, which now extends the active 110+ degree day stretch to 13
days.
Besides the heat today, there are active showers and thunderstorms
in AZ high terrain, with most activity around the White Mountains
early this afternoon. Additional storms are expected down in
Southeast AZ through the afternoon. The White Mtn. storms will
have the potential to develop westward through the afternoon and
spread into Southern Gila County. Brief downpours, lightning and
localized gust winds will be the primary impacts. Mid-level
boundaries/moisture fluxes from this activity during the overnight
and morning hours may again drift over the lower deserts and lead
to some spotty ACCAS showers, even into the Phoenix area.
Models tend to have a difficult time capturing this, but forecast
soundings show sufficient moisture hanging around in the 700-500mb
layer and max HREF reflectivity is indicating the potential as
well.
Additionally, a Wind Advisory has been issued for southwest
Imperial County for this evening/tonight, with wind gusts up to
40-45 mph. HREF has nearly 100% chance of exceeding 40 mph in the
advised area between 5 PM and 5 AM. While some elevated breezes
will likely reach the Imperial Valley, magnitudes are expected to
fall well short of advisory criteria.
Heading through the rest of the week and into this weekend, the
central anticyclone is expected to slide west-northwest or develop
a new center, with increasing H5 heights. The high is expected to
center over central CA this weekend before drifting back over AZ
early next week. This will unfortunately continue the prolonged
excessive heat we have been enduring. Surface temperatures are
expected to go up with the strengthening of the high. NBM has the
hottest temperatures this weekend, pushing 115-120F for many lower
desert locations. Morning lows will also remain quite warm,
ranging from mid-80s to low-90s, and even mid-90s in some
locations like Phoenix. This will lead to widespread Major
HeatRisk with areas of Extreme HeatRisk, especially this weekend.
The Major+ HeatRisk will affect higher terrain areas east of
Phoenix as well, thus the Excessive Heat Warning was expanded to
cover the remainder of the CWA. The warning, however, was not
extended through Wednesday with this forecast package, despite
forecast highs still in the 110-115F range. There are some
potential disruptions to the heat beginning early next week that
is cause for some uncertainty. NBM PoPs jump to 20-40% Monday-
Tuesday, across South-Central AZ. The potential for storms and
more cloud cover is the potential disruption. Regardless, above
normal hot temperatures are expected to continue through the next
7 days with little overnight relief.
&&
.AVIATION...Updated at 1745Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds will continue to contain a W`rly component through this
evening, with some occasional gusts around 15-20 kts. A
reinforcing push of W/SW`rly flow is expected to keep winds
around 10-12 kts through early tomorrow morning. A FEW mid-level
clouds will be present through the period, with the lowest bases
around 12k ft.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the forecast period.
Winds at IPL will contain a W`rly component through the period,
with gusts 20-25 kts this evening before speeds diminish
overnight. At BLH, winds will primarily be out of the S/SW through
tonight before winds become more light and variable early
tomorrow morning. FEW-SCT high level clouds are expected through
the TAF period.
&&
.FIRE WEATHER...
Above normal temperatures will continue as afternoon highs reach 108-
115 degrees across the lower deserts through Thursday. Temperatures
will increase this weekend, ranging between 111-120 degrees
through early next week. Increased moisture across the region will
allow Min RHs to be around 15-25% today, before falling to 10-15%
for the remainder of this week. Max RHs are expected to be
between 30-50% tonight and decrease to 25-45% the next several
days. Afternoon breeziness is anticipated each day, with gusts
near 15-20 mph today and 20-25 mph Thursday. In addition, isolated
high terrain thunderstorms will continue the next couple days
during the afternoon to early evening hours. The chance for
wetting rains remains below 10%, thus a minor threat for dry
lightning exists. Heading into the weekend, drier conditions will
return as MinRHs lower to 10-15% by Friday.
&&
.CLIMATE...
...RECORD HIGH TEMPERATURES...
...PHOENIX... ...YUMA... ...EL CENTRO...
July 13 114 (2020) 115 (1983) 118 (1939)
July 14 116 (2003) 118 (1936) 119 (1936)
July 15 117 (1998) 116 (1998) 116 (2019)
July 16 118 (1925) 116 (1960) 119 (1936)
July 17 116 (2005) 117 (2005) 121 (2005)
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530>544-546-
548>551-553>555-559.
Excessive Heat Warning from 10 AM Friday to 8 PM MST Monday for
AZZ545-547-552-560-561.
Excessive Heat Warning from 10 AM Saturday to 8 PM MST Sunday
for AZZ556>558-562-563.
CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ560>570.
Wind Advisory until 5 AM PDT Thursday for CAZ562.
&&
$$
DISCUSSION...Benedict
AVIATION...RW
FIRE WEATHER...Leffel
CLIMATE...Kuhlman