299
FXUS65 KPSR 121808
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1108 AM MST Sun Oct 12 2025

.UPDATE...Updated Aviation.

&&

.KEY MESSAGES...

- A Flood Watch remains in effect for south-central Arizona
  through tonight.

- Scattered showers and thunderstorms will affect south-central
  Arizona through Monday with the heaviest rainfall potential and
  greatest flood threat over higher terrain areas north and east
  of Phoenix.

- Below normal temperatures will be common throughout the week.

&&

.SHORT TERM /Today through Monday/...
Early morning WV imagery depicts a renewed moisture surge in advance
of the remnants of TC Raymond through central Sonora becoming
sheared into the southern periphery of strong jet energy digging
towards the Southwest. The troughing associated with this jet core
will lift into the Great Basin, though still providing modest height
falls and ascent near the jet right entrance region through Monday.
Meanwhile, a large pool of boundary layer mixing ratios 12-14 g/kg
continues to envelop all of southern Arizona though drier air in the
strengthening SW flow has brought total column PWATs closer to
1.50". While short term modeling is still insistent on developing
numerous elevated showers and storms though the morning across south-
central AZ, ground truth versus early hour forecasts from these
models has exhibited an overzealous forecast. Nevertheless, the
overall pattern remains favorable for saturated ascent around the H7
level tapping MUCape near 1000 J/kg; and feel based on satellite and
recent radar trends, scattered elevated convection will eventually
come to fruition through the mid morning hours. Given the
instability and moisture content, some heavy rainfall may be
possible particularly considering nearly unidirectional flow within
the cloud bearing layer fostering training echoes and efficient
rainfall rates.

Forecast confidence is rather low this afternoon and evening given
the questionable performance of HREF membership already today. The
preponderance of modeling shifts a stronger convective signal into
SE Arizona following the migration of height falls/jet energy and
towards the theta-e ridge and instability axis. However, sufficient
moisture and instability should be present to support persistent
convective chances along the southern CWA border into this evening
with a locally heavy rainfall signal only deteriorating slightly
(mixing ratios 12 g/kg and PWATs 1.30"). Another round of overnight
elevated convection will be possible tonight through Monday morning
though the exact forcing mechanism and location carry greater
uncertainty while the kinematic and thermodynamic fields become even
less favorable for heavy rainfall.

A final round of showers and storms impacting the eastern portion of
the CWA should sweep north in association with a vorticity center
more closely tied with TC Raymond Monday afternoon. Height falls and
jet energy from East Pacific troughing will also come into play
aiding in forced ascent. Lingering boundary layer moisture (10-11
g/kg mixing ratios) should result in MLCape reaching a 500-1000 J/kg
range, and minimal inhibition with a moist upslope should aid in
additional lifting features. By this time, total column moisture
should be eroded closer to 1.00-1.25" resulting in lower
probabilities of heavy rains, particularly given the faster mean
storm motion in the H8-H5 layer. Given this enhancement of midlevel
winds, forecast 0-6km deep layer shear remains quite impressive
(~40kt) and capable of supporting better organizational structure
for any storm that can develop. High resolution models don`t seem to
be particularly bullish on stronger storms within the CWA given
steady scouring of moisture quickly becomes detrimental towards
convective sustenance.

&&

.LONG TERM /Tuesday through Saturday/...
Seasonally strong negative height anomalies along the central
California coast Tuesday will lift and fill into the Great Basin
during the middle of the week bringing pronounced, dry westerly flow
into the forecast area. Boundary layer moisture will rapidly be
scoured Tuesday with mixing ratios tumbling closer to 5-6 g/kg as
deep mechanical mixing promotes both horizontal and vertical
advection of dry air. While NBM output depicts enhanced POPs through
the western CWA as a Pacific cold front moves onshore, downsloping
and rain shadowing effects downstream of the coastal mountains
should preclude much, if any shallow Pacific moisture from breaching
into the leeward side, and appears this output is another typical
blended model artifact. The greater weather impact will likely be
gusty winds Tuesday afternoon and evening, primarily in the most
wind prone locations of SE California where midlevel height falls,
deepening marine layer, and enhanced H8-H& winds should promote
hydraulic jumps and downslope speeds.

Ensemble membership remains in excellent agreement during the latter
half of the week depicting a slowly progressive Conus pattern with
broad troughing somewhere in the northern Rockies/central Conus and
a lingering, positively tilted trough extended into the SW Conus.
This pattern will ensure H5 heights hover in a 572-578dm range into
the weekend, and narrow ensemble numerical spread yields very good
confidence temperatures settling 4F-8F below normal into the weekend
before a likely warming trend just beyond the scope of this forecast
period.

&&

.AVIATION...Updated at 1807Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Showers and storms have come to an end across the Phoenix area,
having shifted to the south, but lingering lower clouds will be
the primary aviation impact through this afternoon. MVFR CIGs are
currently seen in parts of the metro. CIGs are expected to improve
by 19-20Z, back to VFR with CIGs moving to around 7-10K ft AGL.
There is a slight chance (30%) for another round of spotty showers
tonight for a few hours and then a chance (50%) for storms in the
early afternoon tomorrow. There will be a slight chance (30%) for
MVFR CIGs again tonight through tomorrow morning. Otherwise, CIGs
will mostly be around 4-6K ft AGL tonight and tomorrow. Winds will
primarily favor an E`rly component through the TAF period and turn
S`rly tomorrow midday.

Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Monday morning under clear
skies. Winds will generally favor a northerly component through the
period with some modest gusts possible at KBLH. Periods of overnight
variability or a light westerly drift may be common.

&&

.FIRE WEATHER...
Wetting rain chances will continue through Monday over eastern
districts with drying in SE California and SW Arizona. More
widespread drier conditions enter the region Tuesday. Rainfall in
eastern districts may be heavy at times resulting in localized
flooding, especially over higher terrain areas. Elevated moisture
levels will keep humidity levels in eastern districts above 50%
through Monday, then minimum values falling closer to a 30-40% range
during the middle of the week. Western districts will generally
experience afternoon humidity values 15-25%. Erratic and locally
gusty winds will common around showers and thunderstorms the next
several days with more widespread gusty winds affecting the region
Tuesday afternoon/evening.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through this evening for AZZ534-537>563.

CA...None.
&&

$$

SHORT TERM...18
LONG TERM...18
AVIATION...Benedict/18
FIRE WEATHER...18