Plaster City, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

823
FXUS65 KPSR 071048
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
348 AM MST Mon Oct 7 2024

.UPDATE...Updated Aviation Discussion...

&&

.SYNOPSIS...
Well above normal temperatures will persist, though highs are
expected to trend down by about a degree or two per day through the
weekend. Near record highs are likely to continue into the middle of
the week. Dry conditions should prevail through the next 7 days, but
a passing weak disturbance will lead to a modest increase in cloud
cover and could yield some light afternoon showers over mountainous
areas of eastern and northern Arizona during the middle of the week.

&&

.DISCUSSION...
Longwave ridging continues to dominate the weather for the Desert
Southwest this week. Record high temperatures will continue for much
of the region today, with NAEFS mean 850 mb temperatures still near
their climatological maximum values. Forecast highs across the lower
deserts range mostly from 105-110F this afternoon. This will lead to
continued areas of Major HeatRisk, and as such, the Excessive Heat
Warning remains in effect through this evening for the lower deserts
of AZ and Southeast CA, including the Lower Colorado River Valley.
With the approach of a positively tilted weak disturbance during the
middle of this week, heights aloft become slightly dampened and
NAEFS mean 850 mb temperatures begin a gradual downward trend that
will continue into this weekend (though remaining above the 90th
percentile of climatology through at least Saturday), which will
help drop HeatRisk into a moderate category for much of the region
by Tuesday. However, Major HeatRisk remains on Tuesday for the
typically hotter urban corridor through Phoenix, so the Excessive
Heat Warning will remain in effect through tomorrow evening for the
Phoenix Area. Forecast highs, in good agreement with the
aforementioned mean 850 mb temps, trend down about a degree or two
each day into this weekend. This still places lower desert highs
around 10F above normal this weekend, as normals are in low 90s.

The aforementioned weak, positively tilted disturbance that models
advertise to pass over the region during the middle of this work
week will help to increase moisture over the region, though mostly
only above 600 mb. Other than some elevated afternoon showers over
the mountains of northern/eastern AZ on Tuesday/Wednesday,
conditions for much of the state are expected to remain dry through
the next 7 days.

One of the primary forecast uncertainties is the evolution of an
East Pacific shortwave moving onshore late this week. Its influence
should keep midlevel heights from rebuilding substantially, although
all guidance does suggest temperatures persisting in an above normal
range through the weekend. The evolution of this shortwave into the
Rockies appears to be dictated by the resolution of hemispheric
blocking with many ensemble members attempting to form some
temporary Rex block feature over the western or central Conus. Not
surprisingly given this blocking pattern, the deterministic ECMWF,
GFS, and CMC runs all have vastly different solutions. However, most
solutions at this time favor a more northward displaced feature,
leading to near zero NBM PoPs (down from the past few runs) and
continued well above normal temperatures.

&&

.AVIATION...Updated at 1050Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation weather concerns under FEW mid and high-level
clouds are expected through the TAF period. Easterly winds will
prevail into this afternoon with sustained speeds generally under
10 kts although there will likely be a period mid to late morning
of some occasional gusts into the mid to upper teens before
subsiding during the afternoon hours. There is uncertainty of
whether or not wind directions late in the afternoon/early
evening switch out of the west with very light and variable winds
more likely.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns are anticipated through the TAF
period. Extended periods of light and variable winds are expected.
Clear skies will give way to some passing high clouds heading into
the afternoon.

&&

.FIRE WEATHER...
Very dry and extreme heat conditions will continue for many areas
through Tuesday with lower desert highs ranging between 104-110.
MinRH values in the afternoons in the 5-10% range will be common
through at least Tuesday, while MaxRH readings are expected to be
between 20-30% with locally higher values in Yuma and Imperial
Counties. An increase in winds above the surface during the
overnight hours this morning morning may lead to very localized
elevated fire weather conditions in South-Central AZ. Easterly
winds early this morning on and near ridgetops will be capable of
reaching 25-35 mph at times, mostly in the mountains east of
Phoenix.

There will be a very slight increase in moisture beginning midweek
that may keep MinRH values from falling into the single digits,
but most areas will still see 10-20% readings in the afternoon
through the end of this week. There will also be potential for
some regional rain showers with the moisture increase, but at this
time the chances are very low (5% or less) across the lower
deserts and CWR is near zero. Winds, beyond today, will follow
familiar diurnal trends, with occasional afternoon gusts near
15-25 mph.

&&

.CLIMATE...

Record highs through Friday:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Oct 7     104 in 1991    108 in 1987    105 in 1991
Oct 8     104 in 1987    107 in 1996    106 in 1996
Oct 9     103 in 1996    106 in 1996    104 in 1996
Oct 10    105 in 1991    107 in 1991    105 in 1996
Oct 11    102 in 1991    107 in 1950    106 in 1995

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST this evening for
     AZZ530>536-538-539-553>555-559.

     Excessive Heat Warning until 8 PM MST Tuesday for AZZ537-540>544-
     546-548>551.

CA...Excessive Heat Warning until 8 PM PDT this evening for CAZ562-
     566-567-569-570.

&&

$$

DISCUSSION...Whittock/18
AVIATION...Lojero/Kuhlman
FIRE WEATHER...Whittock/Benedict
CLIMATE...18