Severe Thunderstorm Warning 40, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
910 AM MST SUN JUL 25 2010

.SYNOPSIS...MOISTURE WILL REMAIN IN PLACE FOR SCATTERED MAINLY
AFTERNOON AND EVENING THUNDERSTORMS THIS WEEK.

&&

.DISCUSSION...LATEST MORNING IR/WV SATELLITE IMAGERY DEPICT AN UPPER
LEVEL HIGH EXTENDING FROM NORTHERN BAJA INTO THE GREAT BASIN AND AN
UPPER LOW ACROSS TEXAS. A WEAK INVERTED TROUGH IS ALSO LOCATED NEAR
THE NEW MEXICO/ARIZONA BORDER NEAR THE DEMARCATION LINE BETWEEN
RELATIVELY DRY AND MOIST AIR ALOFT. CURRENT RADAR IMAGERY SHOWS A
FEW SHOWERS ACROSS EASTERN GRAHAM/GREENLEE/EASTERN COCHISE COUNTIES
AND A FEW SHOWERS SOUTH OF SELLS. 12Z KTWC SOUNDING IS NOT QUITE AS
FAVORABLE TODAY WITH A BIT LESS MOISTURE COMPARED TO 24 HOURS AGO
WITH PW VALUES OF 1.5 INCHES. THERE HAS BEEN A FEW DEGREES OF
COOLING BETWEEN 400 AND 600 MB WITH 1 TO 3C OF WARMING FROM THE
SURFACE TO 650 MB. MODIFYING THE SOUNDING WITH T=99/TD=54 YIELDS
VALLEY CAPE VALUES NEAR 500 J/KG. WITH BETTER UPPER LEVEL SUPPORT
AND THE AFOREMENTIONED MOISTURE DEMARCATION LINE ALOFT IN EASTERN
AREAS...BELIEVE THE MOST WIDESPREAD CONVECTION WILL BE ACROSS
GRAHAM/GREENLEE/COCHISE COUNTIES. HEADING FARTHER WEST INTO SANTA
CRUZ/EASTERN PIMA/SOUTHEAST PINAL COUNTIES CONDITIONS WILL NOT BE
QUITE AS FAVORABLE BUT STILL EXPECT ISOLATED TO LOW END SCATTERED
SHOWERS AND THUNDERSTORMS WITH SLIGHT CHANCES FOR THE CENTRAL AND
WESTERN DESERTS. STORM MOTIONS WILL BE SIMILAR TO THE PAST COUPLE
OF DAYS...SLOW AND CHAOTIC WITH HEAVY RAIN AND FLOODING THE MAIN
THREATS.

THE INVERTED TROUGH NEAR THE NEW MEXICO BORDER TODAY IS PROGGED TO
MOVE WEST THROUGH THE AREA MONDAY. THIS IN ADDITION TO AN INFLUX OF
MOISTURE FROM A GULF SURGE TONIGHT INTO MONDAY MORNING AND A BIT
STRONGER EASTERLY STEERING FLOW ALOFT SHOULD SET THE STAGE FOR A
MORE ACTIVE DAY MONDAY FOR MUCH OF THE FORECAST AREA INCLUDING THE
TUCSON METRO. CURRENT FORECAST REFLECTS THIS FAIRLY WELL WITH POPS
ABOUT 10 PERCENT ABOVE CLIMO BUT WILL HAVE TO CONSIDER NUDGING THIS
UPWARD A BIT MORE IN THE AFTERNOON PACKAGE. A LOOK AT THE 12Z NAM
INDICATES SOMEWHAT DRIER AIR ACROSS EASTERN ARIZONA TUESDAY WITH THE
WESTERN TWO THIRDS OF OUR FORECAST AREA STILL IN VERY DEEP MOISTURE.
THIS SCENARIO WOULD POTENTIALLY FAVOR LOCATIONS FROM TUCSON
WESTWARD. WILL NOT GET FANCY AT THIS POINT THOUGH FOR TUESDAY/
WEDNESDAY AND MORE OR LESS CONTINUE MID GRADE MONSOON PATTERN. BY
THURSDAY AND INTO NEXT WEEKEND AN UPPER LOW IS PROGGED FOR THE LAST
COUPLE OF RUNS BY THE GFS/ECMWF TO MOVE INTO ARIZONA FROM THE EAST.
THIS WOULD RESULT IN A HIGHER END MONSOON PATTERN THROUGH THIS TIME
AND WILL EVALUATE FULL 12Z MODEL SUITE TO DETERMINE IF WE SHOULD
START RAISING THE POPS DURING THIS TIME FRAME.

&&

.AVIATION...SCT-BKN MID LEVEL CLOUDS CONTINUING INTO THE AFTERNOON
HOURS WITH CEILINGS GENERALLY 8-10K FEET...BUT LOWERING TO 4-6K FEET
NEAR THUNDERSTORMS. ISOLD TSRA/SHRA...MAINLY E OF TUCSON THROUGH
EARLY AFTERNOON WITH GUSTS UP TO 40 KNOTS NEAR STORMS THIS
AFTERNOON. OTHERWISE...SURFACE WINDS AWAY FROM THUNDERSTORMS WILL
GENERALLY BE LESS THAN 10 KNOTS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...NO FIRE WEATHER CONCERNS AT THIS TIME.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

WEATHER.GOV/TUCSON

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1045 AM MST SUN JUL 25 2010

AZZ019-029>035-260700-
NORTHERN GREENLEE COUNTY-SOUTHEAST PINAL COUNTY-
UPPER GILA RIVER VALLEY-WESTERN PIMA COUNTY-TOHONO OODHAM NATION-
TUCSON METRO/MARANA/GREEN VALLEY-SANTA CRUZ COUNTY-COCHISE COUNTY-
1045 AM MST SUN JUL 25 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
ARIZONA AND SOUTHEAST ARIZONA.

.DAY ONE...TODAY AND TONIGHT

A MOIST ATMOSPHERE REMAINS IN PLACE OVER ALL OF SOUTHEAST
ARIZONA. EXPECT SLOW MOVING HEAVY RAINFALL PRODUCING THUNDERSTORMS
WILL CONTINUE TO DEVELOP OVER MUCH OF THE AREA THROUGH THIS
AFTERNOON. ISOLATED STRONG WIND GUSTS WILL BE POSSIBLE IN THE
STRONGER STORMS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

AN ACTIVE MONSOON PATTERN WILL CONTINUE THROUGH THE PERIOD...WITH
HEAVY RAIN THE MAIN THREAT.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

WEATHER.GOV/TUCSON