A positively tilted open-wave trough moved through the Desert Southwest and sent a cold front south along the Lower Colorado River. Strong surface high pressure behind the front led to strong northerly winds during the day, with the strongest gusts occurring during the afternoon.
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The episode as NWS PSR wrote it up.
A positively tilted open-wave trough moved through the Desert Southwest and sent a cold front south along the Lower Colorado River. Strong surface high pressure behind the front led to strong northerly winds during the day, with the strongest gusts occurring during the afternoon. Wind gusts reached over 30 mph across the region and peaked at 58 mph at the Blythe Airport.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Phoenix, AZ wrote its last area forecast discussion before the first event at Dec 9, 3:34 PM PST, 1 hour 21 minutes earlier.
Area Forecast Discussion
National Weather Service Phoenix AZ
434 PM MST Mon Dec 9 2024
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
A weather system and associated cold front will sweep across the
Desert Southwest tonight and Tuesday, bringing breezy to locally
windy conditions and cooler temperatures to the region. Afternoon
highs in the mid 60s are expected across the lower deserts
Tuesday afternoon with much of the high terrain and some rural
desert locations reaching the freezing mark on Wednesday morning.
Temperatures will remain mild throughout the rest of the workweek
before rebounding 3 to 5 degrees above average by this weekend as
ridging rebuilds over the forecast area. Dry conditions are
expected for the next several days.
.DISCUSSION...
Latest mid-lvl wv imagery and 500 mb streamline analysis reveals a
large, positively tilted trough which is now located over the
Intermountain West. At the base of this trough a robust 50-70 kt mid-
lvl jet is now entering the Great Basin region along with a sfc cold
front which has now reached the lower Colorado River Valley. Most
recent sfc observations at KBLH indicated wind gusts up to 35 kts
(40 mph). Winds will continue to be gusty in the wake of the cold
front over the next several hrs, with gusts reaching 30-35 mph at
times, mainly over the mountainous terrain of SE California and
Yuma County. In addition to strong northerly crosswinds, there may
also be patchy blowing dust along the I-10 corridor through this
evening. The aforementioned trough axis will continue to swing
through the Four Corners region tonight, resulting in FROPA across
the remainder of the region including the Phoenix Metro around
03Z-04Z. A dry post-frontal airmass will filter in behind the cold
front early Tuesday along with continued elevated NE flow at the
sfc. This will result in noticeably cooler temperatures Thursday
afternoon with highs forecasted to be near/slightly above normal
(mid 60s across the lower deserts and 50s for the higher terrain
areas). Winds should slacken off across the region after sunset
Tuesday evening as the shortwave trough pulls away from the region
and the sfc pressure gradient weakens.
Wednesday morning will be the coldest that we have seen since mid
November due to the combination of clear skies and dew points in the
single digits. Temperatures across the lower deserts are forecasted
to plummet into the upper 30s and low 40s with some of the rural
desert communities expected to see their first freeze of the season.
Therefore, a Freeze Watch remains in effect Wednesday morning for
the Lower Colorado River Valley, portions of northwest Pinal County,
and the Globe/Miami and San Carlos areas. Locations including
Arizona City and San Carlos will have the best chance (50-60%) of
seeing a hard freeze as temperatures are currently forecasted to be
in the 26-28 degree range. Other locations that may reach freezing
will be Tacna and Aguila/Wickenburg, but areal coverage is too low
to include a watch at this time. For folks in the communities with a
Freeze Watch, make sure to practice the 4 P's; protect people, pets,
pipes, and plants from the cold, Tuesday night/Wednesday morning.
Temperatures will warm by a couple degrees on Wednesday, however
continued NE flow at the sfc will result in a mild afternoon with
highs in the mid 60s to lower 70s.
Heading into the latter half of this week, there will be a tandem of
upper-lvl troughs that move through the Intermountain West. This
will keep the upper-lvl flow quasi-zonal over our forecast region
and thus day-to-day temperatures will not fluctuate much. Highs
are expected to remain around 3 to 5 degrees above average with
dry conditions prevailing. Mean ensemble 500 mb hghts are
indicating that a ridge will strengthen over the forecast area by
this weekend and into early next week which will result in
continued warm and dry conditions across the Desert Southwest.
&&
.AVIATION...Updated at 2325Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns under mostly clear skies can be
expected during the TAF period. Winds will follow familiar diurnal
patterns through this afternoon with speeds aob 8 kts. Winds will
eventually acquire a N'rly component tonight and likely persist
out this direction for most of the overnight hours. A few gusts
around 20-25 kts can't be ruled out in association with these
N'rly winds, especially for KSDL and KDVT. Marginal LLWS may also
be observed but should remain below TAF thresholds.
Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty northerly winds will be the main aviation weather issue
during the next 24 hours, mainly at BLH, where winds are expected
to gust out of the N between 25-30 kts during this
afternoon/overnight. Winds will then relax during the evening and
overnight hours. Periods of reduced visibilities due to blowing
dust may be observed due to the enhanced gusts. At IPL, NE'rly
winds will shift more to the NW by this evening with speeds
generally aob 8 kts. Other than a FEW passing high clouds, skies
will be mostly clear through the forecast period.
&&
.FIRE WEATHER...
Dry conditions will continue through this weekend. Above normal
temperatures continue today, with a slight cool down to near
normal tomorrow before rebounding back to above normal for latter
half of the workweek. This evening through tomorrow morning breezy
to locally windy conditions will develop across the western
districts and the higher terrain areas in the eastern districts.
The highest wind gusts (25-35 mph for the lower elevations and
40-45 mph along the ridgetops) are expected overnight Monday in
southeastern California and along the Lower Colorado River Valley.
Some residual breezy conditions can be expected region wide
Tuesday afternoon. Light winds with some occasional afternoon
gusts into the teens can be expected on Wednesday. MinRHs will be
in the teens across SE CA and SW AZ and in the 20s across south-
central AZ today. Much drier air moves in tomorrow with MinRHs
dropping to 5-10% across the region.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Freeze Watch from late Tuesday night through Wednesday morning
for AZZ530-553-560-562.
CA...Freeze Watch from Tuesday evening through Wednesday morning for
CAZ569.
&&
DISCUSSION...Salerno
AVIATION...Ryan
FIRE WEATHER...BerislavichThe national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
KBLH ASOS measured a peak wind gust of 58 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2024Every state in 2024This day in weather historyWarnings in California, December 2024
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1229024.