Scientific Forecaster Discussion
fxus65 kpsr 120538
Area forecast discussion
National Weather Service Phoenix Arizona
1035 PM MST Mon Nov 11 2019
a quiet weather pattern will continue to bring dry weather with
above normal temperatures and periods of high clouds this week.
Winds will generally be light except tomorrow when a weak back
door cold front moves into the region from the east. Lower Desert
high temperatures will decrease slightly from the mid 80s to lower
80s behind this front, with lows in the 50s and lower 60s.
not much has changed since the previous forecast package. The
weak closed low still remains situated over central Baja
California and continues to slowly be pushed to the south as high
pressure builds from the west. This is putting our forecast area
under northerly flow aloft and pushing moisture and cloud cover
further south. Soundings do show some lingering moisture in the
850-700 mb level mainly across south-central Arizona, and due to
this there will be a few lower-level clouds this afternoon before
clearer skies develop area-wide this evening. With drier
conditions today and mostly clear skies, expect high temperatures
to stay well above normal with most of the warmer deserts rising
into the mid and upper 80s this afternoon .
Tomorrow, while the upper low continues to weaken and remain well
south of Arizona, a back-door cold front moving in from the east
will usher in somewhat cooler conditions dropping the south-
central desert highs into the low 80s. The warmer far southeast
California deserts remain in the mid 80s for the most part. We
will also see increasing breeziness from the east spread across
most of the lower Arizona deserts during the day under sunny
For the remainder of the week, operational and ensemble guidance
continues to paint a very dry picture for our area; no precipitation
is in the picture for the foreseeable future. Naefs pops remain
virtually zero through Friday and then climb into single digits over
the weekend. Gefs quantitative precipitation forecast ensemble members show no accumulation anywhere
near US except one member grazes far southern Gila County on
Saturday with just 0.01 inches forecast. Gefs plumes for Phoenix
show a flat line for the 7 day period at 0.00 inches. Even the 90th
percentile pops from the ecmphx European ensembles stay in single
digits over the weekend as a fast moving open wave trof moves across
the deserts. Overall the changes in heights aloft really do not
translate much to the surface, as high temps Wednesday through
Sunday show very little day to day change with lower deserts staying
in the low to mid 80s each day. Phoenix ranges from 81 to 83 through
the 5 day period. A ridge builds into the area Wednesday into
Thursday but it is weak and will allow quite a bit of high clouds to
move through the ridge, for partly or even mostly cloudy skies at
times. Continued periods of high clouds persist Friday into the
weekend as the aforementioned fast moving open wave moves across the
area. Except for some variation in cloud cover, there will be little
change in the sensible weather for our area for the bulk of the
Aviation...updated at 0535z.
South-central Arizona including kphx, kiwa, ksdl, and kdvt:
persistent and occasionally gusty east winds will be the main
aviation impact through Tuesday evening under mostly clear skies.
There are some indications of a period of gusts with fropa overnight
though typically outside of terminals closer to foothill locations
(i.E. Ksdl), gusts 15-20kt may not materialize until mixing later
Tuesday morning. Some enhanced east winds above the inversion layer
(~1500 ft agl) tonight may result in marginal low level wind shear conditions,
though speeds may fall short of typical low level wind shear thresholds. Confidence
is excellent that east winds will persist the entire day Tuesday.
Southeast California/southwest Arizona including kipl and kblh:
no aviation concerns through Tuesday evening under clear skies.
Winds will be light and variable for prolonged periods, but will
generally favor a west component at kipl and a north/NE component at
Wednesday through sunday:
relatively dry conditions will persist through the period with
increasing high pressure aloft through the work week. Temperatures
will cool slightly as a back door front moves into Arizona on
Tuesday, but will still be a few degrees above normal with highs in
the lower 80s over the lower deserts. Easterly wind gusts up to 25
mph will be possible over south central Arizona on Tuesday, with
light winds following diurnal trends expected for the rest of the
week. Minimum relative humidity values will fall into the mid to
upper teens each day across southeast California and southwest
Arizona while remaining above 20 percent over south central Arizona.
Spotter information statement...
spotters should follow Standard reporting procedures.