Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 280401
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
901 PM MST MON JUL 27 2015

.SYNOPSIS...THE WEATHER PATTERN IS BECOMING MORE FAVORABLE FOR AN
UPSWING IN THUNDERSTORM ACTIVITY THIS WEEK AS DEEPER MOISTURE
RETURNS. OTHERWISE...TEMPERATURES WILL BE AT NEAR NORMAL LEVELS
THROUGH THE UPCOMING WEEKEND.

&&

.DISCUSSION...THE UPPER AIR PATTERN EARLY THIS EVENING IS DEFINED BY
A MEANDERING UPPER LOW OVER THE SOUTHERN BAJA PENINSULA...A MID-
LEVEL RIDGE CENTERED ROUGHLY OVER OKLAHOMA...AND A LARGE TROUGH AXIS
PIVOTING EASTWARD ACROSS THE NORTHERN ROCKIES. IN BETWEEN ALL OF
THESE FEATURES...A DEFORMATION ZONE AND ASSOCIATED COL CAN BE SEEN
SPLITTING THE FLOW ACROSS PARTS OF WESTERN AZ AND ROUGHLY SEPARATING
VERY DRY AIR OVER CA FROM AN INCREASINGLY MOIST AIRMASS TO THE EAST.

WHILE WE PICKED UP SOME DECENT PRECIPITABLE WATER ON THE 12Z
SOUNDING WITH A PWAT VALUE UP TO 1.42 INCHES...WE ALSO MADE QUICK
WORK OF THE SHALLOW LOW-LEVEL MOISTURE THIS AFTERNOON AND MIXED OUT
MOST OF THE INSTABILITY. TO BE FAIR...THE 00Z SOUNDING DID SHOW AN
MLCAPE OF 3 J/KG...UP FROM 0 J/KG THE PAST TWO AFTERNOONS. MOST OF
THE INSTABILITY HOWEVER...HUGGED THE INTERNATIONAL AND AZ/NM
BORDERS TODAY...RIGHT WHERE WE SAW THE BULK OF THE CONVECTIVE
ACTIVITY THIS AFTERNOON AND EVENING. COVERAGE WAS A BABY STEP UP
FROM YESTERDAY BUT CERTAINLY WELL BELOW WHAT WOULD NORMALLY BE
EXPECTED AT THE END OF JULY. PRECIP COVERAGE WILL BE ON THE
DECREASE TONIGHT AS THE ATMOSPHERE NOCTURNALLY STABILIZES AND THE
REMAINING SHOWERS AND STORMS OUTRUN THE LINGERING BUOYANCY. MADE A
FEW EDITS TO THE GOING FORECAST BASED ON CURRENT OBSERVATIONS AND
RADAR/SATELLITE TRENDS.

THE CURRENT THINKING FOR A BIT MORE CONVECTIVE COVERAGE
TOMORROW AND ESPECIALLY WEDNESDAY AND THURSDAY IS EFFECTIVELY
UNCHANGED FROM OUR PREVIOUS FORECASTS. DEEPENING
SOUTHERLY/SOUTHEASTERLY FLOW WILL CONTINUE TO GRADUALLY TRANSPORT A
BETTER MOISTURE PROFILE OUR WAY. AT THIS TIME IT APPEARS THAT
WEDNESDAY MAY BE A PRETTY ACTIVE DAY AS PWAT VALUES FINALLY EXCEED
CLIMATOLOGICAL VALUES...SEVERAL IMPULSES ROUND THE WESTERN PERIPHERY
OF THE SUBTROPICAL HIGH AS HINTED AT BY BOTH THE GFS AND ECMWF...AND
MID-LEVEL FLOW STRENGTHENS INTO THE 20 TO 25 KT RANGE. WE`LL HAVE TO
WAIT AND SEE...

&&

.AVIATION...VALID THRU 29/06Z.
SCT TO BKN CLOUDS 8-12K FT AGL WITH SOME THINNING OF CLOUD LAYERS
OVERNIGHT. ISOLD SHRA/TSRA PRIMARILY SOUTH AND WEST OF KTUS THRU
28/05Z. MORE WIDESPREAD SHRA/TSRA EXPECTED TUESDAY FARTHER NORTH
AND WEST INCLUDING KTUS. BRIEF MVFR CONDITIONS AND VRB WIND GUSTS TO
35 KTS POSSIBLE IN AND AROUND THE STRONGER TSRA. OUTSIDE OF STORM
INFLUENCE...SFC WINDS WILL BE LESS THAN 12 KTS WITH SOME HIGHER
GUSTS FROM FROM THE WEST AND NORTHWEST DURING THE AFTERNOON
ESPECIALLY NEAR KSAD. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...MOISTURE IS ON THE INCREASE UNDER THE INFLUENCE OF
DEEPER SOUTHERLY FLOW. THE RESULT WILL BE AN INCREASE IN SHOWERS AND
THUNDERSTORMS THIS WEEK. TUESDAY THROUGH FRIDAY...MORE WIDESPREAD
CONVECTIVE ACTIVITY WILL OCCUR OVER ALL SOUTHEASTERN ARIZONA ZONES.
STRONG OUTFLOWS NEAR STORMS COULD PRODUCE WIND GUSTS TO 40 MPH.
OTHERWISE...20-FT WINDS WILL GENERALLY BE TERRAIN DRIVEN AND LESS
THAN 15 MPH WITH SOME AFTERNOON GUSTINESS FROM THE WEST OR NORTHWEST
DUE TO DAYTIME HEATING. WINDS WILL DEVELOP MORE OF AN EASTERLY
COMPONENT BEGINNING THURSDAY.

&&

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

&&

$$

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

CARLAW



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