Area Forecast Discussion
Issued by NWS Phoenix, AZ

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KPSR 062147
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 PM MST MON JUL 6 2015

.SYNOPSIS...
THUNDERSTORM CHANCES WILL DWINDLE OVER LOWER ELEVATION COMMUNITIES
THIS WEEK...WITH DRIER SOUTHWESTERLY FLOW DEVELOPING ACROSS THE
REGION. RAINFALL CHANCES WILL PRIMARILY BE RELEGATED TO THE MOUNTAINS
OF NORTHERN AND EASTERN ARIZONA. DESPITE THE LACK OF STORM
ACTIVITY...TEMPERATURES WILL REMAIN SLIGHTLY BELOW NORMAL. DURING
THIS UPCOMING WEEKEND...HIGH PRESSURE WILL BEGIN TO STRENGTHEN
LEADING TO WARMER TEMPERATURES AND POSSIBLY AN INCREASE IN MOISTURE.

&&

.DISCUSSION...

AFTERNOON WV IMAGERY DEPICTS AN UNSEASONABLY DEEP CIRCULATION CENTER
OFF THE CALIFORNIA COAST (37N 130W) WITH OBJECTIVELY ANALYZED DEEP
WESTERLY FLOW ENVELOPING THE SWRN CONUS. 12Z KTWC SOUNDING DATA
SUPPORTS THIS ANALYSIS WITH A MARKED DECREASE IN MOISTURE ABOVE THE
H5 LAYER. VERTICAL MIXING AND INCREASING DEPTH OF DRIER WESTERLY
FLOW SHOULD FURTHER DECREASE MOISTURE PROFILES SUCH THAT MEAN
BOUNDARY LAYER MIXING RATIOS WILL FALL BELOW 10 G/KG OVER MUCH OF
THE FORECAST AREA THIS EVENING...AND AS LOW AS 5-8 G/KG BY
WEDNESDAY. AS SUCH...DEEP CONVECTION WILL BE FOCUSED ALMOST
EXCLUSIVELY TO TERRAIN FEATURES (ESPECIALLY TOWARDS EASTERN ARIZONA)
WITH STRONGER STEERING FLOW PUSHING STORMS TO THE EAST AND
DISRUPTING ORGANIZED OUTFLOW BOUNDARIES.

A LEADING SPOKE OF VORTICITY LIFTING NORTHEAST INTO SRN NEVADA WAS
CREATING FAVORABLE ASCENT FIELDS NORTH OF THE CWA WHERE RESIDUAL
DEEPER MOISTURE STILL RESIDES. THROUGH CENTRAL AND SOUTHERN ARIZONA
LARGER SCALE SUBSIDENCE WAS OVERSPREADING THE REGION...HOWEVER
SUFFICIENT MOISTURE NOT YET SCOURED FROM THE BOUNDARY LAYER WAS
LEADING TO WEAKER PULSE-TYPE SHOWERS/STORMS FORCED OFF TERRAIN
FEATURES. FEELING WITH THIS ACTIVITY ALMOST EXCLUSIVELY DIURNALLY
FORCED...SHOWERS WILL RAPIDLY DISSIPATE WITH SUNSET YIELDING A QUIET
OVERNIGHT.

EVEN LESS CONVECTIVE ACTIVITY WILL COVER THE REGION TUESDAY AND
WEDNESDAY AS MOISTURE PROFILES ARE GRADUALLY REDUCED FURTHER.
FORECAST SOUNDINGS SUGGEST BOUNDARY LAYER MIXING RATIOS POSSIBLY
EVEN FALLING BELOW 5 G/KG (PARTICULARLY THROUGH THE WESTERN HALF OF
THE FORECAST AREA) WHICH WOULD BE A PROXY FOR A COMPLETE LACK OF
CLOUD COVER MUCH LESS STORM ACTIVITY. DESPITE THE LACK OF CLOUD
COVER AND UNLIKE MOST CONVECTIVELY INACTIVE LAPSES DURING MONSOON
SEASON...TEMPERATURES WILL ACTUALLY BE MODERATED AND ALMOST
COMFORTABLE DUE TO DECREASING HEIGHTS/THICKNESSES ALOFT AHEAD OF THE
APPROACHING UPPER LEVEL LOW FROM THE EAST PACIFIC.

