000
FXUS65 KPSR 211111
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
411 AM MST Sat May 21 2022

.UPDATE...Updated Aviation Discussion...

&&

.SYNOPSIS...
A low pressure system will stay positioned just to the north of
the region through early next week, keeping temperatures near
normal while skies remain generally clear. As high pressure
spreads over the region during the latter half of next week, a
warming trend will push highs across the lower deserts above 100
degrees by around Wednesday and likely at or just above 105
degrees late next week.

&&

.DISCUSSION...
Very little change in the weather pattern is expected over the
next several days as broad upper level troughing will remained
positioned over the majority of the Western U.S. The bulk of the
energy and cooler air associated with the trough will stay well to
our north, but we have already seen some cooling from the
dampened heights aloft and will see high temperatures bottom out
today in the lower 90s. The pressure gradient across the region is
relaxing as the trough weakens, but some additional breezy
daytime conditions will be seen over the next several days.

As the trough weakens and slowly begins to shift more toward the
northeast Sunday into early next week, we will see a slight bump
in temperatures but highs will stay around or maybe a couple
degrees above normal through Monday and likely stay sub 100
degrees through Tuesday. Overnight lows should be quite
comfortable with most locations seeing readings well down into the
60s each night through early next week.

Eventually, model ensembles are adamant on another ridge building
over our region from the southwest, but at least model trends have
slowed it down by around a day. The ridge should quickly build
over the region beginning next Wednesday before 500mb heights peak
somewhere around 588dm next Thursday (just below the 90th
percentile of climo). NBM temperature guidance shows a quick warm
up Wednesday into Thursday with highs likely climbing to around
105 degrees, possibly as warm as 107 degrees. Compared to last
night`s model runs, temperatures are not quite as warm for next
Thursday and Friday and have somewhat backed off on the potential
for temperatures reaching excessive heat criteria. Fortunately,
ensembles generally favor the ridge to be short-lived as another
trough is likely to drop out of the northern Pacific before
shifting over the Western U.S. at some point into the following
weekend. If this were to occur, we should see some cooling over
Memorial Day weekend, but its unknown whether it would be enough
to drop lower desert highs below 100 degrees.

&&

.AVIATION...Updated at 1110Z.

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

Winds are light this morning over the metro terminals. Surface
directions will be difficult to pin down through around 15Z at
IWA/PHX. KIWA 88D is sampling a 25KT southerly LLJ at 4KFT. This
is fighting against the usual valley drainage flow. Once mixing
gets going, the quasi-stationary front to our north and pronounced
thermal low over the Colorado Desert will promote another bout of
slowly veering S to SW winds which will gust from 15-25KT through
the afternoon and early evening. Winds slacken off after 3Z and
another period of variability is possible Sunday morning, though
hi-res guidance is currently a little more optimistic on a
pronounced easterly switch around 9Z. Mostly clear skies prevail;
can`t rule out some additional dust being lofted this
afternoon/evening.

Southeast California/Southwest Arizona including KIPL and KBLH:

Jet streak and fairly sharp, though stationary, surface front are
well north of the terminals. Meanwhile, a thermal low is sitting
essentially overhead. Skies in this pattern remain mainly clear.
Winds from the S at BLH today with 15-20KT afternoon gusts. IPL
will remain light and SE for much of the day before sundowner
westerlies approach 15-20KT this evening.

&&

.FIRE WEATHER...
A weather system positioned north of the region will slowly lift
to the northeast through early next week. This will keep
temperatures near normal, while also providing for some daily
afternoon breezes up to 20 mph. Humidities today will remain
somewhat elevated with MinRHs between 15-20%, but with drying over
the region starting Sunday, MinRHs will drop back to around 10%.
High pressure will eventually build back over the region by the
middle of next week leading to a warming trend and temperatures
climbing well above normal later next week. A slight increase in
winds also looks possible late next week with a return of
afternoon gusty winds above 20 mph. The weather pattern will also
keep dry conditions in place through the end of next week with
MinRHs generally between 5-10% and MaxRH values commonly between
20-35%.

&&

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

$$

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DISCUSSION...Kuhlman
AVIATION...Heil
FIRE WEATHER...Kuhlman

NWS PSR Office Area Forecast Discussion