Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 282239
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
340 PM MST WED JAN 28 2015


.SYNOPSIS...
ANOTHER LOW PRESSURE SYSTEM APPROACHES THURSDAY FOR CLOUDY
CONDITIONS THURSDAY AND A SLIGHT CHANCE OF SHOWERS OVER THE HIGHER
TERRAIN. RAIN CHANCES GO UP DRAMATICALLY REGION WIDE THURSDAY NIGHT
AND CONTINUE INTO SATURDAY...MAINLY EAST OF THE LOWER COLORADO RIVER
VALLEY. SNOW LEVELS WILL REMAIN HIGH...LOWERING TO NEAR 7000 FEET BY
SATURDAY MORNING. ANTICIPATE COOLER HIGH TEMPERATURES AS WELL. DRY
CONDITIONS TAKE OVER SUNDAY THROUGH WEDNESDAY ALONG WITH A GRADUAL
WARMING TREND.

&&

.DISCUSSION...
REST OF TODAY THROUGH SATURDAY...
A PACIFIC TROUGH WITH AN AXIS NEAR 127W LONGITUDE WILL CONTINUE TO
SPREAD MORE AND MORE CLOUDINESS OVER THE AREA TONIGHT AND THURSDAY.
THE MAIN EMPHASIS OF THE TROUGH IS LOCATED BETWEEN 20-30N LATITUDE
IN AN AREA OF HIGH PRECIPITABLE WATER VALUES. TRENDS IN BLENDED TPW
DATA SHOW THE SYSTEM IS ADVECTING DEEP MOISTURE NORTHEASTWARD. IN
FACT IT LOOKS LIKE PRECIPITABLE WATER VALUES PEAK AT 1 TO 1.25
INCHES FRIDAY. WITH ABUNDANT MOISTURE LIKE THAT WE ARE DEFINITELY
LOOKING AT A SUBSTANTIAL RAINFALL EVENT. THE TIMING REMAINS ON TRACK
WITH SLIGHT CHANCES STARTING OVER THE HIGHER TERRAIN THURSDAY
AFTERNOON BUT THE MAIN ONSET BEING THURSDAY NIGHT. PEAK OF THE
RAINFALL LOOKS TO BE FRIDAY. ANTICIPATE LESS WIDESPREAD RAINFALL
FRIDAY NIGHT AND SATURDAY WITH MORE OFF AND ON SHOWERS. HEAVIEST
RAIN FOR OUR AREA LOOKS TO BE LA PAZ COUNTY...NORTHERN MARICOPA
...NORTHERN PINAL...AND SOUTHERN GILA. INSTABILITY LOOKS TO BE
MEAGER BUT JUST ENOUGH TO MERIT MENTION OF SLIGHT CHANCES FOR FRIDAY
AFTERNOON AND EARLY EVENING AND AGAIN SATURDAY AFTERNOON. THE
DYNAMICAL FORCING LOOKS TO BE MODEST WHICH IS SOMETHING OF A
LIMITING FACTOR AND THUS HAVE HELD OFF FOR NOW ON ANY FLOOD WATCHES.
HOWEVER...RUNNING WASHES SHOULD BE EXPECTED TO DEVELOP SOMETIME
FRIDAY AND CONTINUE INTO SATURDAY...MAINLY OVER HIGHER TERRAIN. AT A
MINIMUM...PONDING OF WATER IN LOW SPOTS AND ROADWAYS. LESS RAIN IS
EXPECTED OVER SOUTHEAST CALIFORNIA...ESPECIALLY IMPERIAL COUNTY
WHICH WILL SEE ONLY MINOR AMOUNTS. THE SYSTEM IS EXPECTED TO PUSH
SOUTHWARD SATURDAY NIGHT...IF NOT SOONER PER 12Z GFS...FOR A
TAPERING OFF OF PRECIP AS IT MOVES OUT OF THE AREA. SNOW LEVELS
REMAIN HIGH ENOUGH THAT ONLY THE TOPS OF OUR HIGHEST PEAKS...ABOVE
7000 FEET...WILL GET ANY ACCUMULATION.

SUNDAY THROUGH TUESDAY...
SUNDAY LOOKS TO BE A DRY. PATCHY FOG IS A POSSIBILITY BUT THERE MAY
BE ENOUGH LINGERING CLOUDS TO HINDER THE RADIATIONAL COOLING
NECESSARY.  THE RIDGE SLOWLY BUILDS INTO THE WEST MONDAY THROUGH
WEDNESDAY FOR A GRADUAL WARMING TREND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...
THROUGH 16Z THU...LIGHT WIND. INCREASING HIGH CLOUDS...WITH CIGS
LOWERING TO NEAR 18 THSD AGL AFTER 09Z THU.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 16Z THU...LIGHT WIND. INCREASING HIGH CLOUDS WITH CIGS
LOWERING TO NEAR 18 THSD AGL AFTER 07Z THU.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
A PACIFIC LOW PRESSURE SYSTEM WILL BRING ABUNDANT MOISTURE AND RAIN
SHOWERS TO THE DESERT SOUTHWEST FRIDAY AND SATURDAY. COOLER
TEMPERATURES AND IN INCREASE IN WIND ARE ALSO
ANTICIPATED...PARTICULARLY ACROSS PORTIONS OF SOUTHERN GILA COUNTY
FRIDAY MORNING. A WARMING AND DRYING TREND IS EXPECTED SUNDAY
THROUGH TUESDAY AS A RIDGE BUILDS ACROSS THE EASTERN PACIFIC.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...AJ
AVIATION...VASQUEZ
FIRE WEATHER...HIRSCH





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