Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 050402
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 PM MST WED MAY 4 2016

.SYNOPSIS...A PACIFIC STORM SYSTEM WILL BRING WINDY CONDITIONS WITH
AREAS OF BLOWING DUST THURSDAY AND FRIDAY. EXPECT COOLER TEMPERATURES
AND A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THIS WEEKEND. DRY
CONDITIONS WITH A WARMING TREND WILL THEN OCCUR EARLY NEXT WEEK.

&&

.DISCUSSION...CLEAR SKIES PREVAIL ACROSS MUCH OF SE ARIZONA AT THIS
TIME EXCEPT FOR A FEW MID-LEVEL CLOUDS ACROSS SE PINAL/WRN GRAHAM/NRN
COCHISE COUNTIES. SURFACE WINDS HAD DIMINISHED TO LESS THAN 10 MPH
ACROSS MUCH OF THIS FORECAST AREA AS WELL. HOWEVER...FORT HUACHUCA
MEASURED A SUSTAINED WIND SPEED OF 20 MPH FROM THE SOUTHWEST VALID
830 PM MST.

CLEAR SKIES OR MOSTLY CLEAR SKIES WILL OCCUR THE REST OF TONIGHT...
AS THE 05/00Z NAM/GFS DEPICT THE AXIS OF MID-LEVEL MOISTURE WILL
TRANSLATE EWD INTO WRN NEW MEXICO BY DAYBREAK THUR. A FEW CIRRIFORM
CLOUDS MAY ENCROACH UPON WRN SECTIONS BY EARLY THUR MORNING.
OCCASIONALLY GUSTY SOUTH-TO-SOUTHWEST WINDS MAY OCCUR LATE TONIGHT...
PARTICULARLY IN THE FAVORED WIND PRONE LOCALES FOR THIS DIRECTIONAL
COMPONENT SUCH AS FORT HUACHUCA AND SIERRA VISTA.

WIND SPEEDS WILL THEN INCREASE AREA-WIDE LATER THUR MORNING...AND
ESPECIALLY FROM TUCSON WWD INTO THE WRN DESERTS...AHEAD OF A DEEP
UPPER LEVEL LOW PRESSURE SYSTEM CENTERED JUST WEST OF THE SRN
CALIFORNIA COAST. THE MAIN CONCERN THUR AFTERNOON AND EARLY THUR
EVENING WILL BE AREAS OF BLOWING DUST THAT MAY POTENTIALLY IMPACT
TRAVEL DUE TO RESTRICTED VISIBILITIES. IN ADDITION...THE COMBINATION
OF THESE GUSTY SOUTH-TO-SOUTHWEST WINDS...LOW RELATIVE HUMIDITY AND
A HIGH FIRE DANGER RATING WILL CREATE CRITICAL FIRE WEATHER
CONDITIONS. A RED FLAG WARNING IS IN EFFECT GENERALLY FROM TUCSON
WESTWARD INTO WRN PIMA/SOUTH CENTRAL PINAL COUNTIES FROM NOON TO 8
PM MST. PLEASE REFER TO AWIPS PRODUCT PHXRFWTWC /WMO HEADER WWUS85
KTWC/ AS WELL AS THE FIRE WEATHER SECTION IN THIS PRODUCT FOR
ADDITIONAL INFORMATION.

&&

.AVIATION...VALID THRU 05/23Z.
CLEAR SKIES TO SCATTERED CLOUDS ABOVE 25K FT MSL INTO THURSDAY
EVENING. A FEW CLOUDS AROUND 15K FT MSL WILL ALSO OCCUR MAINLY EAST
OF KTUS THRU THE PERIOD. OTHERWISE...SURFACE WIND THE REST OF
TONIGHT WILL GENERALLY BE VARIABLE IN DIRECTION LESS THAN 10 KTS.
HOWEVER...SOUTHWEST WIND AT 10-20 KTS SHOULD OCCUR IN THE VICINITY
OF KFHU. SURFACE WIND THURSDAY INTO THURSDAY EVENING WILL BE SLY/
SWLY AT 12-25 KTS WITH GUSTS TO NEAR 35 KTS. THE STRONGEST SPEEDS
WILL OCCUR THURSDAY AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...A RED FLAG WARNING IS IN EFFECT FROM NOON TO 8 PM MST
THURSDAY FOR FIRE WEATHER ZONES 150 AND 151. A RED FLAG WARNING IS
ALSO IN EFFECT FROM NOON TO 8 PM MST FRIDAY FOR FIRE WEATHER ZONES
151...152 AND THE SOUTHERN PORTION OF 153. THE COMBINATION OF STRONG
AND GUSTY WINDS...LOW RELATIVE HUMIDITY AND A HIGH FIRE DANGER
RATING WILL CREATE CRITICAL FIRE WEATHER CONDITIONS. 20-FOOT WINDS
WILL BE FROM THE SOUTH ON THURSDAY...AND SOUTH TO SOUTHWEST ON
FRIDAY.

