Imperial, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

415
FXUS65 KPSR 220805
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
105 AM MST Sun Dec 22 2024

.SYNOPSIS...
Above normal temperatures will persist throughout the week, though
readings much closer to the seasonal normals will return during the
middle of the week as a weak cold front passes through the region.
While the pattern will become somewhat more active, rain potential
will remain very low with the strongest energy staying north of the
area. Another warming trend is likely next weekend with high
pressure building back into the region.

&&

.DISCUSSION...
Pronounced ridging over the SW Conus will become dampened over the
next 24 hours as a series of decaying East Pacific shortwaves break
over the inland high pressure axis. H5 heights currently analyzed
around 582dm across the CWA will retreat closer to 579dm by this
evening resulting in temperatures marginally cooler than the past
several days. While still around 10F above the daily normals, this
modest cooling should interrupt the string of recent record breaking
highs. Midlevel heights may oscillate slightly the next few days in
advance of a deeper incoming shortwave, however forecast guidance
spread is rather narrow suggesting good confidence of a near
persistence outcome of dry, warm weather through Tuesday.

Models remain in excellent agreement that a stronger, full
latitudinal trough will surge into the western Conus during the
middle of the week resulting in further midtropospheric height falls
across the forecast area. This trough will be more potent and
maintain better definition versus previous shortwaves with notable
negative height anomalies passing through far northern Arizona
Wednesday. While a few ensemble members dig the vorticity center and
cold core closer to central AZ, the vast majority of modeling keeps
these salient features and stronger ascent mechanisms relegated to
near the AZ/UT border. In addition to temperatures retreating much
closer to the seasonal average, modest height falls combined with a
decaying cold front spilling over the San Diego mountains should
yield a period of gusty winds in the typical wind prone areas of far
SW Imperial County Tuesday evening. Otherwise, initialized NBM POPs
are almost laughable given the displaced location of stronger
forcing, lack of entrained moisture, and clearly evident H7-H5
subsidence inversion south of the jet core. Have made significant
cuts to the required NBM output expecting little more than a few
isolated showers over higher terrain upslope regions (and even that
might be a stretch).

A very La Nina-like winter pattern of shortwaves digging and
intensifying well east of the forecast area should continue towards
the end of the week as another Pacific shortwave slides over a mean
longwave ridge and through the four corners area. Ensemble support
for this energy clipping eastern AZ has largely deteriorated with a
pattern evolution of strong subtropical ridging building back into
the SW Conus more preferred. In fact, there`s a growing consensus
that H5 heights 582-585dm will quickly replace any hints of
shortwaves passage by the weekend. While guidance spread naturally
widens towards the end of the forecast period, feel the NBM output
is under representing the upper end of the distribution given
pattern recognition. Thus, it would not at all be surprising if
temperatures warmer than the official NBM output are realized, and
anomalous warmth with near record temperatures return to the region
by the end of the weekend/early next week to close out 2024.

&&

.AVIATION...Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation concerns are anticipated through the forecast period.
Winds will remain light, generally aob 5 kts, and follow typical
diurnal tendencies. There will likely be extended periods of calm
and vrb winds, especially at the SE California terminals early
tomorrow. FEW cirrus will gradually become SCT over the region
throughout the day tomorrow.

&&

.FIRE WEATHER...
Dry weather with above normal temperatures will continue across the
region this week, though a series of passing weather disturbances
will result in modest cooling and marginally higher humidities.
Early this week, minimum afternoon RH values in the teens will be
common following poor to fair overnight recovery of 20-50%. By the
middle of the week, minimum values should increase closer to 20-30%
with overnight recovery in a 40-70% range. While some localized
enhanced breeziness will be possible with the passage of a weak cold
front, very light winds will be more typical across the districts.

&&

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

&&

$$

DISCUSSION...18/Young
AVIATION... Salerno
FIRE WEATHER...18