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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS65 KPSR 191756
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1056 AM MST Fri Apr 19 2024

.UPDATE...
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Updated 18Z Aviation Discussion.
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&&

.SYNOPSIS...
Dry conditions and above normal temperatures will prevail through
early next week. The warmest days are expected to be Sunday and
Monday, with some lower desert locations topping out in the upper
nineties. Otherwise, high temperatures in the low to mid nineties
will be common across the lower deserts through next Tuesday
before a gradual cooling trend takes hold during the latter half
of next week. A weak disturbance will pass over the Desert
Southwest today and another one likely during the middle of next
week, bringing widespread breezy conditions.

&&

.DISCUSSION...
The weather pattern across the CONUS continues to support large
scale upper level ridging which has somewhat flattened out over
the southern states to a progressive wave pattern across the
northern states and southern Canada. Our region will continue to
fall under a quasi-zonal westerly flow pattern through early next
week, but with a series of very weak and dry shortwave
troughs and ridges passing through or near the region. The warm
air mass that is already in place will stay put despite the
passage of any weak disturbances mainly due to the continuance of
the split upper level jet flow regime.

The above normal temperatures with the potential for highs
reaching into the upper 90s on Sunday and Monday is the main
forecast concern through next week. The abundant high clouds from
yesterday have now vacated the region to the east leaving
generally clear skies forecast through the coming weekend.
Temperatures will remain fairly stable today and Saturday with
highs mainly in the lower 90s to around 95 degrees as a weak
trough moving through later today will stall out the warming
trend. By Saturday night into Sunday, a shortwave ridge is
forecast to move into the region boosting H5 heights back to
around 578-580dm, while providing a bit more warming. As a result,
we should see our highs peak on Sunday and Monday reaching into
the mid to upper 90s, or 10-12 degrees above seasonal normals.
Guidance still shows up to around 20% probability for a small
portion of the lower deserts to reach 100 degrees on Sunday and/or
Monday.

Model ensemble guidance is now trending toward a Pacific trough
developing well west of California early next week before
slowly transitioning through our region during the latter half of
next week. There is still a decent amount of uncertainty with
this next weather system, but it should at least lead to a
a gradual cool down next week. The latest NBM suggests highs will
lower closer to 90 degrees by Wednesday and potentially even into
the low to mid 80s at some point late next week as the trough may
stall out over the Southwestern U.S. Any potential for rain still
looks very low at less than 10% as the system looks seasonably
dry and not all that organized. As with any typical spring weather
system for our region, we should expect to see an increase in
winds and this could be over a several day period.

&&

.AVIATION...
-- Changed Discussion --
Updated at 1750Z.

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

Winds will follow their typical diurnal patterns. A brief period
of southerly winds will precede the shift to westerly winds this
afternoon. Wind speeds will generally be aob 10 kt through the
period, although a few gusts into the low-to-mid teens are
possible this afternoon. Skies will remain mostly clear through
the period.


Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will be westerly at KIPL through the period and will remain
light through the afternoon before picking up speed this evening.
Winds will gust 25-30 kt during the evening hours and around 15
kt for the overnight hours. Wind speeds will further calm to aob 6
kt by the early morning hours and through the remainder of the
period. At KBLH, current light and variable winds will become
S/SW`rly this afternoon with occasional gusts of 15-20 kt possible
this evening. Winds will then become light and variable again late
this evening for the remainder of the period. Skies will remain
most clear.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Dry conditions and above normal temperatures will persist through
the coming weekend as lower desert highs top out each day mostly
in the low to mid 90s. Winds today will pick up during the
afternoon with gusts to around 20 mph in most locations. Winds
Saturday will continue to follow diurnal daily trends with any
afternoon breeziness in the mid teens. Min RHs will continue to
fall into the 5-15% range each day, while overnight Max RHs
mostly stay in a 25-45% range for most places. A cooling trend
is forecast by the middle of next week eventually bringing
temperatures back down to around normal or just below normal late
next week. Breezy to locally windy conditions are also expected
for much of next week with daily afternoon gusts commonly reaching
to between 20-30 mph. Humidities are likely to stay quite low
next week with daily MinRHs of 10-15% through the middle of the
week before some improvement is forecast to around 20-25% late
week as temperatures cool down.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...RW
FIRE WEATHER...Kuhlman