Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 011656
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
955 AM MST SAT AUG 1 2015

.SYNOPSIS...AMPLE MOISTURE WILL BRING SCATTERED SHOWERS AND
THUNDERSTORMS TO MUCH OF THE AREA THIS AFTERNOON AND EVENING. A
DRYING TREND SUNDAY THROUGH TUESDAY WILL CONFINE THUNDERSTORMS
MAINLY TO AREAS SOUTH AND EAST OF TUCSON. INCREASING COVERAGE OF
THUNDERSTORMS WILL THEN OCCUR DURING THE LATTER PART OF THE UPCOMING
WEEK.

&&

.DISCUSSION...UPPER RIDGE AXIS EXTENDED FROM THE GREAT BASIN SEWD
ACROSS THE FOUR CORNERS REGION AND CONTINUED SE INTO WEST TEXAS THIS
MORNING. MEANWHILE...WEAK UPPER LOW WAS CENTERED WELL WEST OF THE
CENTRAL CALIFORNIA COAST NEAR 35N/134W...AND A WEAK UPPER LOW WAS
JUST NORTH OF THE BAJA CALIFORNIA SPUR AS PER WATER VAPOR IMAGERY.
01/12Z KTWC SOUNDING TOTAL PRECIP WATER VALUE WAS 1.50 INCHES...AND
MUCAPE YIELDED 934 J/KG. SOUTHERLY 10-15 KT SPEEDS WERE OBSERVED IN
THE 700-300 MB LAYER.

VARIOUS NWP MESOSCALE MODELS DEPICT THE BEST COVERAGE OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING SHOULD OCCUR ACROSS
GREENLEE/GRAHAM/COCHISE COUNTIES EAST OF TUCSON...WITH GRADUALLY
LESSER COVERAGE OF SHOWERS/THUNDERSTORMS FROM TUCSON WESTWARD INTO
WRN PIMA COUNTY. IN FACT...SEVERAL SOLUTIONS SUGGEST THAT WRN PIMA
COUNTY OR AZZ501 WILL REMAIN PRECIP-FREE THIS AFTERNOON/EVENING.

AT ANY RATE...THE INHERITED OFFICIAL FORECAST GENERAL DEPICTION OF
CHANCE-CATEGORY POPS ACROSS MUCH OF SE ARIZONA APPEARS REASONABLE
BASED ON THESE LATEST SOLUTIONS. STORM MOTIONS SHOULD FAVOR NLY/
NELY MOVEMENTS INTO THIS EVENING. FORECAST CONFIDENCE IS STILL TOO
LOW TO MERIT THE INTRODUCTION OF BLOWING DUST INTO THE GRIDDED DATA
WEATHER FIELDS ESPECIALLY ALONG THE INTERSTATE 10 CORRIDOR NORTHWEST
OF TUCSON INTO SOUTH CENTRAL PINAL COUNTY THIS AFTERNOON. THE BULK
OF THESE SHOWERS/TSTMS SHOULD DECREASE IN COVERAGE AND INTENSITY
LATE THIS EVENING FOLLOWED BY GRADUALLY CLEARING SKIES BY DAYBREAK
SUNDAY. HIGH TEMPS THIS AFTERNOON WILL MOSTLY AVERAGE WITHIN A
DEGREE-OR-TWO OF NORMAL.

&&

.AVIATION...VALID THRU 02/18Z.
EXPECT SCATTERED -TSRA/-SHRA ACROSS MUCH OF SE ARIZONA THIS
AFTERNOON AND EVENING. FORECAST CONFIDENCE IS SUFFICIENT TO DENOTE
VCTS FOR THE KTUS/KOLS/KDUG TERMINALS GENERALLY FROM 20Z-22Z UNTIL
AROUND 02/01Z OR SO. BRIEF MVFR CONDITIONS WITH WIND GUSTS TO AROUND
40 KTS SHOULD OCCUR WITH THE STRONGER TSRA. OTHERWISE...CLOUD DECKS
WILL MAINLY BE ABOVE 10K FT AGL AND SURFACE WIND LESS THAN 10 KTS
INTO SUNDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...EXPECT SCATTERED THUNDERSTORMS ACROSS MUCH OF
SOUTHEAST ARIZONA THIS AFTERNOON AND EVENING. THE LEAST FAVORABLE
AREA FOR RAINFALL WILL BE ACROSS WESTERN PIMA COUNTY. A GRADUAL
REDUCTION IN THUNDERSTORM COVERAGE WILL THEN OCCUR SUNDAY THROUGH
TUESDAY...WITH THUNDERSTORMS TUESDAY AFTERNOON CONFINED MAINLY NEAR
THE MOUNTAINS. THEREAFTER...ISOLATED TO SCATTERED AFTERNOON AND
EVENING THUNDERSTORMS WILL PREVAIL MAINLY FROM TUCSON EAST AND SOUTH
WEDNESDAY THROUGH FRIDAY. OUTSIDE OF THUNDERSTORM ACTIVITY...20-FT
WINDS WILL GENERALLY BE TERRAIN DRIVEN AND LESS THAN 15 MPH.

&&

.PREV DISCUSSION...SOME ISSUES TO CONTEND WITH FOR TODAY`S FORECAST
REVOLVE AROUND SLIGHTLY WARMER MID-LEVEL TEMPERATURES...POSSIBLE
ISSUES WITH ANVIL SHADING OWING TO A SOUTH TO SOUTHEASTERLY STEERING
FLOW...AND THE WIDE VARIETY OF SOLUTIONS OFFERED UP BY VARIOUS
CONVECTIVE ALLOWING MODELS. HOWEVER...BOTH THE 05Z RUN OF THE HRRRX
(EXPERIMENTAL HRRR) AND THE 00Z UNIV. OF AZ WRF-NAM SOLUTIONS PAINT
A FAIRLY SIMILAR PICTURE FOR TODAY...WITH THE MAIN CONVECTIVE FOCUS
ACROSS PARTS OF PINAL...PIMA...AND SANTA CRUZ COUNTIES AND GENERALLY
MORE ISOLATED COVERAGE OUT EAST. THESE SOLUTIONS GENERALLY LINE UP
WITH THE RECENT RUNS OF THE NAM/GFS WHICH SHOW THE BEST INSTABILITY
LINING UP FROM TUCSON AND POINTS WEST...EFFECTIVELY WITHIN THE ZONE
OF HIGHER PW AIR AS MENTIONED EARLIER.

FOR SUNDAY AND BEYOND...THE GENERAL PATTERN IS FORECAST TO BEGIN A
RE-ORGANIZATION PHASE AS THE UPPER-HIGH RECONSOLIDATES...EVENTUALLY
NEAR THE FOUR-CORNERS REGION BY THE MIDDLE TO END OF NEXT WEEK. IN
THE MEAN TIME...SOUTHWESTERLY OR WESTERLY MID-LEVEL FLOW WILL USHER
DRIER AIR INTO THE AREA WHICH WILL RESULT IN MARKEDLY REDUCED
PRECIPITATION CHANCES...PARTICULARLY BY TUESDAY. THEREAFTER...MORE
FAVORABLE SOUTHEASTERLY FLOW SHOULD ONCE AGAIN BEGIN TO PUMP
MOISTURE...AND AS A RESULT SOMEWHAT BETTER SHOWER AND STORM
COVERAGE...BACK INTO THE REGION. THE ROLLER COASTER RIDE THAT IS THE
MONSOON 2015 CONTINUES...

&&

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

&&

$$

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

FRANCIS
PREVIOUS DISCUSSION...CARLAW



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