Forecast Discussion for PSR NWS Office
735
FXUS65 KPSR 231105
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
405 AM MST Fri Jun 23 2017
.UPDATE...Updated Aviation and Fire Weather Discussions.
&&
.SYNOPSIS...
A strong high pressure system will remain over the region producing
more excessive heat on the deserts through Monday. A weakening of
the high pressure system next Tuesday will result in lower afternoon
desert temperatures next week, mostly near the 110 degree mark. A
slight chance of afternoon thunderstorms will return to the
mountains of eastern Arizona Sunday and Monday.
&&
.DISCUSSION...
Today through Saturday...
Overnight Low level dewpoints were relatively elevated across the
southwest and south central AZ deserts, including Phoenix, but
moisture was shallow and generally 1500 ft deep. KYUX VAD wind
profiles at midnight continued to detect southern winds under 2 thsd
msl, which should keep surface moisture levels high at night, then
mix out during the day into the lower 40s.
Also, broad 300/250 mb anti-cyclonic flow over most of AZ today and
Saturday should stabilize the airmass to preclude any afternoon
mountain storms in our forecast area.
An Excessive Heat Warning will continue through Monday. Although
afternoon high temperatures today will remain slightly lower than
the record high values of late, temperatures are expected to rebound
Saturday through Monday and remain in the Excessive Heat Warning
range.
Sunday and Monday...
A southward moving cold front from Wyoming and Nebraska Saturday
night will dip into the Texas panhandle. This weak backdoor cold
front will increase low level easterly winds and moisture into
eastern AZ Sunday and Monday. At the same time models forecast a
300/250 mb disturbance to move from off the San Diego coast into
southeast AZ, so an increase in afternoon/evening thunderstorm
activity is expected including over the mountains of our Southern
Gila County zones.
The Excessive Heat Warning continues through Monday as desert high
temperatures are forecast in the 114-118 degree range.
Tuesday through Friday...
A somewhat stable northwesterly flow aloft, i.e. at and above 300
mb, will provide stability over most of AZ. At the same time drier
850/700 mb winds veer from the west to thin the boundary layer
moisture in our forecast area. This should preclude any thunderstorm
activity in our forecast area this period.
High temperatures are forecast to be lower this period as the center
of the high pressure system and thicker atmosphere moves south into
northwest Mexico.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Light easterly winds for most of this morning will switch around to
the west by late morning at 8-13kt with periodic breeziness and gusts
of 17-20kt developing from mid afternoon through this evening.
Otherwise, expect mostly clear skies with occasional high cloud CIGS
passing over late tonight.
Southeast California/Southwest Arizona including KIPL and KBLH:
Light and variable winds at KBLH and light southeasterly winds at
KIPL will become southwesterly and breezy at both sites this
afternoon at 10-13kt with gusts of 17-20kt. Expect mostly clear
skies with occasional high cloud CIGS for late tonight.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
Sunday through Thursday:
A strong high pressure system over the west will shift to the east
and flatten on Tuesday and Wednesday allowing the very hot and above
normal temperatures to continue. Max temps from 113-117F on Sun.
will very gradually fall to 107-109F by Thu. Min RH`s in the 7-11
percent range on Sun. will improve slightly during the middle of the
period, due in part to possible outflows from distant PM t-storms in
the high country to the east and southeast of the region, but will
remain below 15 percent. With a very slight chance of isolated PM t-
storms in the eastern high country through Tue., dry lightning fire
starts are possible. Seasonably gusty winds, as well as possible
outflow breezes from distant storms to the southeast, with gusts of
15-22kt are also expected most afternoons. Overnight recoveries will
generally be poor to fair.
&&
&&
.CLIMATE...
Record highs this week:
Date Phoenix Yuma
---- ------- ----
6/23 116 in 1974 116 in 1959
6/24 118 in 1929 120 in 1957
6/25 120 in 1990 119 in 1994
6/26 122 in 1990 122 in 1990
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Monday for AZZ530-533-534-
537-538-540-542>544-546-548-550-551.
Excessive Heat Warning until 9 PM MST /9 PM PDT/ Sunday for
AZZ531-532-535-536-539-541-545-547-549-552>556-559>562.
Heat Advisory until 9 PM MST Sunday for AZZ557-558-563.
CA...Excessive Heat Warning until 8 PM PDT Monday for CAZ560-561-563-
566>570.
Excessive Heat Warning until 9 PM PDT Sunday for CAZ562-564-565.
&&
$$
Visit us on Facebook, Twitter, and at weather.gov/phoenix
DISCUSSION...Vasquez
AVIATION...Sawtelle
FIRE WEATHER...Sawtelle
CLIMATE...AJ
NWS PSR Office Area Forecast Discussion
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