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490
FXUS65 KPSR 060937
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
237 AM MST Mon May 6 2024

.SYNOPSIS...
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A dry weather pattern is expected all week with a nearly
stationary low pressure system situated just to the north of the
region. This will bring temperatures back to around normal by
Tuesday, lasting through the majority of the week, as well as
breezy conditions each afternoon.
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&&

.DISCUSSION...
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The upper level low that moved across northern portions of the
region yesterday is now ejecting northeastward into the Central
Rockies before reaching the Northern Plains later today. However,
the Desert Southwest is expected to remain under broad troughing
aloft over the next several days, possibly the entire week. For
today, the cooler air mass that moved in on Sunday will still be
enough to keep temperatures 3-5 degrees below normals. However,
starting Tuesday gradual air mass modification and a slight boost
in heights aloft will begin to bring some warming resulting in
readings closer to seasonal normals.

Going into the middle of the week, the upper level trough is
forecast to become more elongated with a piece of energy moving
northeastward into southern Canada and another retrograding
westward back into the Central Rockies to as far west as the Great
Basin. A secondary shortwave trough is also seen tracking from
just northwest of Washington today reaching the Great Basin on
Tuesday. This will help to increase the gradient over our region
on Tuesday, lasting through Wednesday leading to another round of
breezy conditions and daytime gusts upwards of 25-30 mph over the
higher terrain east of Phoenix on Tuesday and over the majority of
the area on Wednesday.

As our region sits just south of the broad upper level low into
the latter part of the week, temperatures will remain fairly
stable through around Thursday or Friday. This should keep
readings right around normal with highs ranging from the upper
80s to the lower 90s across the lower deserts. Eventually by next
weekend, the upper low will weaken enough that it will no longer
keep our temperatures from warming or it will get pushed to the
east by an incoming ridge that will be slowly approaching the
West Coast. Ensemble guidance is still a bit murky with this
eventual evolution and it seems more than likely the ridge will be
in a weakening phase by the time it impacts our region. NBM
temperature guidance does show a decent warming trend next weekend
into early next week with widespread mid to upper 90s highs over
the lower deserts and at least some potential for the warmest
lower deserts to hit 100 degrees early next week.
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&&

.AVIATION...
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Updated at 0550Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Westerly winds prevailing well into the overnight hours will be the
greatest weather issue under clear skies. Forecast confidence is
very good that winds will continue to weaken with a west component
persisting much later into the overnight than is typical. Some
locations (such as KPHX) potentially may never truly switch to the
traditional morning easterly wind forcing runway configurations to
remain the same throughout the period. Regardless, widespread
westerly winds will prevail over the entire metro again by late
morning with only limited afternoon gusts.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather concerns should exist through Monday evening under
clear skies. Any lingering wind gusts should quickly weaken
overnight with trends in directions veering to a more N/NW
direction. Wind speeds should weaken even further during the day
with moderate confidence of becoming more variable in direction by
the afternoon.
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&&

.FIRE WEATHER...
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Drier conditions and overall light winds are expected today as
MinRHs drop to around 10% this afternoon. The weather pattern into
the middle of the week will lead to another round of breezy
conditions starting Tuesday with afternoon gusts commonly
reaching to around 20 mph to as high as 25 mph in some locations.
Temperatures will warm back to around seasonal normals going into
the middle part of the week with highs as warm as the lower 90s
across the lower deserts. MinRHs will stay near 10% through at
least mid week across the lower deserts to around 15% over higher
terrain areas, with overnight recoveries between 20-40%. Weak
high pressure is expected over the region through the rest of the
week as temperatures return to slightly above normal by the
weekend. Winds during the latter half of the week will return to
more typical seasonal trends with daily afternoon gusts up to
around 20 mph.
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&&

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

$$

DISCUSSION...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman