Severe Thunderstorm Warning 91, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
921 AM MST FRI SEP 20 2013

.SYNOPSIS...A BIT OF LOW AND MID LEVEL MOISTURE WILL ALLOW FOR
ISOLATED THUNDERSTORMS ACROSS SOUTHERN ARIZONA EAST OF TUCSON THIS
AFTERNOON AND EVENING.  THIS MOISTURE WILL SPREAD FURTHER WEST
TONIGHT INTO SATURDAY RESULTING IN A SLIGHT CHANCE OF THUNDERSTORMS
ACROSS MOST OF THE AREA LATER SATURDAY. THEREAFTER...A DRY WESTERLY
FLOW WILL DEVELOP OVER THE REGION BRINGING AN END TO THE RAIN
CHANCES NEXT WEEK

&&

.DISCUSSION...NO CHANGES IN THE CURRENT FORECAST THINKING AS A
SLIGHT INCREASE IN MOISTURE THROUGH SATURDAY SHOULD GIVE WAY TO A
FEW MORE SHOWERS AND THUNDERSTORMS ACROSS THE AREA. THIS WILL BE
FOLLOWED BY A DRY SPELL AS A MODERATE WESTERLY FLOW ALOFT SETTLES
OVER THE REGION. PLEASE REFER TO THE ADDITIONAL SECTIONS FOR MORE
DETAILS.

&&

.AVIATION...KTUS VICINITY WWD/NWWD SKC CONDITIONS. FEW-SCT CLOUDS
ABOVE 10K FT FROM KTUS EASTWARD THROUGH AROUND 20/20Z. FROM 20/20Z
THROUGH 21/03Z POSSIBLE ISOLD -TSRA/-SHRA EAST AND SOUTH OF
KTUS...MAINLY NEAR THE NEW MEXICO BORDER AND INTERNATIONAL BORDER
WITH SCT-BKN CLOUDS AROUND 8-12K FT AGL. SURFACE WIND AREA-WIDE
GENERALLY LESS THAN 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...EXPECT ISOLATED THUNDERSTORMS MAINLY NEAR THE NEW
MEXICO BORDER DURING THE AFTERNOON AND EVENING HOURS AGAIN TODAY.
THERE WILL BE SOME INCREASE IN MOISTURE ON SATURDAY AS A STORM
SYSTEM APPROACHES FROM THE NORTHWEST. THUS...THERE IS A SLIGHT
CHANCE OF THUNDERSTORMS ACROSS MUCH OF SOUTHEAST ARIZONA SATURDAY
AND SATURDAY EVENING. THEREAFTER...MARKEDLY DRIER CONDITIONS WILL
PREVAIL EARLY NEXT WEEK. NORMAL DIURNAL WIND TRENDS WILL OCCUR INTO
EARLY NEXT WEEK EXCEPT FOR STRONGER WEST TO SOUTHWEST WINDS LATE
THIS WEEKEND.

&&

.PREV DISCUSSION...PRETTY QUIET ACROSS SE AZ THIS MORNING WITH JUST
A FEW MID LEVEL CLOUDS AROUND.  LATEST MESOSCALE ANALYSIS INDICATES
LOW/MID LEVEL MOISTURE EDGING ITS WAY WESTWARD FROM WHERE IT WAS
LATE YESTERDAY.  THIS FITS LATEST MODEL IDEAS WHICH SHOULD BRING THE
AFTERNOON CONVECTION A BIT FURTHER WEST.  TWEAKED THE FORECAST TO
INDICATE THIS LINE OF THINKING.  BASICALLY BEST CHANCE IS ROUGHLY
BENSON EASTWARD BUT WOULD NOT BE TOO SURPRISED TO SEE SOMETHING POP
OFF THE RINCONS...CATALINAS OR DOWN NEAR THE SANTA RITAS.  WITH
LITTLE CHANGE TO THE THERMAL PROFILE TEMPERATURES SHOULD BE SIMILAR
TO YESTERDAY.

FOR SATURDAY...A DECENT TROUGH MOVING ONTO THE WEST COAST WILL HELP
PULL THE MOISTURE A BIT FURTHER WEST FOR A CHANCE OF THUNDERSTORMS
ACROSS MOST OF THE FORECAST AREA THAT AFTERNOON AND EVENING.  LIKELY
THE LAST CHANCE FOR MONSOONAL THUNDERSTORMS FOR THE 2013 SEASON.
THICKNESS LEVELS RISE A BIT BUT SO DOES THE CLOUD COVER SO THE WITH
THE BLEND OF THESE TWO OPPOSING FORCES TEMPERATURES LIKELY TO BE
SIMILAR TO THE PREVIOUS TWO DAYS.

CHANGES REALLY BEGIN TO TAKE PLACE SUNDAY AS THE UPPER TROUGH MOVES
EAST ACROSS THE AREA DURING THE DAY.  THIS SYSTEM WILL KICK UP A
WESTERLY BREEZE AND FORCE THE MOISTURE OFF TO THE EAST THROUGH THE
DAY.  MODELS HAVE SLOWED UP THE PASSAGE OF THIS FEATURE A BIT AND IF
THAT TREND CONTINUES COULD END UP WITH SOME CONVECTION NEAR THE NEW
MEXICO BORDER THAT AFTERNOON WITH THE LINGERING MOISTURE AND THE
PASSAGE OF THE TROUGH AXIS DURING THE AFTERNOON HOURS.  FOR NOW WILL
LEAVE THE DRY FORECAST IN PLACE BUT WILL NEED TO KEEP AN EYE ON
THAT.  OTHERWISE WE SHOULD HAVE A DECENT WEST TO SOUTHWEST BREEZE
AND SLIGHTLY COOLER TEMPERATURES.

BEYOND THAT...DRY AIR RULES THROUGH THE NEXT WEEK WHICH MEANS NO
SHOWERS OR THUNDERSTORMS AND MOSTLY CLEAR SKIES.  COOLER /NEAR
NORMAL/ TEMPERATURES ARE EXPECTED WITH WESTERLY WINDS PICKING UP A
BIT LATE IN THE WEEK AS ANOTHER UPPER TROUGH PASSES BY TO THE
NORTH.  CERNIGLIA

&&

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

&&

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TUCSON AZ
1146 AM MST FRI SEP 20 2013

AZZ503-513-201930-
DRAGOON/MULE/HUACHUCA AND SANTA RITA MOUNTAINS INCLUDING
BISBEE/CANELO HILLS/MADERA CANYON AZ-UPPER SANTA CRUZ RIVER AND ALTAR
VALLEYS INCLUDING NOGALES AZ-
1146 AM MST FRI SEP 20 2013

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SANTA CRUZ AND
SOUTHWESTERN COCHISE COUNTIES NEAR PARKER CANYON LAKE UNTIL 1230 PM
MST...

AT 1139 AM MST...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A STRONG THUNDERSTORM 13 MILES SOUTHWEST OF SIERRA VISTA NEAR PARKER
CANYON LAKE...MOVING SOUTH AT 5 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH
HEAVY RAIN.

AREAS AFFECTED BY THIS STORM INCLUDE...MAINLY RURAL AREAS OF EXTREME
SOUTHEASTERN SANTA CRUZ AND EXTREME SOUTHWESTERN COCHISE COUNTIES.

LAT...LON 3134 11030 3133 11058 3149 11052 3148 11032
TIME...MOT...LOC 1846Z 011DEG 5KT 3141 11043