Weather Service Report


192 
FXUS65 KPSR 161620
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
920 AM MST WED APR 16 2014

.SYNOPSIS...
DRY WESTERLY FLOW ALOFT WILL PERSIST THROUGH MUCH OF THE WORK WEEK
WITH HIGH TEMPERATURES WARMING INTO THE 90S OVER THE WARMER DESERTS.
A WEAK UPPER LEVEL LOW APPROACHING FROM THE EAST PACIFIC WILL SPREAD
INCREASING MOISTURE AND CLOUDS INTO THE AREA FRIDAY INTO THE
EARLY WEEKEND...LEADING TO A SLIGHT CHANCE OF SHOWERS ACROSS SOUTH
CENTRAL ARIZONA AND THE POSSIBILITY FOR SLIGHTLY COOLER DAYTIME
TEMPERATURES. THE COOL DOWN WILL BE SHORT LIVED...AS HIGH PRESSURE
QUICKLY RETURNS THROUGH THE LATE WEEKEND.

&&

.DISCUSSION...
TEMPERATURES ACROSS THE CENTRAL AND LOWER DESERTS OF ARIZONA AND 
SOUTHEAST CALIFORNIA ARE ALREADY REACHING INTO THE LOW 70S AS OF 9 
AM MST. SKIES REMAINED MOSTLY CLEAR OVERNIGHT...ALLOWING 
TEMPERATURES OVERNIGHT TO COOL TO NEAR MONDAY NIGHTS READINGS. CLOUD 
COVER TODAY WILL INCREASE THROUGH THE DAY AND EVENING HOURS BUT 
SHOULD BE CONFINED AS MID AND HIGH CLOUDS ABOVE 18K FT. NORTHWEST 
FLOW ALOFT WILL BE IN PLACE AS A SHORTWAVE FEATURE SKIRTS BY TO OUR 
NORTH AND A SUBTROPICAL JET REMAINS TO OUR SOUTH. TEMPERATURE 
FORECAST FOR TODAY WILL BE SIMILAR IN NATURE TO TUESDAY...REACHING A 
HANDFUL OF DEGREES ABOVE WHAT WAS OBSERVED TUESDAY AND STILL ABOVE 
SEASONAL NORMAL. THE FORECAST PACKAGE LOOKS GOOD SO NO UPDATES 
NEEDED AT THIS TIME. MORE LATER.

&&

.PREVIOUS DISCUSSION.../ISSUED AT 317 AM MST 16 APRIL/...
MORNING WATER VAPOR IMAGERY INDICATES MOSTLY CLEAR SKIES ACROSS MUCH 
OF ARIZONA AND SOUTHERN CALIFORNIA. SUBTROPICAL JET AND ASSOCIATED 
HIGH CLOUD BANDS CONTINUE TO GRADUALLY SINK SOUTHWARD ACROSS 
NORTHERN MEXICO AS SHORTWAVE ENERGY DROPS INTO THE GREAT BASIN. DRY 
NORTHWEST FLOW WILL CONTINUE FOR THE FORECAST ZONES TODAY...WITH 
RIDGING BUILDING TO OUR WEST AND THE SHORTWAVE IMPULSE BRUSHING BY 
THE FOUR CORNERS. NEIGHBORING RAOBS SHOWED ADDITIONAL WARMING 
THROUGH THE LOWER ATMO LAYERS WHICH SUPPORTED LOW TO MID 90 DEGREE 
READINGS TUESDAY. FORECASTED 850MB TEMPS EXPECTED IN THE 20C/21C 
RANGE BY THIS AFTERNOON...ADDING A FEW DEGREES ON TO OBSERVED HIGH 
VALUES FROM TUESDAY.

THURSDAY THROUGH SATURDAY...
STORM SYSTEM OFF THE PACIFIC WILL MOVE INTO THE AREA...WHILE
TROUGHING ALSO EXPANDS INTO THE WESTERN CONUS. WARM DAYTIME
TEMPERATURES IN THE 90S WILL LINGER INTO THURSDAY AS FLOW BECOMES
SOUTH TO SOUTHWESTERLY AND ADDITIONAL WAA OCCURS UNDER VERY BRIEF
SHORTWAVE RIDGING. THE SYSTEM WILL MOVE ONSHORE THURSDAY NIGHT AND
SLOWLY MOVE THROUGH THE REGION FRIDAY INTO SATURDAY. THE SYSTEM WAS
NEVER PRESENTED AS OVERLY WET OR STRONG/WELL-ORGANIZED...BUT FORECAST
SOUNDINGS AND PWAT PLOTS HAVE INCREASED OVER THE PAST FEW RUNS. THE
16/00 AND 16/06Z NAM MOISTURE FIELDS ARE SOME OF THE MOST
AGGRESSIVE...AND ALSO THE BEST INITIALIZED FROM LAST
EVENING...ATTEMPTING TO DRAW 1 INCH PWAT VALUES FROM OFF THE PACIFIC
AND INTO ARIZONA BY FRIDAY MIDDAY. GFS/SREF/EC SOLNS ARE MORE
CONSERVATIVE...BUT STILL DRAW NEAR THREE QUARTER INCH VALUES INTO THE
AREA FRIDAY. THE BULK OF ANY INCREASE MOISTURE ON ALL THE FORECAST
SOUNDINGS LIE AT 700MB AND ABOVE...WITH INVERTED V TRACES DOWN TO THE
SURFACE.

