Surprise, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

622
FXUS65 KPSR 152015
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
115 PM MST Thu May 15 2025

...Key Messages

1) Gusty winds over the weekend resulting in a locally elevated fire
danger

2) Increased odds for above normal temperatures and widespread
Moderate HeatRisk returning late next week...

.DISCUSSION...
Weather Pattern Overview:

Broad, weakly cyclonic flow lingers over the SW Conus as a closed,
occluded low pressure system lifts into the Upper Midwest. The
weakness left in the midtropospheric flow over the forecast area
from this exiting system will quickly be filled over the weekend by
a series of Pacific negative height anomalies intensifying into an
amplified longwave western trough. The magnitude of the attendant
Pacific jet during this meridional transition will ensure robust
shortwave energy and notable height falls migrate into much of
Arizona. The timing and juxtaposition of height falls and jet core
carving out the trough base will support very gusty winds throughout
the weekend, but particularly Saturday afternoon/evening across SE
California where parameters align nearly optimally. As such,
advisories will almost certainly be necessary in the typical wind
prone locations of Imperial County. These gusty winds combined with
seasonally low humidity values will also result in an elevated fire
danger, though more limited wind speeds in south-central Arizona
Saturday and higher moisture sweeping through the region Sunday may
preclude more critical conditions.

Ensemble membership remains in good agreement depicting several
vorticity centers pivoting through the longwave trough with one
notable and final trailing wave digging into northern Arizona
Monday. Given the inland trajectory of this entire series of
shortwaves, moisture will be extremely limited with boundary layer
mixing ratios never exceeding 5 g/kg. However, given the unusual
depth of the trough and magnitude of the cold core, a few showers
may be squeezed out over higher terrain areas. On the other hand,
recent operational models have shifted the jet streak and cold core
slightly further north resulting in a forecast of a large midlevel
capping inversion locked over the southern half of Arizona. If this
model trend comes to fruition, it would be all but impossible for
anything other than outflow winds to propagate into lower
elevations.

While some subtle midlevel weakness in the height field may hold
over the Southwest during the latter half of the week, ensembles are
far more resolute in building stronger ridging over northern Mexico
and SW Conus. Some of the more extreme members have been
highlighting H5 heights around 594dm, however the preponderance of
output suggests heights closer to 588dm. As a result, widespread
moderate HeatRisk should evolve towards the end of next week with
temperatures nearly 10F above normal. Should any of the more
anomalous solutions be realized (and it could be argued that would
be a likely outcome given the pattern progression), this could be
the first vestiges of major HeatRisk with temperatures 15F above
normal yielding extreme HeatRisk over the holiday weekend.

Forecast Confidence & Deviations:

Good confidence in temperature forecasts exists the next couple
days, but then deteriorates significantly early next week depending
on how far south the cold core migrates. Mandated NBM forecasts have
bumped warmer based mainly on changes in the operational members,
but could flip flop back based on future model iterations. Feel the
automated NBM winds over the weekend are somewhat underforecast and
have made some minor increases during peak mixing hours. Spurious
POP and QPF grids were substantially reduced this cycle, however did
have to make some minor adjustments based on unrealistic model
artifacts. Average confidence exists with respect to temperatures
towards the end of this forecast period, but would not be surprised
if actual readings were even warmer than the current automated NBM
output.

&&

.AVIATION...Updated at 1728Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Winds will follow their typical diurnal tendencies through the TAF
period. Westerly winds will continue throughout the afternoon with
speeds generally aob 8 kt. Some occasional gusts into the mid-teens
will be possible this afternoon. Late tonight into the overnight
period winds are expected to shift out of the east, with speeds aob
5kts. During this time light and variable to calm winds can be
possible. Skies will be mostly clear.


Southeast California/Southwest Arizona including KIPL and KBLH:
Current VRB winds will soon establish out of the E at KIPL and SSE
at KBLH. Winds are expected to shift to a more westerly component by
late tonight at both terminals. Wind speeds at both terminals will
generally be aob 7 kt. Skies will be mostly clear.

&&

.FIRE WEATHER...
With dry conditions prevailing through next week, winds will
increase in speed over the weekend yielding an elevated fire danger
with locally near critical conditions. MinRHs will mostly fall in a
10-15% range through Saturday before a cooler and somewhat more
moist airmass keep minimum readings in a 15-25% range Sunday and
Monday. Poor to fair overnight recovery of 20-50% will improve
closer to a 35-60% range early next week. Winds will be most
pronounced in western districts Saturday with gusts 30-40 mph, then
translating into eastern districts Sunday albeit with somewhat
weaker speeds. Very warm and dry weather will return during the
middle of next week, however wind speeds will be much weaker as high
pressure starts building into the region.

&&

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

&&

$$

DISCUSSION...18
AVIATION...Ryan
FIRE WEATHER...18