Area Forecast Discussion
Issued by NWS Tucson, AZ

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KTWC 251605
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
904 AM MST MON AUG 25 2014

.SYNOPSIS...A SIGNIFICANT CHANGE IN THE WEATHER PATTERN WILL TAKE
PLACE TODAY AND TUESDAY AS DEEPER MOISTURE MOVES BACK INTO ARIZONA.
THIS WILL RESULT IN SHOWERS AND THUNDERSTORMS...SOME WITH VERY HEAVY
RAINFALL...LATER TODAY AND TUESDAY. IMPROVING WEATHER CAN BE
ANTICIPATED WEDNESDAY...WITH DAYTIME TEMPERATURES REBOUNDING TO
SLIGHTLY ABOVE NORMAL READINGS BY THE WEEKEND.

&&

.DISCUSSION...ALTO CUMULUS FIELD OVER THE CATALINA MOUNTAINS THIS
MORNING IS A SIGN OF THINGS TO COME LATER TODAY. AS ADVERTISED...THE
MOIST AIR STREAMING UP FROM THE SOUTH IS NOW INVADING SE ARIZONA.
DEW POINTS IN YUMA ARE IN THE MID 70S...WITH MID 60S IN TUCSON. 12Z
MORNING SOUNDING IN TUCSON AND YUMA SHOWED PRECIP WATER VALUES OVER
1.5 INCHES...BUT RECENT SOUNDER SATELLITE IMAGERY SUGGESTS THE 1.8
INCH AND ABOVE AIR IS NOW IN THE NORTHERN EDGE OF THE GULF OF
CALIFORNIA. LOCAL HI RES WRF MODEL RUNS...ALONG WITH THE U OF A WRF
RUNS SHOWS THE ELEVATED PRECIP WATER VALUES SPREADING ACROSS SANTA
CRUZ...PIMA AND PINAL COUNTIES STARTING AROUND 20Z...CONTINUING
THROUGH TUESDAY. SO...JUST LIKE THE MIDNIGHT SHIFT...I AM STILL
CONFIDENT IN A HEAVY RAIN EVENT IMPACTING SE ARIZONA...AND FURTHER
NORTH FOR THAT MATTER. HOWEVER...TIMING IS STILL THE KEY AND WHERE
THE GREATEST UNCERTAINTY LIES. CURRENTLY THINKING TODAY AND TONIGHT
WILL PROVIDE THE BEST SHOT FOR HEAVY RAIN FROM SAY TUCSON
SOUTH...BUT WE SHOULD SEE THAT HEAVIER PRECIP SHIELD SHIFT NORTH
TOWARD GRAHAM AND GREENLEE COUNTIES ON TUESDAY. WE ARE CONSIDERING A
FLASH FLOOD WATCH FOR TODAY AND WILL FURTHER CONSULT THE HIGHER
RESOLUTION DATA TO DETERMINE IF WE CAN FINE TUNE THE BEST TIME AND
LOCATION FOR THE WATCH.

EITHER WAY...BE AWARE THAT HEAVY RAIN AND FLASH FLOODING ARE A
CONCERN FOR THE NEXT 24 TO 48 HOURS.

