Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251046
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
346 AM MST TUE AUG 25 2015

.SYNOPSIS...EXPECT A DAILY CHANCE OF SHOWERS AND THUNDERSTORMS
ACROSS THE AREA INTO WEDNESDAY. FOR THE SECOND HALF OF THE
WEEK...BUILDING HIGH PRESSURE WILL TEND TO SUPPRESS THUNDERSTORM
COVERAGE WHILE BRINGING HOTTER TEMPERATURES TO THE AREA. NEAR RECORD
HIGHS ARE POSSIBLE FOR THE UPCOMING WEEKEND.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 25/00Z UPPER-AIR PLOTS AND
RECENT MODEL DATA SHOW A RIDGE OVER THE DESERT SOUTHWEST WITH SOUTH
TO SOUTHEAST FLOW ALOFT ACROSS THE REGION. IR SATELLITE IMAGERY
SHOWS A LARGE STORM COMPLEX OVER SOUTHWESTERN/WESTERN SONORA MEXICO
AND MOVING WEST NORTHWEST...WITH A SMALLER SYSTEM OVER SOUTHEAST
ARIZONA NEAR THE SAFFORD AREA OF GRAHAM COUNTY. MODELS...ESPECIALLY
THE GFS SUGGESTING A WEAK VORT MAX RESPONSIBLE FOR THIS LATE
NIGHT/EARLY MORNING ACTIVITY OVER OUR REGION...WITH THE FEATURE
LIFTING NORTH THROUGH THE STATE TODAY. CONSIDERABLE DEBRIS CLOUDS
ASSOCIATED WITH THE NOW MOSTLY DIMINISHING SHOWERS AND STORMS COVER
ALL OF MY FORECAST AREA AND EXTEND NORTH AND NORTHWEST ALONG THE
COLORADO RIVER BASIN...AS WELL AS PORTIONS OF SRN CALIFORNIA AND
INTO SRN NEVADA.

RADAR MOSAIC SHOWS LINGERING SHOWERS AND THUNDERSTORMS OVER MY
FORECAST AREA THAT EXTEND FROM NEAR AJO AND ORGAN PIPE CACTUS
NATIONAL MONUMENT TO THE TUCSON METRO...WITH ADDITIONAL STORMS TO
THE SOUTHWEST BETWEEN SELLS...GREEN VALLEY AND SASABE. FARTHER TO
THE EAST AND NORTHEAST SHOWERS AND STORMS ARE OCCURRING OVER
NORTHWEST COCHISE COUNTY AND A LARGE PART OF GRAHAM COUNTY. A SMALL
STREAM FLOOD ADVISORY CONTINUES FOR SOUTHWEST GRAHAM COUNTY DUE TO
MODERATE TO HEAVY RAIN THAT OCCURRED EARLIER.

AN MCV HAS LIKELY DEVELOPED TO THE WEST OF TUCSON IN THE GENERAL
VICINITY OF THREE POINTS TO NEAR SANTA ROSA IN THE TOHONO O`ODHAM
NATION. THIS FEATURE CAN BE SEEN IN RADAR IMAGERY AS IT SPINS
COUNTER CLOCKWISE IN THAT AREA. THAT SAID...MOTION OF THE SHOWERS
AND STORMS IS A BIT CHAOTIC WITH STORMS TO THE EAST AND SOUTH MOVING
GENERALLY NORTH AND ACTIVITY OUT WEST MOVING WEST.

I ADJUSTED THE POP FORECAST FOR THE EARLY MORNING HOURS TO ACCOUNT
FOR MORE WIDESPREAD ACTIVITY THAN WAS PREVIOUSLY EXPECTED. THAT
MEANS GENERALLY THE HIGHEST THREAT THROUGH THE MID MORNING HOURS
WILL OCCUR FROM AROUND TUCSON NORTHWARD. BASICALLY THE NORTHERN
FRINGES OF THE FORECAST AREA...WITH A MUCH LESSER THREAT FOR COCHISE
COUNTY.

WITH CONSIDERABLE DEBRIS CLOUDS WE SHOULD STRUGGLE TO GET MUCH SUN
TO PEAK THROUGH THE CLOUDS TODAY...OR AT LEAST THROUGH THE MORNING
HOURS. THAT SAID...AFTER MID MORNING I GENERALLY HAVE JUST ISOLATED
TO LOW END SCATTERED ACTIVITY ACROSS MOST OF MY FORECAST AREA...
SINCE MOST OF WHAT IS CURRENTLY ON RADAR OVER NORTHERN SECTIONS
SHOULD HAVE MOVED NORTH INTO THE PHOENIX AREA BETWEEN NOW AND
SHORTLY AFTER SUNRISE. AFTER NOON...I SHOW A SLIGHT INCREASE IN
STORM CHANCES...MOSTLY BECAUSE WE SHOULD STRUGGLE TO GET STORMS TO
FIRE UP WITH LIMITED SUN. BY LATE AFTERNOON AND INTO THE EVENING
HOPEFULLY ENOUGH SUN TO HELP KICK OFF ACTIVITY WITH GENERALLY
SCATTERED STORMS AREA WIDE. LATEST MOS POP NUMBERS...AS WELL AS 00Z
U OF A WRF/NAM AND GFS SUGGEST THIS KIND OF SCENARIO.

