Forecast Discussion for PSR NWS Office
889
FXUS65 KPSR 092315
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
415 PM MST Sun Feb 9 2025
.Update...Updated Aviation Discussion.
&&
.SYNOPSIS...
Tranquil and warm weather will persist through Monday under
partly cloudy skies. By Tuesday, a weak and dry weather system
is expected to pass through our region lowering temperatures back
into the normal range for this time of year and promoting breezy
conditions by Tuesday afternoon. Moisture will then gradually
increase beginning Wednesday, with rain chances increasing late
Wednesday into Thursday before much better chances setup for the
end of the workweek. Temperatures will be near to slightly below
normal through much of the week before high pressure finally
brings a return to warmer weather by early next week.
&&
.DISCUSSION...
Dry conditions continue in the short-term as zonal flow remains in
place over the region. Upper level ridging situated to our southeast
continues to promote 500 mb heights around 575-577 dm over our area
and thus continued above normal temperatures. Afternoon highs
through tomorrow will continue to run about 5-10 degrees above
seasonal normals as temperatures top out in the mid to upper 70s to
around 80 degrees across the lower deserts and low to mid 70s for
higher elevation areas like Globe and San Carlos. The dry and
unseasonably warm conditions currently in place will give way to a
cooler, unsettled weather pattern beyond Monday.
The latest WV imagery and objective analysis show a shortwave trough
still well off the coast of southern California but gradually
approaching the West Coast. Expansive high clouds continue to
steadily stream ahead of the trough and through the southwest
CONUS. The weak trough is then expected to push into our region
later Monday into Tuesday. Meanwhile, a secondary trough is set to
dive down from the northwest on Tuesday. Dry conditions will
persist as these disturbances propagate through the region,
however, we will in response see increasing winds and cooler
temperatures Tuesday. Widespread breezy conditions are expected
Tuesday afternoon/evening with the strongest winds focused across
the southern Gila County high terrain as well as Imperial County.
Will continue to monitor for the potential need of a Wind Advisory
during this time, primarily for parts of Imperial County.
Temperatures Tuesday will return to near to slightly below normal
readings as lower desert highs cool into the upper 60s to low 70s.
Going into the middle part of the week, longwave troughing will be
in place over the western CONUS with several shortwaves tracking
through or just north of our area. Ensemble guidance show moisture
increasing into the region starting Wednesday with PWAT anomalies
climbing upwards of around 150% of normal. Ensembles are trending
toward better moisture getting into our area Wednesday with modeled
soundings now showing better low and mid level moisture later
Wednesday into Thursday. Additionally, a shortwave will dive in from
the northwest during this time, providing the forcing needed to get
better rain chances into the state. Given the trend toward better
moisture in place as this trough passes through, PoPs have trended
up notably Wednesday into Thursday with chances now around 20-25%
across south-central Arizona. QPF with this initial wave are
expected to remain on the light side with much better chances for
rain for the end of the workweek. Temperatures Wednesday are
forecast to dip below normal with highs in the low to mid 60s.
.PREVIOUS DISCUSSION...
Going into Thursday, the broad troughing will mostly push into the
center part of the country leaving a very brief period of ridging
moving through our region. However, the next weather system will
already be approaching from the northwest reaching northern
California by Thursday afternoon and then southern California
Thursday night. Guidance is still pointing at a decent AR
accompanying this trough providing much of California with a good
amount of precipitation, but there are still some questions on how
much of this moisture will reach our area going into Friday. One
disadvantage for our region is the low center is forecast to
weaken considerably as it moves eastward through northern
California into Nevada, but the base of the trough with a good
amount of energy is still expected to push through our region on
Friday. Ensemble output still shows a great deal of spread for how
much moisture and energy will move through our region, but at
least 75% of the combined GEFS and EPS members show at least some
minimal QPF for the Phoenix area.
The timing of the precip chances late week is a bit slower than
yesterday, but at the moment it looks like showers may move into
the western deserts as early as Thursday evening, lasting through
Friday morning before moving across the lower deserts of Arizona
during the daytime hours Friday. There should also be some upslope
forced shower activity developing across the Arizona higher
terrain Thursday night with the best chances seen during the
daytime hours Friday as the main frontal boundary marches through
the area. As the main front moves across southwest and south-
central Arizona, we may also see some embedded weak thunderstorms
Friday, assuming there is enough low and mid level moisture
present and frontal forcing is strong enough. We also can`t rule
out some strong gusty winds with any thunderstorms or even as a
result of the passing frontal boundary on Friday. The latest WPC
QPF show amounts upwards of 0.1" across the western lower deserts
to 0.2-0.4" across the Phoenix area. Higher amounts are likely to
be seen over the foothills areas and into the higher terrain with
amounts between 0.5-1.0" possible. Snow levels are expected to
remain fairly high (6000-6500 feet) throughout the event, so we
are not anticipating any major issues with accumulating snows at
this time.
After the main energy pushes east of our area later on Friday, we
may still have to contend with lingering shower activity across
higher terrain areas east of Phoenix into Saturday. The upper
level trough is likely to be slow to fully exit the region,
resulting in some additional shower potential through Saturday
afternoon. By Sunday, guidance favors a ridge working back into
the region from the west bringing drier conditions and a gradual
warm up into early next week.
&&
.AVIATION...Updated at 2315Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are expected during the TAF period. Winds
will continue to follow familiar light and diurnal trends, with
BKN-OVC high clouds passing over the region through tonight.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the next 24 hours. Winds
will be light as speeds aob 8 kts will be common during the
forecast. Outside of weak NW`rly winds at BLH this evening,
extended periods of variability will be observed at both terminals
through tonight and tomorrow morning. SCT-BKN high clouds will be
present during the next several hours before some clearing takes
place by mid-morning Monday.
&&
.FIRE WEATHER...
Quiet weather conditions will continue during the first part of
this week with above normal temperatures and dry conditions
lasting through Monday. A more unsettled weather pattern will then
settle in across the region for the rest of next week. Lower
humidities are expected starting today with MinRHs dropping into
the teens and lasting through Monday. Overall light winds are
expected through Monday before breezy to locally windy conditions
are likely for Tuesday afternoon. Multiple weather disturbances
are then expected to affect our region during the latter half
week resulting in continued cool temperatures, occasional breezy
winds, and higher humidities. Precipitation chances are also
looking likely by late Thursday into Friday.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Smith
PREVIOUS DISCUSSION...Kuhlman
AVIATION...RW
FIRE WEATHER...Kuhlman
NWS PSR Office Area Forecast Discussion
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