FXUS65 KPSR 062018

AFDPSR



Area Forecast Discussion

National Weather Service Phoenix AZ

118 PM MST Sun Apr 6 2025



.SYNOPSIS...

Ridging aloft entering the area will drive temperatures up well 

above normal this week starting Monday. The ridge will continue to

build, and expand throughout the week reaching peak strength 

Thursday and Friday. Expect highs in the upper 90s with potential 

of reaching 100 degrees across the majority of the region by the 

end of the week. High pressure aloft will keep skies mostly clear,

and dry conditions will persist.



&&



.DISCUSSION...

The main forecast concern for the coming week will be the building

heat and the likely areas of Moderate HeatRisk developing by

Thursday and lingering through Friday. The upper level trough 

is finally ejecting eastward out of our region with increasing 

subsidence and ridging filling in behind the system. As H5 heights

increase to between 577-579dm by later on Monday, our region will

undergo modest warming pushing highs to a few degrees above 

normal on Monday. 



The large scale weather pattern will also become somewhat blocked

with the ridge staying put over the Intermountain West into 

central Canada. By Wednesday, stronger ridging situated to our 

southwest will shift northeastward into the Southwestern U.S. 

Heights aloft will get another boost during this time with H5 

heights rising to 584-586dm before eventually peaking on Thursday 

at around 588dm. Temperatures will continue to trend upward

through the middle part of the week with highs back into the 90s

starting Tuesday and likely just above 95 degrees on Wednesday. 

As the ridging peaks over our region late week, temperatures will 

climb further with some lower desert locales likely reaching or 

even topping 100 degrees on Thursday and Friday. Local daily 

record highs are likely to be in jeopardy for at least Thursday 

and Friday (see CLIMATE section below), as a large portion of the

Phoenix Metro has a 70-90% chance of reaching 100 degrees. We 

also expect areas of Moderate HeatRisk to develop by Thursday 

which will have impacts on those who are sensitive to the heat, 

and/or those who have prolonged exposure to the heat without 

adequate hydration. Boundary layer conditions will remain 

seasonably dry during this time which will at least allow for 

efficient nocturnal cooling and overnight lows mostly in the low 

to mid 60s outside of the urban core areas. 



By next weekend, ensemble guidance favors a large scale trough

moving into at least the Pacific Northwest and likely farther

south toward our region. There is still some model uncertainty

with the strength and the depth of the trough, but there is at

least some evidence it will lead to a brief cooling trend. For 

now, the NBM is showing highs falling back to mid 90 degrees by 

next Sunday. If any weather system does end up passing through our

region, it is quite unlikely it will contain enough moisture for 

any realistic precipitation chances. We have higher chances of 

just seeing an increase in winds which could lead to elevated fire

weather concerns. 



&&



.AVIATION...Updated at 1740Z.



South Central Arizona including KPHX, KIWA, KSDL, and KDVT;

Southeast California/Southwest Arizona including KIPL and KBLH:



No aviation concerns are expected through the forecast period

under mostly clear skies. Winds are expected to follow typical 

diurnal tendencies with speeds remaining aob 8 kts through 

tonight. There will also be extended periods of calm winds with

directional variability at the SE California terminals.



&&



.FIRE WEATHER...

High pressure will spread into the region over the next couple of

days leading to quieter and drier conditions. Expect generally

clear skies with MinRHs falling to less than 10% area-wide each

afternoon. Overnight recovery will generally be poor with MaxRH

values around 20-25%. Temperatures will also quickly warm over 

the next several days with readings reaching above normal starting

Monday before peaking later in the week at around 10-15 degrees 

above normal. Overall light winds are also forecast with 

directions mostly following diurnal patterns.



&&



.CLIMATE...



Record high temperatures this week:



Date       Phoenix        Yuma        El Centro

----       -------        ----        ---------



Apr  9   102 in 1989   102 in 1989   104 in 1989 

Apr 10   100 in 2018   100 in 1960    98 in 2018

Apr 11    99 in 2023   101 in 1936   100 in 2018

Apr 12    99 in 1936   102 in 1962   103 in 1940



&&



.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...None.

CA...None.

&&



$$



DISCUSSION...Kuhlman/Ryan

AVIATION...Salerno

FIRE WEATHER...Kuhlman/Ryan 

CLIMATE...Kuhlman