Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 022032
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
135 PM MST WED SEP 2 2015

.SYNOPSIS...AMPLE MOISTURE IN COMBINATION WITH SEVERAL DISTURBANCES
WILL CREATE ELEVATED CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH
SATURDAY WITH THE POTENTIAL FOR LOCAL FLASH FLOODING.  WE WILL THEN
MAINTAIN ENOUGH MOISTURE FOR ISOLATED TO SCATTERED MAINLY AFTERNOON
AND EVENING THUNDERSTORMS INTO NEXT WEEK WITH POTENTIAL ENHANCEMENT
ON MONDAY.

&&

.DISCUSSION...CONVECTION FIRED UP ON SCHEDULE WITH STORM MOTIONS OFF
TO THE NNE.  SOME EVIDENCE OF BACK BUILDING RESULTING IN TRAINING
ALREADY IN THE SIERRA VISTA AREA AS WELL AS THE BACK SIDE OF THE
RINCONS.  NO PROBLEMS THUS FAR BUT MANAGED TO GET HALF INCH DIAMETER
HAIL WITH THE SIERRA VISTA STORM.

FOR REMAINDER OF THE DAY EXPECT THE STORM DEVELOPMENT TO CONTINUE
THANKS TO 1200-2000 CAPE AND AN IMPULSE JUST SOUTH OF THE BORDER
HEADED THIS WAY.  THE MAIN THREAT WILL BE STRONG WINDS AND HEAVY
RAIN WITH A CONCERN OF TRAINING CELLS BRINGING ABOUT THE POSSIBILITY
OF FLOODING.  A FEW OF THE HIRES MODELS SUGGEST THE POSSIBILITY OF A
CONVECTIVE COMPLEX DEVELOPING AND SENDING AN OUTFLOW TO THE N-NW
WITH THE THREAT OF BLOWING DUST NW OF TUCSON TOWARD PHX.  NOT
CONFIDENT ENOUGH IN THAT SCENARIO JUST YET TO SEND A PREEMPTIVE DUST
ADVISORY YET BUT WILL KEEP AN EYE IT.  SO FAR THE PRIME SHOW IS TOO
FAR TO THE EAST.

FOR TONIGHT THE APPROACHING DISTURBANCE WILL LIKELY KEEP CONVECTION
GOING WELL INTO THE NIGHT SO CONCERN WOULD BE FOR POTENTIAL FOR
LOCAL HIGH WATER PROBLEMS AT NIGHT.

THURSDAY THERE IS ANOTHER IMPULSE ON ITS WAY TO AFFECT THE AREA
ALTHOUGH MODELS INDICATE THAT IT MAY BE A FEW HOURS LATER THAN
TODAYS PUTTING THE FOCUS LATER IN THE DAY AND OVERNIGHT THURSDAY.
AGAIN THE POTENTIAL FOR LOCAL FLOODING AND WET MICROBURST ACTIVITY.
SHOULD BE ENOUGH FLOW ALOFT TO RESET THE ATMOSPHERE SO WILL
MAINTAIN THE RELATIVELY HIGH POPS.

BEYOND THAT WE STILL MAINTAIN A S TO SW FLOW ACROSS THE AREA WITH
MOISTURE STREAMING NORTH SATURDAY AND SUNDAY ALTHOUGH THE MOISTURE
ISN/T QUITE AS HIGH.  COULD/SHOULD ALSO HAVE SOME DISTURBANCES IN
THAT FLOW TO HELP CONVECTION AT TIMES ALTHOUGH TOO EARLY TO TRY TO
CAPTURE AND TIME THOSE.  THROUGH OUT THE THURSDAY THROUGH SUNDAY
TIME FRAME...DUE TO CLOUDS...PRECIPITATION AND LOWER THICKNESS
VALUES HIGH TEMPERATURES WILL BE SEVERAL DEGREES BELOW NORMAL.

THEN BOTH THE GFS (WHICH PICKED THIS WHOLE SCENARIO UP WELL THUS
FAR) AND THE ECMWF INDICATED A MORE SIGNIFICANT DISTURBANCE WILL
ROTATE UP THROUGH HERE WITH A FAIR AMOUNT OF MOISTURE.  THE DETAILS
DIFFER...HOWEVER WITH BOTH SHOWING A SIMILAR IDEA THIS FAR OUT IT
NEEDS TO BE NOTED.  IF IT WERE TO COME TO PASS IT SHOULD PROVIDE FOR
ANOTHER VERY ACTIVE DAY OF CONVECTION.  THEN BEYOND THAT THE TREND
IS TO A MORE WESTERLY FLOW WHICH WOULD SLOWLY DRY OUT THE AIR MASS
WITH TEMPERATURES CLIMBING BACK UP TO NORMAL LEVELS.  CERNIGLIA

&&

.AVIATION...VALID THRU 04/00Z.
SCATTERED TO NUMEROUS TSRA/SHRA ACROSS MUCH OF SE ARIZONA THRU
03/06Z. BRIEF MVFR CONDITIONS AND VRB WIND GUSTS TO 45 KTS WILL
OCCUR WITH THE STRONGER TSRA. OTHERWISE...EXPECT LAYERED CLOUDS
MOSTLY BETWEEN 8K FT AND 15K FT AGL AND SURFACE WIND GENERALLY LESS
THAN 10 KTS. TSRA/SHRA WILL DEVELOP AGAIN AFT 03/19Z. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT SCATTERED SHOWERS AND THUNDERSTORMS ACROSS
MUCH OF SOUTHEAST ARIZONA THROUGH SATURDAY. ISOLATED TO SCATTERED
MAINLY AFTERNOON AND EVENING THUNDERSTORMS WILL PREVAIL SUNDAY
THROUGH TUESDAY. LOCALLY HEAVY RAINFALL AND BRIEF GUSTY WINDS WILL
ACCOMPANY THE STRONGER THUNDERSTORMS. POTENTIAL EXISTS FOR LOCALLY
HEAVY RUNOFF THIS AFTERNOON INTO TONIGHT. TYPICAL T-STORM GUSTS WILL
BE 25-35 MPH WITH STRONGER STORMS GUSTING TO OVER 50 MPH. STORM
MOTION TODAY WILL GENERALLY BE TO THE NORTH OR NORTHEAST AT 10-15
MPH.

&&

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

&&

$$

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