Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 011107
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
406 AM MST MON SEP 1 2014

.UPDATE...AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
ABOVE NORMAL TEMPERATURES WILL CONTINUE THROUGH THE MAJORITY OF THE
WEEK UNDER MOSTLY DRY CONDITIONS. MOISTURE WILL MAKE A GRADUAL
RETURN INTO THE REGION DURING THE LATE WEEK...SUPPORTING INCREASING
CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS OVER THE HIGHER
TERRAIN OF EASTERN AZ. BY THE WEEKEND...A DEEPER TROPICAL MOISTURE
PROFILE MAY BEGIN TO WORK INTO THE REGION BRINGING INCREASING
HUMIDITIES AND CLOUD COVER WITH SLIGHT STORM CHANCES BACK IN THE
FORECAST OVER THE LOWER DESERT ELEVATIONS OF ARIZONA AND TOWARDS THE
LOWER COLORADO RIVER VALLEY.

&&

.DISCUSSION...
DRY WEST-NORTHWEST FLOW REMAINS OVER THE SOUTHWEST STATES TODAY AS
BROAD TROUGHING ENCOMPASSES MUCH OF THE CONUS KEEPING EARLY AM SKIES
OVER THE FORECAST AREA MOSTLY CLEAR. SUBTROPICAL RIDGING REMAINS OVER
THE FAR SOUTHERN TIER OF THE COUNTRY AND MEXICO AS A RESULT WITH HIGH
PRESSURE CENTERS OVER THE GULF OF MEXICO/SE TX COAST AND OVER
NORTHERN SONORA/GULF OF CA. MORE RECOGNIZABLE AMPLIFIED RIDGING
REMAINS OVER THE EASTERN PACIFIC...STARTING JUST OFF THE BAJA COAST
EXTENDING TOWARDS 140W/41N. SHORTWAVE TROUGHING WILL CONTINUE
TRACKING EASTWARD ACROSS THE NORTHERN TIER OF THE COUNTRY THROUGH THE
EARLY WEEK...LIFTING NORTHWARD ENOUGH TO ALLOW THE UPPER RIDGE TO
REORGANIZE AND CONSOLIDATE TO OUR EAST BY TUESDAY.

500MB HEIGHTS WILL GENERALLY HOLD AT OR JUST ABOVE THE 590DM
MARK...SUPPORTING CONTINUED ABOVE NORMAL DAYTIME TEMPERATURES FOR
MUCH OF THE COMING WEEK. 850MB TEMPERATURES NEAR 28/29C EACH
AFTERNOON TRANSLATE TO HIGH TEMPERATURES JUST SHY OF THE 110F MARK
OVER THE SOUTH-CENTRAL DESERTS...AND JUST A FEW DEGREES WARMER OUT
WEST FOR EL CENTRO/YUMA/LOWER COLORADO RIVER VALLEY. WHERE UPPER
RIDGE HEIGHTS WILL WORK TO KEEP OUR WARMER DAYTIME
TEMPERATURES GOING...THE REPOSITIONING OF THE RIDGE TO OUR EAST WILL
TRANSITION LOWER TO MID LEVEL WINDS BACK TO MORE SOUTHERLY HEADINGS.
INVERTED WAVE ACTIVITY OVER NORTHERN MEXICO WILL HELP INCREASE
MOISTURE LEVELS TO OUR SOUTH THROUGH THE EARLY WEEK WITH 8C OR
GREATER 850MB DEWPOINTS ALONG THE INTERNATIONAL BORDER AND FAR
EASTERN AZ BY WEDNESDAY EVENING. MOISTURE LEVELS SLOWLY RETURN TO A
MORE MONSOON LIKE PROFILE WHERE AFTERNOON AND EVENING THUNDERSTORMS
WILL BE POSSIBLE ACROSS THE CENTRAL AND EASTERN AZ HIGHER
TERRAIN...INCLUDING SOUTHERN GILA COUNTY...FOR THURSDAY AND FRIDAY
AFTERNOONS. MOST OF THE ACTIVITY WILL REMAIN NORTH-EAST-SOUTH OF THE
PHOENIX AREA...WITH GREATER CHANCES OF SEEING STORM OUTFLOW
INTRUSIONS AND THE EVER-PRESENT THREAT FOR BLOWING DUST ALONG THOSE
BOUNDARIES ACROSS THE LOWER DESERT ELEVATIONS.

