Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251023
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
300 AM MST SAT JUL 25 2015

.SYNOPSIS...A FEW LIGHT SHOWERS AROUND EARLY THIS MORNING. WE`LL
HOLD ON TO ENOUGH MOISTURE FOR ISOLATED SHOWERS AND THUNDERSTORMS
THIS WEEKEND...MAINLY SOUTH AND EAST OF TUCSON. THE PATTERN WILL
BECOME MORE FAVORABLE NEXT WEEK FOR AN UPSWING IN DAILY THUNDERSTORM
ACTIVITY BY TUESDAY AND WEDNESDAY.

&&

.DISCUSSION...A FEW LIGHT SHOWERS IN THE DEBRIS SPREADING UP FROM
NORTHERN MEXICO THIS MORNING. OTHERWISE...AN INCREASING LOWER LEVEL
WESTERLY COMPONENT TO OUR FLOW WILL START TO ERODE SOME OF OUR
MOISTURE FROM SURFACE TO ABOUT 700MB THROUGH SUNDAY OR MONDAY. MID
LEVEL SOUTHERLY FLOW WILL MAINTAIN MUCH OF OUR MOISTURE ABOVE 600MB
OR SO. THE MID LEVEL RIDGE EAST OF THE AREA IS NOSING INTO SOUTHEAST
ARIZONA OVER NEXT COUPLE OF DAYS...WITH SOME MID LEVEL WARMING ALSO
HELPING TO INCREASE CONVECTIVE INHIBITION. SHOULD BE A RATHER DOWN
WEEKEND FOR THUNDERSTORMS EXCEPT FOR PERHAPS BORDER AREAS.

AS THE TROUGH DEEPENS THROUGH WESTERN STATES WELL NORTH OF OUR
AREA...THE HIGH CENTER RECONSOLIDATES A LITTLE FURTHER EAST ONCE
AGAIN BY MONDAY WHICH WILL STACK AND DEEPEN THE SOUTHERLY TO
SOUTHEASTERLY FLOW ONCE AGAIN. MEDIUM RANGE MODELS RESPOND BY
BRINGING A NICE IMPULSE CURRENTLY EMBEDDED IN THE FLOW SOUTH OF THE
HIGH IN CENTRAL MEXICO NORTHWARD. THIS SHOULD HELP GET THINGS
STARTED AGAIN TUESDAY AS IT ROTATES UP THE WEST FLANK OF THE HIGH.
THE ECMWF ANOTHER WEAKER BUT BETTER PLACED IMPULSE DIRECTLY THROUGH
THE AREA WEDNESDAY AND THURSDAY WHILE THE GFS SIMPLY MAINTAINS AN
ELEVATED FAVORABLE FLOW PATTERN. EITHER WAY WE`LL HIT THE TUESDAY
THROUGH THURSDAY TIME PERIOD WITH ABOVE AVERAGE MONSOON
COVERAGE...EMPHASIZING WEDNESDAY FOR OUR PART OF THE STATE.

AFTER THAT...WE`LL BACK OFF TOWARD CLIMO POP COVERAGE ON THE
FORECAST AS MEDIUM RANGE MODELS ARE SHOWING SUBTLE BUT SIGNIFICANT
DIFFERENCES IN A HIGH CENTER BUILDING BACK WESTWARD AS A TROUGH
INFLUENCES EASTERN STATES. ANYTHING FROM A NICE 4 CORNERS POSITION TO
A LESS FAVORABLE DEEPER BASIN POSITION.

&&

.AVIATION...VALID THRU 26/12Z.
SCT-BKN CLOUDS AT 8-12K FT AGL THIS MORNING ESP NEAR THE
INTERNATIONAL BORDER INCLUDING KOLS/KDUG/KALK.  SOME CLEARING WILL
OCCUR THROUGH THE LATE MORNING ESP ACROSS AREAS WEST OF KTUS. ISO-
SCT SHRA/TSRA ARE EXPECTED TO DEVELOP MAINLY TO THE SOUTH AND EAST
OF KTUS AND IN THE WHITE MOUNTAINS NE OF KSAD THIS AFTERNOON AND
EARLY THIS EVENING. BRIEF MVFR CONDITIONS AND VRB WIND GUSTS TO 30
KTS POSSIBLE IN AND AROUND THE STRONGER TSRA. A FEW
-SHRA MAY LINGER INTO THE LATE EVENING AND OVERNIGHT HOURS NEAR THE
AZ/MEXICO BORDER. OUTSIDE OF STORM INFLUENCE...SFC WINDS WILL FOLLOW
NORMAL DIURNAL TRENDS WITH SPEEDS MAINLY LESS THAN 12 KTS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SOME DRYING THIS WEEKEND WILL LIMIT PRECIPITATION
THROUGH MONDAY...WITH ISOLATED TO SCATTERED ACTIVITY OCCURRING
MAINLY ACROSS SOUTHEASTERN AREAS AND IN THE WHITE MOUNTAINS. HIGH
PRESSURE WILL THEN REPOSITION OVER THE WESTERN STATES WITH MORE
FAVORABLE MONSOONAL FLOW OVER THE SOUTHWEST. THIS WILL RESULT IN
MORE WIDESPREAD SHOWERS AND THUNDERSTORMS TUESDAY THROUGH THURSDAY
AS DEEPER MOISTURE RETURNS TO THE AREA. 20-FT WINDS WILL GENERALLY
BE TERRAIN DRIVEN AND LESS THAN 15 MPH...WITH THE EXCEPTION OF SOME
AFTERNOON GUSTINESS FROM THE WEST DUE TO DAYTIME HEATING. WINDS THEN
DEVELOP AN EASTERLY COMPONENT LATE NEXT WEEK.

&&

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

&&

$$

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

MEYER/FRENCH



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