Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 252046

Area Forecast Discussion
National Weather Service Phoenix AZ
145 PM MST Sat Jun 25 2022

With sufficient moisture in place, shower and thunderstorm
opportunities will persist over much of the region with better
chances entering the picture Sunday and Monday. Storms will have the
potential to produce frequent lightning, brief heavy downpours,
gusty winds, and localized blowing dust. Temperatures will remain
seasonally warm, albeit still near average with lower elevation
afternoon highs still regularly eclipsing 100 degrees.


Objective analysis shows a stable pattern configuration across the
Conus with expansive subtropical ridging aligned over the entire
southern tier of states. With the central H5 positive height anomaly
situated over the lower Mississippi River Valley, a westward
extension of the ridge axis was situated along the Arizona
international border. Along this western periphery, satellite
imagery clearly depicts a nearly stationary MCV spinning over far SE
Arizona with residual moisture encompassing the majority of the
circulation. The larger synoptic pattern next week will generally
feature retrogression in the lower latitudes with more pronounced
high pressure and more frequent subsidence migrating westward
towards the SW Conus, however it will be these convectively
enhanced, sub-synoptic features and interactions similar to this
mornings MCV that will largely dictate daily storm potential and

The aforementioned SE Arizona MCV should meander along the
international border through this evening leading to forced ascent
in advance of the circulation center through far southern AZ.
Entrained midlevel moisture rotating across the eastern CWA this
morning has temporarily restricted instability growth while
bolstering CinH. While this may not be the case the entire day as
clouds erode, the best instability corridor and prime area for
convective initiation as supported by a vast majority of CAMs
aligns from western Pima County through southern Maricopa and
central Yuma and La Paz counties. This includes traditional
initiation points such as Table Top Wilderness and the Kofa
mountains. Objective analysis already indicates MLCApe nearing 1000
J/kg while DCape exceeds 2000 J/kg suggesting any storms forming in
this region later will easily have the potential for strong, gusty
winds and localized blowing dust impacts. Around the Phoenix metro,
the convective environment does not appear as impressive with
boundary layer mixing ratios still hovering around 8-9 g/kg. While
this does not completely preclude thunderstorm development, much
like last evening, multiple colliding outflow boundaries will be
needed to further moisten and dislodge the boundary layer from a
capped scenario.

HREF membership seems in quite good agreement depicting a better
defined vorticity center propagating north out of Sonora Sunday
afternoon acting upon an unstable, and only marginally capped
environment. The prospect for multiple, deeper outflows capable of
triggering deep convection at lower elevations increases markedly as
mixing ratios edge towards 10 g/kg. Not surprisingly, NBM POPs are
notably higher across much of Arizona Sunday evening solidly in a 20-
50% range, even over lower elevations. The primary thunderstorm
impacts will remain similar to the past couple days (i.e. lightning,
gusty outflow winds, and blowing dust) given a similar thermodynamic
structure, just with likely more extensive coverage.

Daily details with respect to thunderstorm formation and coverage
much of next week will be driven by mesoscale influences versus any
larger scale forcing mechanisms. As previously mentioned,
retrogression of the high pressure center will bring the anti-
cyclone center into the Southwest region during the middle/end of
the week, however the vast majority of ensembles keep H5 heights
tempered near 594dm (quite typical for late June) such that the high
pressure induced subsidence should not be the main influence in
determining convective formation and coverage. One key may be the
ultimate location of the pressure ridge: some ensembles build the
ridge into northern AZ which becomes a convectively favorable deep
easterly flow over much of the forecast area while other ensemble
members focus the ridge over northern Mexico/southern Arizona which
would be less convectively encouraging. Regardless of the exact
position, the fact is moisture depth and magnitude have already
become established over the region such that there shouldn`t be any
day completely devoid of storms (at least until moisture is more
thoroughly scoured from the area). Rather, the forecast challenge
any given day will hinge on whether storms remain isolated over
mountains or whether salient mesoscale feature support and/or force
convective sustenance into lower elevations. Thus, the official
forecast much of the week is nearly a persistence forecast with
model trends inching towards lesser storm coverage and impacts late
in the week.


.AVIATION...Updated at 1720Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Scattered mid level clouds will continue through the afternoon with
light southeast flow this morning becoming southwest by early
afternoon and strengthening to near 10 kts with a few gusts of 15-20
kts possible. The main weather concern into this evening will be
gusty outflow winds and abrupt wind shifts from distant
thunderstorms that develop across the higher terrain, primarily
north and east of Phoenix. These t-storms will likely send multiple
outflow boundaries into the area terminals, which will likely
produce gusty as well as erratic winds.

There is around a 50% chance of winds exceeding 30 kts, with about a
20% chance of shower or thunderstorms affecting the terminals.
Therefore, confidence is low to include anything more than VCSH in
the TAFs at this time. Once the outflow boundaries/convective
activity pass through the area by mid- evening, winds will
predominate from an easterly direction.

Southeast California/Southwest Arizona including KIPL and KBLH:
Mostly quiet weather will exist through Saturday evening under clear
skies At KIPL, light southeasterly winds with variable directions at
times will strengthen during the early to mid afternoon hours to
near 10 kts. Westerly sundowner winds of around 10 kts expected
through the evening hours, switching to light southeasterly winds
overnight. At KBLH, southerly winds of around 10 kts are expected
through the period.


Moisture will remain entrenched across most districts through much
of next week with the greatest afternoon thunderstorm and wetting
rain chances focused over higher terrain locations north and east of
Phoenix. However, even lower desert communities may occasionally
experience wetting rainfall at times - more likely early in the
week. Minimum afternoon humidity levels will generally fall in a 15-
30% range with somewhat lower values in far western districts.
Overnight recovery will be poor to fair in lower elevations (20-40%)
and good over eastern district high terrain locations (40-70%).
Aside from occasional late afternoon/early evening thunderstorm
downburst and/or outflow winds, winds should not be a significant





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