Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/08/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 405 PM MST Mon Aug 7 2023

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
An influx of humidity from the Gulf of California will lead to
renewed chances of showers and thunderstorms through at least
Wednesday...mainly east of the Lower Colorado River Valley.
Temperatures will also be much closer to normal than they have been.
A drying trend begins Thursday followed by a warming trend beginning
this weekend.

&&

.DISCUSSION...
An increase in boundary layer moisture was quite evident in the 12Z
soundings from the AZ sites this morning. Ongoing storms over
northern and eastern AZ reflect the improved moisture availability.
The moisture gradient lies over western AZ near the Lower Colorado
River Valley with surface dew points at BLH and Lake Havasu now down
into the 40s. In stark contrast is the unusually strong westerly
flow aloft which typically is associated with dry conditions. The
associated shear is aiding strong storm development over the
aforementioned areas. Aircraft sounding data from PHX early this
afternoon indicates that there is significant CAPE to be had but
also significant CIN. Per SPC mesoanalysis, CIN is even larger over
southwest AZ and far SE CA. It will likely take outflows from
distant storms to generate new activity over the lower elevations of
south-central AZ. But, westerly flow doesn`t tend to bode well for
lower deserts due to a lack of higher terrain upstream. But, it`s
conceivable that a storm may form over to the southwest of the
Greater Phoenix area and maintain itself northeastward. Thus, PoPs
are quite modest (better over our higher terrain areas of southern
Gila County). Precip chances are actually a bit better late tonight
per NBM. The deterministic CAMs support this by depicting long-lived
outflows (originating from storms over the Sierra Madre mountains of
far northern Mexico) reaching south-central AZ (gust front lift).

Far from AZ is rapidly weakening Tropical Storm Eugene which will
quickly become a Depression. The associated upper troughing centered
west of Baja Mexico will linger for at least a few days as it gets
absorbed in the southern branch of the Westerlies. This will favor
resupply of moisture to maintain an ongoing chance of thunderstorms
through Wednesday (mainly east of the Lower Colorado River Valley).
Meanwhile, high pressure will be focused further east which will
help keep temperatures closer to normal than they have been. Thus,
the Excessive Heat Warning will be allowed to expire tonight.

Later in the week, there is good model agreement in the beginning of
a downtrend in moisture availability. Lagging a bit behind that is
an uptrend in temperatures as high pressure expands westward. Thus,
highs of 110+ will become common by early next week.

&&

.AVIATION...Updated at 2305Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Only a very low probability of weather concerns exist through Tuesday
afternoon under periods of mid/high clouds. West winds with a few
gusts 20-25kt will again persist longer into the overnight, but
should complete the typical easterly switch by sunrise. There is a
very slight chance (less than 20%) of isolated TSRA impacting the
Phoenix airspace in a 10-15Z time frame which could also create
highly erratic winds and unexpected wind shifts. Otherwise, west
winds with some higher gusts will resume over the Phoenix metro by
early Tuesday afternoon.


Southeast California/Southwest Arizona including KIPL and KBLH:
Under clear skies, periods of strong gusty winds will be the
greatest weather issue through Tuesday afternoon. Gusts will be most
pronounced at KIPL through the evening potentially exceeding 30kt
with some lofted dust. Gusts should remain closer to 20-25kt at
KBLH. Through the overnight, speeds should gradually decrease,
however gusts around the same magnitude should resume Tuesday
afternoon.

&&

.FIRE WEATHER...
An influx of moisture from the Gulf of California will lead to
improved humidities across the forecast area and an uptrend in
thunderstorm activity over the broader region - mainly for the
higher terrain of northern and eastern Arizona. MinRH values will
range from 15-25% most places through Thursday and MaxRH will range
from 30-60% most places. An exception will be eastern Riverside
County with MaxRH values Tuesday morning of 15-25% increasing 10%
the next morning. Late in the week and over the weekend, humidities
and thunderstorm chances will decline and temperatures will
increase. Apart from thunderstorms, winds will follow familiar warm
season patterns with gustiness in the afternoons and evenings. Of
note, western Imperial County is anticipated to have stronger than
usual westerly winds late this afternoon and evening.



&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST this evening for
     AZZ530>555-559>561.

CA...Excessive Heat Warning until 8 PM PDT this evening for
     CAZ560>570.

&&

$$

DISCUSSION...AJ
AVIATION...18
FIRE WEATHER...AJ