133 
FXUS65 KPSR 160010
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
510 PM MST Sat Nov 15 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- The first in a series of weather systems will affect the region 
this weekend bringing widespread light to moderate rain, but 
limited overall impacts.

- A trailing weather disturbance will bring the next opportunity for 
scattered showers to the area Tuesday and Wednesday.

- Temperatures will cool below normal next week with readings 
substantially below the daily normals during the middle of the week. 

&&

.SHORT TERM /Today through Monday/... 
Deep negative height anomalies continue to hover off the southern 
California coast with several pivoting vorticity centers causing the 
larger circulation to wobble only slowly eastward. The slow forward 
progression has kept more robust height falls centered along the 
coast range with WV imagery indicating the bulk of stronger dynamics 
lifting north rather than surging eastward. Nevertheless, attendant 
moisture with this system remains seasonally anomalous with total 
column PWATs nearing 1.50" aligning along the California coast. 
While a fair proportion of this moisture will be trapped on the 
windward side of the coastal range, sufficient inland southerly sfc-
H8 winds have provided moderate flux of higher theta-e through the 
lower Colorado River valley. In fact, objective analysis suggests 
boundary layer mixing ratios 8-10 g/kg have advected into parts of 
the western CWA ahead of an advancing cold front and organized 
ascent. 

HREF members remain in excellent agreement showing this moisture 
flux combined with vorticity forced ascent and frontal forcing along 
a narrow cold front producing numerous showers through the western 
CWA through this evening. Given the expansive thick clouds, midlevel 
cold core lingering offshore, and poor lapse rates, inland 
instability has been significantly limited with MLCape/SBCape capped 
around 500 J/kg. As a result while the majority of rain accumulation 
should occur with lower rainfall rates, embedded convective elements 
and locally higher rainfall rates may impact some locations along 
the Colorado River this afternoon. At this time with enhanced H7-H3 
steering flow, forward progression of individual elements should 
preclude widespread instances of higher rainfall amounts, however 
unidirectional flow and moisture flux vectors aligning along the 
mean flow may result in periods of smaller Corfidi vectors and some 
training higher reflectivity echoes. Only the most aggressive 12Z 
HREF output indicates notable amounts over 1.00" in any given 
location though a recent convective band likely deposited a narrow 
swath of 1" amounts. Regardless, the larger preponderance of high 
resolution output forecasts rainfall totals under 0.25" with higher 
amounts relegated to orographically favored locations where moist 
SSW flow best aligns orthogonally to ridge tops and mountain peaks.  

As the entire wave structure shifts northeast into NV/UT Sunday, 
another better defined vorticity center will rotate through the 
trough base bringing a steep cold front and associated forcing 
mechanisms through south-central Arizona during the morning hours. 
Forecast confidence is very good that at least a broken line of 
showers will quickly sweep through the metro with activity lifting 
into higher terrain areas during the afternoon. While rainfall 
amounts 0.25" or greater will be favored in foothills and mountains 
north and east of Phoenix, lower elevations amounts should largely 
fall below 0.25" with some locations possibly not even reaching 
0.10". A few showers could linger over mountains Sunday afternoon, 
however a pronounced midlevel subsidence inversion combined with a 
drier post frontal airmass should rapidly cutoff rainfall chances 
and result in partial clearing from Phoenix westward. 

Subsidence and drier weather may be short lived Monday as a 
negatively tilted Pacific shortwaves quickly digs towards the void 
left by the initial exiting wave in an increasingly blocked western 
hemisphere flow pattern. With lingering moisture and strengthening 
jet energy downstream from the approaching shortwave, theta-e 
advection and weak isentropic ascent could support a few pockets 
of elevated showers ahead of a reinforcing, stronger cold front 
surging into the southern California coast. NBM POPs appeared too 
aggressive and widespread (both temporally and areally) with 
unusually high values given the pattern, and have pared back this 
forecast somewhat with activity more likely to produce minor 
impacts Tuesday night. Otherwise, temperatures will tumble next 
week behind the frontal passages - initially falling slightly 
below normal Sunday and Monday (3F-6F below normal), then 
plummeting further during the middle of the week. 

