Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 05/16/16

Area Forecast Discussion
National Weather Service Phoenix AZ
221 PM MST SUN MAY 15 2016

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
454 AM MST SUN MAY 15 2016

.UPDATE...To AVIATION and FIRE WEATHER Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. Breezy conditions are expected today with highs near
normals. This Pacific low is forecast to move into the southwestern
states tonight persisting through Tuesday. This will provide even
cooler temperatures along with slight chances of showers and
thunderstorms. Clearing skies with rebounding temperatures are
forecast for late in the week.

&&

.DISCUSSION...
Drier air has filtered into Arizona as westerly flow aloft moved in
around the southern fringe of the upper low currently situated across
the Pacific Northwest. This drier air has ended any shower or
thunderstorm chances with mainly clear skies expected today. Lowering
heights aloft will allow for some modest cooling to take place today
and as a result highs should only top out in the lower 90s across the
deserts. A deepening surface low over the Great Basin is increasing
pressure gradients across the Desert Southwest resulting in some
breezy winds currently across southeast California. The gradient
will strengthen later today with breezy to windy southwesterly winds
across the majority of the CWA. Winds will remain below advisory
levels, but some gusts to 35 mph are likely across southeast
California and southern Gila County. Elevated fire danger conditions
for a brief time may be realized across southern Gila County this
afternoon, but not enough to warrant any headlines.

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
935 PM MST SAT MAY 14 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a low pressure
system in the northwest U.S. begins to deepen. Breezy conditions are
expected again for Sunday. Another Pacific weather system is
forecast to move into the southwestern states late Sunday through
Tuesday. This will provide even cooler temperatures along with slight
chances of thunderstorms mainly over northern and central Arizona.
Clearing skies with rebounding afternoon temperatures are forecast
for late next week.

&&

.DISCUSSION...

Clearing skies can be seen across southeastern California and the
western half of Arizona this evening. Earlier, a few thunderstorms
swept over the southeastern third of Arizona but that activity has
dissipated and pushed to the east. Low pressure system now over
Oregon continues to gradually deepen and spread its influence further
to the south. Models indicate this system will eventually drop down
towards the south, ultimately moving into northwest Arizona by
Tuesday evening. This will bring a slight chance for thunderstorms to
the region and keep relatively cooler air in place for a few days.
Rain chances are still on the low side but at least there`s a chance
for unsettled weather, particularly Tuesday afternoon through
Wednesday morning. Temperatures should start to climb back above
normals the rest of the week.

&&

.PREVIOUS DISCUSSION...
Latest satellite imagery shows several areas of cumulus congestus,
mainly concentrated across the Mogollon Rim, the CO Plateau and
portions of southeastern AZ. Isolated showers and thunderstorms have
developed, but are mainly relegated to the higher terrain near
Tucson and Flagstaff. Meanwhile, moisture values are running well
above average with dewpoints in the mid 40s. NAEFS PWAT percentiles
are also running above the 90th percentile, though ground based GPS-
IPW and TPW suggest PWATS are somewhat lower. The relatively moist
conditions have also kept temperatures at bay, which have generally
been running in the mid to upper 90s in the lower deserts. At Sky
Harbor Airport, the high has reached 100 degrees.

Preponderance of hi-res CAMs including the operational and
experimental HRRR continue to indicate that isolated convection will develop
across Gila County this afternoon and this evening. PoPs were increased
to around 10 percent in these areas, though in reality most precipitation
that falls will likely evaporate and not measure at the surface. Models
are in excellent agreement that much drier air will be transported
northeastward this evening and overnight, with the GEFS ensemble
mean indicating PWATS dropping as low as 0.40 inches. Consequently,
showers and thunderstorms will dissipate shortly after sunset.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

A weak weather disturbance will continue to produce scattered
cumulus and altocumulus with broken-overcast cirrus this afternoon
before thinning out this evening. Over northern and southeastern
Arizona there will be isolated thunderstorms with some additional
weaker showers which will begin dissipating after sunset. Surface
winds will favor south and southwest directions through the evening
(gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds
will be stronger Sunday afternoon but with significantly less
cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
light winds. The low exits Thursday before another system approaches
Friday and Saturday leading to breezy to windy conditions.
Temperatures will start off below normal Tuesday and Wednesday before
climbing back to normal by Friday. Humidities begin declining
Wednesday with Minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Waters/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
1030 PM MST SUN MAY 15 2016

.UPDATE...To Aviation Discussion...

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Gusty westerly winds to continue to gradually diminish through the
rest of the evening and overnight hours as stronger winds aloft
become decoupled from the surface. wind directions to become
easterly later tonight at the phx area taf sites, while KBLH remains
out of a southerly to sw-ly direction, and KIPL out of a westerly
direction. After a period of light winds on Monday morning, stronger
westerly winds to develop Monday afternoon at the phx area taf sites
and at KIPL as stronger winds once again mix down to the sfc, with
KBLH seeing winds picking up from a southerly direction. Dry
westerly flow aloft to keep skies mainly clear through monday at all
of the taf sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Percha
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
900 PM MST SUN MAY 15 2016

.UPDATE...
Updated Aviation and Fire Weather sections.

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front passing across the deserts this afternoon and evening.
Expect southwest winds to prevail through the evening before
starting to become light and variable. Gusts of 20-25 kts will be
common through 02Z before weakening. However, the Imperial valley
will have stronger gusts (30-35 kts) through 04Z before beginning to
weaken. Could see some local blowing dust/sand there but confidence
not high enough to reflect in KIPL TAF. Winds will be lighter on
Monday afternoon. Otherwise, no significant cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
221 PM MST SUN MAY 15 2016

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
454 AM MST SUN MAY 15 2016

.UPDATE...To AVIATION and FIRE WEATHER Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. Breezy conditions are expected today with highs near
normals. This Pacific low is forecast to move into the southwestern
states tonight persisting through Tuesday. This will provide even
cooler temperatures along with slight chances of showers and
thunderstorms. Clearing skies with rebounding temperatures are
forecast for late in the week.

&&

.DISCUSSION...
Drier air has filtered into Arizona as westerly flow aloft moved in
around the southern fringe of the upper low currently situated across
the Pacific Northwest. This drier air has ended any shower or
thunderstorm chances with mainly clear skies expected today. Lowering
heights aloft will allow for some modest cooling to take place today
and as a result highs should only top out in the lower 90s across the
deserts. A deepening surface low over the Great Basin is increasing
pressure gradients across the Desert Southwest resulting in some
breezy winds currently across southeast California. The gradient
will strengthen later today with breezy to windy southwesterly winds
across the majority of the CWA. Winds will remain below advisory
levels, but some gusts to 35 mph are likely across southeast
California and southern Gila County. Elevated fire danger conditions
for a brief time may be realized across southern Gila County this
afternoon, but not enough to warrant any headlines.

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
935 PM MST SAT MAY 14 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a low pressure
system in the northwest U.S. begins to deepen. Breezy conditions are
expected again for Sunday. Another Pacific weather system is
forecast to move into the southwestern states late Sunday through
Tuesday. This will provide even cooler temperatures along with slight
chances of thunderstorms mainly over northern and central Arizona.
Clearing skies with rebounding afternoon temperatures are forecast
for late next week.

&&

.DISCUSSION...

Clearing skies can be seen across southeastern California and the
western half of Arizona this evening. Earlier, a few thunderstorms
swept over the southeastern third of Arizona but that activity has
dissipated and pushed to the east. Low pressure system now over
Oregon continues to gradually deepen and spread its influence further
to the south. Models indicate this system will eventually drop down
towards the south, ultimately moving into northwest Arizona by
Tuesday evening. This will bring a slight chance for thunderstorms to
the region and keep relatively cooler air in place for a few days.
Rain chances are still on the low side but at least there`s a chance
for unsettled weather, particularly Tuesday afternoon through
Wednesday morning. Temperatures should start to climb back above
normals the rest of the week.

&&

.PREVIOUS DISCUSSION...
Latest satellite imagery shows several areas of cumulus congestus,
mainly concentrated across the Mogollon Rim, the CO Plateau and
portions of southeastern AZ. Isolated showers and thunderstorms have
developed, but are mainly relegated to the higher terrain near
Tucson and Flagstaff. Meanwhile, moisture values are running well
above average with dewpoints in the mid 40s. NAEFS PWAT percentiles
are also running above the 90th percentile, though ground based GPS-
IPW and TPW suggest PWATS are somewhat lower. The relatively moist
conditions have also kept temperatures at bay, which have generally
been running in the mid to upper 90s in the lower deserts. At Sky
Harbor Airport, the high has reached 100 degrees.

Preponderance of hi-res CAMs including the operational and
experimental HRRR continue to indicate that isolated convection will develop
across Gila County this afternoon and this evening. PoPs were increased
to around 10 percent in these areas, though in reality most precipitation
that falls will likely evaporate and not measure at the surface. Models
are in excellent agreement that much drier air will be transported
northeastward this evening and overnight, with the GEFS ensemble
mean indicating PWATS dropping as low as 0.40 inches. Consequently,
showers and thunderstorms will dissipate shortly after sunset.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

A weak weather disturbance will continue to produce scattered
cumulus and altocumulus with broken-overcast cirrus this afternoon
before thinning out this evening. Over northern and southeastern
Arizona there will be isolated thunderstorms with some additional
weaker showers which will begin dissipating after sunset. Surface
winds will favor south and southwest directions through the evening
(gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds
will be stronger Sunday afternoon but with significantly less
cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
light winds. The low exits Thursday before another system approaches
Friday and Saturday leading to breezy to windy conditions.
Temperatures will start off below normal Tuesday and Wednesday before
climbing back to normal by Friday. Humidities begin declining
Wednesday with Minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Waters/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
605 AM MST MON MAY 16 2016

.UPDATE...Updated Aviation and Fire Weather Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Broad upper low circulation covers much of the Intermountain West
this early morning with a few well-defined embedded vorticies along a
weak upper jet intrusion on the western side of the low. This low
pressure system will be the focus on our weather for the early part
of the week, bringing a temperature cool down and shower/thunderstorm
chances across the forecast area. Overnight skies remain clear and
winds have subsided from their elevated westerly breezes last
evening. Continued draw-down of UL heights and few degrees of cooling
through the atmo profile transitioning into the area from yesterday`s
cool front have generated cooler morning temperatures so far,
generally 4 to 5 degrees cooler than this time Sunday. Dry
conditions, afternoon southwesterly breezes and temperatures over the
Deserts in the upper 80s to low 90s are expected today ahead of the
southward sagging Great Basin upper low.

Forecast model consistency has been fairly good with regards to this
upper low - still tracking the main circulation center west across
SoCal by Tuesday afternoon and into central AZ overnight Tuesday into
Wednesday. 500mb heights have already retreated from their higher
values late last week so the height fall differential with the
intruding upper low is not as great as previous events we`ve seen
this Spring. PWAT forecasts on model plots and soundings have flirted
with 0.75 to 1.00 inch values, focused mainly along and either side
of the CO River Valley by Tuesday evening. When comparing these
values to soundings from neighboring offices of Tucson and Las Vegas
these forecast values are in the upper reaches of PWAT sounding
climatology. Also hard not imagine some Gulf of California moisture
advection into the region with southerly flow up the river;
dewpoints for sites along the River have touched the 50F mark
periodically over the weekend. While that is more surface based
moisture, a thin layer of mid-level moisture returns are also
forecast. These are most noticeable in several inverted-V soundings
for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few
hundred joules of mean MU and ML CAPE for Tuesday afternoon and
overnight, in conjunction with the overhead passage of the upper
cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C
and -40 to -44C ranges respectively. Still not an overly favorable
profile to support organized convection in terms of wind and we`ll be
looking for the dry sub-cloud layer to enhance evaporative processes
leading to gusty outflow winds from any showers and storms that do
develop. Given the latest guidance suggesting 1) sufficient moisture
for some high-based activity across the western AZ deserts and 2) hi-
resolution gridded wind fields indicating some outflow boundary
activity emanating from the western AZ deserts, felt that slightly
boosting PoPs across La Paz and western Maricopa counties for Tuesday
afternoon and evening was warranted.

With varying periods of partly to mostly cloudy skies, the South-
Central AZ Deserts can expect a few more degrees of cooling off high
temperatures from today for Tuesday and Wednesday, with widespread
80-degree readings. Tuesday will be cool for most, including
locations west of the CO River Valley with some warming back into the
90s possible by Wednesday. The loosely cut-off system will begin to
become more of an open wave as it clear east of the area overnight
Wednesday, with some slight chances lingering for spotty
thundershower activity over the eastern AZ higher terrain for
Wednesday and Thursday afternoons. For the rest of the forecast area
from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions
will slowly warm back up to near-normal values as very short-lived
ridging passes through the area peaking 1000-500mb thicknesses back
into the mid 570dm range.

Upper level pattern remains active and progressive across the West
for the coming weekend as a broader and deeper Pacific low moves down
the West Coast out of B.C. and the Gulf of Alaska. Beginning
Friday, deep southerly flow filters in across much of the Southwest
states allow for healthy WAA and prolonged warming of temperatures in
spite of the gradually lower UL heights in troughing upstream. What
remained uncertain over previous forecast periods was the southward
extent of the low. It appears now that the main circulation and cold
core stays to our north across the Great Basin. Downstream ridging
would lend us to think the Pacific low would dive further south over
the weekend, but it now looks like ridging over the Plains will
weaken while another upstream Pacific low transitions out of the Gulf
of Alaska late Saturday. This should shift the Great Basin Low over
the Rockies. All-in-all, some variant of troughing will generally
hold over the west with several periods of breezy to gusty winds for
the coming weekend and into early next week. Temperatures shouldn`t
see a significant cool-down, but rather just below mid-May normals
with many lower elevations sites a degree or two either side of 90F.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Light winds this morning will turn westerly and become breezy at
times this afternoon, mainly at Phoenix area terminals. Dry westerly
flow aloft will keep skies mainly clear into early Tuesday before
the next weather system moves into the region bringing a chance of
showers and thunderstorms later Tuesday.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms east of the Lower
Colorado River Valley. Temperatures will be below normal over south-
central AZ and at or slightly above normal across southeast
California and southwest Arizona. The system exits on Thursday for
warmer temperatures and increasing winds. Another system slowly
approaches from the northwest Friday into Sunday for breezy to windy
conditions each day and a cooling trend. Minimum humidities will
generally be in the 15-20 percent range over the lower deserts
through Thursday before declining to near 10 percent by Friday.
Friday afternoon, and possibly Saturday afternoon, will likely have
elevated fire danger conditions over portions of the area.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Nolte
AVIATION...Kuhlman
FIRE WEATHER...Kuhlman



  [top]

Area Forecast Discussion
National Weather Service Flagstaff AZ
358 AM MST MON MAY 16 2016

.SYNOPSIS...Expect breezy west southwest winds today, along with
an increasing chance of showers and thunderstorms by afternoon. A
slow moving storm system will keep a chance of showers and
thunderstorms over the area through at least Thursday.
Temperatures will be below average through midweek and then warm
back to around average second half of the week. &&

.DISCUSSION...A large area of low pressure over the western states will
continue to move southward today...and be over the area Tuesday
and Wednesday. Best chances for showers today will primarily be
north of I-40...with the best lift and instability.

Tuesday and Wednesday...The area of low pressure will drop
southward into portions of northwest and central Arizona on
Tuesday...and then be over the region on Wednesday. Stronger
lift...deeper saturation...and instability will provide for good
chances of showers and thunderstorms. Rainfall amounts look to be
from 0.1 to 0.5 inches with this system, lighter amounts expected
for the lower elevations

Thursday northern Arizona is forecast to transition from a low
pressure trough back to a high pressure ridge pattern, bringing
drier conditions and warming daytime temperatures.

Friday through Sunday...Another low pressure trough is forecast
to approach northern Arizona from the west, producing a dry and
windy southwest flow.

By Monday of next week the low pressure trough is forecast to
move across Arizona...bringing lighter winds...drying
conditions...and slightly below average daytime temperatures.
&&

.AVIATION...For the 12Z package...Expect VFR conditions overnight.
After 18Z Mon...expect isolated to scattered SHRA/TSRA primarily
along and north of a KFLG-KRQE line with brief MVFR cig/vis
possible. Winds becoming westerly Mon afternoon 15-25 kts. In
addition, collapsing TSRA may produce very strong and erratic
surface winds with gusts as high as 50 knots possible in the
vicinity of storms. Aviation discussion not updated for TAF
amendments.


.FIRE WEATHER...A slow moving low will bring increasing moisture
and increasing chances for showers and thunderstorms to northern
Arizona on Monday and Tuesday.

Wednesday through Friday...Chances for showers and thunderstorms
continue through Wednesday with a drying trend starting from
Thursday onward.
&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...TC
AVIATION...RR
FIRE WEATHER...RR


For Northern Arizona weather information visit
weather.gov/flagstaff




Area Forecast Discussion
National Weather Service Phoenix AZ
314 AM MST MON MAY 16 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Broad upper low circulation covers much of the Intermountain West
this early morning with a few well-defined embedded vorticies along a
weak upper jet intrusion on the western side of the low. This low
pressure system will be the focus on our weather for the early part
of the week, bringing a temperature cool down and shower/thunderstorm
chances across the forecast area. Overnight skies remain clear and
winds have subsided from their elevated westerly breezes last
evening. Continued draw-down of UL heights and few degrees of cooling
through the atmo profile transitioning into the area from yesterday`s
cool front have generated cooler morning temperatures so far,
generally 4 to 5 degrees cooler than this time Sunday. Dry
conditions, afternoon southwesterly breezes and temperatures over the
Deserts in the upper 80s to low 90s are expected today ahead of the
southward sagging Great Basin upper low.

Forecast model consistency has been fairly good with regards to this
upper low - still tracking the main circulation center west across
SoCal by Tuesday afternoon and into central AZ overnight Tuesday into
Wednesday. 500mb heights have already retreated from their higher
values late last week so the height fall differential with the
intruding upper low is not as great as previous events we`ve seen
this Spring. PWAT forecasts on model plots and soundings have flirted
with 0.75 to 1.00 inch values, focused mainly along and either side
of the CO River Valley by Tuesday evening. When comparing these
values to soundings from neighboring offices of Tucson and Las Vegas
these forecast values are in the upper reaches of PWAT sounding
climatology. Also hard not imagine some Gulf of California moisture
advection into the region with southerly flow up the river;
dewpoints for sites along the River have touched the 50F mark
periodically over the weekend. While that is more surface based
moisture, a thin layer of mid-level moisture returns are also
forecast. These are most noticeable in several inverted-V soundings
for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few
hundred joules of mean MU and ML CAPE for Tuesday afternoon and
overnight, in conjunction with the overhead passage of the upper
cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C
and -40 to -44C ranges respectively. Still not an overly favorable
profile to support organized convection in terms of wind and we`ll be
looking for the dry sub-cloud layer to enhance evaporative processes
leading to gusty outflow winds from any showers and storms that do
develop. Given the latest guidance suggesting 1) sufficient moisture
for some high-based activity across the western AZ deserts and 2) hi-
resolution gridded wind fields indicating some outflow boundary
activity emanating from the western AZ deserts, felt that slightly
boosting PoPs across La Paz and western Maricopa counties for Tuesday
afternoon and evening was warranted.

With varying periods of partly to mostly cloudy skies, the South-
Central AZ Deserts can expect a few more degrees of cooling off high
temperatures from today for Tuesday and Wednesday, with widespread
80-degree readings. Tuesday will be cool for most, including
locations west of the CO River Valley with some warming back into the
90s possible by Wednesday. The loosely cut-off system will begin to
become more of an open wave as it clear east of the area overnight
Wednesday, with some slight chances lingering for spotty
thundershower activity over the eastern AZ higher terrain for
Wednesday and Thursday afternoons. For the rest of the forecast area
from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions
will slowly warm back up to near-normal values as very short-lived
ridging passes through the area peaking 1000-500mb thicknesses back
into the mid 570dm range.

Upper level pattern remains active and progressive across the West
for the coming weekend as a broader and deeper Pacific low moves down
the West Coast out of B.C. and the Gulf of Alaska. Beginning
Friday, deep southerly flow filters in across much of the Southwest
states allow for healthy WAA and prolonged warming of temperatures in
spite of the gradually lower UL heights in troughing upstream. What
remained uncertain over previous forecast periods was the southward
extent of the low. It appears now that the main circulation and cold
core stays to our north across the Great Basin. Downstream ridging
would lend us to think the Pacific low would dive further south over
the weekend, but it now looks like ridging over the Plains will
weaken while another upstream Pacific low transitions out of the Gulf
of Alaska late Saturday. This should shift the Great Basin Low over
the Rockies. All-in-all, some variant of troughing will generally
hold over the west with several periods of breezy to gusty winds for
the coming weekend and into early next week. Temperatures shouldn`t
see a significant cool-down, but rather just below mid-May normals
with many lower elevations sites a degree or two either side of 90F.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Gusty westerly winds to continue to gradually diminish through the
rest of the evening and overnight hours as stronger winds aloft
become decoupled from the surface. wind directions to become
easterly later tonight at the phx area taf sites, while KBLH remains
out of a southerly to sw-ly direction, and KIPL out of a westerly
direction. After a period of light winds on Monday morning, stronger
westerly winds to develop Monday afternoon at the phx area taf sites
and at KIPL as stronger winds once again mix down to the sfc, with
KBLH seeing winds picking up from a southerly direction. Dry
westerly flow aloft to keep skies mainly clear through monday at all
of the taf sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Nolte
AVIATION...Percha
FIRE WEATHER...AJ



  [top]

Area Forecast Discussion
National Weather Service Tucson AZ
257 AM MST MON MAY 16 2016

.SYNOPSIS...A low pressure system will move south into the desert
southwest by midweek. Cooler temperatures will occur through Tuesday
followed by isolated to scattered thunderstorms from Tucson eastward
Wednesday. A chance of showers continues across the White mountains
Thursday, then dry conditions with warmer temperatures next weekend.

&&

.DISCUSSION...Breezy conditions again today across far southeast
Arizona. Otherwise...mostly clear skies and cooler afternoon
temperatures can be anticipated. Models continued to track a low
pressure system south into northwest Arizona on Tuesday. Moisture
associated with this system appeared to be limited but enough to
warrant the mention of a few showers and thunderstorms Tuesday into
Thursday. The best chance of showers will be across northern and
eastern sections of the state. Cooler air will also accompany this
system with high temperatures lowering to near normal readings this
week. Thereafter, medium range models showed a ridge of high
pressure building over the desert southwest followed by another
storm system which will bring breezy to windy conditions this
weekend.

&&

.AVIATION...VALID THRU 17/12Z.
Clear skies and VFR conditions will prevail through the forecast
period. Surface wind less than 10 kts thru 16/14z...then increasing
surface wind. Sly/swly surface wind at 15-25 kts and gusts to 23-33
kts by 16/19z...with the strongest surface wind east of KTUS in the
vicinity of KALK, KFHU and especially KDUG. Surface wind diminishing
aft 17/02z and generally less than 10 kts by 17/05z. Aviation
discussion not updated for TAF ammendments.

&&

.FIRE WEATHER.... Breezy conditions will persist today across the far
southeastern corner of southeast Arizona...roughly southeast of a
line from the Huachuca mountains to the Chiricahua mountains in
Cochise county. Critical fire weather thresholds may be briefly
exceeded in this area this afternoon. However, widespread conditions
are not expected and therefore no fire weather headlines will be in
effect. Less wind is expected elsewhere across the forecast area
today, along with dry and cooler conditions.

There will be a slight chance of showers and thunderstorms Tuesday
into Thursday, mainly northeast and east of the Tucson metro area.
The best chance of precipitation will be in the White mountains.
Some afternoon breeziness is expected through the upcoming week,
mainly on Tuesday and then again Friday into Sunday of next weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson




Area Forecast Discussion
National Weather Service Phoenix AZ
1030 PM MST SUN MAY 15 2016

.UPDATE...To Aviation Discussion...

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Gusty westerly winds to continue to gradually diminish through the
rest of the evening and overnight hours as stronger winds aloft
become decoupled from the surface. wind directions to become
easterly later tonight at the phx area taf sites, while KBLH remains
out of a southerly to sw-ly direction, and KIPL out of a westerly
direction. After a period of light winds on Monday morning, stronger
westerly winds to develop Monday afternoon at the phx area taf sites
and at KIPL as stronger winds once again mix down to the sfc, with
KBLH seeing winds picking up from a southerly direction. Dry
westerly flow aloft to keep skies mainly clear through monday at all
of the taf sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Percha
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
900 PM MST SUN MAY 15 2016

.UPDATE...
Updated Aviation and Fire Weather sections.

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front passing across the deserts this afternoon and evening.
Expect southwest winds to prevail through the evening before
starting to become light and variable. Gusts of 20-25 kts will be
common through 02Z before weakening. However, the Imperial valley
will have stronger gusts (30-35 kts) through 04Z before beginning to
weaken. Could see some local blowing dust/sand there but confidence
not high enough to reflect in KIPL TAF. Winds will be lighter on
Monday afternoon. Otherwise, no significant cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
221 PM MST SUN MAY 15 2016

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
454 AM MST SUN MAY 15 2016

.UPDATE...To AVIATION and FIRE WEATHER Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. Breezy conditions are expected today with highs near
normals. This Pacific low is forecast to move into the southwestern
states tonight persisting through Tuesday. This will provide even
cooler temperatures along with slight chances of showers and
thunderstorms. Clearing skies with rebounding temperatures are
forecast for late in the week.

&&

.DISCUSSION...
Drier air has filtered into Arizona as westerly flow aloft moved in
around the southern fringe of the upper low currently situated across
the Pacific Northwest. This drier air has ended any shower or
thunderstorm chances with mainly clear skies expected today. Lowering
heights aloft will allow for some modest cooling to take place today
and as a result highs should only top out in the lower 90s across the
deserts. A deepening surface low over the Great Basin is increasing
pressure gradients across the Desert Southwest resulting in some
breezy winds currently across southeast California. The gradient
will strengthen later today with breezy to windy southwesterly winds
across the majority of the CWA. Winds will remain below advisory
levels, but some gusts to 35 mph are likely across southeast
California and southern Gila County. Elevated fire danger conditions
for a brief time may be realized across southern Gila County this
afternoon, but not enough to warrant any headlines.

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
935 PM MST SAT MAY 14 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a low pressure
system in the northwest U.S. begins to deepen. Breezy conditions are
expected again for Sunday. Another Pacific weather system is
forecast to move into the southwestern states late Sunday through
Tuesday. This will provide even cooler temperatures along with slight
chances of thunderstorms mainly over northern and central Arizona.
Clearing skies with rebounding afternoon temperatures are forecast
for late next week.

&&

.DISCUSSION...

Clearing skies can be seen across southeastern California and the
western half of Arizona this evening. Earlier, a few thunderstorms
swept over the southeastern third of Arizona but that activity has
dissipated and pushed to the east. Low pressure system now over
Oregon continues to gradually deepen and spread its influence further
to the south. Models indicate this system will eventually drop down
towards the south, ultimately moving into northwest Arizona by
Tuesday evening. This will bring a slight chance for thunderstorms to
the region and keep relatively cooler air in place for a few days.
Rain chances are still on the low side but at least there`s a chance
for unsettled weather, particularly Tuesday afternoon through
Wednesday morning. Temperatures should start to climb back above
normals the rest of the week.

&&

.PREVIOUS DISCUSSION...
Latest satellite imagery shows several areas of cumulus congestus,
mainly concentrated across the Mogollon Rim, the CO Plateau and
portions of southeastern AZ. Isolated showers and thunderstorms have
developed, but are mainly relegated to the higher terrain near
Tucson and Flagstaff. Meanwhile, moisture values are running well
above average with dewpoints in the mid 40s. NAEFS PWAT percentiles
are also running above the 90th percentile, though ground based GPS-
IPW and TPW suggest PWATS are somewhat lower. The relatively moist
conditions have also kept temperatures at bay, which have generally
been running in the mid to upper 90s in the lower deserts. At Sky
Harbor Airport, the high has reached 100 degrees.

Preponderance of hi-res CAMs including the operational and
experimental HRRR continue to indicate that isolated convection will develop
across Gila County this afternoon and this evening. PoPs were increased
to around 10 percent in these areas, though in reality most precipitation
that falls will likely evaporate and not measure at the surface. Models
are in excellent agreement that much drier air will be transported
northeastward this evening and overnight, with the GEFS ensemble
mean indicating PWATS dropping as low as 0.40 inches. Consequently,
showers and thunderstorms will dissipate shortly after sunset.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

A weak weather disturbance will continue to produce scattered
cumulus and altocumulus with broken-overcast cirrus this afternoon
before thinning out this evening. Over northern and southeastern
Arizona there will be isolated thunderstorms with some additional
weaker showers which will begin dissipating after sunset. Surface
winds will favor south and southwest directions through the evening
(gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds
will be stronger Sunday afternoon but with significantly less
cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
light winds. The low exits Thursday before another system approaches
Friday and Saturday leading to breezy to windy conditions.
Temperatures will start off below normal Tuesday and Wednesday before
climbing back to normal by Friday. Humidities begin declining
Wednesday with Minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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DISCUSSION...Waters/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




AREA FORECAST DISCUSSION

National Weather Service New Orleans LA

 750 AM CDT MON MAY 16 2016

...SOUNDING DISCUSSION...

Most of the lighter radar echos are not reaching the ground due to
dry air lingering in the low to mid-levels early this morning. Much
of the moisture in the column is in the upper levels with a
precipitable water value of 1.04 inches. A temperature inversion
exists from the surface to about 975 feet. Winds from the east at
the surface rotate and blow from the southwest by 700mb and then
from the west above 500mb. A peak wind speed of 89 knots was at
45000 feet.

12Z balloon info: A successful flight lasting 94 minutes and
reaching a height of 19.8 miles bursting northwest of Gulfport 39
miles downrange from the office.

Ansorge

&&

.PREV DISCUSSION...

SHORT TERM...
Thunderstorm coverage looks to be on an upward trend over the
next few days. This will first present itself over the western and
southern shore coastal sections of SE LA today and tonight. The
first of several disturbances can be seen this morning along the
western gulf coast. This area will move slowly westward today and
Tuesday. sh/ts coverage will increase from the west and sw later
today and the sea breeze looks to get active as well during this
entire scenario. Should see the strongest thunderstorms develop
offshore and move inland disipating during the early morning hours
and developing over land during the late morning and afternoon
hours as the cbrz develops and move inland.

This first disturbance moves out of the area Tuesnight. A short
reprieve follows before the next system moves in from the
northwest. This one will be due to a cold front approaching LA. As
it moves out of east Texas...the associated line of sh/ts looks to
dampen as the front begins to slow and the activity moves eastward
away from the front Wednesday morning. But we should see some
redevelopment during the daylight hours.

The third disturbance moves into the area Thursday. This one will
have a little better focus as it rides along the old frontal axis
which will by this time be a stalled trough axis just north of the
coast by Thursday afternoon. The stalled trough will also act as a
conveyor for eastward moving systems on Friday to take advantage
of all sfc variables causing a very efficient rainfall process.

The front that stalls along the coast does so due to winds
becoming uniform in the vertical greatly reducing the progressive
forcing. This is also the same indication that brings about the
thinking of heavy rainfall. This process looks to be most
efficient Thursday through Friday. Tuesday and Wednesday should be
wet days but they will simply help saturate the area first. We
will also see some upper support during the Thursday-Friday frame
as well enhancing the activity.

There will be opportunity to find strong thunderstorms each day
Monday through Friday. There is also a marginal risk of severe
weather for Monday through Tuesday. But the best chances for seeing
severe weather will be Thursday and Friday. Each day will likely
bring the possibility of waterspout activity and wind gusts to 40
mph. Thursday and Friday may see this activity enhanced a bit
along with the heavy rainfall.

LONG TERM...
The stalled boundary gets a weak reinforcement Saturday and moves
just enough southward to bring relatively drier weather for the
weekend. Don`t take the word drier as meaning no rain
around...there will still be some thunderstorm activity just not
nearly as much.

AVIATION...

VFR conditions will be the rule at all of the terminals through the
forecast period.  There is a low chance of convection potentially
developing near KBTR...KHUM...KHDC...and KMCB between 18z and 22z.
If a thunderstorm develops near a terminal, a very brief period of
MVFR and IFR restrictions could occur.  32

MARINE...

An increasing pressure gradient over the coastal waters today could
lead to some exercise caution conditions across the far western
waters through tomorrow morning. Otherwise, light onshore winds of
around 10 knots and seas of 3 feet or less are expected across the
gulf waters through Wednesday.  Winds should turn more variable and
fall to around 5 knots Wednesday night and Thursday as a weak front
stalls along the coast and dissipates.  By Friday, another
approaching low pressure system will once again increase onshore
flow to around 15 knots.  The gradient should ease in the wake of
the system by Saturday with a light westerly wind of 5 to 10 knots
expected.  Seas could increase to around 3 to 5 feet in the gulf
waters on Friday due to the expected period of near exercise caution
winds. 32

DECISION SUPPORT...

DSS code: Green.
Deployed: None.
Activation: None.
Activities: None.

Decision Support Services (DSS) Code Legend
Green  = No weather impacts that require action.
Blue   = Long-fused watch, warning, or advisory in effect or
         high visibility event.
Yellow = Heightened impacts with short-fused watch, warning
         or advisory issuances; radar support.
Orange = High Impacts; Slight to Moderate risk severe; nearby
         tropical events; HazMat or other large episodes.
Red    = Full engagement for Moderate risk of severe and/or
         direct tropical threats; Events of National Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  79  65  82  67 /  20  20  50  50
BTR  81  67  83  70 /  30  30  60  50
ASD  82  69  83  70 /  10  30  50  40
MSY  82  72  82  72 /  20  30  50  40
GPT  81  71  81  72 /  10  30  50  30
PQL  82  67  81  70 /  10  20  50  30

&&

.LIX Watches/Warnings/Advisories...
LA...None.
GM...None.
MS...None.
GM...None.
&&

$$



  [top]

Area Forecast Discussion
National Weather Service Lake Charles LA
558 AM CDT MON MAY 16 2016

.DISCUSSION...
12z taf issuance.

&&

.AVIATION...
Mainly vfr expected this morning with mid level deck ~10000ft or
higher present with intermittent sprinkles, as noted with weak
radar echos across region. Strongest tsra continues further down
TX coast near CRP. With the upper level disturbance moving east-
east northeast today, expect shra/tsra chances increasing by
afternoon. Have placed tempo group for this from 18-22 for
BPT/LCH, and 20-24z for AEX/LFT/ARA.

&&

.PREV DISCUSSION... /issued 414 AM CDT MON MAY 16 2016/

DISCUSSION...Northwest Gulf front becoming less defined
overnight. Winds will be transitioning back to southerly over the
inland area with dewpoints trending higher. Radar at this time
showing a combination of virga inland and a few sprinkles. More
robust convection is located along and just off the mid-Texas
coast. All activity associated with shortwave troffing
approaching the area within a southwesterly flow aloft. Carrying
likely to high end chance pops today area-wide with this feature
in play.

Will be maintaining significant rain chances daily through the
work-week as similar perturbations approach and move across the
area. Some heavy rainfall potential will exist as deep moisture
continues to be transported inland within a southwesterly flow
aloft. SPC maintaining the western portion of forecast area within
a marginal risk of severe today. Marginal to slight risk will be
in play Tuesday across the entire forecast area.

