558
FXUS65 KPSR 222116
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
216 PM MST Wed Jan 22 2025

.SYNOPSIS...
Daily high temperatures will hover right around normal through the
latter half of the week and into the start of the weekend with cool
overnight lows in the mid 30s to lower 40s. By the end of the
weekend and into the start of next week, an area of low pressure is
expected to dive south across the Great Basin, providing our
forecast area with decent chances for rain and higher elevation
snow. Cooler temperatures will accompany this weather system as it
resides over the Desert Southwest, pushing temperatures to below
seasonal normals once again.

&&

.DISCUSSION...
Very dry air continues to be entrenched across the Desert Southwest
as many locations continue to see dew point readings below zero.
This airmass combined with little wind promoted cold morning low
temperatures, with many locations falling to or below freezing. Even
with positive height anomalies overhead promoting warming
temperatures regions, cool northwesterly flow will help to limit the
amount of warming that occurs. Afternoon highs today across lower
desert locations will range from the middle 60s to around 70
degrees, which is right around normal for this time of year. These
near normal temperatures will persist over the next several days,
at least through the start of this weekend, as the overall
pattern will not change much, resulting in little to no day-to-day
temperature variations. One noticeable change in conditions will
be return of breezy to locally windy conditions for parts of the
region this afternoon through Thursday, with gusts upwards of 30
mph across lower elevations areas, especially around the Lower
Colorado River Valley and southwestern Arizona. Advisory level
winds (gusts 40+ mph) would not be surprising around enhanced
terrain features, but the isolated nature of these enhanced gusts
does not support the issuance of any wind products at this time.

The frequently mentioned system for the end of the week and into
the weekend continues to be on track to impact the region during
this timeframe. Model consensus continues to improve, showing
this system diving across the Great Basin through the weekend
before settling over southern California by Monday. The deeper
track of this disturbance will allow for better moisture flux over
our forecast area compared to other systems so far this winter.
PWAT values will increase to the tune 0.5-0.6", which is right
around normal for this point in the winter. One ingredient that
has been missing over the past several months is the presence of
low-level moisture, allowing for rain to actually reach the
ground. Most activity that has been observed has fallen as virga
or very light showers, but that does not appear to be the case
this time as lower atmospheric moisture will promote decent
accumulating rain chances, even across lower desert areas. As of
now, NBM PoPs continue to show 20-40% probabilities from Sunday
through Tuesday. It is not out of the question that periods of off
an on showers will exist during this entire timeframe as the slow
moving nature of this system will promote a prolonged period of
moisture advection over the region. It would also not be
surprising to see some weak thunderstorm activity as model
soundings are hinting at some very marginal instability. Since the
moisture profile will not be overly impressive, significant
rainfall totals are not anticipated, but anywhere from a
0.01-0.25" for lower elevation areas and 0.25-0.75" for higher
elevations areas of south-central Arizona is the most likely
outcome as of now.

This system is also expected to be quite cold, dropping snow
levels to around 4000ft towards the latter portion of the event
(Monday into Tuesday). Periods of light snow therefore will be
possible for portions for higher terrain areas east of the Phoenix
metro, with the potential for areas generally above 4,500 ft
seeing the first accumulating snow of the season, though any
totals should only amount to a few inches at most. After the more
seasonal temperatures prevail through the start of the weekend,
daily highs will take a dip toward below normal levels once again
with lower desert highs in the lower to middle 60s by Sunday.
Tuesday next week looks to be the coolest day out of the next week
or so with highs only reaching into the upper 50s and lower 60s.
NBM probabilities give Phoenix Sky Harbor a 25% chance of not even
reaching 60 degrees, which would be the first time that has
happened since February 10th of last year when the high reached 59
degrees.

&&

.AVIATION...Updated at 1807Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds through the rest of the day will overall exhibit diurnal
tendencies with speeds remaining under 8 kts during this time.
Northeast winds develop this evening with the flow pattern
favorable for the development of localized light southwest winds
overnight at KPHX. The increasing northeast flow aloft over the
region could lead to some LLWS concerns overnight, but for now
expect this to remain below TAF thresholds. Stronger northeast
winds are expected to begin mixing down by around 17Z tomorrow
morning with gusts upwards of around 20-25 kts and perhaps briefly
higher expected. SCT-BKN high clouds will decrease in coverage
going through the day with mostly clear skies prevailing by
tonight.

Southeast California/Southwest Arizona including KIPL and KBLH:
Winds at KIPL will vary between a W and NW component through the
period with speeds mostly under 10 kts. At KBLH, N winds are
favored with speeds increasing going into this afternoon. Gusts
starting this afternoon at KBLH are expected to climb upwards of
20-25 kts. Some LLWS concerns are possible overnight, but
currently expect this to remain below TAF thresholds. SCT-BKN high
clouds will gradually decrease in coverage today with mostly clear
skies prevailing later tonight.

&&

.FIRE WEATHER...
Near normal temperatures and dry conditions will persist through
at least Friday before a more unsettled weather pattern settles
into the region over the weekend, lasting through early next
week. Expect minimum afternoon humidity levels in the 5-10% range
with poor overnight recoveries only to 15-25%. Light winds
initially today will become breezy across the Lower CO River
Valley this afternoon and then additionally over the Arizona
higher terrain beginning tonight. Overall light winds are then
expected on Friday. A weather system is then forecast to move into
the region this weekend, likely bringing chances for wetting rain
across the south-central Arizona lower deserts and snow over the
Arizona higher terrain Sunday and likely lingering through next
Tuesday. Increased moisture levels and cooler temperatures will
help to push MinRHs to between 25-35% over the lower deserts
starting Sunday.

&&

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

$$

DISCUSSION...RW
AVIATION...Smith
FIRE WEATHER...Kuhlman