THURSDAY AND FRIDAY...
AS THE UPPER LOW CENTER MOVES OVER SRN CALIFORNIA THURSDAY...A
DEEPER SOUTHERLY FLOW MAY ACT TO INCREASE MOISTURE OVER THE EASTERN
THIRD OF ARIZONA...THOUGH DRY AIR WILL REMAIN FIRMLY IN PLACE TO THE
WEST. A VORT LOBE MAY ALSO SWING THROUGH SOUTHEAST CALIFORNIA AND
WESTERN ARIZONA...AS DEPICTED BY BOTH THE GFS AND ECMWF. IN
ADDITION...MODELS INDICATE SOME DIFLUENCE RELATED TO UPPER LEVEL
DIVERGENCE FIELDS. NOT KNOWING JUST HOW MUCH MOISTURE WILL BE
AVAILABLE...MADE SOME JUST SOME SUBTLE UPWARD ADJUSTMENTS TO THE
POPS OVER OUR EASTERN AREAS. THE LOW WEAKENS AND SHIFTS
NORTHEASTWARD THURSDAY BUT IS REPLACED WITH RENEWED TROUGHING NEAR
THE CALIFORNIA COAST ON FRIDAY. THUS MOISTURE OVER EASTERN ARIZONA
MAY REMAIN IN PLACE YIELDING LITTLE CHANGE IN THE FORECAST. WITH THE
RIDGE BEING SHIFTED FURTHER EAST...TEMPS COOL A LITTLE BIT.

SATURDAY AND SUNDAY...
FOR NEXT WEEKEND...MEDIUM RANGE MODELS DEPICT A WESTWARD EXPANSION
OF THE HIGH CENTERED TO OUR EAST WITH MOISTURE IMPROVING OVER THE
LOWER DESERTS. THE GFS IS MORE GENEROUS WITH THE MOIST ADVECTION THE
ECMWF. WITH STRONGER HIGH PRESSURE...TEMPERATURES ALOFT WILL BE
WARMER AND WHICH COULD OFFSET TO SOME DEGREE THE MOISTURE INCREASE.
TOOK CONSERVATIVE APPROACH AND ONLY EXPANDED POPS TO PINAL COUNTY.
ANTICIPATE TEMPERATURES TO BE WARMER AT THE SURFACE AS WELL WITH
HIGHS NUDGING UP ABOVE 105.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
LITTLE TO NO AVIATION IMPACTS THROUGH TUESDAY AFTERNOON...WITH
AFTERNOON/EARLY EVENING TSRA CONFINED MAINLY WELL SOUTH AND/OR EAST
OF THE TERMINALS. WHILE A WIND SHIFT FROM DISTANT OUTFLOWS MAY BE
POSSIBLE...LIGHT WESTERLY SFC WINDS SHOULD PREVAIL BEFORE SHIFTING
BACK TO EASTERLY LATE TONIGHT.


SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NO AVIATION IMPACTS UNDER MOSTLY CLEAR SKIES. WINDS WILL GENERALLY
RETAIN A SOUTHERLY COMPONENT THROUGH THE PERIOD...THOUGH COULD
BECOME VARIABLE AT TIME TOWARDS SUNRISE. OCCASIONAL AFTERNOON GUSTS
MAY ALSO BE POSSIBLE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
ATMOSPHERIC FLOW WILL REMAIN SOUTHWESTERLY HEADING INTO THE
WEEKEND...KEEPING THUNDERSTORM CHANCES WELL TO THE EAST OF PHOENIX
OVER HIGHER TERRAIN LOCATIONS. EVEN THE TYPICALLY ACTIVE REGIONS IN
SOUTHERN GILA COUNTY MAY LACK THUNDERSTORMS DURING THE END OF THE
WEEK. MOISTURE MAY RETURN BY THE BEGINNING OF NEXT WEEK BRINGING
BACK MORE EXTENSIVE STORMS. AFTERNOON HUMIDITY LEVELS WILL RETREAT
BACK INTO A 10-15 PERCENT RANGE ACROSS LOWER ELEVATIONS WITH FAIR TO
GOOD OVERNIGHT RECOVERY. SOMEWHAT HIGHER HUMIDITY VALUES WILL BE
EXPERIENCED IN MOUNTAIN LOCATIONS. GENERALLY LIGHT AND DIURNALLY
DRIVEN WINDS SPEEDS AND DIRECTIONS WILL PREDOMINATE ALL WEEK...WITH
SOMEWHAT MORE AFTERNOON UPSLOPE GUSTINESS THAN IS TYPICAL DURING
MONSOON SEASON.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS
ACCORDING TO STANDARD OPERATING PROCEDURES.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.

&&

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...MO/AJ
AVIATION...MO
FIRE WEATHER...MO


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.