Area forecast discussion 
National Weather Service Phoenix Arizona 
300 am MST Sat Oct 25 2014 


Synopsis... 
strong high pressure aloft will bring one more day of well-above 
normal temperatures across the region today...with near-record highs 
possible at some locations across south-central Arizona. A cooling 
trend is then expected from Sunday into early next week as low 
pressure moves inland into the Great Basin...with temperatures 
falling back to near seasonal normals. A return to above normal 
temperatures is then expected from Wednesday Onward through the end 
of next week as high pressure becomes reestablished across the 
western states. 


&& 


Discussion... 
the strong ridging aloft that brought record high temperatures to 
south-central Arizona yesterday is now beginning to weaken and shift 
off to the east as a rather strong upper trough begins to push inland 
into central/northern California. It appears that one more day of 
near-record highs is in the cards for south-central Arizona today. 
However...a combination of increasing cloudiness...a degree or so of 
cooling in the 850-700 mb layer...and a slight lowering of 500mb 
heights should keep Phoenix Sky Harbor a couple of degrees short of 
today/S record high of 96f. 


Scattered to broken middle-high level cloud layers...a result of a 
moisture plume that is expected to briefly surge northward ahead of 
the approaching upper trough...are expected to progress eastward 
across Arizona today and tonight. Although precipitable waters  could briefly 
reach/exceed 1 inch across southern Arizona today...a dry subcloud 
layer is expected to limit any rainfall to an isolated 
sprinkle...with only a remote chance that any location will see 
measurable rainfall. The approaching trough will also increase the 
usual afternoon westerly breezes a bit across southeast California and SW Arizona...but 
sustained wind speed are expected to remain mainly at or below 10 kts. A 
slow drying/clearing trend is then expected on Sunday as the main 
moisture plume moves off to the east as drier air begins to move 
into the region from the northwest. 


Although a cooling trend is expected from Sunday Onward into 
Tuesday as the long-wave upper-level trough shifts eastward across the 
Great Basin into the central rockies...it still appears that 
temperatures will only fall to around...or slightly above seasonal 
normals on Monday and Tuesday...since 850mb temperatures are only 
expected to fall about 4-5c from today/S readings...with even less 
cooling indicated at 700 and 500mb. Skies are expected to be mostly 
sunny through this period as precipitable waters  fall into the 0.40-0.60 inch 
range. 




As far as the forecast of the middle and end of next week is 
concerned...the GFS is now coming into better agreement with the 
Euro on the idea of a return to warmer temperatures as high pressure 
rebuilds back over the region...but it is still not as aggressive as 
the Euro is on the magnitude of the upcoming warming trend. While 
the Euro continues to push high temperatures back into the low to 
middle 90s across the lower deserts by the end of next week...the GFS 
still holds highs back down in the upper 80s due to its forecast of 
somewhat lower 500mb heights. It this point...still giving the nod 
to the better-performing Euro...with many Lower Desert locations 
seeing at least 90f on Friday and Saturday under mostly sunny skies 
with light winds. 


&& 


Aviation... 
south-central Arizona including kphx...kiwa and ksdl...southeast 
California and southwest Arizona including kipl and kblh... 


Moisture spreading northward ahead of a upper low center that will 
be moving inland into central/northern California is expected to produce 
scattered-broken middle-high cloud layers today and tonight...with the 
lowest ceilings/greatest cloud coverage to be across south-central 
Arizona...with even an outside chance of a few sprinkles at one...or 
more of the phx area terminals. The aforementioned upper low center 
is also expected to enhance typical afternoon westerly winds 
today...but speeds are still expected to remain mainly at or below 10 
kts...with typical diurnal trends returning tonight through Sunday. 


Aviation discussion not updated for amended tafs. 


&& 


Climate... 
record high temperatures 


Date Phoenix 
---- ------- 
Sat Oct 25 96 in 1990 


&& 


Fire weather... 
Monday through Friday... 
after a brief period of near-normal temperatures on Monday and 
Tuesday...a warming trend is expected through the rest of next week 
as high pressure slowly builds back eastward across the 
region...with many Lower Desert locations seeing highs near 90f by 
Friday. Mainly clear skies and light winds are expected through the 
forecast period...with afternoon humidities falling into the middle 
teens to lower 20 percent range each day...with good overnight 
recoveries expected. 


&& 


Psr watches/warnings/advisories... 


Arizona...none. 


California...none. 


&& 


$$ 


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