Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 271721
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
1020 AM MST THU AUG 27 2015

.SYNOPSIS...EXPECT SCATTERED THUNDERSTORMS INTO THIS EVENING.
ISOLATED TO SCATTERED THUNDERSTORMS WILL THEN PREVAIL MAINLY FROM
TUCSON EAST AND SOUTH FRIDAY THROUGH NEXT WEDNESDAY. ABOVE NORMAL
HIGH TEMPERATURES WILL ALSO OCCUR INTO THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...IR/VISIBLE SATELLITE IMAGERY INDICATED PARTLY CLOUDY
TO MOSTLY CLOUDY SKIES EAST AND SOUTH OF TUCSON. MEANWHILE...SUNNY
TO MOSTLY SUNNY SKIES PREVAILED FROM TUCSON WWD/NWWD INTO WRN PIMA/
SOUTH CENTRAL PINAL COUNTIES. DEWPOINTS AT LOWER ELEVATIONS VALID
17Z RANGED FROM THE MID 50S-MID 60S...AND THESE TEMPS WERE GENERALLY
3-7 DEGS F LOWER VERSUS 24 HOURS AGO. SURFACE TEMPS VALID 17Z WERE
NEARLY 2-5 DEGS COOLER VERSUS THIS TIME WED. 27/12Z KTWC SOUNDING
TOTAL PRECIP WATER VALUE OF 1.49 INCHES WAS IDENTICAL TO 24 HOURS
AGO. HOWEVER...THIS SOUNDING DEPICTED A MORE WLY/SWLY MID-LEVEL FLOW
VERSUS THE GENERALLY SLY FLOW REGIME FROM WED MORNING. 27/12Z UPPER
AIR PLOTS DEPICTED AN EXPANSIVE RIDGE OVER THE SWRN CONUS AND SRN
CONUS PLAINS...WITH A 595 DM HIGH CENTERED OVER SE NEW MEXICO.

VARIOUS MESOSCALE MODELS DEPICT THE BEST LIKELIHOOD FOR SHOWERS/
TSTMS TO OCCUR THIS AFTERNOON/EVENING TO BE SOUTH-TO-SOUTHEAST OF
TUCSON. THE FORCING ALOFT APPEARS TO BE ASSOCIATED WITH A SHEAR/
DEFORMATION AXIS MAINLY NEAR THE INTERNATIONAL BORDER. THE INHERITED
OFFICIAL FORECAST WAS UPDATED WITH INCREASED POPS...GENERALLY AROUND
20 PERCENT OR SO...VERSUS THE PREVIOUS FORECAST. HOWEVER...THESE
MODELS ALSO DEPICT SHOWERS/TSTMS TO ALSO DEVELOP MAINLY NORTH-TO
NORTHWEST OF TUCSON THIS AFTERNOON. THIS ACTIVITY IS THEN PROGGED TO
MOVE SEWD AND PERHAPS INTO THE TUCSON METRO AREA LATE THIS AFTERNOON
AND/OR EARLY THIS EVENING.

