Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 281022
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 AM MST TUE JUL 28 2015

.SYNOPSIS...EXPECT AN INCREASE IN THUNDERSTORMS TODAY AND ESPECIALLY
WEDNESDAY AS DEEPER MOISTURE RETURNS. WE WILL THEN CONTINUE TO HAVE
A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
INTO THE COMING WEEKEND.

&&

.DISCUSSION...MOISTURE CONTINUES TO INCREASE AND DEEPEN IN THE
INCREASING SOUTHERLY FLOW BETWEEN THE LOW NEAR SOUTHERN BAJA AND
HIGH PRESSURE TO OUR EAST. PRECIPITABLE WATER VALUES UP TO AROUND
1.25 TO 1.4 ON CIRA LPW TOTAL SATELLITE IMAGERY WITH DEEPER VALUES
WEST THROUGH SOUTH.

FOR TODAY A NICE UPPER LEVEL DIFFLUENT FIELD IS SETTING UP ACROSS
SANTA CRUZ COUNTY NORTHWESTWARD THROUGH THE TOHONO O`ODHAM NATION
WEST OF TUCSON. THIS WILL BE OUR FORECAST FOCUS FOR BEST
THUNDERSTORM COVERAGE THIS AFTERNOON...ALTHOUGH MOST LOCATIONS WILL
SEE INCREASING CHANCES TODAY. DECENT CHANCE OF ISOLATED EMBEDDED
CONVECTION LINGERING INTO THE LATE NIGHT PERIOD AS WELL.

WEDNESDAY IS COMING TOGETHER WITH THE BEST MOISTURE AND DYNAMICS FOR
SOUTHEAST ARIZONA. AN IMPULSE IN THE DEEPENING SOUTHERLY FLOW SHOULD
HELP FOCUS STORM COVERAGE...AND AS THE LOW NEAR CENTRAL BAJA LIFTS
NORTHWARD...WE SHOULD SEE STRONGER FLOW AND DECENT SHEAR FOR MUCH OF
SOUTHEAST ARIZONA WEDNESDAY AFTERNOON. ISOLATED SEVERE AND FLASH
FLOOD POTENTIAL. ORGANIZED CONVECTIVE OUTFLOWS POSSIBLE WITH GOOD
SOUTHERLY OR SOUTHEASTERLY ORIENTATION TO PUSH A LOT OF DUST AHEAD
OF STORMS INTO FAVORED LOCATIONS IN PINAL AND NORTHERN PIMA COUNTIES.

THURSDAY WILL STILL HAVE PLENTY OF MOISTURE WITH SOLID THUNDERSTORM
POTENTIAL ON PAPER...BUT WE`LL HAVE TO SEE HOW THE ATMOSPHERE IS
LOOKING IF WEDNESDAY AND WEDNESDAY EVENING GO OFF BIG. BY FRIDAY WE
MAY STRUGGLE A BIT BEHIND THE MID LEVEL IMPULSE LIFTING
NORTHEASTWARD AND SOME SLIGHT MID LEVEL WARMING AS THE HIGH DECIDES
TO SPREAD IN FROM THE EAST.

FOR THE WEEKEND WE SHOULD STILL HAVE SOLID MOISTURE IN THE SOUTHEAST
PART OF THE STATE...BUT WE COULD SEE DIMINISHING THUNDERSTORM
COVERAGE IN WESTERN AREAS DEPENDING ON THE PLACEMENT OF THE HIGH
CENTER. IT SHOULD STILL BE AT LEAST IN A POSITION FOR THUNDERSTORM
COVERAGE NEAR TO JUST UNDER CLIMO FOR EARLY AUGUST WITH THE HIGH A
LITTLE WEAKER THAN WHAT WE WOULD LIKE TO SEE.

&&

.AVIATION...VALID THRU 29/12Z.
SCT TO BKN CLOUDS 8-12K FT AGL WITH SOME THINNING OF CLOUD LAYERS
OVERNIGHT. MORE WIDESPREAD SHRA/TSRA EXPECTED TODAY FARTHER NORTH
AND WEST INCLUDING KTUS. BRIEF MVFR CONDITIONS AND VRB WIND GUSTS TO
40 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 45 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

MEYER/RASMUSSEN



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