Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 270036
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
536 PM MST Sun May 26 2019

.UPDATE...

Updated Aviation section.

&&

.SYNOPSIS...
Another strong low pressure system will slowly move through the
region today into Monday bringing breezy to windy conditions
today along with a big cool down. High temperatures on Memorial
Day are forecast to be around 20 degrees below normal. A warming
trend will then take place during the middle part of the week with
temperatures returning to just shy of normals for the latter half
of the week.

&&

.DISCUSSION...
Upper-level low pressure system continues to dive south and is
currently centered over central California. This low will inch a
little bit further south today before weakening and moving east.
The center of this system will track just north of our forecast
area late tonight through tomorrow afternoon before quickly
skirting off to the northeast.

Earlier this morning, a shortwave circulating around the low and
it`s associated surface front moved across the western portion of
our cwa before stalling out in Central Arizona. Another, stronger
surface cold front, associated with the main low pressure system
will move east across our western CWA this afternoon and across
the remainder of our forecast area tonight and tomorrow morning.

Heights will continue to fall this afternoon ahead of the main
low and continue to enhance the surface pressure gradient. This
has resulted in gusty conditions area wide today, with the
strongest winds west of the Colorado River (CR) Valley (Wind
Advisory for portions of southeast California through this
evening). Gusts to 25-35 mph can be expected in southwest and
south-central Arizona and gusts to 30-40 mph can be expected along
and west of the CR. In addition, with these gusty conditions, we
can anticipate the possibility for patchy blowing dust today.

Isolated showers will be possible as the second cold front moves
through the area, however the greatest chances will be along the
northern fringes of our forecast area as well as in south-central
Arizona. Hi-resolution models support this with the HREF showing a
line of isolated activity moving across the eastern half of our
forecast area early tomorrow morning. Thus, PoPs were raised
tomorrow during the 11 pm - 11 am time frame. Any precipitation
accumulation will remain on the light side and minimal impacts
are expected with this system. Lowering heights and cooling aloft
will allow for some cooling of the boundary layer today with highs
dropping back into the lower to middle 80s across the lower
deserts.

By Monday afternoon, clouds will be thinning out with pretty
pleasant temperatures for this time of year. Highs are forecast to
only rise into the upper 70s (20 degrees cooler than normal and
potentially the coolest Memorial Day on record). Winds will be
weaker tomorrow, but some residual gustiness will be in place
across the entire forecast area (greatest gusts along the higher
terrain).

The western U.S. trough and eastern U.S. ridge pattern will
largely remain intact through the rest of the week, but the upper
level jet will weaken considerably over the eastern Pacific and
western U.S. during the week. This will still result in weak
troughing over the Desert Southwest this week, but heights aloft
will increase to near climatological averages for the period.
Much warmer temperatures will be seen by the middle of the week
with highs topping out in the middle 90s by Thursday and
remaining just a few degrees below normals through the upcoming
weekend. No organized shortwaves are seen affecting our region
after Monday, so winds will be on the lighter side and skies will
be clear to mostly clear.

&&

.AVIATION...Updated at 0030 UTC.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

A low pressure system centered over northern CA as of 00Z will
move east and southeast becoming centered near Lake Powell by 00Z
Tuesday. A batch of thick mid and high clouds with embedded light
showers/sprinkles will brush northern Maricopa County tonight
followed by the passage of a subtle cold front well after
midnight. This latter feature will lead to lower cloud bases but
still anticipate ceilings to be AOA FL080. Higher mountain tops
north and east of metro Phoenix could be obscured. Clearing starts
from west to east by 15Z-16Z. Strong southwest and west flow aloft
will continue through the period. Surface winds will continue to
favor southwest and west directions through the night and during
the day Monday. Anticipate gusts of 15-25 kts as late as 07Z-
08Z. Otherwise, speeds will begin to weaken after 03Z.

Southeast California/Southwest Arizona including KIPL and KBLH:

A low pressure system centered over northern CA as of 00Z will
move east and southeast becoming centered near Lake Powell by 00Z
Tuesday. A batch of thick mid and high clouds with embedded light
showers/sprinkles will continue tracking over eastern Riverside
and La Paz County this evening before thinning out. There will be
a subtle cold front that passes through between about 05Z-09Z
midnight. This latter feature will lead to lower cloud bases AOA
FL080 but anticipate they will be scattered in nature. An
exception would be northern La Paz County where BKN-OVC layers may
occur. Higher mountain tops north and east of metro Phoenix could
be obscured. Clearing starts from west to east by 10Z-11Z. Strong
southwest and west flow aloft will continue through the period.
Surface winds will continue to favor southwest and west directions
through the night and during the day Monday. Winds will be
strongest west of the Lower Colorado River Valley - especially
over Imperial County where gusts of 30-40 kts as late as 05Z-
06Z. Otherwise, speeds will begin to weaken after 05Z.



Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday:
A warming and drying trend will begin Wednesday lasting into at
least the weekend. Thursday through Sunday, minimum RH values over
most of the lower deserts will range between 10 and 15 percent,
and high temperatures will reach the mid to upper 90s over warmer
desert locations. Overnight RH values will reach the 25-45% range
each night for most locations. Wind will be on the light side
during the five day period, tending to follow south to southwest
directions during the afternoon hours with speeds mostly below
15kt.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard operating procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until midnight PDT tonight for CAZ560-564-566-567.

     Wind Advisory until 5 AM PDT Monday for CAZ562.

&&

$$

DISCUSSION...Hernandez/Kuhlman
AVIATION...AJ
FIRE WEATHER...Hernandez



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