MARINE...An onshore flow will become reestablished today over the
northwest gulf as a stationary front washes out. Light to
moderate southerly winds will remain in place through much of the
week. A daily chance for a few showers and thunderstorms will
continue as weather disturbances in a southwesterly flow aloft
advance over the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  80  68  84  69 /  40  30  50  60
LCH  80  71  83  72 /  60  30  40  60
LFT  82  70  84  71 /  50  40  50  60
BPT  80  72  84  73 /  60  30  40  60

&&

.LCH Watches/Warnings/Advisories...
LA...None.
TX...None.
GM...None.
&&

$$


AVIATION...08




Area Forecast Discussion
National Weather Service Lake Charles LA
414 AM CDT MON MAY 16 2016

.DISCUSSION...Northwest Gulf front becoming less defined
overnight. Winds will be transitioning back to southerly over the
inland area with dewpoints trending higher. Radar at this time
showing a combination of virga inland and a few sprinkles. More
robust convection is located along and just off the mid-Texas
coast. All activity associated with shortwave troffing
approaching the area within a southwesterly flow aloft. Carrying
likely to high end chance pops today area-wide with this feature
in play.

Will be maintaining significant rain chances daily through the
work-week as similar perturbations approach and move across the
area. Some heavy rainfall potential will exist as deep moisture
continues to be transported inland within a southwesterly flow
aloft. SPC maintaining the western portion of forecast area within
a marginal risk of severe today. Marginal to slight risk will be
in play Tuesday across the entire forecast area.

&&

.MARINE...An onshore flow will become reestablished today over the
northwest gulf as a stationary front washes out. Light to
moderate southerly winds will remain in place through much of the
week. A daily chance for a few showers and thunderstorms will
continue as weather disturbances in a southwesterly flow aloft
advance over the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  80  68  84  69 /  40  30  50  60
LCH  80  71  83  72 /  60  30  40  60
LFT  82  70  84  71 /  50  40  50  60
BPT  80  72  84  73 /  60  30  40  60

&&

.LCH Watches/Warnings/Advisories...
LA...None.
TX...None.
GM...None.
&&

$$

PUBLIC...23




Area Forecast Discussion
National Weather Service Shreveport LA
109 PM CDT SUN MAY 15 2016

.AVIATION...
VFR conditions are expected to prevail through this
afternoon/evening before shwrs/isold tstms gradually overtake the
region during the overnight hours. Cigs/vsbys will likely
deteriorate as the coverage of convection increases through the
end of the pd. Otherwise...winds will veer around to the SE
overnight...and generally remain between 5 and 10 kts through the
TAF pd. /12/

&&

.PREV DISCUSSION... /issued /

DISCUSSION...
Current forecast is on track this morning. Cool surface high
pressure combined with cloud cover from upper-level disturbance to
allow high temperatures to only climb into the 70s across most
locations. Could see temps approaching 80 in Lufkin.
Otherwise, winds to become East at 5 to 10 MPH as surface high
shifts east. Rain to increase in coverage from the south late
this afternoon as surface frontal boundary retreats back north.
/05/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  60  80  68  83 /  60  60  20  50
MLU  59  78  65  84 /  40  60  30  50
DEQ  55  73  63  77 /  60  70  30  50
TXK  57  75  65  80 /  60  70  20  50
ELD  56  75  64  82 /  50  70  20  50
TYR  64  79  68  81 /  60  60  20  50
GGG  62  79  68  82 /  60  60  20  50
LFK  67  82  69  86 /  60  50  20  50

&&

.SHV Watches/Warnings/Advisories...
AR...None.
LA...None.
OK...None.
TX...None.
&&

$$

12




Area Forecast Discussion
National Weather Service Lake Charles LA
1249 PM CDT SUN MAY 15 2016

.DISCUSSION...
15/18Z TAF issuance.

&&

.AVIATION...
VFR conditions prevail with mostly mid and high level clouds acrs
the area. Sctd showers extend west to east acrs the area, north
of I-10 and south of AEX. HRRR indicates, and regional radar
mosaic confirms, convection developing SW of the area which is
expected to move NE bringing the best chc for showers and storms
to LCH and BPT later today. maintained TEMPO groups at these sites
from 19-23Z...with VCTS further east at LFT/ARA. Convection less
likely at AEX so removed mention of TS there but will continue to
monitor. Otherwise, light NE winds today will gradually veer
around to the SE by Monday morning as sfc high moves east.

24

&&

.PREV DISCUSSION... /issued 1117 AM CDT SUN MAY 15 2016/

DISCUSSION...
All recent model runs coming into agreement with bringing deep
south TX convection newd toward the forecast area this afternoon...
primarily our TX zones which are already seeing pop up convection
with somewhat warmer temps being reported. Therefore adjusted
pops slightly over these zones to account. Max temps look like
they may be a tad warm given so much cloud cover/precip but will
let them ride just in case.

Update out shortly.
25

PREV DISCUSSION... /issued 643 AM CDT SUN MAY 15 2016/

DISCUSSION...
For the 15/12z TAF issuance.

AVIATION...
Starting off with VFR conditions, as surface boundary located
near the coast with light northeast winds and extensive mid and
high level clouds. This surface boundary will waffle around the
forecast area today. The surface boundary, along with any sea
breeze development, will be serve as a focus, with daytime heating
and a moist air mass, for scattered afternoon showers and
thunderstorms. The best chance looks to be over southeast Texas
and southwest Louisiana. Therefore, placed tempo groups from
15/19-15/23 for convection, at KBPT and KLCH, based on timing from
hi-res guidance. VCTS will be placed at remainder of TAF sites
after 15/18z. Any convection that develops is expected to diminish
after 16/02z.

Rua

PREV DISCUSSION... /issued 402 AM CDT SUN MAY 15 2016/

DISCUSSION...Radar now clear of any rains. Satellite imagery
showing widespread mid and upper level cloudiness over the region.
Some healthy rain amounts noted from yesterdays late afternoon and
evening rains. 1/2 inch was fairly common across southeast Texas
and into southwest Louisiana, with numerous pockets of heavier
rainfall in a 2 to 4 inch range. Little change needed in forecast
with a very unsettled weather pattern continuing to be expected
through the week.

Surface analysis suggesting latest frontal boundary to enter the
area is now stalled near the coast. Feature progged to meander
over the area for days to come yielding a low level focus for
convective development. An active southwest to near zonal flow
aloft will be carrying occasional impulses across the forecast
area. The boundary and impulses combined will yield occasional
showers and thunderstorms. A potential for heavy rainfall will
continue as deep moisture and high PWATs linger over the area. A
severe weather threat will be increasing with SPC placing the
western portion of the area within a marginal risk for Monday and
marginal or slight for the entire area Tuesday.

MARINE...Winds will trend rather light and variable today as a
stalled frontal boundary meanders over the northwest gulf. This
front is expected to return onshore Monday with southerlies
then returning. With the front in the area, and disturbances
moving overhead in a west to southwest flow aloft, daily chances
for a few showers and thunderstorms will continue.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  80  62  82  67 /  20  20  50  30
LCH  83  69  82  71 /  50  20  50  40
LFT  84  69  84  70 /  40  20  40  40
BPT  84  70  83  71 /  50  30  60  40

&&

.LCH Watches/Warnings/Advisories...
LA...None.
TX...None.
GM...None.
&&

$$


AVIATION...04




Area Forecast Discussion
National Weather Service Phoenix AZ
255 PM MST MON MAY 16 2016

.SYNOPSIS...
A large Pacific low pressure system is expected to move south from
Idaho, and into Arizona late Tuesday through Wednesday. Increasing
clouds with a chance of showers and thunderstorms are forecast to
spread from southeast California and southwest Arizona late Tuesday
afternoon, into south central Arizona Tuesday night and Wednesday.
Clearing is expected Wednesday night, with dry weather and near
normal temperatures developing toward the end of the work week and
weekend.

&&

.DISCUSSION...

Tonight through Wednesday Night...

An interesting weather pattern will develop over the region the next
few days. A large former Pacific low pressure system, centered over
southwest Idaho since Sunday, will start to move south toward AZ.
Strong ridge building along the Pacific northwest coast, folding
over into southwest Canada, bodes well for the Idaho trof to
retrograde and track southwest into southern CA Tuesday and Tuesday
night. Mid/hi level cyclonic shear will increase the potential for
showers and thunderstorms, with increasing moisture. The San Diego
sounding showed some appreciable low level moisture, and the
Chihuahua Mexico balloon sounding showed a hint of a significant
moisture plume visible south of the border in precip water satellite
imagery. Lastly, the Phoenix and Tucson Radar VAD Wind Profiles were
already detect backing south to southwest winds under 12 thsd feet.

As the trof deepens from Idaho toward southern CA, low level winds
will continue to back from the south, importing more moisture into
the tight mid/hi level cyclonic circulation feature expected
Tuesday/Tuesday night. In other words, as the trof moves slowly west
to east, a threat of showers and thunderstorms will first develop in
southeast CA/southwest AZ late Tuesday afternoon,then spread into
south central AZ, including Phoenix, Tuesday night and Wednesday.
Clearing is expected Wednesday night.


Thursday and Friday...

In the aftermath of Wednesdays eastward moving trof, dry west to
northwesterly flow will develop Thursday over our forecast area.
The flow aloft will change to dry southwesterly in advance of yet
another large Pacific weather system expected to develop

However another Large Pacific weather system will settle into the
western states this weekend, producing gusty south to southwest
winds area-wide Fri, Sat, Sun, and Mon afternoons.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...

