Special Weather Statement, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
218 PM MST TUE JUL 19 2016

.SYNOPSIS...
An increase in clouds and humidity can be expected during the next
couple of days along with a slight chance of showers and
thunderstorms, mainly east of the Lower Colorado River Valley. High
temperatures over the central deserts will stay near seasonal
normals, with hotter conditions over the western deserts. Storm
chances on the lower deserts will be slight, with better chances over
the higher terrain and over southeast Arizona. During the latter half
of the week, storm chances will dwindle, and temperatures will
increase to above normal levels.

&&

.DISCUSSION...

Tonight and Wednesday...

Regional morning weather balloon soundings continued show a rather
healthy amount of monsoon moisture strewn across central and
southern AZ. Monsoon moisture is not excessive by any means, but not
minimal either. And, boundary layer moisture was healthy enough to
result in relatively low afternoon convective trigger temperatures.
This afternoon there seemed to be an early start to convection in
southeast AZ and over southern Gila County zone 24.

Low afternoon convective trigger temperatures will make the lower
desert airmass in south central AZ more susceptible to convection
produced by convective outflows moving in from southeast AZ,
especially with weakness/support aloft.

Upper level weakness and support is what we've been focusing on for
a few days now with the approaching inverted trof (IT) from
Chihuahua Mexico. At 2 pm mst the leading edge of this IT feature
had moved into the southeast AZ corner, with convection breaking out
ahead of its leading edge, and in a weak difluent zone aloft.
Various meso-scale models have widely varying spacial and temporal
solutions for convection, but the bottom line is most of it is
produced in southeast AZ running along a north south line from near
Tucson to our southern Gila County Zone 24.  Additionally, some
models produce a strong convective outflow that spreads northwest
toward Pinal and Maricopa Counties, including Phoenix between 7 pm
and 10 pm mst. The magnitude of this outflow boundary will likely
initiate secondary convection. Therefore the chance of showers and
thunderstorms will continue this evening through late night, with a
slight chance of lingering showers continuing through early
Wednesday morning.

Wednesday...Monsoon moisture will be still be entrenched over the
region. With mid/upper level disturbances departing the area, this
will result in another low grade monsoon forecast Wednesday
afternoon and evening.

Thursday through Monday...monsoon moisture is forecast to thin a
little as drier air from New Mexico and Colorado mix over the area.
At the same time atmospheric height and thickness values increase
dramatically over the region, and if it weren't for remnant monsoon
moisture, afternoon temperatures would be much higher. Therefore
afternoon desert temperatures are forecast to be above the 110
degree mark, but approaching 115 over the driest low humidity area
of southeast CA.

&&

.AVIATION... South-Central Arizona Including KPHX, KIWA, and KSDL:

Thunderstorms are possible this afternoon with development already
occurring over the higher terrain to the north and east of Phoenix.
These storms, along with any that develop around the metro, could
produce outflow winds that could impact any terminal. Current storm
development suggests outflows from the north or the east are more
likely but the exact timing and direction of wind shifts is
difficult pin down at this time

Southeast California/Southwest Arizona including KIPL and KBLH:

Little aviation concerns through with storm activity well off to the
east into central Arizona. Expect mostly clear skies and southerly
winds through the evening and into tomorrow.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Friday through Tuesday...Temperatures will trend back into an above
normal range through the weekend as moisture levels thin and
humidity values drop. Thunderstorm/wetting rain chances dwindle and
become mostly limited to the higher terrain of eastern Arizona by
Friday and Saturday. Consequently, afternoon humidity levels will
drop into the 10-25 percent range this weekend. Outside of any
thunderstorms, winds will be typical with some afternoon gustiness.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation may be required for this evening.

&&

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

Visit us on Facebook...Twitter...and at weather.gov/phoenix

DISCUSSION...Vasquez
AVIATION...Deemer/Iniguez
FIRE WEATHER...Deemer/Iniguez

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
426 PM MST TUE JUL 19 2016

AZZ024-200015-
SOUTHERN GILA/TONTO NF FOOTHILLS AZ-
426 PM MST TUE JUL 19 2016

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  SOUTH CENTRAL GILA COUNTY

UNTIL 515 PM MST

AT 426 PM MST...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 10
MILES NORTH OF CHRISTMAS. THIS STORM WAS NEARLY STATIONARY.

WINDS IN EXCESS OF 40 MPH WILL BE POSSIBLE WITH THIS STORM.

THIS STORM WILL REMAIN OVER MAINLY RURAL AREAS OF SOUTH CENTRAL GILA
COUNTY.

LAT...LON 3314 11059 3315 11063 3313 11064 3309 11070
      3306 11083 3325 11084 3329 11063 3316 11055
TIME...MOT...LOC 2326Z 345DEG 2KT 3321 11072

MP

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
435 PM MST TUE JUL 19 2016

AZZ024-200015-
SOUTHERN GILA/TONTO NF FOOTHILLS AZ-
435 PM MST TUE JUL 19 2016

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  NORTHWESTERN GILA AND NORTHEASTERN MARICOPA COUNTIES

UNTIL 515 PM MST

AT 435 PM MST...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR
PUNKIN CENTER...OR NEAR SUNFLOWER...MOVING NORTHWEST AT 15 MPH.

WINDS IN EXCESS OF 40 MPH AND BRIEF HEAVY RAIN WILL BE POSSIBLE WITH
THIS STORM.

LOCATIONS IMPACTED INCLUDE...
SYCAMORE CREEK...ROUND VALLEY...SUNFLOWER...TONTO BASIN AND PUNKIN
CENTER.

LAT...LON 3399 11142 3396 11139 3393 11132 3382 11123
      3370 11138 3385 11164 3402 11144
TIME...MOT...LOC 2335Z 135DEG 11KT 3382 11137

MP

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
515 PM MST TUE JUL 19 2016

AZZ024-200100-
SOUTHERN GILA/TONTO NF FOOTHILLS AZ-
515 PM MST TUE JUL 19 2016

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  CENTRAL GILA...EAST CENTRAL MARICOPA AND NORTHEASTERN PINAL
  COUNTIES

UNTIL 600 PM MST

AT 514 PM MST...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM
NEAR TOP OF THE WORLD...OR 9 MILES SOUTHWEST OF GLOBE...MOVING
NORTHWEST AT 15 MPH.

WINDS IN EXCESS OF 40 MPH AND BRIEF HEAVY RAIN WILL BE POSSIBLE WITH
THIS STORM.

LOCATIONS IMPACTED INCLUDE...
MIAMI...TOP OF THE WORLD...TOP-OF-THE-WORLD...
CLAYPOOL AND INSPIRATION.

LAT...LON 3324 11094 3324 11096 3344 11128 3363 11106
      3336 11080
TIME...MOT...LOC 0014Z 134DEG 14KT 3334 11094

MP

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