785 
FXUS65 KPSR 082344 AAA
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
444 PM MST Thu Apr 8 2021

.UPDATE...
Updated Aviation Discussion.

.SYNOPSIS... 
With high pressure remaining situated over the region, high 
temperatures will hover around 10 degrees above average through the 
weekend. This area of high pressure will also ensure widespread dry 
weather with no realistic chance of rain. Breezy afternoon 
conditions will be common with some chance of enhanced winds during 
the middle of next week as a weather disturbance slides north of the 
area. This disturbance may also allow temperatures to cool somewhat 
closer to the seasonal average eventually next week. 

&&

.DISCUSSION... 
Early this afternoon, the SW Conus was trapped between a northern 
stream shortwave digging into the central Rockies/high plains and a 
subtropical ridge retrograding into the eastern Pacific. While 
soundings show subtle height falls and cooing aloft, compressional 
heating ahead of a decaying front was yielding temperatures near to 
slightly warmer than Wednesday. In addition, the increased pressure 
gradient was supporting stronger wind gusts though the gradient was 
already beginning to relax. As is typical this time of year, the 
strongest winds will be experienced near downsloping terrain 
features in the far western CWA. Conceivably, a few mountain rotors 
could descend into the Imperial Valley, but the preponderance of 
evidence indicates wind speeds remaining below advisory criteria. 

The entire western hemispheric pattern will remain blocked through 
at least the middle of next week resulting in an extended 
persistence type forecast. Mean longwave troughing will be preferred 
through much of the central/eastern Conus while high amplitude 
ridging becomes anchored near each coastline. Ensemble spreads is 
quite narrow with excellent confidence WNW flow and H5 heights in a 
576-580dm range will settle over the region through the beginning of 
next week. High temperatures around 10F above normal should be 
common equating to lower elevation communities reaching into the 
lower/middle 90s. 

A reconfiguration of the large scale pattern will begin early next 
week as the upstream Pacific blocking retrogrades poleward merges 
with another ridge center over eastern Canada. As this merger 
occurs, negative height anomalies trapped equatorward of the 
northern ridge will also retrograde over much of the north-central 
United States and Great Basin. Ensemble means show this general 
progression, however WPC cluster analysis shows that there is still 
uncertainty with respect to where the deepest negative height 
anomalies will materialize. In general, clusters align along model 
physics packages with the GEFS membership more sheared and dampened 
with the wave structure while EPS members heavily lean towards a 
deeper, more blocked, retrogressive wave structure. As is usual, CMC 
ensembles are far more dispersive covering a wider range of 
outcomes.  

In spite of this pattern uncertainty, given the northerly 
continental flow, it can easily be assumed that the atmosphere will 
be quite dry with very little potential for precipitation. Ensemble 
solutions where the negative height anomalies focus further to the 
west and south are naturally much cooler and windier heading through 
the middle of next week. While the ensemble mean partially washes 
out the signal, feel given the predominant hemispheric blocking 
pattern, a slower, deeper, and more cutoff PV anomaly would be more 
preferred. At this point, it does appear likely that lower elevation 
temperatures will finally cool into the 80s at some point beyond the 
middle of the week, albeit probably staying around the seasonal 
normal. 

&&

.AVIATION...Updated at 2344Z.
 
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Current gusty westerly winds to persist into the early evening 
hours, then gradually diminish and become more nw-ly later this 
evening/overnight as a weather disturbance passes well to the north 
into the central Rockies. A later-than-normal onset of easterly 
drainage winds is expected as well (towards daybreak). More typical 
westerly winds can be expected to return Friday afternoon, with 
lighter westerly winds persisting into Friday evening. Mainly CLR 
skies can be expected through the TAF period, with just some high 
cirrus decks aoa 25k feet passing overhead from time-to-time.


Southeast California/Southwest Arizona including KIPL and KBLH:
Pressure gradient will tighten across southeastern California in 
response to a trough moving through northern Arizona. Westerly gusts 
as high as 25-30 are expected to continue at KIPL/KBLH, before 
subsiding overnight. There also is a slight chance of moderate 
visibility reductions due to localized blowing dust. Lighter 
westerly winds can be expected during the day on Friday at KIPL 
while winds at KBLH become more northerly. Mainly CLR skies can be 
expected through the TAF period, with just some high cirrus decks 
aoa 25k feet passing overhead from time-to-time.

&&

.FIRE WEATHER... 
Sunday through Thursday: 
Temperatures will only slowly cool through next week with readings 
around 10 degrees above the seasonal average early in the week 
falling to only about 5 degrees warmer than normal. Typical spring 
breeziness during the afternoons will be common with the favored 
upslope areas experiencing the strongest gusts. Somewhat stronger 
winds will be possible by the middle of next week potentially 
yielding a period of elevated fire danger. Dry conditions will also 
prevail through the week with afternoon minimum humidity values 
falling to near 10% while overnight recovery will be poor only 
bouncing back to a 20-40% range. Overall, conditions will be quite 
favorable for prescribed burning operations much of the week. 

 

&&

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

&&

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

&&

$$

DISCUSSION...MO/Hodges 
AVIATION...percha/Hirsch
FIRE WEATHER...MO