Winterhaven, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

459
FXUS65 KPSR 211700
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1000 AM MST Wed May 21 2025

...KEY MESSAGES...

1) Temperatures will continue to warm into Thursday with lower
desert highs topping 100 degrees today and likely peaking at around
105 degrees on Thursday. Highs in the upper 90s to the lower 100s
are forecast for the Memorial Day weekend.

2) The hot temperatures will result in an overall Moderate HeatRisk
(Level 2) for today through Friday, posing an increased risk to
vulnerable populations.

3) Afternoon breeziness is expected Thursday and Friday, with the
strongest winds on Friday as gusts as high as 20-30 mph. Dry
conditions will continue to prevail through at least next week.

.UPDATE...
Updated Aviation

&&

.DISCUSSION...
Weather Pattern Overview:
Quasi-zonal dry westerly flow remains in place across the Western
U.S. with a flattening Pacific ridge still centered to our
southwest. H5 heights are gradually rising across the Desert
Southwest due to the influence of the Pacific ridge, despite the
overall zonal flow. Since yesterday H5 heights have risen from
around 582dm to around 584dm currently with guidance showing a peak
of between 586-588dm on Thursday. Heights of this magnitude are not
unusual for this time of year and typically yield daytime highs
anywhere from 5-10 degrees above normal. As heights rise into
Thursday, temperatures will get a further boost with NBM forecast
highs showing readings between 100-104 degrees today and 102-106
degrees on Thursday. These hot temperatures will result in Moderate
HeatRisk developing across much of the area.

Starting Thursday night into early Friday, a weak but quite large
upper level trough is forecast to move into California before
eventually sliding across our region on Saturday. This dry
disturbance will help to begin to lower heights aloft starting
Friday while also lowering daytime highs more into a 100-103 range.
The incoming system will also help to increase winds with gusts
Friday afternoon likely in a 20-25 mph over most of the area, but
with the strongest winds of 30-35 mph possible Friday evening across
Imperial Co., CA. As the trough passes through the region Saturday,
it is likely to briefly drop high temperatures back into the mid to
upper 90s.

Model guidance is starting to come to a better consensus for what to
expect for Sunday and Monday with the potential weak cut-off  low
solution mostly disappearing. Now ensembles mainly suggest a weak
ridge slowly passing through our region with some uncertainty by
next Tuesday and Wednesday with another possible dry system
approaching from the west. NBM temperatures have inched upward a
degree or so for both Sunday and Monday due to the clearer guidance
on the weak ridge, resulting in highs from the upper 90s to the
lower 100s. Beyond Monday, the uncertainty in the position of the
ridge and the incoming trough means lower forecast confidence in
temperatures going into the middle part of next week.

Forecast Confidence & Deviations:
Confidence in the forecast guidance through the rest of the week is
quite good with decreasing confidence going into next week. The only
deviations from the NBM for this current package to increase winds
10-20% across Imperial Co. Friday evening.

&&

.AVIATION...Updated at 1700Z.

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

No major weather issues will exist through Thursday afternoon under
clear skies. Trends in wind speeds and timing of typical wind shifts
will be similar to the past 24 hours. Periods of variability and
nearly calm conditions during these transitional periods will be
common.

&&

.FIRE WEATHER...
High pressure will continue to prevail through the rest of the week
with warming through Thursday. Above normal temperatures are
expected, with afternoon highs reaching the lower 100s across the
lower deserts starting today and lasting through Friday. Very dry
conditions are expected each day, with widespread MinRHs down to 5-
12% and overnight recoveries to 15-30%. Light winds will continue
today before winds increase Thursday with gusts to around 20 mph and
even higher gusts of 20-30 mph possible on Friday. This could bring
another period of elevated fire weather conditions on Friday. The
dry conditions will continue over the upcoming holiday weekend, but
with diminishing winds and temperatures running a few degrees above
normal.

&&

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

&&

$$

DISCUSSION...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman