Plaster City, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

640
FXUS65 KPSR 160901
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
200 AM MST Wed Apr 16 2025

.SYNOPSIS...
Slightly above normal temperatures today will cool into a below
normal range during the latter half of the week as a weather
disturbance moves across the region. This system will also result in
breezy conditions and a local slight chance for light rain showers
Friday. As this system exits the region early next week,
temperatures will quickly rebound back towards the seasonal normal.

&&

.DISCUSSION...
A broad quasi-cutoff low with several embedded vorticity centers
continues to spin off the southern California coast as a split flow
regime characterizes the pattern over the western Conus. Meanwhile,
WV imagery depicts a northern stream PV anomaly quickly propagating
south through Alberta/British Columbia which will partially phase
with the southern stream gyre over the next 48 hours. The
preponderance of ensemble output has shifted towards the development
of a less intense wave with the bulk of the cold core and negative
PV anomaly relegated to northern Arizona, and only skirting the
forecast area Friday into early Saturday. Given this trend, dynamic
forced ascent should be less pronounced over the CWA while cooling
through the middle and lower troposphere more muted and short lived.

The initial round of modest height falls will enter the SW Conus
today as a cyclonic subtropical jet allows the leading edge of the
aforementioned California cutoff to advance inland. H5 heights in a
572-576dm range will still support temperatures in a near to
slightly above normal range while a tightening pressure gradient and
deep mixing depths promote increasingly gusty winds. The combination
of these breezy conditions along with low humidity values will
result in an elevated fire danger, mostly in higher terrain areas
east of Phoenix. The strongest gusts will be experienced in the
typical downsloping locations of far SW Imperial Co; and although
the synoptics don`t reflect a classic setup, timing of height falls
and the thermal/pressure gradient should support an extended evening
and overnight period of advisory level conditions.

A more abrupt cooling trend will arrive Thursday as H5 heights
plummet below 570dm and a decaying cold front slides into the
forecast area. While a few GEFS members still suggest a deeper
trough axis, most ensembles indicate H5 heights bottoming somewhere
near 565dm later this week. With the northern stream system filling
into the mean trough axis developing over the SW Conus, forecast
confidence is good that temperatures will hover some 4F-8F below
normal heading into the first part of the weekend.

The best ascent mechanisms will arrive into the area Friday
afternoon, however with the ensemble trends keeping the cold core
further north, it becomes more uncertain whether moisture advection
along and ahead of another front descend south will be sufficient to
support much in the way of showers. Recent model trends indicate low
level mixing ratios only reaching a 4-5 g/kg range while temperature
aloft are not nearly as cool, yielding a greater struggle to reach
saturation. Pattern recognition would support precipitation in
upslope regions north and east of Phoenix, however analysis of
forecast soundings across lower deserts point towards a lack of
sufficient moisture. Required NBM POPs appear far too high removed
from higher terrain areas likely owing to coarser global ensembles
bleeding QPF into lower elevations, and have made notable reductions
to the forecast POP/QPF during this time frame over lower desert
communities.

Another clear trend in ensemble output is the lack of residence time
for the trough axis over the Southwest with a faster forward
progression eastward. In fact, most model output propagates the
entire trough structure into New Mexico by Saturday afternoon with
large scale subsidence and dry air quickly surging into the CWA. As
a result, have eliminated lingering POPs for much of the forecast
area versus previous forecasts and the mandated NBM initialization
beyond early Saturday morning. In its wake, quasi-zonal flow/flat
ridging will spread into the region with temperatures likely
rebounding very rapidly into a near to slightly above normal range
early next week. Given the rather flat ridge and return to a split
flow regime, H5 heights will probably stagnate in a 572-576dm range
through at least the first half of next week with very tranquil, dry
conditions.

&&

.AVIATION...Updated at 0530Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns are anticipated through the
forecast period under periods of FEW high clouds. Late this evening
into the early overnight hours, the SCT cloud deck with bases around
8-10 kft AGL will gradually scatter out. Expect winds to eventually
settle out of their typical E/SE directions by 07-09Z. Late
Wednesday morning, winds will veer out of the S for a period before
shifting more decidedly out of the SW by 20-22Z in the afternoon.
Speeds will be slightly stronger Wednesday afternoon/evening than
what we have observed today, with sustained speeds in the low teens
and gusts up to around 20 kts.


Southeast California/Southwest Arizona including KIPL and KBLH:
The primary aviation concern through the TAF period will be gusty
southwest winds Wednesday afternoon and evening, under mostly clear
skies. At both terminals, directions will generally favor SSW to
WSW, though periods of variability may occur during the overnight
hours into early Wednesday morning. Speeds will generally remain AOB
10 kts through 20-22Z Wednesday. After that time, expect gusts to
between 25-30 kts at KIPL and to 20-25 kts at KBLH to become common.

&&

.FIRE WEATHER...
Above normal temperatures will cool to below normal levels during
the latter half of the week as a weather system moves through the
region. Ahead of this system, gusty afternoon winds will be common
today while seasonally low humidity values result in an elevated
fire danger. Cooling temperatures and a modest increase in moisture
will allow humidity levels to gradually increase the remainder of
the week precluding widespread critical thresholds. In general,
minimum afternoon humidity levels in the teens will be common today
with values increasing closer to a 20-30% range during the latter
half of the week. Early next week, warming temperatures and lowering
RH values will return to the districts.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory from 6 PM this evening to 6 AM PDT Thursday for
     CAZ562.

&&

$$

DISCUSSION...18
AVIATION...Whittock
FIRE WEATHER...18