Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 040453
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
953 PM MST FRI JUL 3 2015

.SYNOPSIS...SOUTHEAST ARIZONA WILL EXPERIENCE A STEADY INCREASE IN
SHOWERS AND THUNDERSTORMS THIS WEEKEND. SLOWER MOVING STORMS WILL
ELEVATE HEAVY RAINFALL CONCERNS WITH WET MICROBURSTS POSSIBLE.
DAYTIME TEMPERATURES WILL REMAIN CLOSE TO SEASONAL NORMALS.

&&

.DISCUSSION...THE UPPER PATTERN IS DEFINED BY AN UPPER RIDGE OF HIGH
PRESSURE AT 300 MB EXTENDING FROM SOUTHERN UTAH...INTO SOUTHWEST NEW
MEXICO AND NORTHERN CHIHUAHUA MEXICO...WITH THE CENTER POSITIONED
OVER SW NEW MEXICO. AT 500 MB...THE UPPER RIDGE EXTENDS FROM A HIGH
CENTERED IN EASTERN NEVADA AND ANOTHER OVER EXTREME SOUTHEAST
ARIZONA.

THE LATEST RADAR IMAGERY INDICATED PLENTY THUNDERSTORMS ARE PRESENT
IN NORTHERN ARIZONA...WHICH COINCIDES WITH THE WEAKNESS IN BETWEEN
THE TWO 500 MB FEATURES. THIS AREA OF STORMS WILL HAVE LITTLE/NO
IMPACT ON OUR AREA. LOOKING UPSTREAM FROM SE AZ...ACTIVITY IN
NORTHERN SONORA HAS BEEN RELATIVELY DOWN THIS EVENING...MOST LIKELY
THE RESULT OF THE 500 MB POSITIONED OVER THE FAR SE CORNER OF STATE.
THE CONVECTION ACROSS SW NEW MEXICO THIS EVENING IS LIKELY DUE TO
THE COMBINATION OF AN AREA OF LOW LEVEL CONVERGENCE AND DIVERGENCE
ALOFT /300 MB/ THAT WAS ABLE TO OVERCOME THE WARMING AT 500 MB. IN
ANY EVENT...DECIDED TO DRASTICALLY LOW POPS THIS EVENING ACROSS THE
MAJORITY OF SOUTHEAST ARIZONA...WITH THE EXCEPTION OF SOUTHERN
COCHISE/EASTERN SANTA CRUZ WHERE STORMS CONTINUE TO DEVELOP JUST TO
THE SOUTH IN NORTHERN SONORA. GIVEN THE CURRENT TRENDS...CONFIDENCE
IS LOW THAT WE WILL SEE REMNANTS OF A DECAYING COMPLEX MOVE ACROSS
THE AREA OVERNIGHT TONIGHT. HOWEVER...IT APPEARS THAT SOMETHING IS
TRYING TO GET ORGANIZED IN EAST CENTRAL SONORA. GIVEN THAT...I WILL
LEAVE IN A CHANCE FOR SHOWERS IN COCHISE AND GRAHAM COUNTIES AFTER
MIDNIGHT.

&&

.PREV DISCUSSION...

WITH THE RIDGE AXIS SOLIDLY EAST OF OUR AREA SATURDAY THE DEEPER
SOUTHERLY FLOW WILL KEEP ABOVE AVERAGE MOISTURE OVER THE AREA WHILE
ALSO ALLOWING THE FLOW TO ORGANIZE JUST ENOUGH FOR BETTER STORM
STRUCTURE. ADD IN MID LEVELS COOLING BACK TO LEVELS MORE FAVORABLE
FOR STORM ENVIRONMENT AND WE SHOULD SEE AN INCREASE IN THUNDERSTORM
COVERAGE SATURDAY (UNLESS THE COMPLEX DEVELOPING TO OUR SOUTH
BECOMES MORE OF AN ISSUE THAN CURRENTLY EXPECTED). KEEPING FINGERS
CROSSED TO START SHUTTING DOWN CONVECTION AFTER SUNSET SATURDAY.

FOR SUNDAY THE ECMWF AND GFS ARE BOTH HINTING AT BUILDING A BIG DAY
AROUND A REMNANT CIRCULATION LIFTING UP FROM THE SOUTH. WITH
MOISTURE THAT DEEP WHO AM I TO ARGUE. WATCH FOR A BUSY AND WET
SUNDAY WITH HEAVY RAIN AND POTENTIAL FLASH FLOOD ISSUES A CONCERN.

BY TUESDAY...MAJOR FEATURES ARE TRYING TO GIVE A WESTERLY COMPONENT
TO OUR SOUTHERLY FLOW. A BIG DIFFERENCE BETWEEN 170 DEGREES AND 200
DEGREES FOR AREAS OF STORM DEVELOPMENT. WE WILL SHOW A DIMINISHING
THUNDERSTORM TREND SPREADING IN FROM THE WEST BY MID WEEK.

&&

.AVIATION...VALID THRU 05/06Z.                                     A
ALTHOUGH STORM COVERAGE IS DOWN ACROSS SOUTHEAST ARIZONA THIS
EVENING...THERE IS A SLIGHT CHANCE OF WEAK -SHRA/-TSRA OVERNIGHT
TONIGHT IN COCHISE AND GRAHAM COUNTY. CONFIDENCE IN THIS SCENARIO IS
WANING THOUGH SINCE IT IS NECESSARY FOR AN ORGANIZED THUNDERSTORM
COMPLEX TO DEVELOP IN SOUTHWEST SONORA MEXICO LATE THIS EVENING. IN
ANY EVENT...SCATTERED TO NUMEROUS -TSRA/-SHRA WILL BE PRESENT
SATURDAY AFTERNOON/EVENING. THE BEST PERIOD FOR BRIEF WIND GUSTS OF
35-45 KTS WILL BE SATURDAY AFTERNOON. OTHERWISE...CLOUD DECKS WILL
MAINLY BE AT OR ABOVE 8K FT AGL AND SURFACE WIND GENERALLY LESS THAN
10 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SOUTHEAST ARIZONA WILL EXPERIENCE A STEADY INCREASE
IN SHOWERS AND THUNDERSTORMS THIS WEEKEND. FAIRLY SLOW STORM MOTIONS
WILL GIVE A GREATER POTENTIAL FOR HEAVY RAINFALL. DRY CONDITIONS
WILL PREVAIL ACROSS WESTERN PIMA COUNTY WEST OF TUCSON INTO SATURDAY
MORNING. THEREAFTER...EXPECT INCREASED COVERAGE OF SHOWERS AND
THUNDERSTORMS STARTING SATURDAY AFTERNOON AND CONTINUING SUNDAY. THE
MAIN CONCERN WILL BE THE COMBINATION OF BRIEF STRONG AND GUSTY WINDS
AND HEAVY RAINFALL. A CHANCE OF MAINLY AFTERNOON AND EVENING
THUNDERSTORMS WILL THEN CONTINUE DURING THE UPCOMING WEEK.

&&

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

&&

$$

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