Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 260457
AFDTWC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TUCSON AZ
957 PM MST MON AUG 25 2014

.SYNOPSIS...DEEPER MOISTURE IN PLACE ACROSS SOUTHEAST ARIZONA WILL
RESULT IN SHOWERS AND THUNDERSTORMS...SOME WITH VERY HEAVY
RAINFALL...THROUGH TUESDAY. IMPROVING WEATHER CAN THEN BE EXPECTED
WEDNESDAY...WITH DAYTIME TEMPERATURES REBOUNDING TO SLIGHTLY ABOVE
NORMAL READINGS BY THE WEEKEND.

&&

.DISCUSSION...THE UPPER PATTERN IS DEFINED BY A TROUGH OF LOW
PRESSURE OVER THE GREAT BASIN...A CATEGORY 3 HURRICANE /MARIE/
LOCATED AT 19.2N/116.7W MOVING NW@13MPH...AND A WEAK MID-LEVEL
FEATURE POSITIONED NE OF THE BAJA SPUR IN THE SOUTHWEST FLOW ALOFT.

IT HAS BEEN AN ACTIVE AND WET NIGHT ACROSS THE WESTERN HALF OF
FORECAST AREA THIS EVENING. THE MAJORITY OF THE STORMS DEVELOPED
ALONG A MID-LEVEL BOUNDARY THAT TRACKED SLOWLY WEST. ALTHOUGH
INDIVIDUAL STORMS WERE MOVING NORTHEAST...STORMS PROPAGATED WEST ALL
EVENING...WITH STORMS DOWNSTREAM OF THE CIRRUS BLOWOFF STRUGGLING TO
SUSTAIN THEMSELVES. STORMS HAVE BEGUN TO QUIET DOWN LATE THIS
EVENING. HOWEVER...KEMX RADAR IMAGERY INDICATED AN MCV POSITIONED
ACROSS WESTERN PIMA AND SOUTHERN MARICOPA COUNTIES. LOOK FOR THIS
FEATURE TO MOVE NE IN THE UPPER FLOW...INITIATING CONVECTION ACROSS
THE NORTHERN CWA OVERNIGHT. IN ADDITION...A WEAK MID-LEVEL FEATURE
NE OF THE BAJA SPUR WILL MOVE TOWARD NE TONIGHT...HELPING TO TRIGGER
OFF SOME STORMS OVERNIGHT ACROSS THOSE AREAS THAT DIDNT SEE MUCH
RAINFALL TONIGHT...TUCSON EAST. ANOTHER FEATURE IS EXPECTED TO MOVE
NORTH AND INTERACT WITH THE UPPER TROUGH TRACKING THRU TO THE NORTH.
THIS WILL HELP ENHANCE THUNDERSTORM COVERAGE TOMORROW. THERE ARE
STILL SOME DIFFERENCES IN THE 00Z MODELS. THE NAM WANTS TO FINISH
THINGS UP BY LATE TUESDAY EVENING...WITH THE GFS HAVING A MUCH MORE
PRONOUNCED EFFECT FROM THE UPPER TROUGH TRACKING THRU...KEEPING POPS
UP WELL INTO WEDNESDAY MORNING. GIVEN THE MOIST AIRMASS IN PLACE
ACROSS THE REGION...WILL LEAVE FLASH FLOOD WATCH ALONE AS ADDITIONAL
MODERATE TO HEAVY RAINFALL IS POSSIBLE.

&&

.PREV DISCUSSION...CONVECTION...HEAVY RAIN AND SOME FLASH FLOODING
ONGOING ACROSS SOUTHEAST ARIZONA. THE PRIMARY THREAT FOR THE NEXT 24
TO 48 HOURS IS HEAVY RAIN BUT A STRONGER STORM MAY KICK OUT SOME
INTENSE WINDS.

THE GOOD FOLKS AT NESDIS POINTED OUT TODAY THAT THE MOIST AIR IN
PLACE CURRENTLY OVER SE ARIZONA IS LIKELY FROM THE REMNANTS OF
HURRICANE LOWELL AND NOT HURRICANE MARIE WHO IS SITTING OFF THE BAJA
PENINSULA SEVERAL HUNDRED MILES TO THE SOUTH OF AZ. REGARDLESS OF
THE SOURCE...THE AIR IN PLACE RIGHT NOW WILL ONLY BECOME MORE
SATURATED WHEN THE DEEPER MOISTURE FROM MARIE FINALLY WORKS INTO SE
ARIZONA TONIGHT AND TUESDAY. THE BOTTOM LINE...THE FLASH FLOOD
THREAT IS LIKELY TO EXTEND WELL INTO TUESDAY...BUT WE DECIDED TO SET
AN END TIME ON THE FLASH FLOOD WATCH TO 18Z TO AVOID ISSUING A TWO
DAY WATCH.

THINKING THE MAIN THREAT AREA TUESDAY WILL SHIFT TOWARD THE NORTHERN
ZONES...GRAHAM AND GREENLEE COUNTIES...WHERE THEIR WILL BE BETTER
UPPER SUPPORT FROM THE TAIL END OF AN UPPER TROUGH. I AM ALSO
CONCERNED THAT THE SEVERE THREAT MAY INCREASE TOMORROW DUE TO THE
COOLER AIR ALOFT AND STRONGER UPPER JET PUSHING ACROSS THE NORTHERN
ZONES. THE LIMITING FACTOR WILL BE THE ABUNDANT CLOUD COVER AND
LIMITED HEATING.

MODELS THEN SHOW RAPID DRYING STARTING WEDNESDAY WITH CONTINUED
DRYING THURSDAY. POP TRENDS ADEQUATELY SHOW THIS DOWNTURN IN PRECIP
CHANCES. IN ADDITION...THE WARM AIR WILL RETURN WITH THE DRYING SO
TEMPS WILL RISE BACK TO NORMAL OR EVEN SLIGHTLY WARMER THAN NORMAL
BY LATE IN THE WEEK.

&&

.AVIATION...VALID THRU 27/06Z.
VERY MOIST AIRMASS IN PLACE ACROSS SOUTHEAST ARIZONA WILL RESULT IN
WIDESPREAD SHRA/ISOLATED -TSRA ACROSS THE MAJORITY OF THE AREA THRU
TUESDAY EARLY AFTERNOON. CONDITIONS WILL IMPROVE THRU THE DAY
TOMORROW FROM WEST TO EAST...WITH SHOWERS TRACKING OUT OF THE AREA
TUESDAY NIGHT. EXPECT P6SM VCSH SCT8-10KFT BKN12-14KFT MSL THRU THE
MAJORITY OF THE PERIOD...WITH 5SM -SHRA BKN6KFT MSL WITH THE
STRONGER STORMS. ISOLATED TS DEVELOPMENT WILL BE POSSIBLE ACROSS THE
AREA BUT STILL CAN`T PIN POINT DEVELOPMENT NEAR THE TERMINALS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DEEPER MOISTURE IN PLACE ACROSS SOUTHEAST ARIZONA
WILL RESULT IN WIDESPREAD SHOWERS AND THUNDERSTORMS...SOME WITH VERY
HEAVY RAINFALL...THROUGH TUESDAY. IMPROVING WEATHER CAN THEN BE
EXPECTED WEDNESDAY...WITH DAYTIME TEMPERATURES REBOUNDING TO
SLIGHTLY ABOVE NORMAL READINGS BY THE WEEKEND.

&&

$$

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