Dust Storm Warning 4, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
930 AM MST FRI JUL 12 2013

.SYNOPSIS...WITH A BIT LESS ATMOSPHERIC MOISTURE OVER THE AREA EACH
DAY THROUGH SUNDAY THE SHOWER AND THUNDERSTORM ACTIVITY WILL
DIMINISH SOMEWHAT THROUGH THE WEEKEND WITH HIGH TEMPERATURES SLOWLY
RISING.  THEN A WEATHER SYSTEM FROM THE PLAINS STATES WILL MOVE WEST
AND BEGIN TO AFFECT OUR WEATHER EARLY NEXT WEEK WITH MORE MOISTURE
AND INSTABILITY.  THIS WILL INCREASE THE THREAT OF SHOWERS AND
THUNDERSTORMS MONDAY ONWARD WITH HIGH TEMPERATURES COOLING OFF A BIT
ONCE AGAIN.

&&

.DISCUSSION...OVERNIGHT MCS THAT MOVED ACROSS COCHISE COUNTY INTO
GRAHAM AND GREENLEE COUNTIES HAS ALL BUT DISSIPATED. THIS SYSTEM DID
PRODUCE SOME SOLID RAINFALL SO WE WILL NEED TO WATCH FOR FLOOD
THREATS ACROSS THE SATURATED AREAS TODAY. ADDITIONAL MCS ACTIVITY
OVER THE SIERRA MADRES LAST NIGHT TRIGGERED A SERIES OF OUTFLOWS
THAT IN TURN PRODUCED NEW STORM COMPLEXES DOWNWIND. THE HI RES
MODELS ARE HAVING TROUBLE WITH THE COMPLEX CURRENTLY MOVING INTO
SANTA CRUZ AND PIMA COUNTIES. THE HRRR DID SHOW SOME WEAK STORMS
REACHING FAR SOUTHERN AZ...AND IS CURRENTLY ON TOP OF THE CLOUD
COVER. PLUS...MOISTURE CONTENT IS STILL HIGH SO ANY REMNANT OUTFLOWS
FROM THE MCS OVER SOUTHERN AZ MAY KEEP CONVECTION GOING FOR A FEW
MORE HOURS

WITH THAT IN MIND...I TEND TO FAVOR THE HRRR TODAY WHICH SHOWS A
SIMILAR EVOLUTION AS YESTERDAY. THAT DOES MAKE SENSE GIVEN OUR 12Z
SOUNDING WHICH SHOWS A SIMILAR PROFILE AS YESTERDAY. A THICK VEIL OF
CLOUDS SITS OVER MUCH OF SE AZ AND IT WILL TAKE SOME TIME FOR THE
CLOUDS TO DISSIPATE MEANING OUR SURFACE HEATING POTENTIAL WILL BE
LIMITED. CURRENTLY...WE ARE RUNNING ABOUT A DEGREE WARMER THAN
YESTERDAY...AND THE CONVECTIVE TEMP FOR TODAY SHOULD BE SLIGHTLY
LOWER THAN YESTERDAY. SO I DONT THINK THE MORNING CLOUD COVER WILL
COMPLETELY ELIMINATE STORM CHANCES TODAY...BUT IT MAY KEEP THE
INTENSITY AND COVERAGE DOWN TO MORE ISOLATED TO SCATTERED STORMS.

GIVEN OUR RECENT RAIN IN THE SOUTHERN ZONES AND HI MOISTURE CONTENT
IN THE ATMOSPHERE...I AM AGAIN CONCERNED ABOUT FLOODING. AN ISOLATED
DOWNBURST ALSO IS POSSIBLE AS WE ARE CURRENTLY EXPERIENCING GUSTY
WINDS OUT OF THE SOUTHERN AZ MCS.

JJB

&&

.AVIATION...CONTINUED ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS MOVING NNW AT 10-15 KTS THROUGH THIS EVENING OR
08/06Z. ISOLATED CIGS 0F 3-4K FT NEAR THE STRONGER TSTMS WITH VSBYS
POTENTIALLY AS LOW AS 1/2 TO 1SM DUE TO HEAVY RAIN. OUTSIDE OF THE
THUNDERSTORMS...SURFACE WINDS DIURNALLY DRIVEN LESS THAN 10 KTS.
CLOUDS SCT060-080 BKN100-120. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED MAINLY AFTERNOON THROUGH EARLY MORNING
SHOWERS AND THUNDERSTORMS WILL CONTINUE WITH A DIMINISHING
TREND INTO THE WEEKEND. THE STRONGER THUNDERSTORMS WILL PRODUCE
GUSTY AND ERRATIC WINDS AND LOCALLY HEAVY RAINS. OUTSIDE OF THE
THUNDERSTORM ACTIVITY...GENERALLY NORMAL DIURNAL WIND TRENDS ARE
EXPECTED TO OCCUR THROUGH THE WEEKEND. DAYTIME RELATIVE HUMIDITIES
WILL RANGE FROM THE 20S TO 40S WITH GOOD NIGHTTIME RECOVERIES. A
SLIGHT DRYING TREND IS EXPECTED LATE THIS WEEKEND.

