Scientific Forecaster Discussion
fxus65 kpsr 140551
Area forecast discussion
National Weather Service Phoenix Arizona
1051 PM MST sun Oct 13 2019
Update...updated aviation discussion.
a mainly quiet and dry weather pattern will persist
across the region through the coming week. Temperatures will remain
near to slightly above normal with highs in the low to mid 90s
through Friday before dropping to near to slightly below normal in
the mid to upper 80s on Saturday and Sunday as a dry weather systems
skirts by to the north.
a warm and dry airmass remains in place across the region today with
clear skies and maximum insolation. By mid morning surface dewpoints
around Phoenix were running 5-12 degrees higher than yesterday in
the low 30s to low 40s. Although tucson's 12z sounding was drier
than yesterday with the precipitable water down 0.25 in. To 0.40in, along with dry
west-southwesterly flow aloft. The upper air pattern shows the 500 mb
ridge axis just east of the area, a trough axis near the California coast
with southwesterly flow aloft. For this afternoon expect continued
clear skies and seasonably warm temperatures in the upper 80s to low
The mostly dry southwesterly to westerly flow aloft this week will
result in continued clear to occasionally partly cloudy skies, warm
days and mild nights. Expect near to slightly above normal warm
temperatures for most of this week with highs reaching the upper 80s
to low 90s through Monday, and the low to mid 90s from Tuesday
The shortwave trough near coastal California is slightly better organized in
the latest model runs and will move from west to east across the
region on Monday morning through Tuesday. As it approaches from now
through Monday morning a bit of a tropical moisture surge from the
sea of Cortez and adjacent areas will push north in the very low/bl
levels into SW Arizona. This will result in a slight chance of isolated
showers and/or sprinkles in the area, but especially from the
city of Yuma and southeast Imperial County to Yuma and SW Maricopa
counties, and possibly Pinal County beginning early Monday morning
and a bit into Monday afternoon. Href members are in good agreement on any
showers or sprinkles being very small and isolated with little to no
accumulations expected due to the layer of bl moisture being very
shallow and fleeting.
On Thursday afternoon a mainly dry progressive shortwave will move
into southeast California and the rest of the region on Friday bringing some breezy
conditions on Thursday afternoon and a few clouds. Slightly cooler
air will also help bring friday's and saturday's highs down closer
to seasonal norms in the upper 80s.
A progressive Pacific low pressure system will then drop through the
intermountain west on Saturday to near the 4-corners area early
Sunday. Increased cold air advection with a trailing cold front will then help drop
suday's highs to slightly below normal in the mid 80s along with
some breezy northerly winds spreading across the region. Models
are in good agreement on no rain chances with this system but
there is still significant uncertainty on how much cold air will
come with it and just how much cooler it could become.
Aviation...updated at 0551z
South-central Arizona including kphx, kiwa, ksdl, and kdvt:
Dry southwest flow aloft will keep skies generally clear at the taf
sites through Monday morning. Winds will be on the light side,
mostly 6kt or below through the taf period, weakly favoring
typical diurnal tendencies and going variable at times. Few-scattered
mid-level cumulus is possible Monday afternoon through the evening,
with bases around 8-9 kft.
There is a low-end chance for isolated convective showers during
the late morning and afternoon hours Monday, but chances should
remain confined well west of Phoenix and not be a concern to any
Southeast California/southwest Arizona including kipl and kblh:
Dry southwest flow aloft will keep skies clear at the terminals
through tonight. An increase in low-level moisture Monday morning
will yield scattered clouds across the lower Colorado River valley,
mainly east and northeast of kipl. Coverage may briefly become
broken and cigs may fall as low as 3-4 kft at kblh. With diurnal
heating, clouds should rise to ~6 kft by the afternoon. Winds will
remain light and variable through Monday morning at both
terminals. With a surface low near Yuma, kipl will likely switch
northwest in the afternoon, while kblh shifts towards the S, both with
speeds around 7 kts or less.
Aviation discussion not updated for amended tafs.
Wednesday through sunday:
a generally quiet and mainly dry weather
pattern will predominate during most of the period. Expect near to
slightly above normal high temperatures in the low to mid 90s
through Friday to drop to near to slightly below normal in the mid
to upper 80s on Saturday and Sunday. Min relative humidity percentages will stay in
the low to upper teens. Expect mainly light to occasionally moderate
southwesterly winds through Friday with breezy northwesterly winds
spreading west to east across the region on Thursday and again on Sunday
with a dry cold front. Fair to relatively good overnight recoveries will
gradually fall to barely fair by Sunday night as the slightly cooler
air drops into the region.
Spotter information statement...
spotters should follow Standard reporting procedures.