Special Weather Statement, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
125 PM MST WED JUL 24 2013

.SYNOPSIS...AN IMPULSE FROM THE EAST WILL ENHANCE THUNDERSTORM
COVERAGE AND INTENSITY ACROSS MOST OF THE AREA INTO THURSDAY. SOME
STORMS WILL GENERATE HEAVY RAINFALL. OTHERWISE...PLENTY OF MOISTURE
TO PROVIDE A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS INTO THE WEEKEND.

&&

.DISCUSSION...VIS SATELLITE DATA SHOWS CLEARING ACROSS MUCH OF
GRAHAM AND GREENLEE COUNTIES WITH SOME CU DEVELOPMENT OVER THE HIGH
TERRAIN IN COCHISE AND SOUTHWEST GRAHAM COUNTIES. SEVERAL VALLEY
LOCATIONS ACROSS THE EASTERN COUNTIES ARE IN THE UPPER 80S TO LOW 90
RANGE...WHEREAS WESTERN PIMA AND SANTA CRUZ COUNTIES ARE LARGELY
CLOUDED OVER WITH RELATIVELY COOL CONDITIONS IN PLACE. THE BETTER
HEATING IN THE EAST STILL SUGGESTS A THREAT FOR CONVECTION THROUGH
THE AFTERNOON AND EVENING. HOWEVER...THE CLOUDY COOLER COOLER
CONDITIONS ELSEWHERE COMBINED WITH A WARM LAYER AT AROUND 450 TO 500
MB SHOULD KEEP STRONG CONVECTION LIMITED OVER PIMA/SANTA CRUZ AREAS.

THE 18Z HRRR RUN HAD THE BEST HANDLE ON THE CLOUD COVER SO FAR AND
KEEPS ACTIVITY RELATIVELY LIMITED THROUGH THE REST OF THE AFTERNOON.
HOWEVER...THERE ARE SIGNS OF INCREASING ACTIVITY OVERNIGHT IN THE
FORM OF AN MCS DEVELOPING OVER WESTERN NEW MEXICO AND DRIFTING
SOUTHWEST ACROSS AZ. GIVEN THE OUR WEAK LOW PRESSURE SYSTEM IS STILL
HANGING AROUND SE ARIZONA SO THIS WOULD MAKE OVERNIGHT CONVECTION A
REASONABLE SOLUTION. GIVEN THE SATURATED GROUND CONDITIONS IN THE
EASTERN ZONES...THE FLASH FLOOD WATCH STILL APPEARS WARRANTED. WE
ARE ALSO CLOSELY MONITORING THE SAN FRANCISCO AND GILA RIVERS ACROSS
GRAHAM AND GREENLEE COUNTIES. THERE ARE QUICK RESPONSE CHANNELS IN
OUR CWA AND IT WILL NOT TAKE MUCH RAINFALL IN THAT AREA TO CAUSE
RAPID RISES.

THE TROUGH AXIS OF THE WEAK UPPER LOW LAYS OVER SE ARIZONA TOMORROW
AS WELL AND MAY AGAIN SERVE AS A SOURCE OF LIFT FOR ACTIVITY. MODELS
ARE SUGGESTING ANOTHER WET DAY POSSIBLE TOMORROW WITH THE FOCUS
MAINLY ALONG THE INTERNATIONAL BORDER AND HIGHER TERRAIN. WE SHOULD
ALSO SEE A RETURN OF SOUTHERLY FLOW ALOFT TOMORROW ALONG WITH
SUSTAINED MID LEVEL MOISTURE.

THE MONSOON RIDGE BEGIN A MODIFICATION PROCESS TOMORROW AS WELL.
INITIALLY...THE RIDGE AXIS AMPLIFIES OVER THE WESTERN US THROUGH
FRIDAY...KEEPING SE ARIZONA IN FAVORABLE FLOW FOR THUNDERSTORMS.
HOWEVER...STARTING LATE SATURDAY...THE RIDGE BEGINS THE FLATTEN AND
SHIFT SOUTHEAST. THE FLOW ALOFT OVER ARIZONA BECOME MORE WESTERLY
AND STAYS WESTERLY THROUGH MONDAY. THE HIGH CONTINUES DRIFTING SOUTH
THROUGH MIDWEEK AND WHILE OUR FLOW ALOFT BACKS TO THE SOUTH...WE
REMAIN FAIRLY DRY INT THE MIDLEVELS. SO WE MAY HAVE A DECENT BREAK
IN THUNDERSTORM ACTIVITY STARTING SUNDAY AND LASTING FOR SEVERAL
DAYS. THAT MEANS WARMER TEMPERATURES TOO. GFS/ECWMF DID SHOW ANOTHER
INVERTED TROUGH MOVING WEST ACROSS NORTHERN MEXICO MID WEEK BUT THEY
KEEP THE ENERGY FAR ENOUGH SOUTH THAT PRECIP CHANCES WOULD BE
LIMITED OVER ARIZONA.

JJB

&&

.AVIATION... SCT TO NUMEROUS TSRA /SHRA CONTINUING THRU
25/06Z...THEN BECOMING MAINLY ISOLD. MVFR CONDITIONS WITH WIND GUSTS
APPROACHING 45 KTS WITH THE STRONGEST TSRA. OTHERWISE...CLOUD DECKS
MAINLY 6-12K FT AGL AND SURFACE WIND GENERALLY LESS THAN 10 KTS THRU
THURSDAY MORNING OR 25/18Z. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...ENHANCED MOISTURE WILL PROVIDE A BETTER CHANCE OF
SHOWERS AND THUNDERSTORMS THROUGH THURSDAY EVENING.
OTHERWISE...SOUTHEAST ARIZONA WILL KEEP ENOUGH MOISTURE AROUND FOR
MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO CONTINUE
INTO EARLY NEXT WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH FROM 11AM
  UNTIL 9 PM MST FOR AZZ507>514.

&&

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TUCSON AZ
521 PM MST WED JUL 24 2013

AZZ508-250045-
EASTERN COCHISE COUNTY BELOW 5000 FEET INCLUDING DOUGLAS/WILLCOX AZ-
521 PM MST WED JUL 24 2013

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN COCHISE COUNTY UNTIL 545
PM MST...

AT 515 PM MST...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR DOUGLAS...MOVING WEST AT 5 TO 10 MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH VERY HEAVY RAIN.

AREAS AFFECTED BY THIS STORM INCLUDE...PIRTLEVILLE AND BISBEE-DOUGLAS
AIRPORT.

LAT...LON 3133 10978 3152 10981 3151 10946 3133 10945
      3132 10950 3133 10958 3132 10966 3132 10974
TIME...MOT...LOC 0021Z 085DEG 6KT 3141 10956

CERNIGLIA