Dense Fog in California, November 7, 2021

Area Forecast Discussion
National Weather Service Phoenix AZ
356 AM MST Sun Nov 7 2021

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
High pressure over the region will continue to provide above
normal temperatures and dry conditions, but gradual cooling will
take place into the middle of the week as a large trough slowly
passes by to the north. Periods of high cloudiness will be seen
through Wednesday, but even those days will still see plenty of
filtered sunshine. Near normal temperatures starting Tuesday
should persist through the end of the week with some slight
warming possible by next weekend. Precipitation chances through
the next 7 days will be near zero.

&&

.DISCUSSION...
After three days of highs around 90 degrees across the lower
deserts, the high pressure ridge responsible for the above normal
temperatures will shift eastward allowing for the start of a
gradual cool down. The large trough aiding in pushing the ridge to
our east will mostly stay to our north, but it will provide some
increased high level moisture resulting in periods of high clouds,
as well as lowering our heights aloft. Subtle cooling over the
next couple days should push daytime highs into a 80-85 degree
range starting Monday, likely staying within this range through
the rest of the week. Models do show a fast moving shortwave
trough tracking across the Great Basin and northern portions of
our region Tuesday night with breezy northerly winds to follow
Wednesday into Thursday. Wind gusts during this time could
possibly reach into a 25-30 mph range across the Lower CO River
Valley, but elsewhere should mostly stay below 20 mph.

The large scale trough positioned to our north will eventually
weaken and slight to the east during the middle part of the week,
while a high pressure ridge rebuilds across the eastern Pacific.
Ensemble guidance is now nearly certain this ridge will become the
main feature across the Western U.S. late in the week and likely
through next weekend. However, guidance keeps the center of the
ridge and the highest heights to our west. The NBM reflects this
in keeping temperatures below 85 degrees, but if the ridge ends up
a bit farther east over our region we could see highs back into a
85-88 degree range (NBM 75th percentile) as early as Thursday.
Drier conditions during the latter half of this week should also
mark the end of the high clouds. The weather pattern over the next
7 days and likely longer will keep precipitation chances across
the region near zero.

&&

.AVIATION...Updated at 1100Z

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

Light drainage/easterly winds will continue into Sunday early
afternoon before a late shift to weak westerly winds. Easterly
winds return in the late evening. Few-Sct high clouds will develop
this morning and prevail for much of the period.

Southeast California/Southwest Arizona including KIPL and KBLH:

Light diurnally driven winds are expected through the TAF period.
A bank of fog has developed east of Imperial and is gradually
moving towards the terminal. For now this fog is not anticipated
to be very dense, but reduced visibility will be possible through
about 15-16Z.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Dry conditions and weak high pressure will persist across the
region through the period leading to near to slightly above normal
temperatures. Winds will generally be light and favor diurnal
patterns, but some breezy winds are expected mid to late week,
especially across the Lower CO River Valley. Min RH values will
mostly fall into a 15-25% range through Wednesday before lowering
closer to a 10-15% range late in the period.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

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

DISCUSSION...Kuhlman
AVIATION...Hodges/Iniguez
FIRE WEATHER...Kuhlman