Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 212156
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
255 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...SCATTERED SHOWERS AND THUNDERSTORMS WERE OCCURRING
GENERALLY FROM THE FAR ERN PORTION OF THE TUCSON METRO AREA EWD/SWD
AT THIS TIME. MEANWHILE...SUNNY SKIES PREVAILED ACROSS WRN PIMA
COUNTY. EXPECT SCATTERED SHOWERS/TSTMS TO CONTINUE THIS EVENING FROM
TUCSON EWD/SWD WITH DRY CONDITIONS ACROSS WRN PIMA COUNTY. THE BULK
OF ANY PRECIP OF SIGNIFICANCE SHOULD END BY AROUND MIDNIGHT TONIGHT.
THERE IS ENOUGH MOISTURE TO MAINTAIN A SLIGHT CHANCE OF SHOWERS/
TSTMS LATE TONIGHT ACROSS ERN SECTIONS WITH DRY CONDITIONS ELSEWHERE.

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.

&&

.AVIATION...VALID THRU 23/00Z.
SCATTERED SHRA/TSRA EAST OF A KOLS-KTUS-GLOBE LINE EXPECTED INTO
THIS EVENING. EXPECT MVFR CONDITIONS AND BRIEF WIND GUSTS TO AROUND
35 KTS WITH THE STRONGER THUNDERSTORMS. ISOLATED -SHRA/-TSRA MAY
OCCUR EAST OF KTUS LATE TONIGHT AND EARLY MONDAY MORNING...THEN
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 THROUGH 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.

&&

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

&&

$$

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

DISCUSSION...FRANCIS
AVIATION/FIRE WEATHER...DROZD




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