Scientific Forecaster Discussion
fxus65 kpsr 230013
Area forecast discussion
National Weather Service Phoenix Arizona
513 PM MST Tue Oct 22 2019
Update...updated aviation discussion.
dry conditions with mostly sunny skies will persist through the
weekend. High pressure over the eastern Pacific will result in a
warmup through midweek. Temperatures will peak today and
Wednesday with highs in the low 90s across the lower deserts.
Temperatures should cool slightly beginning Thursday through the
weekend in response to a trough passing by to the northeast. A
stronger trough pattern across the western U.S. Early next week
should bring the coolest temperatures of the season.
the current dry, tranquil weather pattern will continue allowing
for clear skies and slightly above normal temperatures to persist
over the next couple of days. Storm Prediction Center mesoanalysis this afternoon
shows a strong high pressure system over the eastern Pacific
resulting in dry northwesterly flow aloft over the Desert
Southwest. A slight eastward shift in the ridge today will result
in warmer temperatures today and tomorrow with temperatures
topping out in the low 90s across much of the lower deserts this
afternoon and tomorrow afternoon.
Operational and ensemble guidance solutions begin to diverge
going into the latter half of the week in regards to an
approaching trough. Operational European model (ecmwf) continues to toy with the
idea of a trough digging into New Mexico before developing into a
cut-off low. Euro guidance shows a notable difference in
temperatures compared to GFS and NAM guidance with Euro ensemble
means showing highs in the low 80s for Phoenix Thursday through
Saturday. GFS and NAM guidance are in better agreement with each
other in digging the trough into northern New Mexico before
ejecting off toward the east. This seems to be the more likely
solution. Right now, continue to go with nbm temperatures, which
keeps temperatures in the mid to upper 80s Thursday through the
end of the week.
Behind the trough, an upstream area of high pressure over the
eastern Pacific will shift to the southwest while simultaneously
weakening as it approaches the region. Meanwhile, a more
impressive longwave trough with multiple embedded shortwaves looks
to dig down from the Pacific northwest early next week, resulting
in much lower temperatures. The first piece of energy to dig into
the southwest Continental U.S. May even bring a small chance of rain but
there is much uncertainty this far out.
Aviation...updated at 0013z
South-central Arizona including kphx, kiwa, ksdl, and kdvt:
light diurnal winds will prevail as high pressure persists along
the West Coast. Northwesterly winds aloft may advect smoke from
distant Forest fires into the Phoenix area producing slant
visibility issues Wednesday morning. Otherwise, mostly clear skies
can be expected.
Southeast California/southwest Arizona including kipl and kblh:
diurnal winds will prevail as high pressure persists along the
West Coast. Wind speeds will generally remain below 10 kt at both
kipl and kblh through Wednesday evening.
Aviation discussion not updated for amended tafs.
Friday through tuesday:
Continued dry conditions with slightly above normal temperatures
and periodic breezy conditions are expected through the period.
Temperatures begin to settle into the mid to upper 80s by Friday
and for most of the remaining period. Breezy conditions on
Thursday begin to taper off on Friday as the responsible weather
system moves off toward the east. Breezy conditions begin to
decrease Friday with light diurnal tendencies favored for the
weekend. Expect min relative humidity values to stay mainly in the 6-12 percent
range across the lower deserts through Saturday and then bump up
into the teens by Sunday.
Spotter information statement...
spotters should follow Standard reporting procedures.