Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 020403
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
901 PM MST SAT AUG 1 2015

.SYNOPSIS...A GRADUAL DAILY REDUCTION IN THUNDERSTORM COVERAGE WILL
THEN OCCUR SUNDAY THROUGH TUESDAY. SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS MAINLY FROM TUCSON EAST AND SOUTH WILL RETURN DURING
THE LATTER PART OF THE UPCOMING WEEK.

&&

.DISCUSSION...SHOWERS AND THUNDERSTORMS CONTINUED TO DIMINISH LATE
THIS EVENING AFTER A RATHER ACTIVE AFTERNOON. LATEST HRRR SOLUTION
SUGGESTED THAT THE REMAINING SHOWERS WILL DISSIPATE BY MIDNIGHT WITH
SKIES CLEARING OVERNIGHT. CURRENT FORECAST LOOKED ON TRACK...SO JUST
SOME MINOR ADJUSTMENTS TO THE GRIDDED POP FIELD THIS EVENING. PLEASE
REFER TO THE ADDITIONAL SECTIONS FOR MORE DETAILS.

&&

.AVIATION...VALID THRU 03/06Z.
EXPECT CLEARING SKIES LATE TONIGHT INTO SUNDAY MORNING BEFORE
REDEVELOPMENT OF ISO-SCT SHRA/TSRA DURING THE EARLY
AFTERNOON...MAINLY E OF KTUS/KOLS AND ESP NEAR TERRAIN. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SOUTHWEST WINDS ALOFT ON SUNDAY WILL USHER DRIER AIR
INTO THE REGION...WHICH WILL LIMIT PRECIPITATION CHANCES ON MONDAY
AND ESPECIALLY ON TUESDAY. HIGH PRESSURE RETURNS TO A MORE FAVORABLE
LOCATION FOR DAILY CHANCES OF MONSOON SHOWERS AND THUNDERSTORMS FROM
WEDNESDAY ONWARD. OUTSIDE OF THUNDERSTORM WIND GUSTS...20-FT WINDS
WILL GENERALLY BE TERRAIN DRIVEN AND LESS THAN 15 MPH. HOWEVER SOME
AFTERNOON AND EARLY EVENING BREEZINESS IS LIKELY DUE TO DAYTIME
HEATING... ESPECIALLY THROUGH THE GILA VALLEY NEAR SAFFORD.

&&

.PREV DISCUSSION...01/12Z NAM/GFS/ECMWF/CMC WERE IN GOOD AGREEMENT
WITH DEPICTING A DRYING TREND TO COMMENCE SUNDAY AND CONTINUE INTO
TUE...AT LEAST. HIGH PRESSURE ALOFT IS PROGGED TO BE CENTERED OVER
FAR WEST TEXAS SUN MORNING...WITH A SHORTWAVE TROUGH OVER THE GREAT
BASIN AND NWRN ARIZONA. 700-300 MB SWLY FLOW SUN WILL BECOME
INCREASINGLY WLY MON AND CONTINUE WITH GENERALLY LIGHT WLY FLOW TUE
AS THE UPPER HIGH BECOMES POSITIONED JUST SOUTH OF THIS FORECAST
AREA OVER NRN SONORA.

THIS WIND REGIME WILL TRANSLATE INTO ISOLATED TO SCATTERED SHOWERS/
TSTMS FROM TUCSON EWD/SWD SUN AND MON. BY TUE...THERE IS ONLY A
SLIGHT CHANCE OF SHOWERS/TSTMS MAINLY NEAR THE MOUNTAINS WITH DRY
CONDITIONS ELSEWHERE. A SIMILAR PRECIP REGIME MAY ACTUALLY OCCUR
WED...AT LEAST BASED ON THE GFS/ECMWF/CMC SOLUTIONS. FOR NOW...
OPTED TO CONTINUE WITH A SLIGHT CHANCE OF SHOWERS/TSTMS ACROSS MUCH
OF SE ARIZONA WED.

THEREAFTER...THE GFS/ECMWF WERE FAIRLY SIMILAR WITH DEPICTING DEEPER
MOISTURE TO RETURN TO THIS FORECAST AREA STARTING THUR AND
CONTINUING INTO NEXT SAT. THESE SOLUTIONS SEEM PLAUSIBLE AS THE MID-
LEVEL STEERING FLOW BECOMES INCREASINGLY SLY IN RESPONSE TO THE
UPPER HIGH BECOMING POSITIONED AGAIN OVER WEST TEXAS...AND AN UPPER
TROUGH ADJACENT THE CALIFORNIA COAST. THUS...SCATTERED SHOWERS/TSTMS
WILL RETURN THUR-SAT MAINLY FROM TUCSON EWD/SWD TO THE NEW MEXICO/
INTERNATIONAL BORDERS.

EXPECT ABOUT A DEGREE-OR-TWO OF DAILY WARMING SUN-TUE FOLLOWED BY A
VERY GRADUAL REDUCTION IN DAYTIME TEMPS DURING THE LATTER PART OF
THE UPCOMING WEEK.

&&

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

&&

$$

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