Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 301014
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
245 AM MST THU JUL 30 2015

.SYNOPSIS...AN ELEVATED CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
SOUTHEAST ARIZONA WILL CONTINUE THIS WEEK WITH SOME STORMS PRODUCING
LOCALLY HEAVY RAIN AND STRONG WINDS. RAIN CHANCES WILL CONTINUE OVER
THE WEEKEND INTO EARLY NEXT WEEK...BUT COVERAGE WILL DECREASE WITH A
WEAKER FLOW AS HIGH PRESSURE INCREASES ALOFT.

&&

.DISCUSSION...LESS DEBRIS CLOUD THIS MORNING WITH MUCH OF IT NORTH
AND NORTHEAST OF TUCSON ASSOCIATED WITH AN IMPULSE LIFTING INTO
NORTHEAST ARIZONA. THAT SHOULD HELP THE CLEARING TREND THIS MORNING
WITH MORE SUNSHINE TO START THE DAY COMPARED TO THE LAST FEW DAYS.
THE FLOW IS STILL WEAK BUT GOOD MOISTURE REMAINS IN PLACE WITH
PRECIPITABLE WATER VALUES RANGING FROM 1.3 TO 1.5 INCHES ACROSS
SOUTHEAST ARIZONA ACCORDING TO CIRA LPW TOTALS. WE MAY HAVE TO WORK
WITH WHAT WE HAVE FOR A BIT WITH THE WEAK FLOW NO LONGER REINFORCING
OUR MOISTURE SUPPLY. THAT WILL BE EVIDENT WITH AFTERNOON MIXING OF
SURFACE DEW POINTS DOWN INTO THE 50S IN MANY VALLEY LOCATIONS TODAY
(WE HELD ONTO OUR 60S THROUGH THE DAY YESTERDAY). IN ADDITION...BY
THIS AFTERNOON WE MAY SEE A TEMPORARY MODEST WARMING TREND IN MID
LEVELS AS A SECONDARY MID LEVEL HIGH CENTER CONSOLIDATES CLOSER TO
NEW MEXICO DURING THE DAY. THAT WILL MAKE FOR EASY MOUNTAIN
DEVELOPMENT AND ABOVE AVERAGE COVERAGE IN THE MOUNTAINS...BUT LESS
SUPPORT IN GENERAL FOR VALLEY STORMS. ONLY AVERAGE TO MAYBE BELOW
AVERAGE COVERAGE IN VALLEYS.

THE FLOW...THOUGH WEAK...REMAINS FAVORABLE INTO THE WEEKEND. AN
EMBEDDED IMPULSE IN THE FLOW CURRENTLY JUST SOUTH OF CHIHUAHUA WOULD
BE A NICE ASSIST FOR STORMS FRIDAY AFTERNOON AND
EVENING...ESPECIALLY FROM TUCSON SOUTH AND WESTWARD.

AFTER THAT THERE IS LESS TO FOCUS ON IN THE FLOW THAT WILL GENERALLY
MAINTAIN WEAK SOUTHERLY AND EASTERLY COMPONENTS. MEDIUM RANGE MODELS
INITIALLY MAINTAIN FAVORABLE H7 THETA-E TRENDS...SO WE WILL KEEP
THUNDERSTORM COVERAGE NEAR SEASONAL AVERAGES OVER THE WEEKEND INTO
EARLY NEXT WEEK. AS ALWAYS...MUCH DEPENDS ON THE ORIENTATION AND
LOCATION OF THE RIDGE. SOMETHING TO WATCH IS A NEW TREND WITH THE
ECMWF REBUILDING THE RIDGE INTO A BLOCKING POSITION EARLY NEXT
WEEK...WHICH WOULD REDUCE AVAILABLE MOISTURE AND THUNDERSTORM
COVERAGE.

&&

.AVIATION...VALID THRU 31/12Z.
SOME DEBRIS CLOUD FROM EARLIER CONVECTION THIS MORNING WITH A
PARTIAL CLEARING TREND EXPECTED TO CONTINUE THROUGH MID MORNING.
SCT-NUMEROUS SHRA/TSRA DEVELOPING AGAIN AFT 30/17Z LASTING INTO THE
EVENING HOURS. MVFR CONDITIONS AND VRB WIND GUSTS TO 40 KTS POSSIBLE
IN AND AROUND THE STRONGER TSRA. 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...WE WILL KEEP ENOUGH MOISTURE FOR A CHANCE OF SHOWERS
AND THUNDERSTORMS ACROSS MUCH OF SOUTHEAST ARIZONA INTO NEXT WEEK.
WEAK DRYING IN WESTERN AREAS IS EXPECTED TO SEE LESS OF A CHANCE OF
THUNDERSTORMS WEST OF TUCSON STARTING THIS WEEKEND. STRONG WINDS ARE
EXPECTED NEAR THUNDERSTORMS WITH OUTFLOWS POSSIBLE FURTHER AWAY FROM
STORMS. 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.

&&

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

&&

$$

MEYER/RASMUSSEN

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