FORECAST CONFIDENCE IS HIGHER REGARDING THE CONVECTIVE DEVELOPMENT
TO OCCUR SOUTH-TO-SOUTHEAST OF TUCSON VERSUS THE NORTH-TO-NORTHWEST
OF TUCSON SCENARIO. AT ANY RATE... MOISTURE WILL BE ADEQUATE TO
SUPPORT SCATTERED SHOWERS/TSTMS ACROSS MUCH OF THE AREA INTO THIS
EVENING. AS WAS THE CASE WED...A FEW THUNDERSTORMS WILL HAVE THE
POTENTIAL TO PRODUCE BRIEF STRONG AND GUSTY WINDS AS WELL AS LOCALLY
HEAVY RAINFALL SUFFICIENT FOR MINOR FLOODING. A SLIGHT CHANCE OF
SHOWERS/TSTMS WILL CONTINUE MAINLY EAST OF TUCSON LATE TONIGHT.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.AVIATION...VALID THRU 28/18Z.
SCT-BKN LAYERED CLOUDS WITH BASES GENERALLY 8 TO 13 KFT. SCATTERED
-TSRA/-SHRA WILL OCCUR THIS AFTERNOON AND EVENING...WITH A FOCUS
FROM KTUS SOUTH AND EAST. TSRA ACTIVITY WILL DECREASE AFTER 28/04Z.
BRIEF MVFR CONDITIONS AND GUSTS TO 40 KTS WILL BE POSSIBLE IN AND
AROUND STRONGER STORMS. OUTSIDE OF TSRA INFLUENCE...SURFACE WINDS
WILL GENERALLY BE UNDER 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...THERE IS ADEQUATE MOISTURE FOR SCATTERED
THUNDERSTORMS INTO THIS EVENING. EXPECT ISOLATED TO SCATTERED
THUNDERSTORMS MAINLY FROM TUCSON EAST AND SOUTH FRIDAY THROUGH NEXT
WEDNESDAY. HOWEVER...MOSTLY DRY CONDITIONS ARE FORECAST TO OCCUR
ACROSS FIRE ZONE 150 FRIDAY THROUGH WEDNESDAY. ABOVE NORMAL DAYTIME
TEMPERATURES WILL PREVAIL ACROSS MUCH OF SOUTHEAST ARIZONA INTO THE
MIDDLE OF NEXT WEEK.

&&

.PREV DISCUSSION /258 AM MST/...MODELS SHOW A WEAK SHORTWAVE TROUGH
MOVING INTO THE NORTHERN PLAINS AND UPPER MIDWEST ON FRIDAY AND THE
HIGH IN RESPONSE SHIFTS TO A POSITION OVER ARIZONA AND NORTHERN
SONORA WITH AN AMPLIFIED RIDGE AXIS EXTENDING NORTH INTO THE
NORTHERN ROCKIES/PLAINS. THIS WILL RESULT IN A DECREASE IN MOISTURE
FOR A LESSENING OF RAIN CHANCES...WITH ACTIVITY REMAINING AGAIN
GENERALLY EAST OF TUCSON TO NEW MEXICO. A SIMILAR FORECAST FOR
SATURDAY AS THE HIGH WILL REMAIN QUASI-STATIONARY.

BY SUNDAY THE HIGH WILL SHIFT TO OUR SOUTH AND EAST AS A PACIFIC
TROUGH MAKES ITS WAY TOWARD THE WEST COAST. AS THIS OCCURS...
ARIZONA WILL BE IN A SQUEEZE PLAY BETWEEN THESE TWO SYSTEMS WITH
MODELS SHOWING A PLUME OF MOISTURE PULLING UP FROM THE SOUTH ACROSS
PARTS OF ARIZONA AND NEW MEXICO. THIS SETUP WILL CONTINUE EACH DAY
THROUGH WEDNESDAY...WITH AN INCREASE IN ACTIVITY SUNDAY AND MONDAY
AND THEN TAPERING OFF TUESDAY AND WEDNESDAY...BUT STILL ISOLATED TO
SCATTERED IN NATURE AND MAINLY FROM TUCSON EASTWARD.

FOR TUCSON...HIGH TEMPS WILL GENERALLY BE A FEW TO SEVERAL DEGREES
ABOVE NORMAL EACH DAY...ALTHOUGH THE WARMEST DAYS WILL OCCUR ON
FRIDAY AND SATURDAY...WHEN HIGHS WILL RANGE FROM 4 TO 6 DEGS ABOVE
NORMAL. LOW TEMPS WILL RANGE FROM 3 TO 5 DEGS ABOVE NORMAL EACH DAY.

&&

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

&&

$$

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

FRANCIS
PREVIOUS DISCUSSION...MOLLERE
AVIATION/FIRE WEATHER...HUMPHREYS


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