997
FXUS65 KPSR 091126
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
426 AM MST Mon Mar 9 2026

.UPDATE...12Z Aviation Discussion.

&&

.KEY MESSAGES...

- A low pressure system moving through the Southwest will result in
scattered showers and thunderstorms today along with cooler
temperatures.

- Thunderstorms will be capable of producing small hail, strong
gusty winds, and brief heavy rainfall.

- Strong high pressure will build into the region by midweek leading
to dry weather and temperatures rapidly warming much above normal.

&&

.SHORT TERM /Today through Wednesday/...
A deep cutoff low continues to wobble west of the Baja peninsula
early this morning with all indications in objective height fall
data and satellite imagery suggesting the primary vorticity core
slowly shifting east towards northern Mexico. Synoptic ascent
mechanisms remain excellent north of the cold core where moisture
advection and low level convergence becomes juxtaposed with left
front jet quadrant dynamics. This is already reflected in banded,
nocturnal storms along the international border, though this
activity may wane after sunrise. The aforementioned cutoff will only
slowly migrate into central/northern Sonora over the next 36 hours
providing an extended time frame of favorable synoptic scale ascent
over the forecast area resulting in scattered showers and embedded
thunderstorms.

One aspect of forecast uncertainty and a primary limiting factor for
more expansive and intense storms will be only modest 6-7 g/kg
mixing ratios advected into the CWA combined with seasonably warm
midtropospheric temperatures. As a result, CAPE measures largely
only peak in a 250-500 J/kg range forming a tall, skinny unstable
profile. However, 0-6km deep layer shear should increase close to
45kt providing the opportunity for organized structure and brief
supercellular characteristic to the most robust and persistent
updrafts. There`s a general consensus among high resolution models
indicating multiple bands of showers and embedded storms blossoming
initially in SW Arizona during mid afternoon, then formulating
eastward through the evening and overnight. Individual shower
elements should propagate rapidly north (20-30kt) under the strong
shear profiles limiting rainfall accumulations in any single
location, though conceivably some areas over 0.25" totals would not
be unexpected. Otherwise while some small hail is possible, the
larger threat appears to be strong, gusty winds due to momentum
transport tapping the strong jet aloft within the strongest storms.

Subsidence should gradually filter into much of the forecast area
Monday night, however forecast confidence is good that the slow
forward motion of the attendant cutoff will maintain moist ascent
into the form of deformation banding and light showers across
southern Gila County through Tuesday afternoon. Cloud cover and the
proximity of the cold core will force temperatures holding near the
climatological normal through Tuesday before rapid height rises
ahead of building subtropical ridging envelops the SW Conus
Wednesday.

&&

.LONG TERM /Thursday through Sunday/...
Forecast confidence for the latter half of the week is excellent
given remarkable ensemble agreement showing a low amplitude northern
stream jet constricting poleward towards a Hudson Bay vortex
allowing strong subtropical ridging to expand into the SW Conus. H5
heights will settle into a 585-588dm range through the majority of
the period with only a marginal chance of heights/thermal fields
dampening over the weekend due to shortwave energy digging into the
Upper Midwest/Great Lakes. Ensemble guidance spread is extremely
narrow and reflects climatologically anomalous tropospheric
height/thermal measures. Surface temperatures 15F-20F above normal
will become common by the end of the week resulting in widespread
minor HeatRisk while also setting daily records (see Climate
section). It would also not be out of the question for some the
warmer, lower desert communities to achieve the first 100F of the
season as the NBM 75th percentile easily covers this threshold. Just
beyond this forecast period, essentially all ensemble members
indicate even warmer weather as East Pacific blocking edges into the
SW Conus and subsident ridging builds stronger. The ensemble
guidance envelop is solidly above the 100F threshold for all lower
desert communities portending a prolonged period of record setting
warmth.

&&

.AVIATION...Updated at 1123Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation hazard for the forecast period will be the
possibility of VCTS/TS by this evening where the main impacts will
be gusty winds and small hail. Before this evening`s activity no
significant aviation concerns are expected with VFR conditions
persisting until then. Wind directions are expected to switch from
NE to NW throughout the morning hours today then beginning to
shift SW`rly by the early afternoon. Wind speeds through the
morning and afternoon hours will be generally aob 10kts, then by
the evening (~00Z), wind speeds above 10 kts will be possible,
most notably at KIWA. SCT-BKN mid-lvl clouds with bases around
8-10 kft will develop over the region by this afternoon with bases
expected to decrease to no lower than 6 kft. Most of the activity
is expected to the east of the terminals by late tonight but
lingering VCSH may be possible after the main passage.


Southeast California/Southwest Arizona including KIPL and KBLH:
The main aviation concerns at the southeast CA terminals will be
scattered SHRA and a low chance (10-20%) of a thunderstorm this
afternoon and early evening. Winds will favor a E-SE component at
KIPL and will predominantly S-SW at KBLH through the afternoon.
Wind speeds at both terminals should generally be around 8-11 kt,
before becoming light and VRB by the end of the TAF period. By
early tomorrow afternoon, SHRA/VCSH is expected to materialize
over SE California. There is also a low chance (10-20%) of an
isolated t-storm impacting either terminal, mainly between
21Z-00Z. SCT-BKN mid-high clouds with bases around 10-12 kft will
persist through the evening hours.

&&

.FIRE WEATHER...
A weather system moving through the region today through early
Tuesday will bring cooler temperatures, increased humidity levels,
and chances for wetting rainfall. Dry weather with unusually warm
temperatures and low humidities will return during the latter half
of the week. Minimum humidity levels will only fall into a 25-40%
range this afternoon with good to excellent overnight recovery.
Better than a 50% chance of wetting rain with embedded thunderstorms
will exist in eastern districts through Tuesday afternoon before a
drying trend enters the region. Conditions will trend markedly drier
through the week with minimum afternoon humidities falling into a 5-
15% range by the end of the week while poor to fair overnight
recovery of 15-30% materialize. Outside of thunderstorm wind gusts
today, winds will be fairly light with only modest afternoon upslope
gustiness limiting a greater fire weather danger.

&&

CLIMATE...

Daily record highs later this week/early next week:

Date      Phoenix         Yuma         El Centro
----      -------         ----         ---------
3/12     94 in 1920    100 in 1916     95 in 2017
3/13     92 in 2017     95 in 2017     95 in 2017
3/14     95 in 2013     96 in 2017     97 in 2017
3/15     92 in 2013     98 in 1934    100 in 1934
3/16     99 in 2007     99 in 2007    100 in 2007
3/17     99 in 2007    101 in 2007    101 in 2007
3/18     95 in 2017     96 in 2017     95 in 2007

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...18
LONG TERM...18
AVIATION...Ryan/Salerno
FIRE WEATHER...18
CLIMATE...18