COOLER TEMPERATURES AND INCREASED MOISTURE WILL THEN MOVE INTO THE
AREA LATE FRIDAY THROUGH THE WEEKEND. THIS WILL RESULT IN A SLIGHT
CHANCE OF SHOWERS FOR MOST LOCATIONS ALONG WITH BREEZES PERSISTING
THROUGH THE WEEKEND. A FEW SHOWERS MAY LINGER ACROSS THE WHITE
MOUNTAINS MONDAY. OTHERWISE...DRY CONDITIONS WITH A WARMING TREND
WILL PREVAIL MONDAY THROUGH NEXT WEDNESDAY.

&&

.PREV DISCUSSION /305 PM MST/...OUR STRETCH OF RELATIVELY BENIGN
WEATHER WILL BE INTERRUPTED THURSDAY AND INTO THE WEEKEND BY A
LARGE UPPER LOW CURRENTLY SPINNING JUST OFF THE CALIFORNIA COASTLINE.
OUT AHEAD OF THIS SYSTEM...THE MID-LEVEL GRADIENT WILL CONTINUE TO
TIGHTEN...WHICH WILL RESULT IN STRONG SOUTHERLY WINDS OVERSPREADING
THE REGION THURSDAY. THE MAIN CORE OF STRONG WINDS WILL THEN SHIFT
TO THE EAST ON FRIDAY...WITH EVEN STRONGER WIND SPEEDS EXPECTED FROM
ROUGHLY TUCSON AND POINTS EAST. A WIND ADVISORY MAY BE NEEDED IN
SUBSEQUENT FORECASTS FOR PORTIONS OF THE FORECAST AREA ON FRIDAY.
BASED ON THE COMBINATION OF STRONG WINDS AND DRY AIR AT THE
SURFACE...WE HAVE UPGRADED THE FIRE WEATHER WATCHES ON THURSDAY
AND FRIDAY AFTERNOONS TO RED FLAG WARNINGS. FOR MORE INFORMATION
PLEASE SEE THE FIRE WEATHER DISCUSSION BELOW.

IN ADDITION TO FIRE WEATHER CONCERNS...WE WILL NEED TO WATCH OUT FOR
BLOWING DUST. RECENT VOLUMETRIC SOIL MOISTURE MEASUREMENTS FROM
THE NASA SPORT LAND INFORMATION SYSTEM SHOW VALUES IN THE 9 TO 13
PERCENT RANGE ACROSS MANY OF OUR DUST PRONE LOCATIONS. THESE ARE
CERTAINLY LOW ENOUGH TO CAUSE ISSUES WITH WINDS GUSTING TO 35 TO
50 MPH.

AN OVERALL DEARTH OF MOISTURE AND GENERALLY MODEST MID-LEVEL HEIGHT
FALLS MEAN PRECIP CHANCES WILL REMAIN RELATIVELY LOW WITH THIS
SYSTEM. STILL...THE PRESENCE OF NON-ZERO BUOYANCY (MUCAPE VALUES OF
100-300 J/KG) AND PLENTY OF VORT LOBES ROTATING AROUND THE PERIPHERY
OF THE UPPER LOW ARE ENOUGH TO WARRANT SLIGHT CHANCE POPS WEST OF
TUCSON FRIDAY EVENING...AND THEN MAINLY NORTH AND EAST OF TUCSON
THROUGH THE WEEKEND. WE SHOULD HANG ONTO ENOUGH INSTABILITY TO KEEP A
SLIGHT CHANCE POPS GOING IN THE WHITE MOUNTAINS ON MONDAY AS WELL.
AS THIS LOW MOVES EAST NEXT WEEK...HEIGHTS WILL RISE UNDER SHORTWAVE
RIDGING WHICH WILL RESULT IN ANOTHER WARMING TREND INTO THE MIDDLE OF
NEXT WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    RED FLAG WARNING FROM NOON TO 8 PM MST THURSDAY FOR AZZ150-151.

    RED FLAG WARNING FROM NOON TO 8 PM MST FRIDAY FOR AZZ151>153.

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

DISCUSSION...FRANCIS
PREVIOUS DISCUSSION...CARLAW



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