&&

.PREV DISCUSSION...SOME SHOWERS AND THUNDERSTORMS ARE NOW MOVING
ACROSS EXTREME SE AZ EARLY THIS MORNING AND THESE SHOULD CONTINUE
NNW AND SLOWLY DIE OFF OVER THE NEXT SEVERAL HOURS.  THEN AS WE MOVE
INTO THE DAY...WITH ABUNDANT LOW LEVEL MOISTURE AND SUFFICIENT
INSTABILITY IN PLACE ACROSS THE REGION...CONVECTION IS EXPECTED TO
FIRE UP LATE THIS MORNING RESULTING IN SCATTERED SHOWERS AND
THUNDERSTORMS FOR THE AFTERNOON AND EVENING HOURS.  TIMING OF THE
DEVELOPMENT WILL BE SIMILAR TO YESTERDAY WITH SIMILAR STEERING FLOW
PUSHING THE STORMS TO THE NNW.  WITH A BIT LESS MID AND UPPER LEVEL
MOISTURE TO WORK WITH THE STORMS SHOULD BE SLIGHTLY LESS EFFICIENT
RAINFALL PRODUCERS AND WITH A LACK OF A STRONG LIFTING MECHANISM THE
INTENSITIES SHOULD BE HELD IN CHECK FOR THE MOST PART.

THIS THEME CONTINUES INTO THE WEEKEND WITH LOWER LEVELS OF
ATMOSPHERIC MOISTURE FOR THE CONVECTION TO WORK WITH SO WILL HAVE AN
OVERALL TREND OF LESS SHOWER AND STORM COVERAGE EACH DAY AND LESS
INTENSE RAINFALL WITH THE STORMS.  HOWEVER...LESS MOISTURE WILL
BRING ABOUT A SOMEWHAT ENHANCED THREAT OF STRONG OUTFLOW WINDS WITH
THE STRONGER STORMS DUE TO A DRIER BOUNDARY LAYER.  LESS MOISTURE
ALSO MEANS MORE SUNSHINE RESULTING IN HIGHER AFTERNOON
TEMPERATURES.  THE HIGH TEMPERATURES WILL BE A COUPLE OF DEGREES
WARMER EACH DAY THROUGH SUNDAY WITH SUNDAY LIKELY THE WARMEST DAY
BEFORE TEMPS BEGIN TO COOL A BIT AGAIN.

THE AFOREMENTIONED COOL DOWN IS THE RESULT OF AN INTERESTING
SITUATION THAT WILL RESULT IN AN ACTIVE PATTERN NEXT WEEK IF IT
COMES TO PASS AS CURRENTLY MODELED.  AN UPPER LEVEL LOW CURRENTLY
CENTERED OVER OHIO IS PROGGED TO MOVE WSW ACROSS THE COUNTY THIS
WEEKEND EVENTUALLY ENDING UP IN THE VICINITY OF NEW MEXICO TOWARD
THE END OF NEXT WEEK.  WHILE DEFINITELY NOT THE NORM NEARLY ALL
MODEL SOLUTIONS HAVE PICKED UP ON THIS AND THE LAST FEW HOURS OF THE
WATER VAPOR LOOP SHOWS THE LOW BEGINNING TO TURN TOWARD THE
SOUTHWEST AT THIS TIME.  WHAT THIS WOULD RESULT IN IS AN INCREASE IN
DEEP MOISTURE FROM EAST TO WEST BEGINNING MONDAY AND REMAINING OVER
THE AREA THROUGH THE WEEK WITH ENHANCED INSTABILITY JUST FOR ADDED
FUN.  WITH THIS SETUP WE WOULD END UP WITH PLENTY OF CONVECTION EACH
DAY THAT WOULD LIKELY LAST WELL INTO THE NIGHT AND THE STORMS WOULD
BE EFFICIENT RAINFALL PRODUCERS DUE TO THE HIGH LEVEL OF
PRECIPITABLE WATER VALUES FORECAST.  THE INCREASE IN CONVECTIVE
ACTIVITY AND THE ASSOCIATED CLOUD COVER WILL SUPPRESS AFTERNOON
TEMPERATURES TO A FEW DEGREES BELOW NORMAL TUESDAY ONWARD.  WILL BE
INTERESTING TO SEE HOW THIS PLAYS OUT.  CERNIGLIA

&&

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

&&

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

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