No aviation weather impacts expected through Tuesday afternoon.
Southeasterly flow will veer to westerly this afternoon, peaking
around 10 kt with occasional gusts to around 15 kt. Onset of
the downslope easterly flow will occur near the climatological
average of 09-10z.

Southeast California/Southwest Arizona including KIPL and KBLH...

Typical diurnal winds expected at the terminals, generally less than
15 kt at KIPL and KBLH. Looking ahead, scattered showers and
thunderstorms will likely develop ahead of an approaching low
pressure system Tuesday afternoon. The strongest storms will be
capable of producing strong downdraft winds.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms east of the Lower
Colorado River Valley. Temperatures will be below normal over south-
central AZ and at or slightly above normal across southeast
California and southwest Arizona. The system exits on Thursday for
warmer temperatures and increasing winds. Another system slowly
approaches from the northwest Friday into Sunday for breezy to windy
conditions each day and a cooling trend. Minimum humidities will
generally be in the 15-20 percent range over the lower deserts
through Thursday before declining to near 10 percent by Friday.
Friday afternoon, and possibly Saturday afternoon, will likely have
elevated fire danger conditions over portions of the area.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Vasquez
AVIATION...Hirsch
FIRE WEATHER...Kuhlman




Area Forecast Discussion
National Weather Service Phoenix AZ
605 AM MST MON MAY 16 2016

.UPDATE...Updated Aviation and Fire Weather Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Broad upper low circulation covers much of the Intermountain West
this early morning with a few well-defined embedded vorticies along a
weak upper jet intrusion on the western side of the low. This low
pressure system will be the focus on our weather for the early part
of the week, bringing a temperature cool down and shower/thunderstorm
chances across the forecast area. Overnight skies remain clear and
winds have subsided from their elevated westerly breezes last
evening. Continued draw-down of UL heights and few degrees of cooling
through the atmo profile transitioning into the area from yesterday`s
cool front have generated cooler morning temperatures so far,
generally 4 to 5 degrees cooler than this time Sunday. Dry
conditions, afternoon southwesterly breezes and temperatures over the
Deserts in the upper 80s to low 90s are expected today ahead of the
southward sagging Great Basin upper low.

Forecast model consistency has been fairly good with regards to this
upper low - still tracking the main circulation center west across
SoCal by Tuesday afternoon and into central AZ overnight Tuesday into
Wednesday. 500mb heights have already retreated from their higher
values late last week so the height fall differential with the
intruding upper low is not as great as previous events we`ve seen
this Spring. PWAT forecasts on model plots and soundings have flirted
with 0.75 to 1.00 inch values, focused mainly along and either side
of the CO River Valley by Tuesday evening. When comparing these
values to soundings from neighboring offices of Tucson and Las Vegas
these forecast values are in the upper reaches of PWAT sounding
climatology. Also hard not imagine some Gulf of California moisture
advection into the region with southerly flow up the river;
dewpoints for sites along the River have touched the 50F mark
periodically over the weekend. While that is more surface based
moisture, a thin layer of mid-level moisture returns are also
forecast. These are most noticeable in several inverted-V soundings
for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few
hundred joules of mean MU and ML CAPE for Tuesday afternoon and
overnight, in conjunction with the overhead passage of the upper
cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C
and -40 to -44C ranges respectively. Still not an overly favorable
profile to support organized convection in terms of wind and we`ll be
looking for the dry sub-cloud layer to enhance evaporative processes
leading to gusty outflow winds from any showers and storms that do
develop. Given the latest guidance suggesting 1) sufficient moisture
for some high-based activity across the western AZ deserts and 2) hi-
resolution gridded wind fields indicating some outflow boundary
activity emanating from the western AZ deserts, felt that slightly
boosting PoPs across La Paz and western Maricopa counties for Tuesday
afternoon and evening was warranted.

With varying periods of partly to mostly cloudy skies, the South-
Central AZ Deserts can expect a few more degrees of cooling off high
temperatures from today for Tuesday and Wednesday, with widespread
80-degree readings. Tuesday will be cool for most, including
locations west of the CO River Valley with some warming back into the
90s possible by Wednesday. The loosely cut-off system will begin to
become more of an open wave as it clear east of the area overnight
Wednesday, with some slight chances lingering for spotty
thundershower activity over the eastern AZ higher terrain for
Wednesday and Thursday afternoons. For the rest of the forecast area
from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions
will slowly warm back up to near-normal values as very short-lived
ridging passes through the area peaking 1000-500mb thicknesses back
into the mid 570dm range.

Upper level pattern remains active and progressive across the West
for the coming weekend as a broader and deeper Pacific low moves down
the West Coast out of B.C. and the Gulf of Alaska. Beginning
Friday, deep southerly flow filters in across much of the Southwest
states allow for healthy WAA and prolonged warming of temperatures in
spite of the gradually lower UL heights in troughing upstream. What
remained uncertain over previous forecast periods was the southward
extent of the low. It appears now that the main circulation and cold
core stays to our north across the Great Basin. Downstream ridging
would lend us to think the Pacific low would dive further south over
the weekend, but it now looks like ridging over the Plains will
weaken while another upstream Pacific low transitions out of the Gulf
of Alaska late Saturday. This should shift the Great Basin Low over
the Rockies. All-in-all, some variant of troughing will generally
hold over the west with several periods of breezy to gusty winds for
the coming weekend and into early next week. Temperatures shouldn`t
see a significant cool-down, but rather just below mid-May normals
with many lower elevations sites a degree or two either side of 90F.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Light winds this morning will turn westerly and become breezy at
times this afternoon, mainly at Phoenix area terminals. Dry westerly
flow aloft will keep skies mainly clear into early Tuesday before
the next weather system moves into the region bringing a chance of
showers and thunderstorms later Tuesday.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms east of the Lower
Colorado River Valley. Temperatures will be below normal over south-
central AZ and at or slightly above normal across southeast
California and southwest Arizona. The system exits on Thursday for
warmer temperatures and increasing winds. Another system slowly
approaches from the northwest Friday into Sunday for breezy to windy
conditions each day and a cooling trend. Minimum humidities will
generally be in the 15-20 percent range over the lower deserts
through Thursday before declining to near 10 percent by Friday.
Friday afternoon, and possibly Saturday afternoon, will likely have
elevated fire danger conditions over portions of the area.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Nolte
AVIATION...Kuhlman
FIRE WEATHER...Kuhlman



  [top]

Area Forecast Discussion
National Weather Service Flagstaff AZ
358 AM MST MON MAY 16 2016

.SYNOPSIS...Expect breezy west southwest winds today, along with
an increasing chance of showers and thunderstorms by afternoon. A
slow moving storm system will keep a chance of showers and
thunderstorms over the area through at least Thursday.
Temperatures will be below average through midweek and then warm
back to around average second half of the week. &&

.DISCUSSION...A large area of low pressure over the western states will
continue to move southward today...and be over the area Tuesday
and Wednesday. Best chances for showers today will primarily be
north of I-40...with the best lift and instability.

Tuesday and Wednesday...The area of low pressure will drop
southward into portions of northwest and central Arizona on
Tuesday...and then be over the region on Wednesday. Stronger
lift...deeper saturation...and instability will provide for good
chances of showers and thunderstorms. Rainfall amounts look to be
from 0.1 to 0.5 inches with this system, lighter amounts expected
for the lower elevations

Thursday northern Arizona is forecast to transition from a low
pressure trough back to a high pressure ridge pattern, bringing
drier conditions and warming daytime temperatures.

Friday through Sunday...Another low pressure trough is forecast
to approach northern Arizona from the west, producing a dry and
windy southwest flow.

By Monday of next week the low pressure trough is forecast to
move across Arizona...bringing lighter winds...drying
conditions...and slightly below average daytime temperatures.
&&

.AVIATION...For the 12Z package...Expect VFR conditions overnight.
After 18Z Mon...expect isolated to scattered SHRA/TSRA primarily
along and north of a KFLG-KRQE line with brief MVFR cig/vis
possible. Winds becoming westerly Mon afternoon 15-25 kts. In
addition, collapsing TSRA may produce very strong and erratic
surface winds with gusts as high as 50 knots possible in the
vicinity of storms. Aviation discussion not updated for TAF
amendments.


.FIRE WEATHER...A slow moving low will bring increasing moisture
and increasing chances for showers and thunderstorms to northern
Arizona on Monday and Tuesday.

Wednesday through Friday...Chances for showers and thunderstorms
continue through Wednesday with a drying trend starting from
Thursday onward.
&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...TC
AVIATION...RR
FIRE WEATHER...RR


For Northern Arizona weather information visit
weather.gov/flagstaff




Area Forecast Discussion
National Weather Service Phoenix AZ
314 AM MST MON MAY 16 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Broad upper low circulation covers much of the Intermountain West
this early morning with a few well-defined embedded vorticies along a
weak upper jet intrusion on the western side of the low. This low
pressure system will be the focus on our weather for the early part
of the week, bringing a temperature cool down and shower/thunderstorm
chances across the forecast area. Overnight skies remain clear and
winds have subsided from their elevated westerly breezes last
evening. Continued draw-down of UL heights and few degrees of cooling
through the atmo profile transitioning into the area from yesterday`s
cool front have generated cooler morning temperatures so far,
generally 4 to 5 degrees cooler than this time Sunday. Dry
conditions, afternoon southwesterly breezes and temperatures over the
Deserts in the upper 80s to low 90s are expected today ahead of the
southward sagging Great Basin upper low.