JJB

&&

.AVIATION...VALID THRU 26/12Z.
FEW-SCT CLOUDS AT 10-14K FT AGL AND SCT CLOUDS AOA 20K AGL THRU
25/17Z. BETWEEN 25/17Z AND 25/22Z...SCT CLOUDS AT 7-11K FT AGL AND
SCT-BKN CLOUDS AT 10-14K FT AGL. AFT 25/22Z...SCT-BKN CLOUDS AT
6-10K FT AGL AND BKN-OVC CLOUDS AT 10-14K FT AGL. INCREASING CHANCES
OF PRECIPITATION THROUGH THE FORECAST CYCLE...WITH A SLIGHT CHANCE
OF -SHRA/-TSRA THRU 25/19Z...THEN ISOLD-SCT SHRA/TSRA TIL 26/01Z.
AFT 26/01Z...SCT-NUMEROUS SHRA/TSRA. EXPECT MVFR VISIBILITIES AND
WIND GUSTS TO NEAR 45 KTS WITH THE STRONGER TSRA...ESPECIALLY THIS
AFTERNOON AND TONIGHT. OUTSIDE OF THUNDERSTORM OUTFLOWS...SURFACE
WIND WILL GENERALLY BE LESS THAN 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A NOTICEABLE INCREASE IN SHOWER AND THUNDERSTORM
ACTIVITY WILL OCCUR TODAY THROUGH WEDNESDAY AS DEEPER MOISTURE
PUSHES BACK INTO SOUTHERN ARIZONA. EXPECT ISOLATED TO SCATTERED
AFTERNOON SHOWERS AND THUNDERSTORMS TODAY...WITH SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS TONIGHT...TUESDAY...AND TUESDAY
NIGHT. A LITTLE LESS ACTIVITY IS THEN EXPECTED ON WEDNESDAY...WITH
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS. THE STRONGER
THUNDERSTORMS WILL PRODUCE STRONG...GUSTY AND ERRATIC WINDS. A
DRYING TREND WILL TAKE PLACE BY WEEKS END AND OVER THE UPCOMING
WEEKEND...WITH ONLY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
MAINLY OVER THE EASTERN MOUNTAINS.

&&

.PREV DISCUSSION...A BIG CHANGE IN THE WEATHER PATTERN WAS SHAPING
UP FOR THE NEXT COUPLE OF DAYS AS DEEPER MOISTURE RETURNS TO THE
REGION. LATEST MODELS CONTINUED TO SHOW 2 LARGE SCALE WEATHER
FEATURES THAT WILL BECOME A FACTOR IN BRINGING WIDESPREAD RAIN TO
SOUTHEAST ARIZONA LATER TODAY AND TUESDAY. HURRICANE MARIE
POSITIONED WELL OFF THE SOUTHERN TIP OF BAJA THIS MORNING WILL
CONTRIBUTE TO THE NORTHWARD PUSH OF MOISTURE POOLED SOUTH OF THE
INTERNATIONAL BORDER TODAY AND TUESDAY. RECENT SURFACE OBSERVATIONS
SUGGESTED THAT THIS MOISTURE INCREASE WAS ALREADY MATERIALIZING AS
DEWPOINTS HAVE CLIMBED INTO THE LOW TO MID 70S IN YUMA ALONG WITH
READINGS IN THE MID 60S BEING REPORTED IN TUCSON EARLY THIS MORNING.
THIS DEEPER MOISTURE WILL INTERACT WITH THE TAIL END OF A LOW
PRESSURE SYSTEM MOVING THROUGH NEVADA AND UTAH TONIGHT INTO EARLY
WEDNESDAY. THERE WAS A HIGH DEGREE OF CONFIDENCE THAT THE
INGREDIENTS FOR HEAVY RAINFALL AND SUBSEQUENT FLASH FLOODING WILL
COME TOGETHER DURING THE NEXT 12 TO 36 HOURS ACROSS SOUTHEAST
ARIZONA. CONFIDENCE REMAINED RATHER LOW...HOWEVER...ON THE TIMING OF
THE HEAVIEST RAINFALL AS MODEL SOLUTIONS DIFFER. SOME POINT TO
TONIGHT AND OTHERS SUGGEST TUESDAY AFTERNOON AND EVENING WILL BE THE
HEAVIEST. THAT SAID...NOT CONFIDENT ENOUGH ON THE TIMING TO JUSTIFY
POSTING A FLASH FLOOD WATCH ON THE MORNING FORECAST PACKAGE. FOR
NOW...WILL BANK ON TUESDAY AFTERNOON AND EARLY EVENING FOR BEING THE
BEST TIME FRAME FOR THE BULK OF THE HEAVY RAINFALL AREAWIDE. ALONG
WITH THE CLOUDINESS AND RAIN...COOLER DAYTIME TEMPERATURES CAN BE
ANTICIPATED. BY WEDNESDAY...THE RAPID DECREASE IN MOISTURE SHOULD
START THE DRYING TREND THROUGH THE WEEKEND. THIS DRYING TREND WILL
TRANSLATE TO A WARMING TREND AS WELL...WITH PROJECTED HIGH
TEMPERATURES REBOUNDING TO SLIGHTLY ABOVE NORMAL READINGS THIS
WEEKEND.

&&

$$

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









USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.