Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/02/20
Area Forecast Discussion
National Weather Service Phoenix AZ
421 PM MST Sat Aug 1 2020
.UPDATE...Update Aviation Discussion.
&&
.SYNOPSIS...
Strong high pressure aloft will persist over the desert southwest
the into next week. As a result, very hot temperatures can be
expected area wide today and into early next week. Thunderstorm
chances will remain minimal through early next week with any isolated
activity remaining over the higher terrain of southern Gila County. A
modest return of moisture during the latter part of the week will
bring a limited but noticeable return of storm chances.
&&
.DISCUSSION...
Latest streamline analysis depicts a well-defined anticyclone
sprawled across the Desert Southwest. The mid-level center is
positioned near Yuma, which is resulting a northerly flow across
south-central Arizona, while at 850 mb the flow is southwesterly
around an anticyclonic cell across Sonora. Meanwhile, latest
observations indicate that conditions are considerably cooler and
more moist than this time yesterday, owing to a moderately strong
Gulf surge that developed overnight. Widespread dewpoints in the 60s
and even lower 70s are still prevalent this afternoon, which has
inhibited heating.
With the widespread moisture in place, MLCAPEs are quite high,
but this is offset by low-level convective inhibition. ACARS obs
depict an onion-type sounding, which is generally not favorable for
thunderstorm activity. Latest CAMs have been consistent, depicting
isolated thunderstorms around the periphery of the anticyclone,
which points to portions of southern Gila County. With downdraft
CAPE exceeding 1500 J/kg, 12z HREF suggests the potential for storms
capable of producing severe winds.
Storms generally remain unlikely across the lower deserts, including
the Phoenix area, despite the favorable convective parameters.
Conditions appear to be a bit too dry between 850 mb and 500 mb
within the subsidence of the anti-cyclone. Lack of a lifting
mechanism will also inhibit storms across the lower deserts, however
there is a non-zero chance that an isolated cell could develop in
the foothills along a southwestward-propagating outflow boundary.
&&
.PREVIOUS DISCUSSION...
Temperatures remain above normal as we start off the new week.
HeatRisk keeps high to very high heat risk across parts of the lower
deserts Sunday and Monday. The Excessive Heat Warning will continue
beyond today for the Phoenix, Yuma, and El Centro areas, going
through 8 PM local time Monday. The upper-level ridge shifts
eastward into New Mexico by mid next week with temperatures across
the region further dropping. As the ridge shifts eastward, southerly
flow will promote better moisture advection into the state, which in
return will help to promote better storm chances. EPS guidance
continues to indicate potential for convection getting into the
lower deserts around Wednesday, but there is still plenty of time to
work out the details around this.
&&
.AVIATION...Updated at 1825Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Mostly sunny skies will continue through the overnight hours.
Thunderstorms are anticipated along the high terrain to the
northeast, east, and southeast of the terminals, but this should
stay well clear of the Phoenix area. There is also the outside
chance of an outflow boundary moving into the area, but as this is
low confidence the TAF does not include this at the time.
Otherwise, breezy westerly winds will weaken but continue well
into the night. Easterly diurnal winds will probably develop very
late, but will remain quite weak. Westerly winds return again by
Sunday late morning.
Southeast California/Southwest Arizona including KIPL and KBLH:
Mostly clear skies will continue, but increasing cirrus clouds
will be possible south of KIPL due to convection in the area. No
rain or thunder is anticipated near the terminal sites. Otherwise,
at KIPL winds should remain out of the south to southeast for
much of the next 24 hours with speeds below 15 kts. At KBLH wind
will generally be southerly with a few gusts over 20 kts this
afternoon and then remaining 5-10 kts on Sunday.
&&
.FIRE WEATHER...
Tuesday through Saturday:
High pressure will continue across Arizona, resulting in
relatively dry conditions and above normal temperatures. Wetting
rains are generally not anticipated Tuesday, but the threat of
isolated/scattered storms will return to the higher terrain
Wednesday. Min RHs will generally fall into the teens each
afternoon with single digit values over portions of the lower
western deserts. Overnight max RH should range around 25-45
percent with locally higher values possible across southern Gila
County. Meanwhile, winds will be mostly light and diurnal each day
along with afternoon breezes.
&&
.CLIMATE...
Record High Temperatures
Date Phoenix Yuma El Centro
---- ------- ---- ---------
8/1 116 in 1972 117 in 1993 118 in 1993
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Monday for AZZ532-537-
540>544-546-548>551.
Excessive Heat Warning until 8 PM MST this evening for AZZ530-
531-533>536-538-539-545-547-552>556-559>563.
Heat Advisory until 8 PM MST this evening for AZZ557-558.
CA...Excessive Heat Warning until 8 PM PDT Monday for CAZ565-567.
Excessive Heat Warning until 8 PM PDT this evening for
CAZ560>564-566-568>570.
&&
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Smith
AVIATION...Hodges
FIRE WEATHER...Hirsch/Sawtelle/Smith
CLIMATE...MO