Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251627
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
925 AM MST THU SEP 24 2014

.SYNOPSIS...THE CHANCES FOR SHOWERS AND THUNDERSTORMS WILL INCREASE
TODAY THROUGH SATURDAY AS A FRONT APPROACHES THE AREA FROM THE
NORTHWEST. INCREASED RISK FOR STRONGER AND WETTER STORMS SATURDAY.
DRIER AND COOLER NEXT WEEK AS THE MONSOON SEASON COMES TO A CLOSE.

&&

.DISCUSSION...A COUPLE OF INTERESTING THINGS THIS MORNING. THAT
IMPULSE/LARGE MCC WE WERE WATCHING YESTERDAY TRAVELING QUICKLY UP
THE WESTERN COAST OF MEXICO HELPED TRIGGER ADDITIONAL ORGANIZED
CONVECTION THROUGH CENTRAL WESTERN SONORA LAST NIGHT. DECENT OUTFLOW
FROM THAT COULD BE SEEN ON IR IMAGERY EARLY THIS MORNING INTO
CENTRAL AND WESTERN PIMA COUNTY. IN ADDITION WE ARE SEEING A SHALLOW
TO MEDIUM DEPTH SURGE FROM THE GULF OF CALIFORNIA THIS MORNING.
SURFACE DEWPTS ARE UP 10 TO 20 DEGREES COMPARED TO 24 HOURS AGO INTO
SOUTHERN YUMA AND WESTERN TO CENTRAL PIMA COUNTIES. IT`S ONLY ABOUT
3K FT DEEP AT THIS POINT. WE ARE ON TRACK FOR BETTER STORM COVERAGE
WEST AND SOUTHWEST OF TUCSON THIS AFTERNOON AS THE MOISTURE DEEPENS
FROM THE SOUTH.

THE SECOND ITEM OF NOTE TODAY WOULD BE A BRISK ENOUGH EASTERLY FLOW
COMBINED WITH JUST ENOUGH MOISTURE IN EASTERN AREAS FOR A POTENTIAL
ORGANIZED OUTFLOW FROM THE MOGOLLON RIM THROUGH GRAHAM...GREENLEE
AND EASTERN PINAL COUNTY. NOT SURE IF CONDITIONS ARE QUITE FAVORABLE
ENOUGH TO BRING THIS AS AN ACTIVE ORGANIZED THUNDERSTORM OUTFLOW
INTO TUCSON EARLY THIS EVENING. IT WILL MOST LIKELY COME IN AS AN
INTACT WIND OUTFLOW WITH LIMITED CONTINUED THUNDERSTORM DEVELOPMENT
AT THAT POINT. SOMETHING TO KEEP AN EYE ON.

OTHERWISE SATURDAY IS SHAPING UP AS A STRONG THUNDERSTORM DAY FOR
THE STATE WITH THE TROUGH. WE CONTINUE TO TWEAK COVERAGE UP EVEN
WHILE WE CONTINUE TO FOCUS ON CENTRAL AND NORTHERN PORTIONS OF THE
STATE FOR THE MOST WIDESPREAD ACTIVITY. GREAT DYNAMICS AND SHEAR
FAVORABLE FOR AN INCREASED RISK OF SEVERE THUNDERSTORMS SATURDAY.

&&

.AVIATION...VALID THRU 26/17Z.
MOISTURE WILL CONTINUE TO INCREASE TODAY WITH A BETTER CHANCE OF
SHOWERS AND THUNDERSTORMS THIS AFTERNOON...AFTER 25/18Z. STILL
PROBABLY NOT ENOUGH COVERAGE TO MENTION STORMS AT THIS POINT WITH
GREATEST RISK FOR KOLS AND KSAD AFTER 25/21Z. BRIEF MVFR AND GUSTY
WINDS ASSOCIATED WITH ANY STORMS. OTHERWISE NORMAL DIURNAL SURFACE
WIND TRENDS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...INCREASING MOISTURE WITH INCREASING SHOWER AND
THUNDERSTORM COVERAGE INTO SATURDAY. STORMS MAY BE PARTICULARLY
STRONG SATURDAY AS A FRONT APPROACHES FROM THE WEST. MUCH DRIER AND
RELATIVELY COOLER CONDITIONS BEHIND THE TROUGH EARLY NEXT WEEK.

