Area Forecast Discussion
Issued by NWS Phoenix, AZ
FXUS65 KPSR 051443
Area Forecast Discussion
National Weather Service Phoenix AZ
745 AM MST Mon Dec 5 2016
Seasonable temperatures and a few passing high clouds are in store
across the region for the next few days. Another storm system will
pass to the north late Tuesday into Wednesday bringing a slight dip
in temperatures and breezy conditions. Temperatures will rebound once
again towards the end of the week.
Morning regional weather balloon data showed noticeably dry
anticyclonic flow aloft with warm mid level temperatures, all of
which will provide a very stable atmosphere and seasonably warm
surface temperatures today.
However, a series of fast moving Pacific disturbances Tue and Wed
moving across the northern tier of the western region will edge
south and closer to AZ. A west to east orientated dry cold front
across southern UT today is forecast to shift south into central AZ
tonight and remain quasi-stationary through Wednesday. In our
forecast area, southeast CA to south central AZ, should provide
slightly cooler afternoon temperatures, however variable high clouds
at times will remind us the strong track has dipped south closer to
Current dry forecasts look ok. No short term updates necessary.
.PREVIOUS DISCUSSION...455 AM MST...
Broad troughing encompasses much of the North American continent this
morning, with a deep/sharp trough moving through west Texas and
other embedded shortwave emanating off a large low pressure feature
over the central Canadian provinces. Area of high level moisture and
slight ML/UL wind field divergence has supported broken to overcast
cirrus through the evening, now currently moving into Arizona from
the northwest. One could also trace the clouds up to a weak parent
shortwave moving through the Northern Rockies. With a fairly dry
surface airmass settled over the region (dewpoints in the teens to
upper 20s), temperatures overnight have cooled down into the low to
mid 40s for most desert sites. Slightly cooler values were seen in
the open desert locales between Tucson and Phoenix, with
Coolidge/Casa Grande down around 37F along with Globe at 40F.
Through Wednesday, the region will be under the removed influence of
passing shortwaves through the jet flow/storm pattern to our north.
The upper jet does sag southward Tuesday/Wednesday draping 90-110kt
300mb winds across northern portions of Arizona and the Four Corners.
Shortwave core associated with that jet streak will briefly lower
heights through the area and enhance westerly surface winds most
notably on Tuesday. CAA follows in the wake of the system, cooling
daytime temperatures for Wednesday 3 to 4 degrees from those on
Tuesday. Limited number of CMC ensemble members and the EC
deterministic still try to indicate some shower activity possible
over the higher terrain/Rim country overnight Tuesday into Wednesday
while the majority of other NCEP ensemble and GEFS Reforecast tools
indicate any precipitation will remain well north of the forecast
area and focused towards the Four Corners. Cannot rule out some brief
and light shower activity over the highest terrain of southern Gila
County, but the majority of the CWA will remain precip-free.
Beyond Wednesday, benign and dry flat ridging develops over the
Southwest/SoCal. Resulting sensible forecast will be one of fair
weather conditions with near normal temperatures and periodic passing
high level clouds. Subtropical 500mb ridge heights head towards the
upper 580dam/lower 590s just west of the Baja Peninsula tip, nudging
580-582dam heights into our area. Widespread upper 60s/low 70s will
make for a pleasant late week/weekend period with mildly cool
.AVIATION... South-Central Arizona including KPHX, KIWA, and KSDL:
Periods of high clouds will move across the terminals from time to
time, mostly few-sct with some thin bkn decks possible, embedded in
a northwest flow aloft. Light gradients will result in light winds
following typical diurnal patterns at KPHX and KIWA. Winds mostly
light variable at KSDL. No aviation concerns for at least the next
Southeast California/Southwest Arizona including KIPL and KBLH:
Few-sct high clouds decks at times through Tuesday morning with
winds mostly light/variable at the terminals. No aviation concerns
for at least the next 24 hours.
Aviation discussion not updated for amended TAFs.
Wednesday through Sunday: Near normal temperatures and mostly dry
conditions are likely through the week. A passing weather system to
the north will bring breezy northerly winds down the Lower Colorado
River Valley on Wednesday. Other days will feature mostly light
winds with occasional afternoon breeziness. From Wednesday through
Friday, minimum RH values will be elevated across Arizona with
values mostly above 20 percent; from the lower Colorado River Valley
west we can expect values between 10 and 17 percent. Readings become
elevated area-wide over the weekend, with minimum RH values mostly
between 20 and 30 percent.
.SPOTTER INFORMATION STATEMENT...
Spotters activation is not expected this week.
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