Forecast model consistency has been fairly good with regards to this
upper low - still tracking the main circulation center west across
SoCal by Tuesday afternoon and into central AZ overnight Tuesday into
Wednesday. 500mb heights have already retreated from their higher
values late last week so the height fall differential with the
intruding upper low is not as great as previous events we`ve seen
this Spring. PWAT forecasts on model plots and soundings have flirted
with 0.75 to 1.00 inch values, focused mainly along and either side
of the CO River Valley by Tuesday evening. When comparing these
values to soundings from neighboring offices of Tucson and Las Vegas
these forecast values are in the upper reaches of PWAT sounding
climatology. Also hard not imagine some Gulf of California moisture
advection into the region with southerly flow up the river;
dewpoints for sites along the River have touched the 50F mark
periodically over the weekend. While that is more surface based
moisture, a thin layer of mid-level moisture returns are also
forecast. These are most noticeable in several inverted-V soundings
for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few
hundred joules of mean MU and ML CAPE for Tuesday afternoon and
overnight, in conjunction with the overhead passage of the upper
cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C
and -40 to -44C ranges respectively. Still not an overly favorable
profile to support organized convection in terms of wind and we`ll be
looking for the dry sub-cloud layer to enhance evaporative processes
leading to gusty outflow winds from any showers and storms that do
develop. Given the latest guidance suggesting 1) sufficient moisture
for some high-based activity across the western AZ deserts and 2) hi-
resolution gridded wind fields indicating some outflow boundary
activity emanating from the western AZ deserts, felt that slightly
boosting PoPs across La Paz and western Maricopa counties for Tuesday
afternoon and evening was warranted.

With varying periods of partly to mostly cloudy skies, the South-
Central AZ Deserts can expect a few more degrees of cooling off high
temperatures from today for Tuesday and Wednesday, with widespread
80-degree readings. Tuesday will be cool for most, including
locations west of the CO River Valley with some warming back into the
90s possible by Wednesday. The loosely cut-off system will begin to
become more of an open wave as it clear east of the area overnight
Wednesday, with some slight chances lingering for spotty
thundershower activity over the eastern AZ higher terrain for
Wednesday and Thursday afternoons. For the rest of the forecast area
from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions
will slowly warm back up to near-normal values as very short-lived
ridging passes through the area peaking 1000-500mb thicknesses back
into the mid 570dm range.

Upper level pattern remains active and progressive across the West
for the coming weekend as a broader and deeper Pacific low moves down
the West Coast out of B.C. and the Gulf of Alaska. Beginning
Friday, deep southerly flow filters in across much of the Southwest
states allow for healthy WAA and prolonged warming of temperatures in
spite of the gradually lower UL heights in troughing upstream. What
remained uncertain over previous forecast periods was the southward
extent of the low. It appears now that the main circulation and cold
core stays to our north across the Great Basin. Downstream ridging
would lend us to think the Pacific low would dive further south over
the weekend, but it now looks like ridging over the Plains will
weaken while another upstream Pacific low transitions out of the Gulf
of Alaska late Saturday. This should shift the Great Basin Low over
the Rockies. All-in-all, some variant of troughing will generally
hold over the west with several periods of breezy to gusty winds for
the coming weekend and into early next week. Temperatures shouldn`t
see a significant cool-down, but rather just below mid-May normals
with many lower elevations sites a degree or two either side of 90F.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Gusty westerly winds to continue to gradually diminish through the
rest of the evening and overnight hours as stronger winds aloft
become decoupled from the surface. wind directions to become
easterly later tonight at the phx area taf sites, while KBLH remains
out of a southerly to sw-ly direction, and KIPL out of a westerly
direction. After a period of light winds on Monday morning, stronger
westerly winds to develop Monday afternoon at the phx area taf sites
and at KIPL as stronger winds once again mix down to the sfc, with
KBLH seeing winds picking up from a southerly direction. Dry
westerly flow aloft to keep skies mainly clear through monday at all
of the taf sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Nolte
AVIATION...Percha
FIRE WEATHER...AJ



  [top]

Area Forecast Discussion
National Weather Service Tucson AZ
257 AM MST MON MAY 16 2016

.SYNOPSIS...A low pressure system will move south into the desert
southwest by midweek. Cooler temperatures will occur through Tuesday
followed by isolated to scattered thunderstorms from Tucson eastward
Wednesday. A chance of showers continues across the White mountains
Thursday, then dry conditions with warmer temperatures next weekend.

&&

.DISCUSSION...Breezy conditions again today across far southeast
Arizona. Otherwise...mostly clear skies and cooler afternoon
temperatures can be anticipated. Models continued to track a low
pressure system south into northwest Arizona on Tuesday. Moisture
associated with this system appeared to be limited but enough to
warrant the mention of a few showers and thunderstorms Tuesday into
Thursday. The best chance of showers will be across northern and
eastern sections of the state. Cooler air will also accompany this
system with high temperatures lowering to near normal readings this
week. Thereafter, medium range models showed a ridge of high
pressure building over the desert southwest followed by another
storm system which will bring breezy to windy conditions this
weekend.

&&

.AVIATION...VALID THRU 17/12Z.
Clear skies and VFR conditions will prevail through the forecast
period. Surface wind less than 10 kts thru 16/14z...then increasing
surface wind. Sly/swly surface wind at 15-25 kts and gusts to 23-33
kts by 16/19z...with the strongest surface wind east of KTUS in the
vicinity of KALK, KFHU and especially KDUG. Surface wind diminishing
aft 17/02z and generally less than 10 kts by 17/05z. Aviation
discussion not updated for TAF ammendments.

&&

.FIRE WEATHER.... Breezy conditions will persist today across the far
southeastern corner of southeast Arizona...roughly southeast of a
line from the Huachuca mountains to the Chiricahua mountains in
Cochise county. Critical fire weather thresholds may be briefly
exceeded in this area this afternoon. However, widespread conditions
are not expected and therefore no fire weather headlines will be in
effect. Less wind is expected elsewhere across the forecast area
today, along with dry and cooler conditions.

There will be a slight chance of showers and thunderstorms Tuesday
into Thursday, mainly northeast and east of the Tucson metro area.
The best chance of precipitation will be in the White mountains.
Some afternoon breeziness is expected through the upcoming week,
mainly on Tuesday and then again Friday into Sunday of next weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson




Area Forecast Discussion
National Weather Service Phoenix AZ
1030 PM MST SUN MAY 15 2016

.UPDATE...To Aviation Discussion...

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Gusty westerly winds to continue to gradually diminish through the
rest of the evening and overnight hours as stronger winds aloft
become decoupled from the surface. wind directions to become
easterly later tonight at the phx area taf sites, while KBLH remains
out of a southerly to sw-ly direction, and KIPL out of a westerly
direction. After a period of light winds on Monday morning, stronger
westerly winds to develop Monday afternoon at the phx area taf sites
and at KIPL as stronger winds once again mix down to the sfc, with
KBLH seeing winds picking up from a southerly direction. Dry
westerly flow aloft to keep skies mainly clear through monday at all
of the taf sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Percha
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
900 PM MST SUN MAY 15 2016

.UPDATE...
Updated Aviation and Fire Weather sections.

&&

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
upper low pressure, that is now moving into the northern Great
Basin, has begun to bring cooler temperatures to the region today,
with the high at Phoenix Sky Harbor ending up at 95 today, down 6
degrees from yesterday`s high of 101. Along with the cooler
temperatures, locally gusty winds also occurred today as the winds
aloft increase ahead of the upper low. westerly winds in the 15-20
mph range with gusts to 30 mph were observed at many locations
across South-Central and SW Arizona, with even stronger winds over
parts of SE CA. Along with the winds, a few pockets of blowing dust
were also observed. The latest (00z) GFS and NAM model suites
continue to show the upper low moving toward the region through the
early and middle parts of this week, with temperatures cooling even
further, and even a chance for showers from late Tuesday into
Wednesday, as the upper low center moves across the region. As far
as the very short term is concerned, other then some downward
adjustment in the hourly dewpoint forecasts and some minor
adjustments to the other hourly grids, inherited forecasts are
holding up well.

&&

.PREVIOUS DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front passing across the deserts this afternoon and evening.
Expect southwest winds to prevail through the evening before
starting to become light and variable. Gusts of 20-25 kts will be
common through 02Z before weakening. However, the Imperial valley
will have stronger gusts (30-35 kts) through 04Z before beginning to
weaken. Could see some local blowing dust/sand there but confidence
not high enough to reflect in KIPL TAF. Winds will be lighter on
Monday afternoon. Otherwise, no significant cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday...
An upper level low will begin weakening on Wednesday with just a
slight chance of showers and thunderstorms (east of the Lower
Colorado River Valley). Temperatures will be below normal over
south-central AZ (at or slightly above normal west of there). Winds
will be light. The system exits on Thursday for warmer temperatures
and more noticeable afternoon breezes. Another system slowly
approaches from the northwest Friday into Sunday for breezy
conditions (especially southeast California) and a cooling trend.
Minimum humidities will generally be in the 15-20 percent range on
the lower deserts before declining to near 10 percent by Friday.
Overnight recovery also trends down but remains fair. Portions of
southeast California and the Lower Colorado River Valley may
occasionally flirt with critical thresholds during the Friday-Sunday
time frame.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Percha/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
221 PM MST SUN MAY 15 2016

.SYNOPSIS... Cooler air is beginning to move into the region as a
Pacific low pressure system in the northwest U.S. begins to deepen
and sag further south. The Pacific low is forecast to move into the
southwestern states early this week persisting through Wednesday.
This will provide even cooler temperatures along with slight chances
of showers and thunderstorms Tuesday. Clearing skies with rebounding
temperatures are forecast for late in the week.

