Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/13/20

Area Forecast Discussion

National Weather Service Phoenix AZ

 503 PM MST Sun Apr 12 2020

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
After a sunny and pleasant afternoon today, another disturbance
will bring a chance of rain to portions of northeast La Paz,
northern Maricopa, and southern Gila Counties on Monday. Very
isolated thunderstorms will be possible across the higher terrain
north and east of Phoenix with little to no chance into the lower
deserts. Much drier conditions will move into the region for
Tuesday through the bulk of the coming week as temperatures warm a
few degrees above normal on Thursday and Friday.

&&

.DISCUSSION...
A beautiful day is in place across the lower deserts of Arizona
and southeast California with mostly sunny skies and temperatures
in the 70s for most locations. Greater coverage of stratocumulus
clouds are present over Gila County and northern portions of
Maricopa County in closer proximity to the showers and isolated
embedded thunderstorms that are ongoing across the northern
Arizona High Country from northern Mohave County through Sedona
and Flagstaff into central Apache County. This activity is
associated with a shortwave embedded within a very broad and
positively-tilted longwave trough currently centered over the
Canadian province of Saskatchewan. Hi-res models keep this
activity north of the Yavapai-Maricopa County border through
tonight due to relative lack of dynamic forcing this far south
and significant capping inversion present from 700-800 mb on
aircraft soundings into PHX. Therefore, the main impact for today
will be breezy west-southwesterly winds with gusts up to 25 mph
for most of the region except Imperial County where downsloping
winds will cause gusts up to 30-35 mph tonight in the Imperial
Valley. Far southwestern Imperial County along the I-8 pass will
see frequent 45-55 mph wind gusts, so a Wind Advisory has been
issued for them through 8 AM PDT on Monday morning.

Another shortwave embedded within the broader longwave trough
will cause an enhancement in shower and thunderstorm activity on
Monday across the Arizona High Country. This wave will make a bit
more of a southward push than today`s wave, which combined with
stronger upper-level divergence associated with a 100-125 kt jet
streak, should result in greater coverage in showers and embedded
thunderstorms to our north. Although the global and hi-res model
ensembles are a bit less bullish on this activity making into the
Valley than they were yesterday, several models show convection
pushing into northeast La Paz, northern Maricopa, and Gila County
late tomorrow afternoon and early evening. There may be a very
brief window of weak instability over far northern and eastern
portions of the Phoenix metro tomorrow afternoon, but enhanced
stability above 650-700 mb makes it unlikely that any convection
that moves off the Rim will hold together too far south into the
Phoenix metro. Thus, 10-20 PoPs are in place for most of the
Phoenix metro, with the better chances along and northeast of a
line from Wickenburg to north Scottsdale to Superior.

On Tuesday, the flow aloft is forecast to eventually turn more
northerly later in the day with drier air filtering in from the
north. This drying will end any rain chances through at least
Friday. Temperatures through the latter half of the week will
warm back to around seasonal normals with highs likely peaking in
the upper 80s on either Thursday or Friday. Models are still
showing some sort of a cut-off low forming to our west late in the
week, but the ensemble cluster favoring a deeper trough with the
coolest temperatures and slight chance of rain currently captures
less than a quarter of the global runs. The vast majority of model
ensembles favor a flatter trough or more zonal flow that should
just result in a slight decrease in temperatures and typical
enhancements in our westerly winds. Therefore, our forecast
remains dry for now through next weekend with our highest lower
deserts temperatures forecast to top out in the upper 80s for most
locations. Assuming the trough cools temperatures down a couple
degrees, the Phoenix metro and maybe even Yuma may continue to
stave off 90 degree temperatures for yet another week! The Phoenix
metro will already have the latest 90 degree day since at least
1999 (April 18th), and potentially back to at least 1995 (April
26h) if we make it past Friday without hitting 90 degrees.

&&

.AVIATION...Updated at 0002Z.

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

Breezy westerly winds, with gusts upwards of 17 to 20 kts, will
taper off over the next couple of hours as daytime mixing subsides.
West/southwest winds below 8 kts will continue into tonight before
transitioning to a light east to southeast component. By early
tomorrow afternoon, breezy westerly winds with gusts into the upper
teens resume. Otherwise, FEW-SCT cloud decks around 6-8 kft will
continue throughout the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:

Strong gusty winds, with gusts upwards of 25-30 kts, will continue
into tonight at both terminals before subsiding by early Monday
morning. Winds will favor the west at KIPL while winds remain out of
the south at KBLH. Otherwise, clear to mostly clear skies will
continue through the next 24 hours.

&&
.FIRE WEATHER...
Tuesday through Saturday:
Increasing high pressure will lead to a drying trend during the
middle part of the week. A potential low pressure may then affect
portions of the region by next weekend. Below normal temperatures
will still continue through Wednesday before warming to around
normal readings starting Thursday. Dry conditions through the
period will result in daily min RH values in the 10-20% range.
Winds will remain fairly light through Thursday before becoming
breezy during the daytime hours for Friday and Saturday.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 8 AM PDT Monday for CAZ562.

&&

$$

DISCUSSION...Hopper
AVIATION...Smith
FIRE WEATHER...Kuhlman