Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 222139 CCA
AFDPSR

Area Forecast Discussion...CORRECTED
National Weather Service Phoenix AZ
239 PM MST Sun Apr 22 2018


.SYNOPSIS...
Gradual additional warming can be expected the next several days
with highs approaching 100 degrees at many lower desert locations
by Thursday. Some modest cooling is anticipated by the end of the
week.

&&

.DISCUSSION...
Very weak upper low centered over southern AZ this afternoon. A
vort lobe rotating around the southern end of it was helping to
kick off some isolated weak showers over southeast Arizona.
With such dry low levels, precip likely not reaching the ground.
The low will damp out quickly as it gets kicked eastward by a more
significant trough to the northwest. Though the ridge has been
temporarily flattened, the affects are pretty much limited to
higher altitudes as surface warming has continued today. The ridge
rebounds Monday and expect a little bit more warming yet. A weak
disturbance, embedded within southwesterly flow aloft, moves in
Tuesday bringing a batch of high clouds but no other discernible
impact. In fact, ridging over the western CONUS amplifies
Wednesday into Thursday aided by a deep upper low off the West
Coast. Thursday may be our warmest day with many locations in the
upper 90s to near 100.

Forecast confidence starting Friday drops considerably due to the
potential deep Pacific low models keep advertising. Models are in
good agreement with the low developing off the West Coast during
the middle part of the week and keeping the low fairly stationary
through Thursday, possibly into Friday. Model spread increases
starting Friday into next weekend with considerable differences
between the European and GFS operation runs and ensemble means.
Given the propensity of models being inaccurate with these deep
lows, forecast temperatures starting next Saturday are mostly a
blend between two extremes. If the Pacific low end up lifting
northeast missing our region completely, temperatures will remain
well above normal. On the other hand if the low ends up close to
or into the Desert Southwest, then temperatures will dip closer to
normals and we will have to contend with another windy system.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL and Southeast
California/Southwest Arizona including KIPL and KBLH:

No aviation concerns exist through our TAF period as only a FEW to
SCT high clouds will pass by.  For the Phoenix area terminals,
diurnal winds will prevail with speeds generally staying at or below
10 kts. Further west at KBLH, southerly winds will develop each
afternoon with light northerly drainage winds possible for a few
hours overnight (10-15Z). Typical diurnal tendencies are expected
at KIPL with speeds at or below 10 kts.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
Well above normal temperatures continue through Friday before modest
cooling arrives over the weekend. With the cooling however, comes
more significant breeziness. At this time, no critical fire weather
thresholds are anticipated.


&&

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

&&

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

$$

DISCUSSION...AJ/Kuhlman
AVIATION...Wilson
FIRE WEATHER...AJ



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