Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/14/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 541 PM MST Wed Sep 13 2023

.SYNOPSIS...
Thunderstorm chances will remain focused across parts of northern
and southeastern Arizona the rest of this afternoon, with low
chances in south-central Arizona. All thunderstorms will be
capable of producing strong to severe wind gusts, small hail, and
localized flash flooding should any develop over the lower
deserts. Chances for rain drop to near zero for the end of the
week with temperature gradually trending upward through the
weekend.

&&

.DISCUSSION...
Shower and thunderstorm activity has diminished across South-
Central AZ following an active night/morning in and east of
Phoenix. Recent aircraft soundings in Phoenix this afternoon are
showing a notable drying in the atmosphere above ~700mb. This dry
air is likely one of the leading causes to the reduction in
activity in the local region this afternoon. There is still good
PBL moisture, with dew point temperatures remaining in the low to
mid 60s in Maricopa County and points east. This is at least
leading to development of convective cumulus, but most in most
areas, cumulus are struggling to see much vertical growth. Even
the couple of storms that developed in the Table Top Mesa area
southwest of Phoenix were relatively short-lived. West of
Maricopa County, the PBL has really dried out with widespread dew
points in the 30s and 40s. The better storm environment through
the rest of this afternoon will likely remain in northern and
southeastern AZ. The 12Z HREF has 40dBZ paintballs and
neighborhood probabilities focused mainly east to southeast of
Phoenix, and even outside southern Gila county. The instability
and shear are still supportive for strong to locally severe
storms, but it will be tough for additional development through
the remainder of the afternoon. There is always the potential for
an outflow from storms to the north or southeast that could spark
off isolated development later this afternoon and evening, but
overall PoPs through the rest of the afternoon are generally 15%
or less.

By early Thursday, a drier airmass will begin to take hold with
ensemble guidance showing PWATs falling below an inch. This will
act to eliminate rain chances through the rest of the week with
NBM PoPs near zero. Ensemble guidance show good agreement in
ridging building into the western CONUS for the end of the week
with 500 mb heights across the forecast areas climbing upwards of
588-590 dm. This will lead to temperatures gradually rising near
to slightly above seasonal normals heading into this weekend.

&&

.AVIATION...Updated at 0040Z.

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

East/Southeasterly winds are expected to continue the rest of the
night and through the morning before transitioning to
southwest/westerly during the afternoon. A stray shower is still
possible until about sunset and would most likely emanate from the
Estrellas and White Tank Mountains. This would make KPHX the most
likely TAF site to experience a shower. The potential for a
thunderstorm to initiate there can`t be ruled out but is less
likely and is decreasing as daylight declines. A potential fly-
in-the-ointment is outflow from storms over southeast Pinal
County generating follow-on storms closer to the Valley which in
turn could lead to new storm development. Another factor for
the calendar day Thursday is a weather disturbance moving through
which could also generate new shower/storm activity over the
Valley. But, drier air is expected to move in and preclude that.
Overall, at this time, the potential for thunderstorms tonight is
too low to reflect in the TAFs. Otherwise, sky cover will be
limited to cumulus and altocumulus with bases AOA FL090 until
about 03Z with mostly clear skies afterward.


Southeast California/Southwest Arizona including KIPL and KBLH:

Southwest/west winds will predominate at KIPL through Thursday
afternoon with some potential for light and variable in the
afternoon. Southwest winds will be shorter lived at KBLH and be
primarily limited to the evening hours followed by light and
variable conditions through Thursday afternoon. As for sky cover
across southeast CA, expect clear conditions.


&&

.FIRE WEATHER...
Thunderstorms have mostly moved out of all districts this
afternoon and are focus more over northern and southeastern AZ.
Rain chances the rest of the day are low, ~15% or less. Still, any
storm will be capable of producing gusty erratic winds and
locally heavy rainfall. Drier conditions begin to settle in
heading into Thursday, reducing rain chances to near zero through
the remainder of the week. Min RHs will drop over the next several
days with values around 15-25% by the end of the week. Outside of
any thunderstorms, winds will generally favor diurnal tendencies.

&&

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

$$

DISCUSSION...Benedict/Smith
AVIATION...AJ
FIRE WEATHER...Benedict/Smith