Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/19/22

Area Forecast Discussion

National Weather Service Phoenix AZ

 358 PM MST Mon Jul 18 2022

.UPDATE...0Z Aviation Discussion...

&&

.SYNOPSIS...
Showers and storms this afternoon and evening will favor the high
terrain of northern and southeast Arizona, with low chances for
progression into the lower deserts. Starting Tuesday, chances for
showers and thunderstorms should then become more confined to the
eastern Arizona high terrain, likely lasting through Friday, with
high pressure repositioning over Arizona. Above normal
temperatures will prevail through the entire week with high
temperatures across the lower deserts around or just shy of 110
degrees today, and then mainly in a 110 to 114 degree range during
the latter half of the week.

&&

.DISCUSSION...
Yesterday was a good example of a low probability, but high impact
potential that came to fruition. The environment was volatiles,
but capped and the cap was broken. This afternoon is anticipated
to be a quieter. Aircraft soundings from Phoenix and mesoanalysis
show more of a stable boundary layer. WV satellite this afternoon
is very unique with a southerly pull of sub-tropical moisture
through AZ in between low pressure circulations to the west and
north and a 597dm H5 anticyclone centered over northwest NM.
Isolated showers and storms were able to develop in this axis of
moisture earlier this morning, but have since pushed north and
dissipated. Also noted on WV is a push of drier mid level air
across southern NM and northern Mexico. Forecast soundings and 500
mb RH forecasts show this dry air continuing to push into the
local region. HREF neighborhood probabilities for convection
(dBZ>40) this afternoon is less than 10% across the lower deserts.
NBM PoPs are also very low, less than 5% most places. However,
considering hi-res models have at times struggled with
initialization the past couple days and mesoanalysis shows capped
1000-1500 J/kg, isolated storms still cannot be ruled out, with
enough forcing. Steering flow and shear is a bit lower than
yesterday, so the storm motion will likely be slower with less
organization.

Through the rest of the week, daily AZ high terrain storms are
still expected with low probabilities over the lower deserts,
mostly 10% or less. Debris clouds with lower impact high-based
showers may on occasion spread over the lower deserts heading into
the overnight hours. Some of what may hinder afternoon/evening
storm chances over the lower deserts will be the repositioning of
the monsoon high further west to over AZ by Wednesday, PWATs
falling back down to around 1.2-1.4", minimal steering flow. With
the repositioning of the high temperatures will increase again.
A few days ago it was looking like most of this week would feature
sub-110 degree highs, but that no longer looks to be the case.
Highs have been trending up. While temps may fail to reach 110F
this afternoon, the rest of the week is now forecast to reach
110-114F across the lower deserts with low level thermal heating
peaking Wednesday through Friday as 850mb temps approach 32C. The
HeatRisk product is beginning to show pockets of High HeatRisk
beginning tomorrow in Southeast CA. If highs continue to trend up
Excessive Heat products may need to be issued.

Looking ahead at the weekend into early next week, model ensembles
heavily favor a return of active monsoon conditions, with the
monsoon high shifting back east. Moisture is forecast to increase
substantially into the weekend and persist through early next
week with hints of a significant easterly wave at some point late
Sunday into early next week. This potential scenario could bring a
return of widespread shower and storm chances and some relief
from the heat.

&&

.AVIATION...Updated at 23Z.

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

No convective activity is nearby the terminals at this time. The
chance of outflow winds reaching the metro of 30+KT is less than
10% this evening: the latest high-res models continue to indicate
a very quiet night as drier air moves into the region. Winds for
the evening to remain mainly westerly with early evening gustiness
into the 15-25 kt range. Westerly winds to then persist through
the night with just a short period of light easterly winds Tuesday
morning before another earlier- than- normal switch to westerly
by late morning Tuesday with some gustiness likely on Tuesday
afternoon/evening. A few occasional CI will float by.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will favor the south at KBLH and the southeast at KIPL, with
some early evening breeziness. Any storms should remain confined
to the higher terrain well south of IPL over Mexico this evening.
Will watch for remote possibility of an outflow reaching the
Imperial Valley. Skies will remain mostly clear with few to
scattered clouds mainly aoa 15 kft.

&&

.FIRE WEATHER...
Drier air will settle into the area over the next couple days with
isolated storm chances today and then likely confined across the
eastern Arizona high terrain through the rest of the week.
Temperatures are likely to remain above normal through the period
with Wed-Fri likely being the hottest days with lower desert
readings at or a few degrees above 110 degrees. MinRH values of
20-30% today will trend lower through mid week, ending up at
10-15% over the lower deserts and 17-25% over the high terrain by
Thursday. Moisture and humidities are likely to improve next
weekend. Winds will remain fairly light most of the time, with
the exception being some enhanced afternoon upslope breeziness as
well as any thunderstorm activity resulting in strong and erratic
winds.

&&

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

$$

DISCUSSION...Benedict/Kuhlman
AVIATION...Heil/Percha
FIRE WEATHER...Kuhlman