Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 260404
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
904 PM MST SAT JUL 25 2015

.SYNOPSIS...A DRYING TREND WILL CONTINUE THIS WEEKEND...BUT ENOUGH
MOISTURE WILL LINGER FOR ISOLATED SHOWERS AND THUNDERSTORMS MAINLY
SOUTH AND EAST OF TUCSON. THE PATTERN WILL BECOME MORE FAVORABLE
NEXT WEEK FOR AN UPSWING IN DAILY THUNDERSTORM ACTIVITY BY TUESDAY
AND WEDNESDAY.

&&

.DISCUSSION...EVEN WITH THE INFLUENCE ON AN INVERTED TROUGH AND
ASSOCIATED UPPER-LOW PIVOTING THROUGH PARTS OF SONORA MEXICO THIS
EVENING...WE SIMPLY COULD NOT OVERCOME THE INCREASINGLY DRY AIRMASS
AND SAW MINIMAL CONVECTIVE COVERAGE THIS AFTERNOON. THE 00Z KTWC
SOUNDING SHOWS A PWAT VALUE OF 1.25 INCHES...DOWN 0.25 INCH FROM 24
HOURS AGO WITH SIGNIFICANT DRYING IN THE LOWEST 300 MB...WHICH SHOWS
UP IN SURFACE OBSERVATIONS INDICATING 24-HR DEWPOINT CHANGES OF -9
TO -16 F OVER PARTS OF THE CWA. MADE SOME SMALL UPDATES TO THE SHORT
TERM FORECAST TO REDUCE POPS AND LINE THE GRIDS UP MORE WITH CURRENT
OBSERVATIONAL TRENDS.

WE WILL CONTINUE THE DRYING TREND TOMORROW AS OUR TYPICALLY MOISTURE-
STARVED WESTERLY/SOUTHWESTERLY LOW TO MID-LEVEL FLOW DROPS PWAT
VALUES TO NEAR 1 INCH. A GLANCE AT THE MOST RECENT 00Z NAM/GFS SHOWS
EVEN LESS CONVECTIVE COVERAGE TOMORROW AFTERNOON...CONFINED MAINLY
TO NEAR THE INTERNATIONAL BORDER AND PERHAPS ACROSS THE WHITE
MOUNTAINS. THEN ON MONDAY...CURRENT INDICATIONS POINT TO SOME
INCREASE IN MOISTURE AS SOUTHEASTERLY FLOW INCREASES AS THE
AFOREMENTIONED INVERTED TROUGH EXITS OFF THE BAJA COAST WHICH MAY
FACILITATE A SLIGHT UPTICK IN CONVECTIVE COVERAGE TO START THE WEEK.

&&

.AVIATION...VALID THRU 27/06Z. SCT-BKN CLOUDS AT 6-10K FT AGL MAINLY
SOUTH AND EAST OF KTUS WITH SCT-BKN CLOUDS 10-15K FT AGL ACROSS MOST
OF THE REMAINDER OF SOUTHEAST ARIZONA. A FEW -SHRA MAY LINGER INTO
THE LATE EVENING AND OVERNIGHT HOURS...PRIMARILY NEAR THE AZ/NM AND
INTERNATIONAL BORDERS. ISO-SCT SHRA/TSRA EXPECTED SUNDAY...CONFINED
MAINLY TO THE INTL BORDER AND ACROSS THE WHITE MOUNTAINS. OUTSIDE OF
STORM INFLUENCES...SFC WINDS WILL FOLLOW NORMAL DIURNAL TRENDS WITH
SPEEDS MAINLY LESS THAN 12 KTS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...SOME DRYING WILL LIMIT PRECIPITATION THROUGH
MONDAY...WITH ISOLATED TO SCATTERED ACTIVITY OCCURRING MAINLY ACROSS
SOUTHEASTERN AREAS AND IN THE WHITE MOUNTAINS. HIGH PRESSURE WILL
THEN REPOSITION OVER THE WESTERN STATES WITH MORE FAVORABLE
MONSOONAL FLOW OVER THE SOUTHWEST. THIS WILL RESULT IN MORE
WIDESPREAD SHOWERS AND THUNDERSTORMS TUESDAY THROUGH THURSDAY AS
DEEPER MOISTURE RETURNS TO THE AREA. 20-FT WINDS WILL GENERALLY BE
TERRAIN DRIVEN AND LESS THAN 15 MPH...WITH THE EXCEPTION OF SOME
AFTERNOON GUSTINESS FROM THE WEST DUE TO DAYTIME HEATING. WINDS THEN
DEVELOP AN EASTERLY COMPONENT LATE NEXT WEEK.

&&

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

&&

$$

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

CARLAW



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