&&

.DISCUSSION...
Upper low across the Great Basin continues to drift eastward this
afternoon. Latest satellite imagery shows widespread cloudiness out
ahead of this system across the Rockies with a smattering of showers
and thunderstorms extending southward into Chihuahua. Across the
desert southwest, skies have been mostly clear with temperatures in
the lower 90s across the lower deserts, a drop of roughly 6 to 8 from
those observed yesterday. Dewpoints are also significantly lower east
of Phoenix, though moisture is already increasing again across
western Arizona ahead of a vort max traversing the Mojave Desert.
This vort max will also strengthen wind fields across the region and
breezy conditions are anticipated through this evening across much of
the area.

No major changes were made to the forecast in the short-term.
Temperatures tonight will be near or slightly above average with
subsiding winds and mostly clear skies.

&&

.PREVIOUS DISCUSSION...

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
454 AM MST SUN MAY 15 2016

.UPDATE...To AVIATION and FIRE WEATHER Discussions...

&&

.SYNOPSIS...
Cooler air is beginning to move into the region as a Pacific low
pressure system in the northwest U.S. begins to deepen and sag
further south. Breezy conditions are expected today with highs near
normals. This Pacific low is forecast to move into the southwestern
states tonight persisting through Tuesday. This will provide even
cooler temperatures along with slight chances of showers and
thunderstorms. Clearing skies with rebounding temperatures are
forecast for late in the week.

&&

.DISCUSSION...
Drier air has filtered into Arizona as westerly flow aloft moved in
around the southern fringe of the upper low currently situated across
the Pacific Northwest. This drier air has ended any shower or
thunderstorm chances with mainly clear skies expected today. Lowering
heights aloft will allow for some modest cooling to take place today
and as a result highs should only top out in the lower 90s across the
deserts. A deepening surface low over the Great Basin is increasing
pressure gradients across the Desert Southwest resulting in some
breezy winds currently across southeast California. The gradient
will strengthen later today with breezy to windy southwesterly winds
across the majority of the CWA. Winds will remain below advisory
levels, but some gusts to 35 mph are likely across southeast
California and southern Gila County. Elevated fire danger conditions
for a brief time may be realized across southern Gila County this
afternoon, but not enough to warrant any headlines.

The upper low eventually will start to dig southward through the
Great Basin on Monday into the Desert Southwest on Tuesday. Models
have been consistent with the overall track of this system, but have
shifted it further west slightly over the past 24 hours. Some
moisture advection is expected over our area Tuesday into early
Wednesday with PWATS increasing to between 0.50-0.75 inches. Though
this system is not very cold aloft (500mb temps near -16C) there
should be sufficient moisture and instability for some isolated
showers and thunderstorms starting Tuesday afternoon. Overall timing
has shifted a bit later, so rain chances will linger into Wednesday,
especially from Phoenix eastward. Have added in slight chance POPs
across south-central Arizona for Tuesday night and Wednesday morning
with chances remaining through Wednesday evening across the higher
terrain east of Phoenix. We could see a shot at some gusty thunderstorm
winds with an inverted V forecast sounding structure, but winds aloft
will be light, so would only rely on evaporative cooling effects.

Temperatures through Wednesday are forecast to be at or below normals
with Monday and Tuesday being the coolest days with highs mostly in
the upper 80s across the lower deserts. We will start to see some
warming across our western zones on Wednesday under rising heights
aloft as highs climb back into the middle 90s.

Model consensus continues to show a deep Pacific low digging
southward into the Pacific Northwest late this week, but what happens
thereafter is less certain as model spread increases into next
weekend. For the Desert Southwest, heights aloft and temperatures
will certainly rise on Thursday and Friday resulting in highs at or
just above normals (middle to upper 90s). Have low confidence in the
forecast picture for next weekend as it is not clear if the Pacific
low will dig far enough south to affect the Desert Southwest.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

Dry cool front will make its way across the region today increasing
winds while promoting less cloud cover. Typical AM wind headings will
transition through south to southwest during the day while increasing
in speed. Gusts in the upper teens to low twenty knot range will be
possible for the Phoenix area terminals and KBLH, while stronger
winds off the mountains are expected for KIPL with gusts at or
greater than 30kts. West winds to linger later into the evening than
usual, losing their gustiness but remaining elevated. One final band
of mid-level clouds will continue to track E-SE with mostly clear
skies filling in behind the exiting SCT-BKN layers by the afternoon
and evening.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
mostly light winds. The upper low exits Thursday before another
system approaches Friday and Saturday leading to breezy to windy
conditions. Winds, under current forecast guidance, look to be
stronger for the late week system than the one responsible for the
winds over the late weekend and early in the work week. Temperatures
will start off below normal Tuesday and Wednesday before climbing
back to normal by Friday. Humidities begin declining Wednesday with
minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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

DISCUSSION...Kuhlman
AVIATION...Nolte
FIRE WEATHER...Nolte/AJ




Area Forecast Discussion
National Weather Service Phoenix AZ
935 PM MST SAT MAY 14 2016

.SYNOPSIS...
Cooler air is beginning to move into the region as a low pressure
system in the northwest U.S. begins to deepen. Breezy conditions are
expected again for Sunday. Another Pacific weather system is
forecast to move into the southwestern states late Sunday through
Tuesday. This will provide even cooler temperatures along with slight
chances of thunderstorms mainly over northern and central Arizona.
Clearing skies with rebounding afternoon temperatures are forecast
for late next week.

&&

.DISCUSSION...

Clearing skies can be seen across southeastern California and the
western half of Arizona this evening. Earlier, a few thunderstorms
swept over the southeastern third of Arizona but that activity has
dissipated and pushed to the east. Low pressure system now over
Oregon continues to gradually deepen and spread its influence further
to the south. Models indicate this system will eventually drop down
towards the south, ultimately moving into northwest Arizona by
Tuesday evening. This will bring a slight chance for thunderstorms to
the region and keep relatively cooler air in place for a few days.
Rain chances are still on the low side but at least there`s a chance
for unsettled weather, particularly Tuesday afternoon through
Wednesday morning. Temperatures should start to climb back above
normals the rest of the week.

&&

.PREVIOUS DISCUSSION...
Latest satellite imagery shows several areas of cumulus congestus,
mainly concentrated across the Mogollon Rim, the CO Plateau and
portions of southeastern AZ. Isolated showers and thunderstorms have
developed, but are mainly relegated to the higher terrain near
Tucson and Flagstaff. Meanwhile, moisture values are running well
above average with dewpoints in the mid 40s. NAEFS PWAT percentiles
are also running above the 90th percentile, though ground based GPS-
IPW and TPW suggest PWATS are somewhat lower. The relatively moist
conditions have also kept temperatures at bay, which have generally
been running in the mid to upper 90s in the lower deserts. At Sky
Harbor Airport, the high has reached 100 degrees.

Preponderance of hi-res CAMs including the operational and
experimental HRRR continue to indicate that isolated convection will develop
across Gila County this afternoon and this evening. PoPs were increased
to around 10 percent in these areas, though in reality most precipitation
that falls will likely evaporate and not measure at the surface. Models
are in excellent agreement that much drier air will be transported
northeastward this evening and overnight, with the GEFS ensemble
mean indicating PWATS dropping as low as 0.40 inches. Consequently,
showers and thunderstorms will dissipate shortly after sunset.

&&

.AVIATION...
South-Central Arizona including KPHX...KIWA and KSDL...
Southeast California/Southwest Arizona including KIPL and KBLH...

A weak weather disturbance will continue to produce scattered
cumulus and altocumulus with broken-overcast cirrus this afternoon
before thinning out this evening. Over northern and southeastern
Arizona there will be isolated thunderstorms with some additional
weaker showers which will begin dissipating after sunset. Surface
winds will favor south and southwest directions through the evening
(gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds
will be stronger Sunday afternoon but with significantly less
cloudiness.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
A low pressure system will be centered over northwest Arizona on
Tuesday and Wednesday leading to a slight chance of thunderstorms
over south-central Arizona. Temperatures will be below normal with
light winds. The low exits Thursday before another system approaches
Friday and Saturday leading to breezy to windy conditions.
Temperatures will start off below normal Tuesday and Wednesday before
climbing back to normal by Friday. Humidities begin declining
Wednesday with Minimum values dipping to about 10% late in the week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

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

$$


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DISCUSSION...Waters/Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AJ
FIRE WEATHER...AJ