938
FXUS65 KPSR 141146
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
445 AM MST Tue Jan 14 2025

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
The below normal temperatures and freezing overnight lows will not
last much longer as readings return to normal on Wednesday and even
briefly warm to above normal areawide on Thursday. A mostly dry
weather system is then expected to push through the region late
Thursday into Friday bringing slight chances for precipitation over
the eastern Arizona higher terrain. This system will also cool
temperatures back to normal beginning Friday before even colder air
settles into the region over the coming weekend.

&&

.DISCUSSION...
The chilly and very dry air mass in place over the region is again
bringing freezing to near freezing temperatures over much of the
south-central Arizona lower deserts this morning. The broad upper
level trough largely responsible for this air mass will begin to
break down later today into Wednesday, while a Pacific ridge
currently coming onshore into the Pacific Northwest before shifting
southeastward into our region. This ridge will quickly raise heights
over our region tonight into Wednesday leading to a decent warm-up
with highs around 70 degrees Wednesday and even into the lower 70s
for the Phoenix area on Thursday.

At the same time the ridge is moving into our region over the next
couple of days, a cut-off low will be spinning off the coast of
southern California. The latest guidance has somewhat reversed
course with this cut-off low with it now looking a bit stronger as
it is likely to track east northeastward through our region later
Thursday into Friday. As a result, forecast moisture levels have
improved some over the southeastern 1/3 of Arizona with PWATs
peaking around normal in the Phoenix area to 125% of normal across
far eastern Arizona. Despite the slightly stronger system and
marginally better moisture, nearly all of this moisture will be
above 10K feet with forecast soundings showing an inverted V
structure and surface dew points at most reaching into the mid 20s.
Latest NBM PoPs still seem too high, so we continue to dial back
PoPs some with only virga showers/sprinkles expected in the south-
central lower deserts to at most some slight shower activity with
less than 0.05" QPF in the higher terrain. Some cooling will also be
realized as the system passes through the region with highs dropping
back to around normal starting Friday.

Once the cut-off low exits east of our region during the latter half
of Friday, our pattern will return back to what we have experienced
over the past week. An even colder arctic air mass is forecast to
dive southward down the Plains into much of the Eastern CONUS this
weekend with some of this cold air likely filtering southwestward
over the Rockies into our region. We very well could see very
similar temperatures later this weekend into early next week like we
just experienced over the last couple of days. The NBM does show
some low end PoP chances this weekend mainly focused over eastern
Arizona, but this is likely overdone as any shortwaves that drop
into or just past our region will be coming directly out of the
north and should be quite moisture starved.

&&

.AVIATION...Updated at 1145Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather issues will exist through Wednesday morning under
clear skies. Primarily east winds will prevail well into the
afternoon hours though some directional variability may exist this
morning. Otherwise, confidence is moderate that a brief period of
light W/NW winds will develop around sunset before reverting back to
an easterly fetch by mid evening.


Southeast California/Southwest Arizona including KIPL and KBLH:
No significant weather concerns will exist through Wednesday morning
under clear skies. W/NW winds will be preferred through the period
with some potential for afternoon gusts up to 20kt at KBLH.

&&

.FIRE WEATHER...
Temperatures will gradually warm to slightly above normal over the
next few days as a dry air mass remains in place. Elevated northerly
winds will also continue across much of the western districts
through Wednesday with gusts up to around 25 mph. For the eastern
districts, expect higher terrain breeziness with gusts of 20-25 mph
mainly focused more during the morning hours through Wednesday.
MinRHs will continue to be between 10-15% over the lower deserts to
around 20% in higher terrain areas. A mostly dry weather system
later this week is likely to marginally raise humidities Thursday
into Friday, but little to no precipitation is expected while winds
remain fairly light.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Freeze Warning until 9 AM MST this morning for AZZ535>540-
     542>544-546-548-550-551-553-554-559.

CA...None.

&&

$$

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