Area Forecast Discussion
Issued by NWS Phoenix, AZ

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883
FXUS65 KPSR 181131
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
431 AM MST Fri Oct 18 2019

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Dry and generally sunny conditions will persist across the region
through next week. A passing low pressure system and associated cold
front will drop temperatures sharply today with highs falling into
the mid to upper 80s over the lower deserts. It will also remain
breezy from the north over the deserts west of Phoenix. Additional
dry weather disturbances will keep temperatures near seasonal norms
Saturday through early next week. A warming trend can be expected
again by Tuesday next week as highs climb back into the low to mid
90s.

&&

.DISCUSSION...
Early this morning, a fast moving open wave trof continued to dive
southeast and into western Arizona; the system brought breezy
conditions to the western deserts yesterday and we are still seeing
winds over 50 mph in far SW Imperial County (Mountain Springs Grade)
as of 2 am. IR imagery showed a few mid clouds over high terrain
east of Phoenix but otherwise skies were clear. Surface dewpoints
were a bit elevated over the lower central deserts, ranging from
upper 30s to low 50s. Latest 00z plots showed 571dm heights over far
southern Nevada; heights over the central deserts will drop well
below 580dm this afternoon and we can expect highs over the lower
deserts to fall sharply and into the mid to upper 80s this
afternoon. Heights were nearly 589dm a couple days ago when Phoenix
reached 98, so a fall of at least 120m should allow highs to fall
over 10 degrees from that mark today.

The Wind Advisory for far SW Imperial county will be extended until
5am today given the strong gusty winds still occurring at Mountain
Springs Grade. Will leave the advisory in place until 10 am for
Joshua Tree NP although conditions are really quite borderline at
this time.

After the low pressure trof quickly moves off to the east today, a
rather zonal west to northwest flow aloft will settle in over the
desert southwest through the weekend and into early next week. By
Sunday flow amplifies as a deep upper trof develops to our east and
over the central CONUS, but we will simply see dry northwest flow
aloft and sunny days/clear nights. Given the proximity to the deep
trof to our east, high temps will stay nearly unchanged through next
Monday as the lower deserts continue to see mid to upper 80s
readings.

As we move through the early and middle part of next week,
operational and ensemble guidance remains consistent in calling for
ridging aloft to build inland and into the desert SW, with 500mb
heights climbing to around 590dm by late Monday and Tuesday. ECMPHX
ensemble MOS continues to give 50th percentile high temps from 91 to
93 for next Tuesday and Wednesday, and if heights come close to what
is forecast, low to mid 90s seems a pretty good bet for our warmer
deserts. For now we will continue to call for highs 91-92 in Phoenix
next Tuesday through Thursday under continued sunny skies. Still no
rain in sight for the foreseeable future as the very dry weather
pattern persists across the area.

&&

.AVIATION...Updated at 1130Z

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No significant aviation weather concerns for today. The westerly
shift is expected to occur earlier than normal, between 16Z-18Z,
this morning. Wind speeds will be fairly light mostly at or below
10kts through the TAF period. Wind directions will remain westerly
through the day before becoming easterly again Friday night
around 5Z-7Z.

Southeast California/Southwest Arizona including KIPL and KBLH:
Wind speeds will be significantly weaker than yesterday mostly
between 10-15 kts. Some stronger gusts upwards of 20-25 kts may
occur at KBLH during the early afternoon before tapering off by
the evening. Otherwise, winds will maintain a mostly westerly to
northwesterly direction.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Sunday through Thursday:
A dry weather pattern with a developing warming trend is expected
during the period. Expect near normal high temperatures in the upper
80s through Monday to warm to above normal by Tuesday with highs
reaching the low to mid 90s. Breezy northerly to northwesterly winds
on Sunday with a dry weather system will begin in SE CA and spread
east into remaining areas by the late afternoon with gusts of 20-25
mph. Breezes will linger on Monday with mostly light winds expected
thereafter.  Expect min RH values to stay mainly in the 7-12 percent
range across the lower deserts. Fair overnight recoveries through
Wednesday night will fall to poor by Thursday night.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 5 AM PDT early this morning for CAZ562.

     Wind Advisory until 10 AM PDT this morning for CAZ560.

&&

$$

DISCUSSION...CB
AVIATION...Deems
FIRE WEATHER...Sawtelle



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