Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 312125
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
225 PM 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...MAINLY ALONG THE INTERNATIONAL
BORDER AS WELL AS THE MOUNTAIN TOPS.

&&

.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.

WHAT A DIFFERENCE 12 HOURS CAN MAKE. YESTERDAYS 31/00Z KTWC SOUNDING
REVEALED A PW OF 1.10 INCHES AND THE 31/12Z KTWC SOUNDING CAME IN
WITH A PW OF 1.68 INCHES. THIS MORNINGS SOUNDING PARAMETERS SHOWED A
MU CAPE OF AROUND 2200 J/KG AND A LIFTED INDEX OF MINUS 6. THE MOST
RECENT RADAR MOSAIC SHOWS SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS CONTINUING TO PROGRESS WESTWARD WEST OF AJO AND ORGAN
PIPE. ELSEWHERE ACROSS SOUTHEAST ARIZONA...ISOLATED TO SCATTERED
THUNDERSTORMS HAVE BEEN DEVELOPING DURING THE PAST HOUR OR TWO...
WITH CELLS EXTENDING FROM EAST OF ELOY TO PICTURE ROCKS AND TOWARD
ARIVACA. WEAK SHOWERS HAVE ALSO DEVELOPED OVER PARTS OF THE TUCSON
METRO AS WELL. ADDITIONAL CELLS ARE OCCURRING OVER THE HIGHER
TERRAIN OF GRAHAM...GREENLEE AND SANTA CRUZ COUNTIES...WITH ACTIVITY
MOVING WEST OR WEST NORTHWEST AT 5 TO 10 MPH.

U OF A 12Z WRF/NAM & GFS...AS WELL AS HRRR ALL SUGGEST THAT STORMS
WILL CONTINUE TO BLOSSOM OVER CENTRAL AND WESTERN PORTIONS OF THE
FORECAST AREA THIS AFTERNOON AND PUSH TO THE WEST OR WEST NORTHWEST
EARLY THIS EVENING. ACTIVITY NOT AS WIDESPREAD BETWEEN TUCSON AND
THE NEW MEXICO BORDER...WITH THE EXCEPTION OF THE MOUNTAIN TOPS.

KEPT 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. THIS ALSO MESHES WELL
WITH THE FORECAST FROM THE PHOENIX OFFICE.

MODELS INDICATE THAT A WEAK DISTURBANCE COMING UP FROM THE SOUTH
WILL MOVE ACROSS SOUTH CENTRAL ARIZONA THIS EVENING AND THEN OVER
SOUTHWEST ARIZONA EARLY SATURDAY AND WESTERN ARIZONA MIDDAY
SATURDAY. AS THIS OCCURS...THIS SYSTEM WILL HELP TO ENHANCE ACTIVITY
THIS AFTERNOON AND EVENING...BUT BY SATURDAY WE SHOULD SEE LESS
THUNDERSTORM ACTIVITY AS THIS SYSTEM WILL BE OVER SRN NEVADA LATE IN
THE AFTERNOON AND MOISTURE IS EXPECTED TO DECREASE A BIT LATE IN THE
AFTERNOON OR INTO THE EVENING.

BY SUNDAY AND CONTINUING THROUGH AROUND WEDNESDAY THE HIGH IS
EXPECTED TO RECONSOLIDATE IN A WEST TO EAST ORIENTATION ACROSS
NORTHERN MEXICO AND THEN MOVE NORTH OVER THE DESERT SOUTHWEST BY
TUESDAY. AS A RESULT...DRIER SOUTHWEST TO WEST FLOW WILL REDUCE RAIN
CHANCES A BIT AND KEEP THE BEST THREAT FOR SHOWERS AND
THUNDERSTORMS...MAINLY BETWEEN NOGALES AND DOUGLAS AS WELL AS THE
WHITE MOUNTAINS. THIS WILL ALSO RESULT IN WARMER DAYTIME TEMPS
MONDAY THROUGH WEDNESDAY.

FOR LATE WEEK THE HIGH WILL SHIFT TOWARD THE EAST AND RESULT IN A
RETURN FLOW FROM THE SOUTH TO SOUTHEAST AND PULL IN MORE MOISTURE
AND INCREASING THUNDERSTORM CHANCES...BUT STILL JUST ISOLATED TO
SCATTERED IN NATURE.

FOR TUCSON...HIGHS WILL BE NEAR NORMAL SATURDAY...THEN 4 TO 7 DEGS
ABOVE NORMAL EACH DAY THROUGH FRIDAY. HOWEVER...THE WARMEST DAY WILL
LIKELY OCCUR TUESDAY. LOWS WILL RANGE FROM 2 TO 4 DEGS ABOVE NORMAL
EACH MORNING. HOWEVER...THE COOLEST MORNINGS WILL LIKELY OCCUR
MONDAY AND TUESDAY.

&&

.AVIATION...VALID THRU 02/00Z.
SCT TO BKN CLOUDS 7-10K FT AGL WITH SCT-NMRS SHRA/TSRA GENERALLY
BEFORE 01/04Z...AND MAINLY WEST OF A LINE FROM KOLS TO KSAD AND IN
THE WHITE MOUNTAINS. BRIEF MVFR CONDITIONS WITH ERRATIC WIND GUSTS
TO 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. SHRA/TSRA WILL OCCUR AGAIN
SATURDAY AFTERNOON...ALTHOUGH WITH LESS COVERAGE THAN TODAY.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
TODAY WITH STRONG OUTFLOW WINDS LIKELY...ESPECIALLY FROM TUCSON
WEST. SATURDAY WILL SEE SLIGHTLY LESS CONVECTION. INCREASING SW
WINDS ALOFT ON SUNDAY WILL BRING DRIER AIR INTO THE REGION FOR
ISOLATED TO SCATTERED THUNDERSTORM COVERAGE TO BEGIN NEXT
WEEK...WITH A FOCUS MAINLY SOUTH AND EAST OF TUCSON. OUTSIDE OF
THUNDERSTORM WIND GUSTS...20-FT WINDS WILL GENERALLY BE TERRAIN
DRIVEN AND LESS THAN 15 MPH. HOWEVER SOME AFTERNOON AND EARLY
EVENING BREEZINESS IS LIKELY DUE TO DAYTIME HEATING...ESPECIALLY
THROUGH THE GILA VALLEY NEAR SAFFORD.

&&

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

&&

$$

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...FRENCH

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON



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