Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 220336
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
835 PM MST SUN SEP 21 2014

.SYNOPSIS...DRIER CONDITIONS WILL LEAD TO REDUCED COVERAGE OF
SHOWERS AND THUNDERSTORMS BY MIDWEEK. THE CHANCES FOR SHOWERS AND
THUNDERSTORMS WILL THEN INCREASE DURING THE LATTER PART OF THE WEEK.
A GRADUAL WARMING TREND WILL OCCUR THROUGH WEDNESDAY FOLLOWED BY
COOLER TEMPERATURES NEXT WEEKEND.

&&

.DISCUSSION...EARLIER CONVECTION ACROSS OUR AREA CONTINUES TO
DECREASE IN COVERAGE AND INTENSTIY THIS EVENING. AN AREA OF RAIN
ASSOCIATED WITH A STORM COMPLEX OVER SONORA MEXICO...WHICH PRODUCED
A QUICK 1-2 INCHES NEAR BISBEE...IS ALSO WANING THIS HOUR. GIVEN THE
LINGERING SHOWERS/STORMS ACROSS OUR EASTERN ZONES...NO CHANGES ARE
NEEDED TO THE INHERITED GRIDS AT THIS POINT.

&&

.AVIATION...VALID THRU 23/06Z.
ISOLATED -SHRA/-TSRA MAY OCCUR EAST OF KTUS LATE TONIGHT AND EARLY
MONDAY MORNING. MAIN AREA OF STORMS AS OF 03Z BETWEEN KOLS AND KDUG
WITH OUTFLOW BOUNDARY MOVING TOWARDS KOLS TERMINAL WHICH WILL SHIFT
WINDS TO E WITH THE POSSIBILITY OF A BRIEF GUST TO 20 KTS. SCATTERED
-SHRA/-TSRA AGAIN MONDAY AFTERNOON...ESPECIALLY EAST OF KTUS.
OTHERWISE...SURFACE WIND WILL BE MAINLY LESS THAN 10 KTS THRU MONDAY
AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED MAINLY AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS WILL OCCUR ESPECIALLY FROM TUCSON EASTWARD AND
SOUTHWARD ON MONDAY. DRIER CONDITIONS WILL PRODUCE MARKEDLY LESS
COVERAGE OF SHOWERS AND THUNDERSTORMS TUESDAY AND WEDNESDAY.
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS WILL THEN PREVAIL
THURSDAY INTO NEXT WEEKEND. BRIEF GUSTY OUTFLOWS WILL OCCUR WITH THE
STRONGER THUNDERSTORMS. OTHERWISE...20-FOOT WINDS WILL GENERALLY BE
LESS THAN 15 MPH THIS WEEK.

&&

.PREV DISCUSSION...THE COVERAGE OF SHOWERS/TSTMS SHOULD BE QUITE
SIMILAR MON AFTERNOON/EVENING VERSUS TODAY...AS DEEPER MOISTURE IS
PROGGED TO CONTINUE ACROSS LOCALES MAINLY EAST AND SOUTH OF TUCSON.
THUS...HAVE OPTED FOR ISOLATED TO SCATTERED SHOWERS/TSTMS FROM
TUCSON EWD/SWD MON AFTERNOON/EVENING. EXPECT DRY CONDITIONS ACROSS
WRN PIMA COUNTY. ANY SHOWERS/TSTMS LATE MON NIGHT WILL BE NEAR THE
NEW MEXICO BORDER WITH DRY CONDITIONS ELSEWHERE.

HIGH PRESSURE ALOFT CENTERED OVER THE NRN GULF OF CALIFORNIA TUE IS
PROGGED TO AMPLIFY OVER THE SWRN CONUS WED. WARMER MID-LEVEL TEMPS
IN COMBINATION WITH DECREASED MOISTURE WILL TRANSLATE INTO MARKEDLY
REDUCED PRECIP CHANCES TUE-WED. ISOLATED SHOWERS AND THUNDERSTORMS
WED AFTERNOON/EVENING SHOULD BE CONFINED TO NEAR THE HIGHER TERRAIN
EAST AND SOUTH OF TUCSON.

LOWER AND MID-LEVEL MOISTURE SHOULD INCREASE THUR-SAT AHEAD OF A
DEEPENING UPPER TROUGH OVER THE WRN CONUS. THERE WERE SOME FAIRLY
PRONOUNCED DIFFERENCES BETWEEN THE 21/12Z GFS/ECMWF REGARDING THE
EVOLUTION OF THIS TROUGH BY NEXT WEEKEND. IN ESSENCE...THE GFS
DEPICTED A MORE-PROGRESSIVE SYSTEM VERSUS THE ECMWF...WITH THE GFS
ADVANCING THE MID-LEVEL TROUGH AXIS EAST OF THE AREA BY SUN.
MEANWHILE...THE ECMWF PROGGED SWLY FLOW AND MORE-ROBUST MOISTURE
FIELDS TO BE ACROSS SE AZ SUN IN RESPONSE TO A 568 DM LOW CENTERED
OVER THE GREAT BASIN.

AT ANY RATE...ISOLATED SHOWERS/TSTMS THUR SHOULD INCREASE TO
SCATTERED COVERAGE OF SHOWERS/TSTMS BY SAT. THERE ARE SOME
SIGNATURES VIA THE GFS/ECMWF THAT SUGGEST THE POTENTIAL FOR SEVERE
TSTMS TO OCCUR SAT. HAVE OPTED FOR A MIDDLE-GROUND APPROACH BETWEEN
THE GFS/ECMWF FOR POPS NEXT SUN. THIS TRANSLATES TO ISOLATED SHOWERS/
TSTMS GENERALLY FROM TUCSON EWD WITH DRY CONDITIONS ACROSS
WRN/CENTRAL PIMA COUNTY.

EXPECT A DEGREE-OR-TWO OF DAILY WARMING MON-WED FOLLOWED BY HIGH
TEMPS FALLING BELOW SEASONAL NORMALS NEXT WEEKEND.

&&

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

&&

$$

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