ONLY MINOR ADJUSTMENTS WERE MADE TO THE POP GRIDS...WHICH ALREADY HAD
SLIGHT CHANCES FOR THE FOOTHILLS/HIGHER TERRAIN NORTH AND EAST OF
PHOENIX. SLIGHT CHANCES WERE ADDED TO THE FOOTHILL TERRAIN OF LA PAZ
COUNTY AND NORTHERN MARICOPA FOR FRIDAY GIVEN THE MODEL CONSENSUS AND
SLIGHT BOOST IN MOISTURE FIELDS. WHILE SIGNIFICANT RAINFALL IS NOT
EXPECTED BY ANY MEANS...LIGHT SPRINKLES AND VIRGA ARE MORE LIKELY
FROM NORTHERN LA PAZ/MARICOPA COUNTY EASTWARD. HIGH BASED SHOWERS AND
DRY SUB-CLOUD LAYERS COULD ENHANCE WIND GUSTS AND ANY OUTFLOWS FROM
SHOWERS/STORMS FOR FRIDAY AND SATURDAY.

CLOUDS WILL INCREASE FROM THE WEST BEGINNING LATE THURSDAY...WITH
MOSTLY CLOUDY TO OVERCAST SKIES EXPECTED FRIDAY. DAYTIME TEMPERATURES
FRIDAY WILL SEE SEVERAL DEGREES OF COOLING...BUT ONLY BACK TOWARDS
MID APRIL NORMALS...MID TO UPPER 80S AND A FEW ISOLATED 90 DEGREE
POCKETS. CLOUDS WILL CLEAR OUT TO THE EAST SATURDAY...ALONG WITH THE
MAIN BODY OF TROUGH. FRIDAY'S COOL DOWN WILL BE SHORT LIVED AS UPPER
80S/LOW 90S RETURN UNDER HIGH PRESSURE ALOFT FOR THE WEEKEND.

NEXT WEEK... 
MEDIUM RANGE OPERATIONAL AND ENSEMBLE MODEL FORECASTS ARE IN DECENT
AGREEMENT FOR THE EARLY PART OF NEXT WEEK'S FORECAST COMPARED TO
THEIR PERFORMANCE JUST 24 HOURS AGO. HIGH PRESSURE FROM OVER THE
WEEKEND WILL TRANSITION EASTWARD BEGINNING MONDAY...AS A LARGE AND
POTENT PACIFIC STORM MOVES INTO THE WEST COAST. IN GENERAL...LOWER
STORM HEIGHTS AND THE POTENTIAL FOR THE UPPER JET AS FAR SOUTH AS
ARIZONA COULD BRING SIGNIFICANT COOLING BY THE EARLY TO MIDDLE PART
OF NEXT WEEK (POTENTIALLY INTO THE LOW TO MID 80S ATTM). THE BULK OF
THE BEST WAVE ENERGY LOOKS REMAINS TO OUR NORTH...SO ONLY BLENDED A
FEW PERCENT OF CLIMO POPS INTO THE EXTENDED GRIDS FOR NOW.

&&

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

WEAK TROUGH WILL MOVE THROUGH THE AREA TODAY BRINGING A FEW HIGH 
CLOUDS BUT NO PRECIPITATION. WINDS WILL TURN AROUND OUT OF THE WEST 
A FEW HOURS EARLIER THAN USUAL TODAY AND COULD BRIEFLY GUST TO NEAR 
20KTS THIS AFTERNOON...BUT IMPACTS SHOULD BE MINIMAL. SKIES WILL 
QUICKLY CLEAR AFTER SUNSET AND WINDS WILL TAKE ON THEIR USUAL 
DIURNAL DIRECTIONS. 

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.  

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
UPPER LEVEL TROUGH APPROACHES THE AREA ON FRIDAY BRINGING A SLIGHT 
INCREASE IN HUMIDITIES TO THE AREA BUT LITTLE IN THE WAY OF  
RAINFALL. IF ANYTHING...ANY STORMS THAT DEVELOP WOULD LIKELY PRODUCE 
LOCALLY GUSTY WINDS ALONG WITH AN INCREASED FIRE DANGER IN LIEU OF A 
MUCH NEEDED WETTING RAIN. STILL...WIDESPREAD CRITICAL THRESHOLDS 
SHOULD NOT BE REALIZED WITH THIS TROUGH AND IT DOESN\T APPEAR ANY 
RED FLAG WARNINGS WILL BE NEEDED. HIGH PRESSURE RETURNS FOR THE 
WEEKEND INTO EARLY NEXT WEEK AND CONSEQUENTLY...TEMPERATURES WILL 
REMAIN ABOVE NORMAL AND HUMIDITIES WILL DROP INTO THE SINGLE 
DIGITS/LOWER TEENS EACH AFTERNOON.

BETTER AGREEMENT AMONG THE EXTENDED MODELS FOR NEXT WEEK...NOW BOTH 
THE EURO/GFS INDICATING A LARGER UPPER TROUGH MOVING THROUGH 
TUESDAY/WEDNESDAY. COOLER TEMPS AND HIGHER HUMIDITIES APPEAR 
POSSIBLE WITH THIS TROUGH BUT CHANCES OF A WETTING RAIN STILL LOOK 
REMOTE. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...DEWEY
PREVIOUS DISCUSSION...NOLTE
AVIATION...LEINS
FIRE WEATHER...LEINS




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