BY WEDNESDAY THE HIGH SHOULD BE OVER THE TEXAS PANHANDLE WITH SOUTH
TO SOUTHWEST FLOW ALOFT...WITH STILL PLENTY OF MOISTURE ACROSS THE
REGION...WITH PW`S EXPECTED TO RANGE FROM AROUND 1 INCH TO THE
EXTREME EAST AND 1.4-1.5 OVER CENTRAL LOCATIONS AND 1.5-1.7 FOR THE
WEST. SO...POPS AGAIN SCATTERED IN NATURE FOR ALL BUT EXTREME
WESTERN ZONES WHERE JUST ISOLATED. A SIMILAR FORECAST FOR THURSDAY.

BY FRIDAY THE HIGH RETROGRADES TO A POSITION NEARLY OVERHEAD AND
THIS CONTINUES ON SATURDAY. PW`S PROGGED TO BE 1.0 INCHES EAST...1.2
CENTRAL AND 1.4 WEST. THAT SAID...LOOKING AT MAINLY ISOLATED TO LOW
END MAINLY MOUNTAIN STORMS BOTH DAYS FROM TUCSON EASTWARD.

BY SUNDAY AND INTO MONDAY HIGH BECOMES ORIENTED SOUTHWEST TO
NORTHEAST FROM CENTRAL BAJA ACROSS NORTHERN MEXICO AND INTO EASTERN
NEW MEXICO AND WEST TEXAS. THIS IS IN RESPONSE TO AN UPSTREAM TROUGH
AND MODELS SHOWING A SLIGHT MOISTURE PLUME ACROSS PARTS OF ARIZONA
AND NEW MEXICO WITH AN UPTICK IN ACTIVITY BY MONDAY...MAINLY EAST.

FOR TUCSON...HIGHS GENERALLY AT OR SLIGHTLY BELOW NORMAL
TODAY...THEN NEAR NORMAL WEDNESDAY. THEREAFTER...HIGHS AROUND 4 TO 8
DEGS ABOVE NORMAL WITH THE WARMEST DAYS FRIDAY THROUGH SUNDAY.

&&

.AVIATION...VALID THRU 26/12Z.
SCT-BKN CLOUDS AT 6 TO 10 KFT AGL AND ISOLATED TO SCATTERED
SHRA/TSRA THROUGH 25/12Z. GRADUAL DECREASE IN COVERAGE THEREAFTER
WITH MULTIPLE CLOUD LAYERS ABOVE 10 KFT AGL. SCT SHRA/TSRA WILL ONCE
AGAIN DEVELOP LATER THIS AFTERNOON...WITH MOST ACTIVITY AFT 26/00Z
INTO THE EVENING. BRIEF MVFR CONDITIONS IN AND AROUND STRONGER TSRA
ALONG WITH GUSTY AND ERRATIC WINDS TO 40 KTS. AWAY FROM TSRA...
SURFACE WINDS TERRAIN DRIVEN AND GENERALLY LESS THAN 12 KTS OUTSIDE
OF TYPICAL AFTERNOON GUSTINESS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS LINGERING EARLY
THIS MORNING...MAINLY NORTH OF A LINE FROM TUBAC TO VAIL TO WILLCOX.
THESE SHOULD CONTINUE MOVING NORTH WITH ONLY ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS EXPECTED THROUGH THE LATE AFTERNOON BEFORE
INCREASING AGAIN DURING THE EARLY EVENING HOURS. A BIT DRIER AIR
WILL BEGIN TO MOVE INTO THE REGION STARTING WEDNESDAY...BUT WE
SHOULD STILL HOLD ONTO ENOUGH MOISTURE FOR SOME LIMITED SHOWER AND
STORM COVERAGE. THEREAFTER...AN UPPER RIDGE WILL BUILD OVER THE AREA
LATE IN THE WEEK INTO NEXT WEEKEND RESULTING IN A SIGNIFICANT
DECREASE IN SHOWERS AND THUNDERSTORMS WITH TEMPERATURES RISING
THROUGH THE WEEKEND. OUTSIDE OF POTENTIALLY STRONG THUNDERSTORM
WINDS...WINDS WILL BE TYPICAL FOR MID AUGUST AND GENERALLY LESS THAN
15 MPH WITH AFTERNOON GUSTINESS...ESPECIALLY IN THE GILA RIVER
VALLEY.

&&

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

&&

$$

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...HUMPHREYS

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