Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 200410
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
910 PM MST TUE MAY 19 2015

.SYNOPSIS...PERIODS OF GUSTY WINDS THIS WEEK AS WEATHER SYSTEMS
CONTINUE TO PASS MAINLY NORTH OF THE AREA. TEMPERATURES WILL BE NEAR
TO BELOW AVERAGE INTO THE WEEKEND.

&&

.DISCUSSION...MOSTLY CLEAR SKIES WITH A FEW CIRRIFORM CLOUDS AND
LIGHT WEST TO NORTHWEST WINDS ACROSS SE ARIZONA AT THIS TIME. BASED
ON SATELLITE TRENDS AS WELL AS 500-300 MB MOISTURE FIELDS PER THE
20/00Z NAM/GFS...WILL MODIFY THE GRIDDED DATA SKY VALUES TO DEPICT
MOSTLY CLEAR SKIES VERSUS CLEAR SKIES THE REST OF TONIGHT.
OTHERWISE...EXPECT LIGHT WINDS THE REST OF TONIGHT WITH MINIMUM
TEMPS AROUND DAYBREAK WED TO AVERAGE A COUPLE OF DEGS OR SO BELOW
NORMAL.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.AVIATION...VALID THRU 21/06Z.
A FEW CLOUDS ABOVE 20K FT AGL THE REST OF TONIGHT FOLLOWED BY
SCATTERED TO BROKEN CIRRUS CLOUDS WEDNESDAY AND WEDNESDAY EVENING.
SURFACE WIND INTO EARLY WEDNESDAY MORNING MAINLY LESS THAN 10 KTS.
SURFACE WIND 16Z-20Z WEDNESDAY AND CONTINUING INTO WEDNESDAY EVENING
SLY/SWLY AT 12-20 KTS WITH GUSTS OF 20-30 KTS. THE STRONGEST WIND
WILL BE SOUTH-TO-SOUTHEAST OF KTUS. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...AN ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH THE
COMING WEEKEND WITH SEVERAL PERIODS OF ELEVATED WINDS. WARMER
TEMPERATURES ARE EXPECTED WEDNESDAY BEFORE A SLIGHT COOL-DOWN TAKES
PLACE THURSDAY THROUGH SATURDAY.

THE MAIN HIGHLIGHT OF THIS PERIOD CONTINUES TO BE THE DEVELOPMENT OF
STRONG SOUTHWESTERLY WINDS THURSDAY AND FRIDAY AFTERNOONS. CURRENT
INDICATIONS ARE THAT THE STRONGEST AND MOST WIDESPREAD WINDS WILL
OCCUR ON FRIDAY. IN ADDITION...MINIMUM RH VALUES ARE EXPECTED TO
FALL TO AROUND 10 PERCENT OVER SOUTHEASTERN PORTIONS OF 152...AND 10-
15 PERCENT OVER SOUTHERN PORTIONS OF 151...WHICH COMBINED WITH
SEVERAL DAYS FOR ADDITIONAL DRYING OF FINE FUELS...MAY LEAD TO
CRITICAL FIRE WEATHER CONCERNS FOR THESE ZONES. FIRE CREWS ARE
ENCOURAGED TO MONITOR SUBSEQUENT FORECASTS FOR THE POTENTIAL
ISSUANCE OF FIRE WEATHER PRODUCTS. A MORE LOCALIZED CRITICAL FIRE
WEATHER THREAT EXISTS ON THURSDAY WITH SLIGHTLY SLOWER WIND SPEEDS.

&&

.PREV DISCUSSION...WATER VAPOR IMAGERY AND 19/12Z UPPER-AIR PLOTS
SHOW A BROAD AREA OF LOW PRESSURE OVER THE GREAT BASIN...WITH A
LARGE SWATH OF DRY MID TO UPPER LEVEL AIR OVER MUCH OF THE EASTERN
PACIFIC...CENTRAL BAJA...SONORA AND CHIHUAHUA MEXICO...AS WELL AS
EXTREME SOUTHEAST ARIZONA AND WEST TEXAS. THE UPPER LOW WILL
CONTINUE TO MOVE TO THE EAST NORTHEAST AND SHEAR OVER THE NORTHERN
PLAINS BY EARLY WEDNESDAY. MEANWHILE...AN UPPER LOW WILL BECOME
REESTABLISHED OVER THE COASTAL WATERS OF CALIFORNIA WEDNESDAY INTO
THURSDAY WITH A VORT LOBE ROTATING THROUGH ARIZONA LATE THURSDAY.
ANY MOISTURE ASSOCIATED WITH THIS SYSTEM SHOULD REMAIN WELL TO THE
NORTH OF MY FORECAST AREA FOR A MAINLY DRY SYSTEM. THIS SYSTEM WILL
THEN MOVE BODILY OVER NORTHERN PARTS OF ARIZONA DURING THE DAY AND
INTO THE EVENING. BY SATURDAY THE CENTER OF CIRCULATION WILL BE
GENERALLY OVER THE CENTRAL ROCKIES WITH THE ASSOCIATED TROUGH AXIS
EXTENDING SOUTH SOUTHWEST ACROSS WESTERN ARIZONA. CONTINUED MOSTLY
DRY WITH THE PASSAGE OF THIS TROUGH SINCE THE BULK OF THE MOISTURE
WILL RESIDE TO OUR NORTH.

SURFACE WINDS WILL BE THE BIGGEST CONCERN FOR THURSDAY AND FRIDAY
WITH BREEZY TO LOCALLY WINDY CONDITIONS EXPECTED. COULD SEE SOME
AREAS HIT RED FLAG CONDITIONS ON EITHER OF THOSE DAYS...BUT
ESPECIALLY FRIDAY (SEE THE FIRE WEATHER SECTION BELOW FOR ADDITIONAL
DETAILS).

BEYOND FRIDAY THE MODELS SHOW SOME SIGNIFICANT DISCREPANCIES WITH
REGARD TO POSITION OF TROUGH/SHORTWAVES...BUT A DRY FORECAST IS
STILL EXPECTED THROUGH EARLY NEXT WEEK.

FOR TUCSON...HIGH TEMPERATURES WILL BE BELOW NORMAL EACH DAY...
ALTHOUGH THE COOLEST DAYS WILL OCCUR FRIDAY AND SATURDAY WHEN HIGHS
ARE EXPECTED TO BE 10 TO 12 DEGS BELOW NORMAL. OTHERWISE... HIGHS
GENERALLY AROUND 3 TO 6 DEGS BELOW NORMAL. LOW TEMPS WILL ALSO BE
BELOW NORMAL THROUGH THE FORECAST PERIOD...BUT THE COOLEST DAYS WILL
OCCUR FRIDAY THROUGH SUNDAY WHEN LOWS WILL RANGE FROM 5 TO 6 DEGS
BELOW NORMAL. OTHERWISE...LOWS AROUND 2 TO 4 DEGS BELOW NORMAL EACH
MORNING.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE

&&

$$

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

DISCUSSION/AVIATION...FRANCIS
PREVIOUS DISCUSSION...MOLLERE
FIRE WEATHER...CARLAW


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