Scientific Forecaster Discussion
fxus65 kpsr 140515
Area forecast discussion
National Weather Service Phoenix Arizona
1015 PM MST Fri Dec 13 2019
updated aviation section
high pressure will result in near to slightly above normal
temperatures for the beginning of the weekend. Skies will remain
mostly sunny with occasional increases in high clouds. A mostly
dry weather system will arrive Sunday bringing cooler temperatures
across the area with chilly morning low temperatures Monday and
Tuesday. Temperatures will rebound slowly through the first half
of next week.
upper-level ridging continues to promote dry conditions across
the Desert Southwest with only some passing cirrus to be noted on
GOES west visible satellite imagery this afternoon. Mostly clear
skies will continue through the remainder of this afternoon and
through much of the day tomorrow.
Much of the day Saturday will be similar to today with mild
temperatures remaining near to slightly above normal. Windy
conditions are expected to develop across parts of southwest
Imperial County tomorrow afternoon into Sunday so have issued a
Wind Advisory. Increasing upper-level moisture ahead of a
developing Pacific trough will promote an increase in upper-level
cloud coverage late Saturday night. The trough axis will pass over
The Four Corners area fairly quickly Sunday and move off to the
east by Monday. The greatest moisture with this system will remain
over northern Arizona with only a few showers possible across the
higher terrain over southern Gila County. Cooler air moves in
behind this system resulting in temperatures dropping into the low
to mid 60s for highs across the lower deserts Sunday through
Tuesday with Monday looking to be the coolest of those days.
Overnight lows Monday night into Tuesday morning look to be chilly
with low temperatures dipping down into the upper 30s to low 40s
around the Phoenix Metro.
Behind the aforementioned trough, a transient upper-level ridge
will build into the southwest Continental U.S. Tuesday into Wednesday before
the next trough approaches the region later next week. GFS and
European model (ecmwf) guidance differs on how deep this trough will dig. As of
now, pops continue to remain low across south-central Arizona and
southeast California with this system.
Aviation...updated at 0515z.
South-central Arizona including kphx, kiwa, ksdl, and kdvt:
Passing high clouds at 20-25k feet are expected through Thursday
afternoon. Light easterly flow overnight will gradually veer to
southerly during the late morning on Saturday, and eventually to
westerly by Saturday afternoon. Saturday evening wind speeds will
increase and the wind direction will shift to the south-southeast leading to
a period of potential cross winds along west-east runways. A few
clouds at 8-10k feet are also possible.
Southeast California/southwest Arizona including kipl and kblh:
Passing high clouds at 20-25k feet are expected through Saturday,
with a few clouds near 10k feet possible by Saturday afternoon.
At kipl winds will be light and variable overnight, but westerly
winds will increase to around 15 knots on Saturday afternoon with
higher gusts. Kblh should remain light and variable until later
Saturday afternoon but will also see westerly winds increase to
Sunday through thursday: a weak low pressure system affects the
region Sunday into Monday mainly ushering in cooler conditions.
Moisture levels with the late weekend system should be rather dry,
hindering precipitation chances although there is a chance of rain
or high elevation snow on Sunday over high terrain east of Phoenix.
Cooler conditions develop Sunday with highs falling below normal by
Monday and into the lower 60s over the cooler lower deserts. Minimal
warming returns returns Tuesday into Thursday as highs approach
seasonal normal levels.Minimum humidity levels initially should
stick around 25-35% much of the period, lowering into early next
week with desert readings falling into the teens before humidity
levels increase again later in the period. Breezy conditions move in
for Sunday and Monday, mainly over deserts west of Phoenix. Light
winds return again by Tuesday as weak high pressure aloft returns to
Spotter information statement...
spotters should follow Standard reporting procedures.
California...Wind Advisory from 1 PM Saturday to 10 am PST Sunday for caz562.