National Weather Service Raw Text Product

062 
FXUS65 KPSR 071713
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1013 AM MST Fri Jul 7 2023

.UPDATE...18Z Aviation Discussion.

&&

.SYNOPSIS...
High pressure will continue to predominate the overall weather 
pattern across the region through next week and likely beyond. 
High temperatures of around 110 degrees are expected across the 
lower deserts through the weekend. Dry and breezy conditions each 
afternoon will result in elevated fire weather concerns. For next 
week, as high pressure strengthens over the region, even hotter 
conditions are anticipated with widespread areas of major to 
extreme HeatRisk. Enough moisture moving into the southern half of
Arizona next week will offer some chances for isolated high 
terrain storms. 

&&

.DISCUSSION...
The hot and dry air mass over the region will remain in place
through the weekend with the subtropical high center now near El 
Paso, TX. This subtle shift to the east of the high center along 
with a dry upper level shortwave trough that is forecast to slowly
move through California into the Great Basin this weekend will
slightly lower heights aloft keeping temperatures from getting 
any worse through Sunday or Monday. For today through Sunday, NBM 
forecast temperatures are between 108-111 degrees across southeast
California and southwest Arizona to 108-114 degrees across the 
lower deserts of south-central Arizona, including the Phoenix 
metro area. The drier than normal conditions will persist through
much of the weekend, but by Monday there will be a noticeable 
uptick in boundary layer moisture as the flow turns more 
southerly. By late Monday, forecast PWATs rise to 1.10-1.40" 
across the southern Arizona lower deserts. This increasing 
moisture should be enough to spark off some isolated high terrain 
storms east of Phoenix as early as Sunday afternoon, but with 
higher chances (15-30% chances) starting Monday. However, since 
this moisture will still be quite limited compared to what we 
would need for more widespread monsoon activity, chances for any 
lower desert storms will be less than 10%. Due to the limited 
moisture, the more likely impacts for the south-central Arizona 
lower deserts next week will be gusty outflow winds and maybe 
blowing dust.

We are still anticipating this current heat wave to continue
through next week and likely beyond with it rivaling some of the
worst heat waves this area has ever seen. This week has been hot
with temperatures on average five degrees above normal in the
Phoenix area to a few degrees above normal across the western 
deserts, but there is very high confidence this heat will get even
worse next week. Model ensembles remain in excellent agreement 
showing the subtropical ridge strengthening once again next week, 
while also drifting back to the northwest before centering itself 
over Arizona by the middle of next week. Forecast H5 heights are 
shown to rise to between 594-597dm by next Tuesday from the 
current 588-592dm. So, from next Tuesday through the rest of the 
week, temperatures across the region may be some of the hottest we
have ever seen. 

The latest forecast NBM temperatures shows highs peaking during 
the middle of next week with highs anywhere from 113-118 degrees 
across the lower deserts on Wednesday and Thursday, but this isn't
the upper end of potential temperatures as there are pockets of 
5-10% probability of reaching 120 degrees. The atmospheric set up 
for the latter half of next week also looks to have similarities 
to the conditions on July 28, 1995 that led to Phoenix reaching 
121 degrees and Yuma hit 124 degrees. Even if we do not get quite 
that hot during this current heat wave, this should go down as one
of the longest, if not the longest duration heat wave this area 
has ever seen. In fact, both the GEFS and EPS do not show an end 
to this heat wave as it goes through the entire 360 hour run. The 
only thing that could disrupt this heat wave is if more moisture 
is added to provide for more convection, but so far there are no 
strong indications this will occur. The best moisture the 
ensembles show occurs next Monday and Tuesday, before PWATs drop 
closer to 1.00-1.20" by Wednesday and then staying within this 
range at least through next weekend. So, starting next Tuesday the
majority of the area should fall under a major to extreme 
HeatRisk with this potentially lasting through the following 
weekend and possibly longer. Given this scenario, very dangerous 
to potentially life-threatening heat conditions are expected 
through next week and it is very essential that all the necessary 
heat precautions be taken to avoid any heat- related illnesses. 

&&

.AVIATION...Updated at 1715Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Quiet weather to continue for the TAF locations through the period
with mostly clear skies and typical diurnal wind shifts. Westerly
winds take hold this afternoon, gusts will generally range between
15-20 kts through the evening. Winds will shift around to the east
overnight into the morning hours tomorrow. 

Southeast California/Southwest Arizona including KIPL and KBLH:
Quiet weather to continue for the TAF locations through the period
with mostly clear skies and typical diurnal wind shifts. Afternoon
breeziness is anticipated as gusts reach between 20-25 kts, before
weakening early this evening at KBLH and later tonight at KIPL.
Wind directions will generally favor a west to southwest component
at KIPL through the period, while KBLH will vary between southerly
to southwesterly directions. 

&&

.FIRE WEATHER...
Elevated fire weather conditions will continue to be an issue
during the afternoon and early evening hours for much of the area
for the next few days. This is due to the continued above normal 
temperatures, drier than normal conditions and breezy daytime 
winds. Daily MinRHs of 5-10% over the lower deserts to 10-15% over
the higher terrain are expected through Saturday with a subtle
improvement in RHs starting Sunday. Overnight moisture recovery 
will range from poor to fair each night with RHs topping out 
between 20-35%. Winds will be breezy during the afternoon and 
early evening hours with gusts reaching 20-25 mph across much of 
the area today and to around 20 mph on Saturday. For next 
week, even hotter conditions are expected with an increase in 
moisture early next week likely leading to isolated thunderstorm 
chances over the eastern Arizona high terrain.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Watch from Tuesday morning through Sunday evening 
     for AZZ530>533-535-536.

     Excessive Heat Warning until 8 PM MST Sunday for AZZ534-537>544-
     546-548>551-553>555-559.

CA...Excessive Heat Watch from Tuesday morning through Sunday evening 
     for CAZ560>570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Frieders
FIRE WEATHER...Kuhlman