Scientific Forecaster Discussion
fxus65 kpsr 202045
Area forecast discussion
National Weather Service Phoenix Arizona
145 PM MST Thu Jun 20 2019
Synopsis... a weak weather disturbance slowly passing by to our
north through Saturday will bring breezy conditions and a slight
cool down into the weekend. This will result in below normal
temperatures and highs mostly in the upper 90s to around 100
degrees this weekend. High pressure will slowly build across the
region next week leading to temperatures warming back to around
normal readings while dry conditions prevail.
there has been little appreciable change to the forecast. With clear
skies, daytime temperatures will warm to near seasonal normal
values this afternoon. The well anticipated upper level low is
clearly seen pushing south-southwest through the Pacific northwest
on the upper-level water vapor channel of the GOES-17 satellite.
While the core of this system will remain to our north, we will
see a tightening of the pressure gradient that will translate to
breezy conditions. Stronger gusts are already impacting the
Mountain Springs grade in southwest Imperial County with gusts
over 40 mph but we will see the spread of gusts across Imperial
County and Joshua Tree National Park through this afternoon with
gusts in excess of 30 mph. Western and south-central Arizona,
including Phoenix, will see some breezes this afternoon as well.
However, stronger gusts will impact the Arizona desert Friday
afternoon as the aforementioned upper low penetrates into the
intermountain west. Expect lingering breezes Saturday and Sunday,
particularly across the higher terrain north and east of Phoenix.
Aside from the wind, atmospheric heights will decrease to
unseasonable levels as the trough broadens across the west
through the weekend leading to a cooling trend with high
temperatures dropping 5-7 degrees below normal. General trough
conditions persist into next week but even with modest height
rises and clear skies, temperatures will again approach normal.
Long range ensembles are not producing a clear signal but there
are hints at the return of the subtropical high building into the
southwest near the end of the month with some moisture seeping
into eastern Arizona. In the meantime, our area will remain dry
and fairly seasonable all things considered.
Aviation...updated at 1814 UTC.
South-central Arizona including kphx, kiwa, ksdl, and kdvt;
Southerly Crosswinds this morning will remain below 10 kts before
transitioning to a westerly component this afternoon. Periodic
gusts up to 20 kts will be possible into the afternoon, tapering
off this evening. Otherwise, sky clear conditions prevail through the
taf period as dry westerly flow aloft persists.
Southeast California/southwest Arizona including kipl and kblh:
Breezy to windy conditions are expected this afternoon into the
evening with gusts reaching up to 25-30 kts at the terminals. At
kipl, southerly winds this morning will give way to a westerly
component while kblh maintains a S/SW component. Gusts taper off
later tonight with sustained speeds falling to around 10 kts.
Otherwise, sky clear conditions prevail through the period as dry
westerly flow aloft dominates.
Aviation discussion not updated for amended tafs.
Sunday through thursday:
no significant change to the forecast outlook...cooler
temperatures through this weekend will eventually give way to a
steady warmup to near seasonal temperatures next week. Daytime
humidity values will still remain near 10% each afternoon with
overnight recovery into the 20-30% range. Gusty winds will remain
a concern through Sunday, especially across the tonto nf and rim
area, with gusts upwards of 20 mph. Winds should follow typical
diurnal trends through much of the period.
Spotter information statement...
spotter activation is not expected.
California...Wind Advisory until 11 PM PDT this evening for caz560.
Wind Advisory until 2 am PDT Saturday for caz562.
Wind Advisory from 2 PM to 11 PM PDT Friday for caz564>567.