535
FXUS65 KPSR 270525
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1025 PM MST Fri Apr 26 2024

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
Breezy to windy conditions are expected through this evening with
the highest wind gusts up to 40 to 50 miles per hour expected in
southeast California as a weather system moves through the region.
There will also be a slight chance for rain showers and a few
thunderstorms this evening in south-central Arizona, mainly north
and east of the Phoenix metro area. The weather system will depart
through Saturday, but still with some lingering breezy conditions
before high pressure sets in late this weekend and temperatures warm
back into the nineties next week.

&&

.DISCUSSION...
Very breezy and windy conditions are already occurring across the
region. The elevated wind speeds and gusts will continue and
strengthen in some areas through this afternoon and evening as an
upper level jet max passes over southern CA and AZ and as afternoon
mixing increases. The dynamic synoptic pattern driving today`s
weather is detailed well in the air mass satellite product from GOES-
West, with the strong upper level jet evident extending northwest
through CA and out into the Pacific. Also evident is a vort max
southwest of Vegas. This vort max is expected to track eastward
through this evening through Central AZ and help generate convection
across the region, with slight chances (20-30%) in the AZ lower
deserts.

As previously mentioned, a vorticity maximum at the base of the
shortwave trough is expected to track pretty much due eastward
across central AZ later this afternoon through this evening,
triggering elevated convection in the region. The exact track looks
to be along the northern county borders of of La Paz and Maricopa
counties. This track will keep most of the convection over the
northern half of AZ. However, the dynamic forcing will still be
close enough to bring slight chances for rain and thunderstorms (10-
30%) to portions of the lower deserts, including Phoenix. There is
some uncertainty how far south the convection will extend, but it is
conceivable for the convection to extend south through all of
Phoenix. The convection will be fast moving, moving westward upwards
of 35-45 mph, given the strong winds above the surface. So, do not
expect much more than a brief (10 min or less) downpour. As
mentioned, the environment will be suitable for isolated
thunderstorms, which will pose a lightning threat and strong gusty
wind threat. Any storm in South-Central AZ this evening could
produce localized wind gusts over 40 mph. HREF conditional
probability of wind gusts over 35 mph in the vicinity of convection
this evening is upwards of 50-70%. Main timing of convection in
South-Central AZ will be between 6 PM - 12 AM MST.

On Saturday, the trough will quickly move northeastward towards the
central Rockies. There will still be some residual breeziness, but
noticeably lighter compared to today as peak gusts area wide are
expected to remain under 30 mph. There will also be some additional
afternoon convection Saturday, but the activity is expected to
remain just to the north and east in the AZ higher terrain. Once the
trough has fully cleared the Desert Southwest, the ensemble model
guidance is in good agreement of low amplitude ridging developing
overhead through next week with dry and tranquil conditions
prevailing.

Under the influence of the troughing feature, high temperatures
today and Saturday will remain below normal with highs across the
lower deserts topping out in the low to mid 80s. Beginning on Sunday
and continuing through early next week, as high pressure builds over
the region, temperatures will be on a strong warming trend. High
temperatures on Sunday will rise back up to near normal levels with
readings in the mid to upper 80s before rising further into the low
90s on Monday and then into the mid to upper 90s by Tuesday. Not
much change in temperatures is expected during the middle to latter
half of the week with readings remaining steady state, in the mid to
upper 90s, with a low chance (10-20%) that some areas, including
Phoenix, reach 100 degrees.

&&

.AVIATION...Updated at 0525Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds will be the primary weather issue through Saturday night as
isold SHRA/TSRA and associated 080-100 AGL cigs currently skirting
the far northern parts of the Phoenix metro quickly exit the region
around midnight. Low forecast confidence exists regarding exact
evolution of winds overnight given the effects of the SHRA creating
oscillations between a NW and SW component, but model evidence
continues to support a lack of the traditional easterly switch
overnight. Renewed gusts around 20kt should be common across the
area Saturday afternoon with more usual directional/speed behavior
resuming Saturday evening.


Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty winds will continue to be the primary weather concern through
Saturday evening under mostly clear skies. W/SW winds should
continue to gust above 25kt at KIPL into the overnight hours with
less gustiness at KBLH. Through the mid/late morning, trends among
forecasts suggest a veering to a NW direction during daylight hours
Saturday. Periodic gusts may resume Saturday afternoon and evening
though forecast confidence regarding the duration of stronger gusts
is low.

&&

.FIRE WEATHER...
On Saturday, winds will trend downward with peak gusts of only 20-30
mph. Rapid drying will result in lower MinRHs Saturday, down to 10-
20% most areas. Temperatures tomorrow will remain below normal with
highs only topping out in the low to middle 80s across the lower
deserts. Thereafter, a significant warming trend takes place Sunday
through early next week with little change in temperatures expected
by the middle and latter half of the week. With the warming trend,
RH values will trend downward with MinRHs bottoming out at around 10-
15% starting on Monday. Winds through most of next week will be
lighter with the typical afternoon upslope breeziness expected.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory until midnight MST tonight for AZZ532.

CA...Wind Advisory until midnight PDT tonight for CAZ560-563-565>567.

     Wind Advisory until 5 AM PDT Saturday for CAZ562.

&&

$$

DISCUSSION...Benedict/Lojero
AVIATION...18
FIRE WEATHER...Benedict/Lojero