Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/13/20

Area Forecast Discussion

National Weather Service Phoenix AZ

 515 PM MST Sat Sep 12 2020

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Temperatures will warm this weekend and end up slightly above normal
by Sunday. High temperatures Sunday through much of next week will
run about five degrees above normal. Dry conditions will continue
for at least another couple days with only a slight chance of storms
over higher terrain areas Sunday and Monday. Periods of hazy skies
will continue for several days due to elevated smoke from wildfires
across the West.

&&

.DISCUSSION...
The UL anticyclone is working inland and is now centered over NW NV
with dry westerly flow aloft just south of a weak trough axis
cutting across N-central AZ. The high pressure system coincides with
a warm, dry airmass across the western states and into the
Southwest. The 12Z Phx sounding and a 16:30Z ACARS sounding are
significantly dryer than normal, both with a PWs of 0.61. Midday
satellite imagery continues to show a pronounced plume of elevated
smoke/haze continuing to drift into AZ from S CA and N Baja.
Additional thick smoke from central CA wildfires is seen diverting
to the west and northwest away from the region along the
southwest and western flank of the Great Basin high. The thin
layer of haze was reported by a midday pilot on approach to Sky
Harbor airport at 11 Kft AGL. With a thinner layer of haze and
significantly more insolation than yesterday, look for highs to
top out in the upper 90s to near 100 around Phoenix and the lower
deserts, and the low 100s in SW AZ and SE CA.

From tomorrow and for much of the week models are in good agreement
on maintaining the strong high pressure system over the Southwest and
West CONUS. A modest influx in regional tropical moisture from the
southeast will likely be seen beginning tonight through Sunday night
with PW`s climbing up to near 1" near seasonal norms. Combined with
a weak UL low pressure disturbance near the E AZ border tomorrow and
Monday, expect a few relatively modest isolated showers and
thunderstorms across parts of far E AZ and S Gila cty including
San Carlos and possibly Globe on Sunday and Monday afternoons. The
latest HREF CAMs guidance are also in good agreement on keeping
the convection during those periods rather isolated as well.

The persistent regional high pressure will combine with a drying
trend beginning late Monday to support a warm-up as models trend
slightly warmer.  Highs are expected to be several degrees above
normal for much of the week. Highs in and around Phoenix could reach
105-108 by mid to late week and a bit warmer out west. Although
isolated areas of high heat risk could develop, a new excessive
heat watch or warning is not overly likely at this time.

Late in the week a trough possibly moves into coastal CA putting
the area under dry cyclonic flow aloft along with a possible
uptick in breezy southwesterly winds across the region.

&&

.AVIATION...Updated at 0013Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Light southwest to west winds are favored through the rest of the
afternoon through around 4Z before shifting back to the east. East
winds are then favored through Sunday. Confidence is low in a west
shift Sunday afternoon. Winds speeds through Sunday afternoon will
remain light around 8 kts or less. The layer of smoke over the
area is expected to thin out through Sunday afternoon, but hazy
conditions will likely persist. FEW to SCT cumulus are likely to
develop Sunday afternoon, favoring the high terrain to the north
and east, with bases around 10 kft. An isolated shower cannot be
fully be ruled out, but chances will be best of the higher
terrain as well.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will remain very light through the TAF period, around 8 kts
or less, with periods of variability. The thin layer of smoke up
around 20-25 kft AGL will persist through Sunday. Besides this
skies should remain mostly free of clouds.

&&

.FIRE WEATHER...
Tuesday through Saturday:
A generally warm and dry weather pattern is anticipated next week
with temperatures remaining slightly above normal. Mainly light
winds will favor normal diurnal patterns through Wednesday, with
light to moderate winds favored for the latter half of the period.
Daily min RH values will fall into the 10-15% range with overnight
recovery around 25-35% for lower elevations and 30-50% for higher
elevations.

&&

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

&&

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

$$

DISCUSSION...Sawtelle
AVIATION...Benedict
FIRE WEATHER...Sawtelle