Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 210946
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
245 AM MST THU AUG 21 2014

.SYNOPSIS...AN UPPER LOW OVER SOUTHERN CALIFORNIA THIS MORNING WILL
WEAKEN TODAY AS IT MOVES ACROSS ARIZONA THROUGH EARLY FRIDAY. EXPECT
SCATTERED SHOWERS AND THUNDERSTORMS INTO THIS EVENING BEFORE
ACTIVITY ENDS FROM WEST TO EAST OVERNIGHT. DRIER AIR BEHIND THE LOW
WILL LIMIT THUNDERSTORMS TO MAINLY EAST AND SOUTH OF TUCSON FRIDAY
AND THROUGH THE WEEKEND. AFTER A COUPLE OF COOLER THAN NORMAL DAYS
HIGH TEMPERATURES WILL WARM BACK UP TO NORMAL OVER THE WEEKEND.

&&

.DISCUSSION...CLOSED UPPER LOW OFF SRN CALIFORNIA COAST THIS MORNING
HAS TAPPED INTO SOME MID TO HIGH LEVEL MOISTURE FROM THE OUTER EDGES
OF TROPICAL STORM LOWELL AND SPREAD IT NORTH ACROSS WESTERN ARIZONA.
THE YUMA DOPPLER RADAR AT 230 AM SHOWED A FEW LIGHT SHOWERS OVER THE
NORTHERN GULF OF CALIFORNIA...NEAR ROCKY POINT AND SOUTH OF
LUKEVILLE. PRECIPITABLE WATER VALUES THIS MORNING WERE AROUND 1.30"
AREAWIDE WITH MODELS SUGGESTING THAT THESE VALUES WILL RISE INTO
1.50"-1.60" RANGE THIS AFTERNOON. THIS CLOSED UPPER LOW WILL SLOWLY
DIG S THIS MORNING BEFORE MAKING THE TURN EAST INTO NORTHERN BAJA
CALIFORNIA. EXPECT SCATTERED SHOWERS TO DEVELOP WEST OF TUCSON THIS
MORNING AND SLOWLY SPREAD/DEVELOP ACROSS THE REMAINDER OF THE
FORECAST AREA THIS AFTERNOON INTO THIS EVENING. NOT GOING OVERLY
WILD ON QPF VALUES...MOSTLY LESS THAN A QUARTER OF AN INCH...BUT
COULD SEE SOME LOCALIZED 1" RAIN AMOUNTS WHERE STORMS GET SOME MORE
SUN. CAN`T RULE OUT THAT A STORM OR TWO WILL GETTING PRETTY STRONG
EITHER WITH WIND GUSTS UP TO 50 MPH. WITH THE CLOUD COVER AND
SHOWERS...HIGH TODAY WILL REMAIN BELOW NORMAL WITH SOME LOCALS
RUNNING 7-10 DEGREES BELOW NORMAL...ESPECIALLY OUT WEST. OVERALL
THIS IS NOT YOUR TYPICAL AUGUST MONSOON DAY.

THIS CLOSED LOW OPENS UP THIS EVENING AS IT MOVES INTO SW AZ AND
CONTINUES TO LIFT NE ACROSS THE STATE OVERNIGHT INTO FRIDAY MORNING.
SCATTERED STORMS CONTINUING ACROSS MOST OF THE AREA THIS EVENING
BEFORE DRIER AIR PUNCHES INTO WESTERN AREAS AND MOVES ACROSS THE
AREA OVERNIGHT. THUS EXPECT STORMS TO END FROM WEST TO EAST.

UPPER TROF AXIS OVER THE EASTERN AREAS FRIDAY AFTERNOON. ALTHOUGH PW
VALUES WILL BE DOWN VERSUS TODAY...STILL WILL SEE ISOLATED TO
SCATTERED STORMS FRIDAY AFTERNOON. HIGHS WARMER THAN TODAY BUT STILL
BELOW NORMAL.

LOW GRADE MONSOON FORECAST FOR THE WEEKEND AS AN UPPER TROF PASSING
BY TO THE NORTH KEEPS DRIER WESTERLY FLOW OVER THE AREA. HOWEVER
WILL HAVE ENOUGH RESIDUAL MOISTURE FOR SLIGHT CHANCE OF STORMS
MAINLY SOUTH AND EAST OF TUCSON. WARMER WITH HIGHS SLIGHTLY ABOVE
NORMAL BOTH DAYS.

NEXT WEEK...WITH UNCERTAINTY ON AMOUNT OF TROPICAL MOISTURE BEING
SENT OUR WAY FROM THE NEXT PACIFIC TROPICAL STORM...WENT WITH BASIC
CLIMO POPS AREAWIDE. MODELS ARE SUGGESTING THAT WE COULD SEE LIGHT
SOUTHERLY WINDS MOVING UP THE GULF OF CALIFORNIA AS EARLY AS SUNDAY
WITH STRONGER WINDS ON MONDAY WHICH WILL BRING GULF SURGE LIKELY
MONDAY NIGHT INTO TUESDAY. HIGHS WILL REMAIN SLIGHTLY ABOVE NORMAL.

&&

.AVIATION...VALID THRU 22/12Z.
BKN-OVC CLOUDS MAINLY ABOVE 12K FT AGL THRU 21/15Z...THEN SCT-BKN
CLOUDS AT 6-10K FT AGL AND BKN-OVC CLOUDS AOA 12K FT AGL. ISOLD-SCT
SHOWERS AND THUNDERSTORMS DEVELOPING DURING THE MID MORNING HOURS
AND PERSISTING THRU TONIGHT. PRECIPITATION CHANCES WILL BE HIGHEST
WEST OF A KOLS TO KTUS TO KCGZ LINE THIS MORNING THRU THE MID
AFTERNOON HOURS...AND THEN EAST OF THIS LINE LATE THIS AFTERNOON AND
TONIGHT. MVFR VISIBILITIES AND WIND GUSTS TO 45 KTS WILL BE POSSIBLE
WITH THE STRONGER TSRA. OUTSIDE OF THUNDERSTORM OUTFLOWS...SURFACE
WIND WILL GENERALLY BE LESS THAN 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE
EXPECTED THROUGH EARLY NEXT WEEK. THE STRONGER THUNDERSTORMS WILL
PRODUCE STRONG...GUSTY AND ERRATIC WINDS. OUTSIDE OF THUNDERSTORM
OUTFLOWS...20-FOOT WINDS WILL EXHIBIT NORMAL DIURNAL TRENDS AND WILL
BE MOSTLY LESS THAN 15 MPH.

&&

$$

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