ALONG WITH ADDITIONAL GULF MOISTURE SPREADING OVER NORTHERN
MEXICO...FORECAST MODELS CONTINUE TO DEPICT THE FORMATION OF A
TROPICAL SYSTEM OFF THE CENTRAL MEXICAN COAST AND ANYWHERE FROM
300-500 MILES SOUTH OF THE BAJA TIP BY LATE WEDNESDAY. WHERE EARLIER
NHC FORECASTS HAD A 50 PERCENT PROB FOR DEVELOPMENT IN THE NEXT 5
DAYS...THEIR LATEST FORECASTS ARE NOW IN THE HIGH CHANCE RANGE AT 70
PERCENT. BY THE LATE FRIDAY/SATURDAY TIME PERIOD...THE TROPICAL
SYSTEM COULD BE TRACKING UP ALONG THE SOUTHWESTERN BAJA COAST.
ALSO FAR TO OUR NORTHWEST...RENEWED TROUGHING DEVELOPS OVER THE
PAC NORTHWEST COAST...EVENTUALLY SLIDING DOWN THE CA COAST BY THE
LATE WEEK. THE COMBINATION OF INCREASING HUMIDITIES AND CLOUDINESS
FROM THE POTENTIAL TROPICAL MOISTURE TAP ALONG WITH FALLING UPPER
HEIGHTS WILL ALLOW DAYTIME TEMPERATURES TO COOL DOWN BY THE LATE
WEEK/WEEKEND.

LATE FRIDAY THROUGH THE COMING WEEKEND...DISAGREEMENTS BETWEEN THE
MEDIUM RANGE OPERATIONAL AND ENSEMBLES MEMBERS CONTINUE WITH HOW THEY
HANDLE 1) THE TROPICAL SYSTEM AND 2) THE STRENGTH...EVOLUTION AND
RESIDENCE TIME OF THE TROUGHING TO OUR NORTHWEST. THE TROPICAL
SYSTEM IS BROUGHT NORTHWARD AND QUICKLY MOVES INTO THE BROAD MEAN
TROUGH FLOW OVER THE REGION IN THE GFS BY EARLY NEXT WEEK...THE
ECMWF KEEPS THE SYSTEM COMPACT AND TRACKS IT WEST OUT INTO THE OCEAN
BEFORE ATTEMPTING TO TURN IT BACK TOWARDS THE SOUTHWEST U.S. DURING
THE SAME TIME FRAME. TROUGHING OVER THE WEST COAST FOR THE WEEKEND
IS STRONGER WITH THE GFS SOLUTION BUT STRONG FOR EARLY NEXT WEEK
WITH THE ECMWF. WHILE THE PATTERN CONTINUES TO DEVELOP MADE MINOR
ADJUSTMENTS TO THE POP FORECAST...INTRODUCING SOME SLIGHT CHANCE
COVERAGE TOWARDS THE COLORADO RIVER VALLEY AND SOUTHEAST CA FOR
SUNDAY AND NUDGING POPS FROM PHOENIX EASTWARD UPWARDS A BIT AS THERE
IS SOME MODEL CONSENSUS ABOUT THE DEEP MONSOON MOISTURE PROFILE AND
ENERGY EXPANDING INTO THE REGION FROM THE GULF OF CA. TEMPERATURE
FORECAST FOR THE WEEKEND AND EARLY NEXT WEEK BECOMES TRICKY WITH THE
RETURN OF MOISTURE AND STORM CHANCES...BUT ALL THE CONSENSUS AND
BEST PERFORMING EXTENDED TEMPERATURE GUIDANCE WERE INDICATING A
SIGNIFICANT COOL DOWN BY EARLY NEXT WEEK...WITH WELL-BELOW NORMAL
TEMPERATURES AND SOME LOWER DESERT ELEVATIONS POSSIBLY STRUGGLING TO
HIT THE 100F MARK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...AND
SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA INCLUDING KIPL AND KBLH...

THROUGH 03Z TUE...DRY WESTERLY FLOW ALOFT ACROSS THE REGION
PROVIDING CLEAR SKIES AND LIGHT WIND AT ALL TAF SITES.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
MONSOON MOISTURE WILL SLOWLY INCREASE ACROSS ARIZONA WEDNESDAY
THROUGH SUNDAY. A CHANCE OF AFTERNOON AND EVENING MOUNTAIN THUNDER-
STORMS WILL REDEVELOP OVER THE NORTH THROUGH EAST OF PHOENIX
THURSDAY THROUGH SUNDAY. MINIMUM HUMIDITIES WEDNESDAY WILL RANGE
FROM 12 TO 16 PERCENT...INCREASING SUBSTANTIALLY BY SUNDAY INTO THE
30 TO 35 PERCENT RANGE. GOOD RECOVERY AT NIGHT. AFTERNOON
TEMPERATURES WILL CONTINUE IN THE ABOVE NORMAL RANGE WEDNESDAY
THROUGH FRIDAY...THEN FALL BELOW NORMAL SATURDAY AND SUNDAY DUE TO
INCREASING HUMIDITY...CLOUDS...AND A CHANCE OF SHOWERS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ







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