&&

.LONG TERM /Tuesday through Saturday/...
Within broader troughing remaining in place across the Western 
Conus, a second shortwave will dive into the Southwest early next 
week. Guidance is now showing better agreement with the progression 
of this second system with a closed low first developing across 
California on Monday before tracking south southeastward into our 
region on Tuesday. There is still some slight timing and position 
differences within the ensemble members, so that in turn means there 
is uncertainty with the rainfall totals and exactly when the peak 
rain will occur. Some showers may begin to develop late Monday and 
Monday night, especially across higher terrain areas before more 
widespread rain is likely to occur on Tuesday. 

This system should bring better dynamics and forcing, potentially 
allowing for a more organized rain event. Forecast moisture levels 
will be lower than this weekend's system, but given the Tuesday 
system will be colder that should compensate for the lower available 
moisture. Potential rainfall amounts are still fairly uncertain, but 
the higher end of potential shows upwards of an inch possible across 
south-central Arizona to 0.25-0.5" across the southeast California 
lower deserts. As of right now, we are going with a more 
conservative 0.1-0.25" for SE CA and around 0.5" for the south- 
central Arizona lower deserts. Higher terrain areas north and east 
of Phoenix may end up getting another 0.75-1.25" by the time the 
rain ends either Tuesday night or early Wednesday.

The active weather period is expected to continue through the rest 
of next week with a third somewhat cold system quickly moving from 
off the Pacific Northwest on Thursday into our region around Friday 
or Saturday. Model uncertainty is even higher with this third 
system, but it could end up being the best precip maker. There are 
around 30% of the ensemble members that show a more progressive 
system which would not provide much additional precipitation, but 
another 30-50% show a much slower closed off low which may stick 
around for a couple of days. 

Temperatures next week will be fairly chilly all week with highs 
mostly staying below 70 degrees each day. As of right now, Wednesday 
may end up being the coldest day with highs only in the lower 60s 
for some lower deserts locations. The persistent higher boundary 
layer moisture and clouds should at least keep overnight lows fairly 
close to normal readings most nights.

&&

.AVIATION...Updated at 0010Z. 

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: 
The main aviation concerns during the TAF period will be VFR CIGS
(5-8 kft AGL) this evening into Sunday, SHRA activity mainly
focused Sunday morning, and low confidence on wind directions
until showers move out of the area mid-late Sunday morning. The
typical W'rly wind shift may not occur until around sunset at some
terminals, with others potentially observing more of a S-SE
tendency through this evening. 

By Sunday morning (likely between 11-13Z based on current trends) a 
more pronounced W'rly component will take hold with perhaps a few 
gusts around 15-20 kts as a line of showers moves into the PHX
airspace. Even though chances for MVFR visibilities and CIGs 
exist (10-25%) in conjunction with any SHRA activity, confidence 
is too low to include in the TAF. A rogue shower cannot be 
completely ruled out in the vicinity of the terminals from this 
evening through early Sunday, as well as an isolated TS as the 
line of showers moves through Sunday morning.

Southeast California/Southwest Arizona including KIPL and KBLH: 
One more line of SHRA with embedded TS will move through over the
next few hours, which could result in brief FEW-SCT decks as low
as 2-3 kft AGL and brief MVFR or lower visibilities in RA. Gusty
and erratic winds will be possible with any SHRA or if a TS moves
within the vicinity of a terminal, but winds should eventually
settle out of the SW by 02-03Z and through the overnight hours. No
major aviation concerns are expected once this final line of
showers moves east/northeast of the terminals. 

&&

.FIRE WEATHER...
A large weather system will slowly move through the region this 
weekend bringing cooler temperatures, increased humidities, and 
fairly widespread rainfall. Rain chances will peak across the 
western districts during the daytime hours today and during the 
first half of Sunday for the eastern districts. A few isolated 
thunderstorms will be possible, which may produce locally heavier 
rainfall amounts. MinRHs today will range from 25-30% over the 
eastern districts to 50-70% for the western districts. Sunday will 
bring MinRHs of 40-60% areawide. Expect periodic breeziness over the 
weekend. The active weather will continue through next week with 
another weather system affecting the area by Tuesday and another 
later in the week. Expect below normal temperatures and elevated 
humidities for all of next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Flood Watch until 10 PM PST this evening for CAZ560-568.

&&

$$

SHORT TERM...18
LONG TERM...Kuhlman
AVIATION...Whittock/RW
FIRE WEATHER...Kuhlman