Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/04/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 401 PM MST Tue Oct 3 2023

.Update...Updated Aviation

&&

.SYNOPSIS...
Dry and tranquil conditions will prevail the next several days as
high pressure builds into the region. As a result, above normal
temperatures return during the latter half of the week with many
lower elevation communities likely reaching 100 degrees by Friday. A
slight moisture increase will occur over the weekend, which may
produce a few light showers over the eastern Arizona high terrain.

&&

.DISCUSSION...
Pronounced troughing and colder midtropospheric temperatures were
lifting through the central Rockies early this afternoon with
weakened northwest flow lingering over the SW Conus. While height
rises aloft are currently modest, in situ ACARS soundings data has
sampled more notable warming (2-3C) of the full atmospheric profile.
Over the next 48 hours, height rises will accelerate over the region
as East Pacific ridging links with retrograding subtropical ridging;
and H5 heights reaching or exceeding 588dm by Thursday across the
CWA. As such, temperatures will continue a warming trend entering
into an above normal category during the latter half of the week. In
fact, model guidance has consistently depicted lower elevation
communities flirting with the 100F threshold Friday (NBM
probabilities of KPHX hitting 100F stand near 75%).

While some measure of ridging and anomalously high heights over the
SW Conus have excellent ensemble agreement, a couple subtle
shortwaves embedded in the East Pacific subtropical jet combined
with a backdoor front/moisture seep, and even the far outer
influences of tropical cyclone Lidia will present the greatest
forecast challenge over the weekend. Rather large spread and
uncertainty still exists with respect to the magnitude of moisture
flux with model means suggesting PWATs nearing 1" following a peak
in southeast flow Saturday morning. Corresponding boundary layer
mixing ratios should reach near 6-7 g/kg potentially yielding 200-
300 J/kg MLCape, albeit capped by a warming inhibiting layer atop
the mixing depth. The most likely outcome Saturday remains isolated
showers (and possibly an embedded storm) developing over mountains
of northern and eastern AZ creating outflows feeding on a higher
DCape environment. The areal and temporal duration any showers
should be limited given the lower moisture availability and reduced
seasonal insolation, but doesn`t discount locally gusty winds being
generated and propagating towards lower elevations.

Heading through early next week, model ensembles are in good
agreement that temperatures cool as H5 heights slowly decrease in
response to a series of incoming progressive Pacific systems. This
should be a slower erosion of heights aloft with the bulk of energy
focused well to the north and stronger ridging amplitude maintaining
H5 levels in a 582-585dm range. Thus, forecast confidence is quite
good that temperatures will hover above normal with any lingering
moisture quickly scoured from the region.

&&

.AVIATION...Updated at 2300Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are expected during the TAF period.
Wind will favor light and diurnal tendencies, with speeds
generally less than 10 kts. Skies will be clear through the
period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are anticipated during the forecast period.
Winds at IPL will generally be out W/NW through tomorrow morning.
BLH will see winds more established out of the NW through the
overnight hours. Speeds are expected to be less than 10 kts. Skies
will be clear through tomorrow morning.

&&

.FIRE WEATHER...
Temperatures will gradually warm the next several days reaching
above normal levels during the latter half of the week. Dry
conditions with afternoon minimum humidity levels in the teens will
give way to a modest moisture increase over the weekend where
humidities rise towards a 15-25% range. Similarly, poor to fair
overnight recovery of 20-50% during the middle of the week should
improve closer to 35-70% over the weekend. While this moisture
increase may result in a few light showers over higher terrain of
eastern districts this weekend, wetting rainfall should not be
expected. Light winds the next couple days will give way to enhanced
easterly winds Friday and Saturday where eastern districts could
experience occasional gusts 25-30 mph - especially over ridge tops
and through terrain gaps.

&&

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

$$

DISCUSSION...18/Leffel
AVIATION...RW
FIRE WEATHER...18