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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 100 °
• Low: 72 °
• Clear

• Thursday
• 
• High: 99 °
• Low: 73 °
• Clear

• Friday
• 
• High: 93 °
• Low: 73 °
• Clear

• Saturday
• 
• High: 93 °
• Low: 72 °
• Clear

• Sunday
• 
• High: 97 °
• Low: 72 °
• Clear

Area forecast discussion 
National Weather Service Phoenix Arizona 
605 am MST Wednesday may 16 2012 


Update...to aviation and fire weather discussions. 


&& 


Synopsis... 
temperatures will remain well above average through Thursday with 
mostly clear skies and low desert highs exceeding 100 degrees. A dry 
low pressure system will move through the area on Friday...allowing 
temperatures to fall closer to the seasonal normal...but more 
importantly supporting strong gusty winds Friday afternoon. High 
pressure will build back over the region later in the 
weekend...leading to much warmer high temperatures returning to the 
area by early next week. 


&& 


Discussion... 
strong high pressure aloft persists over the Desert Southwest early 
this morning...with a dry stable airmass in place over the state. 
Precipitable water values were below one quarter inch per the latest flg/tus 
soundings and 3 am surface dewpoints over the Arizona deserts were 
mostly in the 20s. Infrared imagery early this morning depicted clear 
skies across the area. A weak upper low embedded in the ridge moving 
eastward across northern Arizona/southern Utah will act to cool the airmass 
slightly today into Thursday...however high temperatures will still be well 
above seasonal normals and into the triple digits. Dry westerly 
flow aloft will keep clear skies in the forecast today into Thursday. 


Both the GFS and European model (ecmwf) call for a progressive open wave trough to move 
across the western Continental U.S. Thursday evening through Friday evening. 
As is most often the case this time of year...this system will bring 
US nothing but increased wind along with some cooler temperatures... 
and maybe a few high clouds. Given the dry airmass in place and the 
expected low humidities...fire weather concerns will be in play with 
the passage of this trough. On Thursday evening...gusty winds across 
Joshua Tree National Park will produce a few hours at red flag 
thresholds but it will be unlikely that we will meet the 6 hour time 
criteria. Thus no watch for Thursday. On Friday however...as the 
trough pushes into eastern Arizona the gradients across our eastern 
zones tighten quite a bit. Good mixing will cause breezy to windy 
conditions to develop...especially over the higher terrain east of 
Phoenix. As such we have issued a Fire Weather Watch for 
azz024...southern Gila County...from 20z Friday to 03z Saturday. 
This meshes well with our neighboring offices. The trough passage will 
also drop high temperatures over the deserts into the middle to upper 90s 
Friday...and these highs are expected to continue on Saturday as 
well as cooler air remains in the boundary layer. 


For Sunday into the early part of next week...ECMWF...GFS and GFS 
ensembles continue to support another episode of strong high 
pressure building in over the Desert Southwest as another Pacific 
trough gradually approaches the West Coast. By next Monday 500 mb heights 
near 590dm are prognosticated to set up over the southeastern California and southern Arizona 
deserts. As such...under sunny skies...high temperatures Monday into 
Tuesday will likely range between 105 and 110 degrees over the 
hottest lower deserts. It is possible that excessive heat warning 
thresholds may be reached and an excessive heat warning will be 
needed for some of our lower deserts. This will have to be watched 
closely. 


&& 


Aviation... 
south central Arizona including kphx...kiwa and ksdl... 
clear skies with typical diurnal winds expected through the taf 
period. West-southwest winds up to 12kts possible in the afternoon 
before becoming light and variable after 17/0300z. Slight potential 
for wildfire smoke impacts on slantwise visibilities remain for 
terminals across the northern through eastern portions of the 
Phoenix metropolitan area this morning...including kdvt...ksdl and kiwa. 


Southeast California and southwest Arizona...including kipl and kblh... 
generally light morning winds will become south-southeasterly 
through the day. Typical west winds less than 10 kts expected after 
sunset and overnight with clear skies. 


Aviation discussion not updated for amended tafs. 


&& 


Fire weather... 
Friday through Tuesday... 
broad low pressure trough will move through the western United 
States increasing winds Friday across the southwest region. Along 
with increased winds...temperatures will cool from their well above 
average readings earlier in this week. However...they still will 
remain above seasonal normals. Continued dry conditions combined 
with strong gusty winds and dry fuels will lead to critical fire 
weather conditions across southern Gila County and the Tonto 
National Forest foothills Friday midday through evening. Ridge of 
high pressure rebounds over the region during the weekend...keeping 
daytime humidities very low with fair to at times poor recoveries 
overnight. Temperatures will warm for the beginning of next 
week...pushing well above normal readings once again. 


&& 


Psr watches/warnings/advisories... 


Arizona...Fire Weather Watch on Thursday...1 PM through 8 PM...for azz024. 


California...none. 


&& 


$$ 


National Weather Service Phoenix is on the internet at 


Weather.Gov/Phoenix 


Discussion...cumulonimbus 
aviation...Nolte 
fire weather...Nolte