Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 311610
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
910 AM MST FRI JUL 31 2015

.SYNOPSIS...A MORE ACTIVE THUNDERSTORM DAY ACROSS SOUTHEAST ARIZONA
TODAY. ALTHOUGH SOME DRIER AIR WILL MOVE ACROSS THE AREA THIS
WEEKEND INTO NEXT WEEK...THERE WILL BE ENOUGH MOISTURE AROUND FOR A
CHANCE OF SHOWERS AND THUNDERSTORMS.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 31/12Z UPPER-AIR PLOTS SHOW
THE CENTER OF HIGH PRESSURE IN THE GENERAL VICINITY OF THE TEXAS
PANHANDLE...WITH A PACIFIC LOW PRESSURE SYSTEM WELL OFF THE SOUTHERN
CALIFORNIA AND NORTHERN BAJA COASTS. AN MCS DEVELOPED LATE LAST
NIGHT OVER NORTHERN CHIHUAHUA MEXICO AND PUSHED INTO SOUTHWEST NEW
MEXICO AND EVENTUALLY RESULTED IN STORMS OVER EASTERN COCHISE
COUNTY...WHICH PRODUCED 1.34 INCHES IN 6 HOURS AT THE LONG PARK
GAUGE IN THE CHIRICAHUA MOUNTAINS. THIS ACTIVITY HAS SINCE
DISSIPATED WITH SOME RESIDUAL LIGHT SHOWERS OVER CENTRAL COCHISE
COUNTY.

WHAT A DIFFERENCE 12 HOURS CAN MAKE. YESTERDAYS 31/00Z KTWC SOUNDING
REVEALED A PW OF 1.10 INCHES AND ACTIVITY YESTERDAY AFTERNOON AND
EVENING WAS RATHER SPARSE. HOWEVER...THE 31/12Z KTWC SOUNDING CAME
IN WITH A PW OF 1.68 INCHES. THIS MORNINGS SOUNDING PARAMETERS SHOW
A MU CAPE OF AROUND 2200 J/KG AND A LIFTED INDEX OF MINUS 6. THE
MOST RECENT RADAR MOSAIC SHOWS ISOLATED SHOWERS AND THUNDERSTORMS
WEST OF THE TUCSON METRO BETWEEN PICTURE ROCKS AND THREE POINTS AND
THESE SHOWERS/STORMS ARE MOVING WEST. ADDITIONAL SHOWERS ARE ALSO
OVER NORTHERN SONORA JUST SOUTH OF NOGALES. WE SHOULD BE FAIRLY
ACTIVE TODAY AND THE 31/00Z RUN OF THE U OF A WRF/NAM SHOWS ACTIVITY
MOSTLY OVER CENTRAL AND WESTERN LOCATIONS...BUT ALSO THE MOUNTAINS
OVER GREENLEE...GRAHAM AND COCHISE COUNTIES. 00Z WRF/GFS SHOWS A
SIMILAR OUTCOME BUT THE ACTIVITY IS LESS INTENSE THAN THE NAM. 12Z
HRRR ALSO SHOWS US TO BE MOST ACTIVE WEST OF TUCSON. INHERITED POP
FORECAST FOR THIS AFTERNOON AND EVENING REFLECT THIS NOTION QUITE
WELL...SO NO CHANGES ARE PLANNED TO THE POP FORECAST AT THIS
TIME...BUT WILL CONTINUE TO MONITOR SATELLITE AND RADAR TRENDS AND
WILL MAKE ADJUSTMENTS LATER IN THE MORNING/EARLY AFTERNOON...IF
NEEDED.

NIGHT SHIFT INCLUDED A MENTION OF BLOWING DUST OVER PARTS OF PIMA
AND PINAL COUNTIES LATE THIS AFTERNOON AND EARLY THIS EVENING AS
STORMS EXPECTED TO FIRE OFF AND MOVE IN THAT GENERAL DIRECTION.

DAYTIME HIGHS TODAY WILL BE RATHER TRICKY WITH CLOUD COVER IN PLACE.
YESTERDAYS TEMPS REBOUNDED VERY QUICKLY AFTER CLOUDINESS ERODED...SO
SUSPECT THE SAME FOR TODAY. THAT SAID...I DON`T PLAN ON MAKING ANY
CHANGES TO THE TEMP FORECAST...BUT WILL MONITOR THROUGHOUT THE
MORNING.

PLEASE REFER TO PREVIOUS DISCUSSION BELOW FOR INFO REGARDING
FORECAST DETAILS BEYOND TODAY.

&&

.AVIATION...VALID THRU 31/18Z.
ISOLD -SHRA/TS MAINLY W AND S OF KTUS THRU 31/18Z. OTRW DECREASING
CLOUDS THRU 31/18Z. SCTD SHRA/TSRA DEVELOPING AFT 31/18Z. BRIEF WIND
GUSTS BTWN 35-45 KTS POSSIBLE IN AND AROUND THE STRONGER TSRA. AREAS
OF BLDU PSBL W AND NW OF KTUS AFT 31/22Z. OUTSIDE OF STORM
INFLUENCES SFC WINDS WILL GENERALLY BE LESS THAN 12 KTS WITH A FEW
HIGHER GUSTS IN THE AFTERNOON/EARLY EVENING HOURS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS TODAY WITH
STRONG OUTFLOW WINDS LIKELY...ESPECIALLY FROM TUCSON WEST. WITH THE
POTENTIAL FOR TODAY TO BE AN ACTIVE DAY...SATURDAY MAY SEE LIMITED
ACTIVITY. INCREASING SW WINDS ALOFT ON SUNDAY WILL BRING DRIER AIR
INTO THE REGION FOR ISOLATED TO LOW SCATTERED THUNDERSTORM COVERAGE.
LOW GRADE MONSOON ACTIVITY NEXT WEEK...MAINLY SOUTH AND EAST OF
TUCSON. STRONG OUTFLOW WINDS WILL BE POSSIBLE NEAR THUNDERSTORMS.
OTHERWISE...20-FT WINDS WILL GENERALLY BE TERRAIN DRIVEN AND LESS
THAN 15 MPH...WITH SOME AFTERNOON AND EARLY EVENING BREEZINESS DUE
TO THE STRONG DAYTIME HEATING.

&&

.PREV DISCUSSION...SATURDAY FORECAST HIGHLY DEPENDENT ON WHAT
HAPPENS TODAY AND WITH THE FORECAST FOR AN UP DAY TODAY...WENT WITH
LOWER POPS AS SOME DRIER AIR STARTS TO FILTER IN AS FLOW ALOFT
STARTS TO TURN OUT OF THE SW.

SUNDAY...INCREASING SW FLOW ALOFT WILL PUSH DEEPER MOISTURE TO THE
EAST LIMITING THUNDERSTORM COVERAGE TO AREAS EAST AND SOUTH OF
TUCSON.

NEXT WEEK...STANDARD LOW GRADE MONSOON FORECAST.

&&

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

&&

$$

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