Area Forecast Discussion
Issued by NWS Tucson, AZ

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310
FXUS65 KTWC 042205
AFDTWC

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

.SYNOPSIS...A PACIFIC STORM SYSTEM WILL BRING WINDY CONDITIONS TO
THE REGION TOMORROW AND FRIDAY...ALONG WITH COOLER TEMPERATURES
AND A SLIGHT CHANCE OF SHOWERS THIS WEEKEND.

&&

.DISCUSSION...EARLY AFTERNOON VISIBLE SATELLITE IMAGERY SHOWS
JUST A FEW FAIR WEATHER CUMULUS BUBBLING OVER PARTS OF THE CWA
THIS AFTERNOON. SURFACE OBSERVATIONS INDICATE THAT GUSTY SOUTH TO
SOUTHEAST WINDS CONTINUE...BUT SHOULD BEGIN TO GRADUALLY SUBSIDE
LATER THIS AFTERNOON AND EVENING.

OUR STRETCH OF RELATIVELY BENIGN WEATHER WILL BE INTERRUPTED
TOMORROW 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
TOMORROW. 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`LL 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 PERIPHERPY OF THE UPPER LOW ARE ENOUGH TO WARRANT SLIGHT
CHANCE POPS WEST OF TUCSON FRIDAY EVENING...AND THEN NORTH AND
EAST OF TUCSON THROUGH THE WEEKEND. WE SHOULD HANG ONTO ENOUGH
INSTABILITY TO KEEP 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.

&&

.AVIATION...VALID THRU 05/23Z.
MOSTLY CLEAR SKIES WILL PREVAIL ACROSS MUCH OF THE AREA...WITH
JUST A FEW TO SCT CLOUDS AT 12-15K FT AGL ESPECIALLY OVER THE
HIGHER TERRAIN. SURFACE WINDS ELY/SELY AT 10-17 KTS WITH GUSTS TO
AROUND 25 KTS THRU 05/03Z...THEN DIMINISHING SURFACE WIND THIS
EVENING...WITH SPEEDS GENERALLY LESS THAN 10 KTS THRU 05/14Z. AFT
05/14Z...INCREASING SURFACE WIND...WITH SLY/SWLY SURFACE WIND AT
20-25 KTS AND GUSTS TO AROUND 30-35 KTS AFT 05/18Z. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...GUSTY EAST TO SOUTHEAST WINDS WILL CONTINUE MAINLY
ACROSS THE EASTERN HALF OF THE FORECAST AREA FROM THE NEW MEXICO
BORDER TO TUCSON THROUGH THE EARLY EVENING HOURS TONIGHT.

STRONG AND GUSTY SOUTH TO SOUTHWEST WINDS ARE EXPECTED THURSDAY
AND FRIDAY AS A STORM SYSTEM MOVES INTO THE REGION FROM THE WEST.
THE STRONGEST WINDS ON THURSDAY WILL MAINLY BE FROM THE TUCSON
METRO AREA WESTWARD...WITH THE CORE OF THE STRONG WINDS SHIFTING
EASTWARD FROM TUCSON INTO COCHISE COUNTY AND AREAS ADJACENT TO THE
NEW MEXICO BORDER ON FRIDAY. THEREFORE...THE FIRE WEATHER WATCHES
ON THURSDAY (FOR FIRE WEATHER ZONES 150 AND 151) AND FRIDAY (FOR
FIRE WEATHER ZONES 151...152 AND SOUTHERN 153) HAVE BOTH BEEN
UPGRADED TO A RED FLAG WARNING FOR STRONG AND GUSTY WINDS...LOW
RELATIVE HUMIDITIES AND A HIGH FIRE DANGER RATING. 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.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TO 8 PM MST FRIDAY FOR AZZ151>153.

RED FLAG WARNING FROM NOON TO 8 PM MST THURSDAY FOR AZZ150-151.

&&

$$

DISCUSSION...CARLAW
AVIATION/FIRE WEATHER...ZELL

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



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