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National Weather Service Tucson Arizona
HOME > Back to products page | Weather Glossary

AREA FORECAST DISCUSSION

 
 FXUS65 KPSR 092217
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
315 PM MST TUE FEB 9 2010

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL BRING RAIN AND MOUNTAIN SNOW SHOWERS...
AS WELL AS A SLIGHT CHANCE OF THUNDERSTORMS...OVER FAR SOUTHEAST
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY TONIGHT INTO EARLY
WEDNESDAY...AND MAINLY OVER SOUTHWEST AND SOUTH-CENTRAL ARIZONA
WEDNESDAY AND WEDNESDAY EVENING. DRIER CONDITIONS WILL PREVAIL
THURSDAY AS THE LOW MOVES OFF TO OUR EAST...THOUGH IT WILL REMAIN
RATHER COOL. DRY AND WARMER WEATHER WILL COMMENCE FRIDAY AND
CONTINUE THROUGH EARLY NEXT WEEK AS A RIDGE OF HIGH PRESSURE BECOMES
ESTABLISHED OVER THE WESTERN UNITED STATES. TEMPERATURES WILL BE
SEVERAL DEGREES ABOVE NORMAL SATURDAY THROUGH AT LEAST NEXT TUESDAY.

&&

.DISCUSSION...
UPPER LOW THAT WILL AFFECT OUR WEATHER DURING THE NEXT COUPLE OF
DAYS WAS CENTERED SW OF SAN FRANCISCO AS OF 21Z (2 PM MST)...AND
CONTINUED TO MOVE TOWARD THE SSE AT ABOUT 20 KNOTS. AS MENTIONED
THIS MORNING...NUMERICAL MODELS ARE IN GOOD AGREEMENT REGARDING
TRACK OF THIS LOW...KEEPING IT ON A PATH THAT PARALLELS THE
CALIFORNIA COAST DURING THE NEXT 18 HRS...PLACING IT JUST WEST OF
SAN DIEGO BY 12Z WEDNESDAY...THEN MOVING IT SLOWLY EAST ALONG THE
INTERNATIONAL BORDER TO JUST SOUTH OF THE ARIZONA-NEW MEXICO BORDER
BY 12Z THURSDAY. AS SUCH...STRONGEST FORCING/UVV AND BEST CHANCE FOR
PRECIPITATION WILL TRACK ACROSS FAR SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA TONIGHT...ACROSS SOUTHERN QUARTER OF ARIZONA ON
WEDNESDAY...AND OVER SOUTHEAST ARIZONA WEDNESDAY NIGHT (PRINCIPAL
UPPER SUPPORT AND BEST CHANCE FOR PRECIPITATION DOES AN `END RUN`
AROUND SOUTH-CENTRAL ARIZONA). GIVEN ONLY MODEST MOISTURE
AVAILABILITY AS WELL AS THE FACT THE STORM WILL TRACK WELL SOUTH OF
OUR FORECAST AREA...PRECIP TOTALS FROM THIS STORM WILL BE RATHER
MODEST...LESS THAN ONE HALF INCH AT MOST LOCALES. TOTALS IN EXCESS
OF ONE THIRD INCH...BUT LESS THAN ONE HALF INCH...WILL BE MOST
LIKELY OVER FAR SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA TONIGHT
INTO WEDNESDAY MORNING...AND OVER THE HIGHER TERRAIN OF SOUTH-
CENTRAL ARIZONA WEDNESDAY NIGHT. PRECIP AMOUNTS WILL VARY QUITE A
BIT FROM SITE TO SITE...SINCE CONVECTIVE SHOWERS AND A FEW
THUNDERSTORMS ARE EXPECTED. STRONG RIDGING DEVELOPS BEHIND THE LOW
THURSDAY WHICH WILL QUICKLY BRING THE THREAT OF PRECIP TO AN END.

GFS/ECMWF IN GOOD AGREEMENT THAT A MUCH DIFFERENT AND RATHER
PERSISTENT LONG WAVE PATTERN WILL BECOME ESTABLISHED THIS WEEKEND
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. RIDGE AXIS SETS UP NEAR
120W (FAR WESTERN UNITED STATES) WHILE BROAD TROUGH WILL BE CENTERED
NEAR 90W (EASTERN UNITED STATES). THIS PATTERN PROMISES TO BRING DRY
CONDITIONS WITH DAYTIME HIGHS SEVERAL DEGREES ABOVE NORMAL THIS
WEEKEND INTO EARLY NEXT WEEK...WITH WARMEST DAYTIME HIGHS TOWARD THE
END OF THIS FORECAST PACKAGE (EARLY NEXT WEEK).

&&

.AVIATION...
KPHX AND KIWA...
SFC WINDS FROM THE SOUTH/SOUTHEAST SLOWLY INCREASING ACROSS THE
PHOENIX AREA THIS AFTN. FAIR CONFIDENCE WINDS WILL REMAIN FROM
THE SOUTH TONIGHT...AHEAD OF THE DEEP UPPER LOW IN CALIF.
ALSO...CLOUDS AT/ABOVE 15 THSD FT ON THE INCREASE...WITH PRECIP
SPREADING FROM WEST TO EAST AFT 10/12Z. BY 10/15Z THE LOWER
CIGS...8-10 THSD FT WILL FILTER INTO THE METRO AREA ALONG WITH LGT
RAIN.

KIPL AND KBLH...
NORTH-SOUTH LINE OF LGT SHOWERS WITH CIGS 6-8 THSD FT WILL BRUSH
ACROSS CALIF DESERTS THRU 10/00Z. ADDITIONAL SHOWERS LIKELY TO BRING
BEST CHANCE OF SHOWERS AFT DARK AT BOTH KIPL/KBLH. GOOD CONFIDENCE
THAT LOWER VSBYS WILL ACCOMPANY THE PRECIP AND CIGS...AND 5-7 MILES
VSBYS STILL LOOK GOOD. GUSTY WINDS ALSO MAY REACH 20-25 KTS SPCLY
ASSOCD WITH ISOLD TSTMS. TIMING OF CLEARING TREND STILL GOOD BY WED
AFTERNOON.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY NIGHT THROUGH MONDAY...
SOME LINGERING SHOWERS ARE EXPECTED WEDNESDAY NIGHT...MAINLY EAST OF
PHOENIX. HIGH PRESSURE ALOFT FROM THE PACIFIC WILL BRING A RETURN TO
RELATIVELY DRIER AIR AND A RECOVERY OF TEMPERATURES THURSDAY AND
FRIDAY WITH FURTHER WARMING THIS COMING WEEKEND. MINIMUM RELATIVE
HUMIDITY IS EXPECTED TO GENERALLY REMAIN ABOVE 20 PERCENT WITH GOOD
TO EXCELLENT RECOVERY AT NIGHT. SOME BREEZINESS FROM THE NORTH AND
NORTHEAST IS EXPECTED THIS WEEKEND...ESPECIALLY DOWN THE LOWER
COLORADO RIVER VALLEY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 10 AM PST
WEDNESDAY CAZ030.


&&




NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...DG
AVIATION...SIPPLE
FIRE WEATHER...ELLIS




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