Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/19/22

Area Forecast Discussion

National Weather Service Phoenix AZ

 455 PM MST Tue Oct 18 2022

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Seasonably warm and dry weather will persist through Friday. An
area of low pressure will arrive across the West from Saturday
into Sunday. Clouds will increase, and there is a chance of rain
showers across Central and Eastern Arizona from late Saturday
through early Monday. Temperatures will turn cooler by the end of
the weekend as a dip in the jet stream overtakes the region.

&&

.DISCUSSION...
High pressure is now fully in control of the weather across
Arizona and California. A broad 500mb ridge axis, with heights
from 580-585 dam, extends from near Glacier NP south to San Diego.
Strong, cool surface high pressure sits over the Great Plains,
extending westward into New Mexico.

The anomalous surface high is bumping against relatively lower
pressures across the Colorado Desert. This will continue to
promote easterly breezes. Already today, we have had a few gusts
over 30 mph along the Gila River Valley. HRRR depicts another
nocturnal 850mb jet (ESE 30-40KT) overnight. This will mix out
early tomorrow, allowing for a few 25-35 mph gusts to reach across
the lower AZ deserts at that time. High terrain locations east of
Phoenix, above 4,000 feet and near our mountain peaks, could
experience brief gusts over 40 mph for a few hours Wednesday
morning. Bumped winds and gusts a bit above NBM deterministic to
account for this.

ACARS soundings out of Sky Harbor exhibit classic characteristics
of an upper high pressure system. A deep layer of dry, subsident
air resides above 700mb. The ridge axis moves little through
Friday. This will continue to provide sunny, warm weather through
the end of the work week. Ensemble-averaged 850mb temperatures
will peak from +19C to +20C Wednesday - Friday. This corresponds
to high temps 88-91F over the lower deserts the next three
afternoons. NBM probability of reaching 90F on Phoenix is 50-60%
Thu/Fri.

We are still tracking a significant pattern change during the
course of the weekend. A 130KT jet streak is forecast to
eventually carve out full-latitude trough over the interior West
by Sunday. A closed low offshore of California will feel the
influence of this trough, pulling it eastward as it either
weakens or becomes absorbed.

Unsurprisingly, a close look at cluster analysis revealed a few
changes from yesterday. More members now show the cut-off feature
lagging the base of the trough. +PW anomalies return for a time,
but this disjointed configuration increases the odds we will have
to rely more solely on northern stream PVA to provide ascent. A
quick comparison of the ensemble suite also shows somewhat less
available CAPE from earlier runs. The timing of the better
moisture is a little later now, centered on Sunday. The best
chance for appreciable rain is still immediately NE of Phoenix.
PoPs are holding relatively steady from before: <10% near the CO
River, 20-30% near Phoenix, 30-50% in Gila County. Drier air
overtakes the pattern beginning Monday, squelching rain chances.

500mb heights fall to near 570 dam Sunday before quickly rising
back to near 580 dam Tuesday. Temps will cool off, but not to the
extent that is expected off to our north. NBM drops MaxT`s for
Phoenix into the upper 70s to low 80s early next week; this would
be 4-7F below normal. More noticeable will be our MinT`s, with
widespread 50s now in the forecast.

&&

.AVIATION...Updated 2345Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
There is good confidence that stiff E flow will persist throughout
the period without the typical W switch on Wed afternoon. Although
wind speeds will be variable tonight and range from light to
periodically moderate and breezy with some gusts upwards of 20 kt
possible. Also late tonight into early Wed morning during the
lighter wind speed periods, some LLWS is likely to develop.
However only at KSDL does guidance favor it meeting criteria as
shown in its TAF. On Wed, winds become mostly breezy again by mid
morning with daytime gusts in the upper teens to upwards of 25 kt.
The strongest gusts are forecast during late morning to early
afternoon and again during the late afternoon to early evening.
skies will be mostly clear with occasional FEW-SCT high decks,

Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns should exist through Wed under clear skies.
Confidence is very good that winds will favor mostly light N
component and lgt/vrb at KIPL, with light to moderate N-NE
components at KBLH with breezy NE conditions during the day with
gusts of 15-20 kt. Skies to remain mostly clear.

&&

.FIRE WEATHER...
A warming and drying trend will continue through Thursday. High
temperatures will climb into the low 90s, with minimum RH`s dropping
back into the low 20s percent by Thursday. Cooling temperatures and
moistening conditions going through the weekend will bring minimum
RH`s up into the low to mid 30s by Sunday. Winds expected to be
easterly for the most part 5-10 mph with late morning to early
afternoon breezy conditions through Wednesday across the lower
deserts. Strong easterly gradient 15-25 mph expected in higher
terrain east of the Phoenix metro during this time period. Afternoon
south to southwest favored directions are expected to develop as
early as Thursday.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Heil
AVIATION...Sawtelle
FIRE WEATHER...Young