Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 021541
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
841 AM MST TUE SEP 2 2014

.SYNOPSIS...DRY CONDITIONS WILL OCCUR THROUGH TONIGHT. THE CHANCE OF
THUNDERSTORMS WILL THEN INCREASE STARTING WEDNESDAY AND ESPECIALLY
BY THIS WEEKEND AS DEEPER MOISTURE MOVES INTO SOUTHEAST ARIZONA.
EXPECT ABOVE NORMAL DAYTIME TEMPERATURES THROUGH THURSDAY FOLLOWED
BY MARKEDLY COOLER TEMPERATURES THIS WEEKEND AND EARLY NEXT WEEK.

&&

.DISCUSSION...SHORT TERM FORECAST LOOKED ON TRACK AS DRY CONDITIONS
AND ABOVE NORMAL DAYTIME TEMPERATURES PREVAIL AGAIN TODAY. THESE
CONDITIONS WILL UNDERGO SOME CHANGES THIS WEEK THOUGH. PLEASE REFER
TO THE PREVIOUS DISCUSSION SECTION IN THIS PRODUCT FOR MORE DETAILS
ON THE UPCOMING CHANGES IN THE WEATHER FOR SOUTHEAST ARIZONA.

&&

.AVIATION...VALID THRU 03/18Z.
A FEW TO SCATTERED CLOUDS AT 8-12K FT AGL THIS AFTERNOON AND THIS
EVENING. THE BULK OF THESE CLOUDS WILL BE SOUTHEAST OF KTUS AND
ESPECIALLY IN THE VICINITY OF THE KDUG TERMINAL. MOSTLY CLEAR SKIES
TO PARTLY CLOUDY SKIES WILL THEN PREVAIL LATE TONIGHT AND WEDNESDAY
MORNING. SURFACE WIND WILL BE MAINLY LESS THAN 10 KTS INTO WEDNESDAY
MORNING. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WITH ABOVE NORMAL TEMPERATURES WILL
OCCUR THROUGH TONIGHT. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS
FROM TUCSON SOUTH TO SOUTHEAST TO THE INTERNATIONAL BORDER WEDNESDAY
AFTERNOON. THEREAFTER...ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS THURSDAY AND FRIDAY WILL BECOME MORE WIDESPREAD THIS
WEEKEND AS DEEPER TROPICAL MOISTURE MOVES INTO THE AREA. THE
POTENTIAL FOR AT LEAST LOCALLY HEAVY RAINFALL EXISTS THIS WEEKEND
AND EARLY NEXT WEEK. 20-FOOT WINDS WILL BE GENERALLY BE LIGHT AND
TERRAIN DRIVEN TODAY. THEREAFTER...GUSTY OUTFLOWS ASSOCIATED WITH
THUNDERSTORMS WILL OCCUR STARTING WEDNESDAY AND CONTINUE INTO THIS
WEEKEND.

&&

.PREV DISCUSSION...UPPER LEVEL RIDGE AXIS EXTENDED FROM WEST OF THE
SRN CALIFORNIA COAST EWD INTO THE SERN CONUS EARLY THIS
MORNING...WITH HIGH PRESSURE CENTERS OVER WEST TEXAS AND THE FLORIDA
PANHANDLE. MEANWHILE...AN AREA OF LOW PRESSURE WAS CENTERED ABOUT
300 MILES SOUTHWEST OF MANZANILLO MEXICO. ABUNDANT SUNSHINE WILL
OCCUR AGAIN TODAY...WITH A FEW TO SCATTERED CUMULOFORM CLOUDS THIS
AFTERNOON MAINLY SE OF TUCSON TO THE INTERNATIONAL BORDER.

STILL APPEARS THAT ANY MOISTURE INCREASE TO OCCUR INTO TONIGHT
ACROSS NERN SONORA AND ENCROACH UPON SERN SECTIONS WILL BE TOO
SHALLOW TO GENERATE SHOWERS/TSTMS. THUS...DRY CONDITIONS WILL
PREVAIL THRU WED MORNING. THERE IS ALSO A CHANCE THAT THE
AFOREMENTIONED LOW PRESSURE SYSTEM SW OF MANZANILLO MAY BECOME
TROPICAL SYSTEM NORBERT LATER TODAY OR TONIGHT.

02/00Z NAM/GFS/ECMWF/CANADIAN WERE SIMILAR WITH DEPICTING HIGH
PRESSURE ALOFT TO BE CENTERED OVER THE LOWER MISSISSIPPI RIVER
VALLEY WED AFTERNOON WITH A WEAK UPPER TROUGH OFF OF THE CALIFORNIA
COAST. WEAK ELY/SELY MID-LEVEL FLOW WILL ADVECT MOISTURE SUFFICIENT
TO JUSTIFY ISOLATED SHOWERS/TSTMS FROM TUCSON SWD/SEWD WED AFTERNOON
AND WED EVENING. DRY CONDITIONS SHOULD PREVAIL AREA-WIDE WED NIGHT.

THUR-FRI...
PERSISTENT SELY/SLY MID-LEVEL FLOW WILL PRODUCE INCREASING MOISTURE
ACROSS SE AZ. THUS...EXPECT ISOLATED TO SCATTERED SHOWERS/TSTMS
DURING THE AFTERNOON/EVENING HOURS...AND A SLIGHT CHANCE OF SHOWERS/
TSTMS LATE THUR NIGHT/EARLY FRI MORNING.

SAT-MON...
GFS/ECMWF WERE SIMILAR WITH DEPICTING TROPICAL SYSTEM NORBERT TO BE
CENTERED MIDDAY SAT WEST OF THE SRN BAJA CALIFORNIA COAST NEAR
25N/115W OR SO. THE TROPICAL SYSTEM IS PROGGED VIA THESE TWO
SOLUTIONS TO REMAIN QUASI-STATIONARY SUN...THEN MOVE SLOWLY WWD
TO NEAR 24N-26N/120W MON AFTERNOON. MEANWHILE...MARKEDLY DEEPER
MOISTURE IS PROGGED TO MOVE NWD INTO SE AZ...ESPECIALLY SUN-MON.

THE OFFICIAL FORECAST DEPICTS SCATTERED SHOWERS/TSTMS SAT AFTERNOON/
EVENING...THEN SCATTERED TO NUMEROUS SHOWERS/TSTMS SUN-MON. THERE
CONTINUED TO BE DIFFERENCES BETWEEN THE GFS/ECMWF MOISTURE FIELDS
THIS PERIOD. IN ESSENCE...THE ECMWF DEPICTED MORE-ROBUST MOISTURE
FIELDS VERSUS THE GFS. A BLEND OF THESE SOLUTIONS WOULD ARGUE FOR
THE POTENTIAL OF HEAVY RAINFALL CAPABLE OF FLASH FLOODING TO OCCUR
SOMETIME THIS WEEKEND AND EARLY NEXT WEEK. THE UPSHOT FOR SAT-
MON...A PERIOD FOR PRONOUNCED RAINFALL IS LIKELY ON TAP FOR SE AZ.

HIGH TEMPS TODAY-WED WILL BE NEARLY IDENTICAL TO TEMPS ACHIEVED
MON...AND WILL AVERAGE ABOUT 2-7 DEGS F ABOVE NORMAL. EXPECT ABOUT
2-3 DEGS F OF DAILY COOLING TO OCCUR THUR-MON...WITH BELOW NORMAL
DAYTIME TEMPS PREVAILING THIS WEEKEND AND EARLY NEXT WEEK.

&&

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

&&

$$

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