523
FXUS65 KPSR 041207
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
507 AM MST Fri Apr 4 2025

.UPDATE...Updated 12Z Aviation Discussion.

&&

.SYNOPSIS...
A slow moving weather system will continue to bring chances for
isolated light showers mainly across higher terrain areas in
Arizona through Saturday afternoon. A warming trend will begin
today and continue well into next week as high pressure builds
into the region later in the weekend into next week. Temperatures
are expected to warm to above normal starting Monday with highs
climbing well into the nineties to around 100 degrees across the
lower deserts later next week.

&&

.DISCUSSION...
Very little has changed over the past 24 hours with the upper
level trough making little headway across the region. The system
continues to support isolated light showers mainly focused across
eastern and central Arizona with the low center now situated
just to the west of Phoenix. The trough is also gradually filling
with the air mass beginning to warm, particularly across the
western deserts where highs today will likely reach into the upper
70s. The rest of the area, including Phoenix, will remain more
underneath the low center today resulting in highs closer to 70
degrees. CAMs continue to show additional light shower development
by the afternoon mainly east and north of Phoenix, but the
overall dry air in place will keep most locations from seeing
measurable rainfall. Guidance shows the low center exiting the
area to the southeast tonight, but a trailing vort max within the
western fringes of the trough is likely to provide lingering
chances of showers across eastern Arizona again on Saturday. Upper
level ridging will also quickly edge into the region from the
west on Saturday allowing highs to warm into the lower 80s across
the western lower deserts to near 80 degrees in Phoenix. An
increased gradient in between the two weather systems will also
provide for breezy to locally windy conditions from this afternoon
through Saturday afternoon across southeast California and the
Lower CO River Valley.

The ridge that builds over the region Sunday into Monday will push
H5 heights to between 577-580dm, or on the upper end of normal
for this time of year. Under generally clear skies, this will help
to boost temperatures to around five degrees above normal by
Monday as highs climb to around 90 degrees across the western
lower deserts to the mid to upper 80s in the Phoenix area. The
weather pattern will support consistent strengthening of the
ridge over the east-central Pacific and the Southwestern U.S.
through the middle of next week as H5 heights over our region are
forecast to climb to between 585-588dm. Ensembles show forecast H5
heights likely peaking next Thursday at around 588dm which would
be near record for the climatological period. As the high
strengthens over our region Monday through Thursday, the
atmosphere will heat up pushing highs into the lower 90s by
Tuesday before peaking near 100 degrees for next Thursday and
Friday. NBM deterministic forecast temperatures have shifted
slightly lower during the latter half of next week, but given that
forecast H5 heights are even higher than the March 24-26th event
that saw upper 90s for highs, we should see highs a few degrees
warmer. Eventually, a large Pacific trough is favored to shift
farther to the south just off the West Coast by next weekend. If
this occurs, it would flatten out the ridge over our region
prompting a cooling trend by around next Saturday.

&&

.AVIATION...Updated at 1205Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Light winds with some variability will continue through the
morning. Winds will tend to be out of the west at the southern
terminals (KPHX and KIWA) and out of the N/NE at the northern
terminals (KSDL and KDVT). By this afternoon westerly winds will
develop at all terminals with speeds generally aob 8 kt. Then this
evening (~00-01Z) models show a northerly outflow boundary moving
through the Phoenix Metro. Wind speeds with this outflow are
expected to be in the 10-15 kt range, wind speeds may be up into
the upper teens with the initial push of the outflow. In
conjunction with this northerly outflow VCSH has been continued in
the KSDL and KDVT TAFs. Hi-res models also show some downbursts
developing in the Metro around 22-23Z, however, confidence in
these is low so they have not been included in the TAF at this
time. A few hours after the initial push of the outflow winds are
expected to go light and variable for a few hours before
developing a light (aob 7 kt) E/NE component for the remainder of
the TAF period. Cloud decks will be SCT-BKN throughout the period
with bases aoa 9 kft.

Southeast California/Southwest Arizona including KIPL and KBLH:
At KIPL, W/NW winds will become northerly late this morning before
going back westerly this evening. Wind speeds will generally be
aob 10 kt with the exception of some occasional gusts up around 20
kt this afternoon. At KBLH, winds will be N/NW through the whole
period. Speeds will generally be aob 10 kt with gusts of 20-25 kt
this afternoon. Skies will be mostly clear with FEW-SCT mid-level
clouds this afternoon.

&&

.FIRE WEATHER...
Below normal temperatures and mainly afternoon isolated shower
chances will continue into Saturday before the warming trend
really gets going by Sunday. Due to the isolated nature of the
shower activity, the chances for wetting rainfall will remain
less than 10%. A gradual drying trend will also transpire through
this weekend as MinRHs lower from 15-25% today to around 10-15%
by Sunday. Winds are expected to increase out of the north
northwest beginning this afternoon with western district gusts
upwards of 30 mph to around 20 mph across the eastern districts.
Similar breezy conditions are expected for Saturday afternoon.
High pressure will settle back into the region by Sunday into
early next week resulting in above normal temperatures returning
and seasonably dry conditions.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Berislavich
FIRE WEATHER...Kuhlman