Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 250401
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
901 PM MST Tue Apr 24 2018

.UPDATE...Updated Aviation discussion.

&&

.SYNOPSIS...
Very warm and dry conditions will last into the coming weekend
with periods of high clouds. Lower desert high temperatures will
reach into the middle to upper 90s each day, or roughly 10 degrees
above normal. Some modest cooling is possible this weekend, but
above normal temperatures should still persist. A slight chance
for showers will exist across southern Gila County Friday and
Saturday afternoon as a weak storm system moves across the area.

&&

.DISCUSSION...
Upper ridge across the western United States is becoming deformed
by a positively tilted trough moving across the Central Plains.
High clouds are streaming north-northeastward from the eastern
Pacific and northwest Mexico, and will bring intermittent cloud
cover across the region for the next 24 hours or so. The primary
impact for the next few days will remain the seasonably warm
temperatures, with daytime highs continuing to reach the upper
90s through this weekend. The hottest day currently appears to be
Thursday, with Phoenix forecast to reach a high of 99 degrees
(about 10 degrees above normal). Records are above 100 each day
this week in Phoenix and Yuma, so currently not anticipating those
to be broken.

Still looking at a modest increase in moisture Friday/Saturday
from New Mexico in the wake of a progressive shortwave moving
across the central U.S. Precipitable water values are expected to
be under one inch, but still above climatological values for the
year. Most of the moisture appears to be confined to the mid-
levels, so any precipitation that does occur will remain on the
light side. However, enough destabilization should occur each
afternoon to support a slight chance of thunderstorms across
southern Gila County both Friday and Saturday afternoon. Weak
westerly steering flow will keep any thunderstorms/precipitation
away from the lower deserts, but can`t rule out a weak outflow
boundary or two progressing eastward off the higher terrain. There
may also be elevated fire weather concerns related to lightning
strikes across the higher terrain (see fire weather discussion
below for more details).

Into early next week, mean troughing looks to persist across the
Southwest and will moderate temperatures closer to seasonal
normals. Also can`t rule out some low chances for precipitation
during this period as a closed low potentially develops somewhere
over the region, but confidence in this is low given
climatological norms and the meager moisture available.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Essentially a persistence forecast with no aviation weather
impacts expected. Light diurnal winds will prevail at all TAF
sites through at least Wednesday evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will retain a southerly component through the period at
KIPL/KBLH with speeds generally remaining below 10 kt.

Aviation Discussion not updated for amended TAFs.

&&


.FIRE WEATHER...
Friday through Tuesday... Very warm temperatures will continue on
Friday. A weak weather disturbance and modest increase in moisture
aloft will yield a slight chance of thunderstorms across southern
Gila County. Dry boundary layer conditions and fuels may support
an elevated threat for lightning ignitions, with rainfall totals
expected to remain lights. Gusty outflow winds are also possible.
Slight chance of thunderstorms will continue on Saturday
afternoon, but should remain confined to the far eastern portions
of southern Gila County. Afternoon breezes will be possible each
day, especially into Tuesday, with surface conditions likely to
remain dry.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters are encouraged to follow standard reporting procedures.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Hirsch
FIRE WEATHER...Rogers



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