THE STRONGER THUNDERSTORMS MAY PRODUCE SOME GUSTY OUTFLOW WINDS.
OTHERWISE...20-FOOT WINDS WILL GENERALLY BE LESS THAN 15 MPH THROUGH
FRIDAY. SOUTHWEST WINDS OF 10 TO 20 MPH ARE THEN EXPECTED SATURDAY
AND SUNDAY AFTERNOON AS A TROUGH OF LOW PRESSURE PASSES TO THE NORTH.

&&

.PREV DISCUSSION...10Z SFC TEMPS RANGED FROM THE 60S AT HIGHER
ELEVATIONS/NEAR THE INTERNATIONAL BORDER...TO THE LOW 80S IN THE WRN
DESERTS. DEWPOINTS WERE HOLDING STEADY IN THE 50S AND 60S CWA-WIDE.
10Z IR SATELLITE IMAGERY WAS SHOWING MOSTLY CLEAR SKIES OVER MUCH OF
THE WRN CWA WITH SCT CLOUDS FILTERING INTO GREENLEE/GRAHAM COUNTY
FROM THE EAST. A SMALL COMPLEX LOCATED JUST EAST OF THE AZ/NM BORDER
NEAR GLENWOOD NM WAS PROPAGATING SWWD AND WEAKENING. BLENDED TOTAL
PRECIP WATER VALUES WERE CLOSE TO 1.2 NEAR THE INTERNATIONAL BORDER.
WATER VAPOR IMAGERY WAS SHOWING UPPER LVL TROF DIGGING SE OFF THE
COAST OF THE PAC NW...AS RIDGE OVER THE WRN CONUS CONTINUES TO
PROGRESS EWD. THE CONVECTIVE COMPLEX THAT WAS MOVING NORTHWARD FROM
THE SOUTHERN GULF OF CALIFORNIA LAST NIGHT DISSIPATED JUST S OF THE
INTERNATIONAL BORDER. THE INHERITED FORECAST SUGGESTED THE POTENTIAL
FOR A MOISTURE SURGE FROM THIS SYSTEM TO OCCUR...WITH INCREASED POPS
FOR AREAS FROM NOGALES WWD TOWARD ORGAN PIPE CACTUS NATIONAL
MONUMENT FOR THIS AFTERNOON AND EVENING. HAVE CHOSEN TO CONTINUE
WITH THIS TREND AS MULTIPLE MODELS CONTINUED TO PICK UP ON ITS
INFLUENCE LATER THIS AFTERNOON.

INCREASING THUNDERSTORM COVERAGE WILL BEGIN TODAY AND LAST THROUGH
AT LEAST SATURDAY AHEAD OF A STRONG UPPER LVL TROF/COLD FRONT. THIS
FEATURE WILL BRING DECENT RAIN CHANCES TO THE AREA...WITH A FOCUS ON
NRN PORTIONS OF THE CWA...ALONG WITH SOME GUSTY SWLY WINDS. A FEW
LINGERING SHOWERS/THUNDERSTORMS WILL BE POSSIBLE THROUGHOUT THE DAY
SUNDAY...ESPECIALLY IN THE MOUNTAINS AND FOR AREAS MAINLY EAST TO
NORTHEAST OF TUCSON. THE TROF THEN WILL SWING THRU NRN AZ AND LIFT
OUT TO THE NE MONDAY MORNING. SIGNIFICANT COOLING IS EXPECTED IN THE
WAKE OF THE COLD FRONT...WITH HIGH TEMPS SUNDAY THROUGH MID-WEEK
ONLY IN THE MID TO UPPER 80S...HELLO FALL!

DRIER CONDITIONS WILL THEN SET IN BEHIND THE TROUGH. LOOKING A
LITTLE FURTHER OUT...NOTHING IN THE UPPER LVL PATTERN TO SUGGEST THE
RETURN OF A FOUR CORNERS HIGH. GOODBYE MONSOON 2014!

&&

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

&&

$$

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

MEYER/FRENCH





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