Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 292058
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
158 PM MST Sat Apr 29 2017

.SYNOPSIS...
Below normal temperatures can be expected today as a storm system
slowly shifts eastward into the southern Rockies. Breezy
conditions will also be possible through this afternoon, but wind
speeds will generally be much weaker than yesterday. Still, high
fire danger will continue across the lower Colorado River Valley
through the late afternoon. A warming trend will begin Sunday into
next week, with the first 100 degree reading of the year forecast
for Thursday at Phoenix.

&&

.DISCUSSION...
Latest satellite imagery shows scattered CU wrapping around the
western periphery of the New Mexico low pressure system.
Sprinkles and even some isolated showers have developed across
mainly the Colorado Plateau within an area of steeper mid-lapse
rates and marginal instability. Latest consensus amongst the hi-
res CAMS indicates that the isolated sprinkles/showers could make
it as far west as southern Gila County, however they will likely
dissipate around sunset. Meanwhile, across the lower elevations
where dewpoints are in the teens, PoPs remain near 0 through
tonight, as any precipitation that develops will have a difficult
time penetrating the relatively dry sub-cloud layer.

Further west, the main weather story continues to be the windy
conditions. Blythe California reported a gust above 40 mph earlier this
afternoon. The persistent windy conditions along with the low RHs
will continue to promote the spread of any new or existing
wildfires down the Colorado River Valley into this evening.

The aforementioned low pressure system will slide eastward into
the Plains overnight. In its wake, sharp height rises will
overspread Arizona and portend a warming trend for Sunday.
However, temperatures in the near-term will remain below average
again tonight.

&&

.PREVIOUS DISCUSSION...

Unfortunately, the cool temperatures will be short-lived, and the
heat will return with a vengeance into the middle part of next
week as a pronounced ridge of high pressure builds over the
Southwest. Confidence is increasing that the first 100 degree
reading of the year will be reached at Phoenix on Thursday, with a
repeat performance on Friday. More uncertainty into next weekend
as deterministic models are hinting at the development of
potentially an anomalously deep upper trough over the Pacific
coasts. A wide range of scenarios could occur, including
increasing moisture over the Southwest and significantly cooler
temperatures. However, with low confidence at this point, trended
more towards climatological norms during this period for all
forecast parameters.

&&

.AVIATION... South-Central Arizona including KPHX, KIWA and KSDL:
Gusty west to northwest winds will diminish this evening as speeds
drop below 10 kts.  Additionally, the FEW CU around 10-14kft
observed this afternoon will also clear after sunset.  Winds will
follow their typical diurnal directions through tomorrow with clear
skies starting tonight and persisting through Sunday.

Southeast California/Southwest Arizona Including KIPL and KBLH:
Gusty northwesterly winds will weaken this evening with winds
dropping to 5-10 kts after 02Z.  Skies will remain clear into Sunday
under a light northerly flow.  No other aviation concerns exist.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Friday: A ridge of high pressure will slowly build
over the west next week with the lower deserts making another run at
100 degrees during the latter half of next week. No strong wind
events are anticipated. Minimum humidities will remain low - below
15% for most areas with the low deserts generally in the single
digits. Overnight recoveries will range from 25-35% and up to 40% in
the elevated portions of Gila county.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation will not be needed through the middle of next
week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Red Flag Warning until 7 PM MST this evening for AZZ131.

CA...Red Flag Warning until 7 PM PDT this evening for CAZ231.

&&

$$

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DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Rogers
AVIATION...Wilson
FIRE WEATHER...Wilson



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