Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 190405
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
905 PM MST FRI JUL 18 2014

.SYNOPSIS...INCREASING MOISTURE IS EXPECTED TO BRING SOMEWHAT BETTER
THUNDERSTORM COVERAGE THIS WEEKEND. HOWEVER...MUCH OF NEXT WEEK MAY
SEE BELOW AVERAGE MOISTURE. MUCH HOTTER TEMPERATURES ARE FORECAST
TUESDAY THROUGH THURSDAY...WITH NEAR RECORD HIGHS POSSIBLE. WE
SHOULD THEN SEE A MARKED INCREASE IN THUNDERSTORM ACTIVITY ONCE
AGAIN BY THE END OF THE WEEK.

&&

.DISCUSSION...ISOLATED SHOWERS PRODUCING MOSTLY SPRINKLES OR ONLY A
FEW HUNDREDTHS OF AN INCH WERE OCCURRING ACROSS WRN/CENTRAL PIMA
COUNTY AT THIS TIME. IR SATELLITE IMAGERY AND SURFACE OBSERVATIONS
INDICATED MOSTLY CLOUDY SKIES ACROSS SE AZ...WITH MAINLY BROKEN MID
AND HIGH-LEVEL CLOUDINESS. DEWPOINTS AT LOWER ELEVATIONS VALID
19/04Z WERE MOSTLY IN THE 40S-MID 50S F...AND THESE TEMPS WERE
GENERALLY 2-7 DEGS F HIGHER VERSUS 24 HOURS AGO. 19/00Z KTWC
SOUNDING TOTAL PRECIP WATER VALUE WAS ABOUT 1.40 INCHES...OR NEARLY
0.30 INCH HIGHER VERSUS THUR EVENING.

CYCLONIC CIRCULATION SYSTEM EVIDENT VIA WATER VAPOR IMAGERY OVER
WEST CENTRAL SONORA WILL MOVE NWWD THE REST OF TONIGHT. THE FAVORED
AREA FOR ISOLATED SHOWERS/TSTMS LATER TONIGHT WILL BE WEST OF TUCSON
IN ADVANCE OF THIS SYSTEM. HAVE MADE A FEW MINOR ADJUSTMENTS TO THE
GRIDDED DATA POP/WEATHER FIELDS BASED ON RADAR TRENDS. OTHERWISE...
DIFFLUENT FLOW ALOFT SHOULD MAINTAIN PARTLY CLOUDY TO MOSTLY CLOUDY
SKIES ELSEWHERE.

INCREASING MOISTURE SHOULD TRANSLATE INTO SOMEWHAT GREATER COVERAGE
OF SHOWERS/TSTMS SAT. HOWEVER...HAVE NOTED THAT THE 19/00Z NAM POP/
QPF FIELDS HAVE TRENDED MARKEDLY DOWNWARD FOR SAT VERSUS PREVIOUS NAM
SOLUTIONS. THIS MAY BE ATTRIBUTED TO MORE OF THE AREA BEING IN
GREATER SUBSIDENCE BEHIND THE DEPARTING CYCLONIC CIRCULATION SYSTEM
VERSUS EARLIER SOLUTIONS. WILL DEFER TO THE MIDNIGHT SHIFT TO MAKE
ANY POTENTIAL DOWNWARD ADJUSTMENTS TO POPS SAT AFTER RECEIPT OF THE
19/00Z GFS/ECMWF. AT ANY RATE...HIGH TEMPS SAT ARE FORECAST TO BE
QUITE SIMILAR TO TEMPS ACHIEVED THIS AFTERNOON...AND WILL GENERALLY
AVERAGE WITHIN A DEGREE-OR-TWO OF NORMAL.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.AVIATION...VALID THRU 20/06Z.
ISOLATED -TSRA/-SHRA WILL OCCUR WEST OF KTUS THE REST OF TONIGHT.
INCREASING MOISTURE SHOULD THEN PROVIDE SOMEWHAT GREATER COVERAGE OF
TSRA/SHRA SATURDAY AFTERNOON AND SATURDAY EVENING. THE BEST PRECIP
CHANCES WILL OCCUR ACROSS THE WHITE MOUNTAINS NE OF KSAD...AND SOUTH
OF KTUS ESPECIALLY IN THE VICINITY OF THE KOLS/KDUG TERMINALS. MVFR
VISIBILITIES MAY OCCUR WITH THE STRONGER TSRA...AS WELL AS BRIEF
WIND GUSTS TO AROUND 35 KTS. OTHERWISE...CLOUD DECKS WILL GENERALLY
BE AT 10-15K FT AGL THRU SATURDAY EVENING. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT SOMEWHAT GREATER COVERAGE OF THUNDERSTORMS
THIS WEEKEND AS MOISTURE INCREASES ACROSS THE AREA. STRENGTHENING
HIGH PRESSURE ALOFT WILL THEN BRING HOTTER TEMPERATURES BY THE
MIDDLE OF NEXT WEEK. THEREAFTER...A PRONOUNCED INCREASE IN
THUNDERSTORM ACTIVITY SHOULD OCCUR LATE NEXT WEEK.

&&

.PREV DISCUSSION...THE IMPULSE EVIDENT ON WATER VAPOR IMAGERY
PUSHING THROUGH SONORA AND THE NORTHERN GULF OF CALIFORNIA WILL
PROBABLY HELP ANY POSSIBLE OVERNIGHT TO EARLY MORNING ACTIVITY. SOME
SUBSIDENCE BEHIND THIS FEATURE POSSIBLE DURING THE DAY TOMORROW FOR
OUR PART OF THE STATE...BUT WE SHOULD STILL FIRE NEAR THE BORDER
DURING THE AFTERNOON AND HAVE A DECENT CHANCE TO PUSH A FEW STORMS
INTO THE TUCSON AREA LATE SATURDAY AFTERNOON OR EARLY EVENING.
OVERALL COVERAGE FOR THE WEEKEND SHOULD BE UP COMPARED TO YESTERDAY
AND TODAY...BUT NOT AS BUSY AS WHAT WE SAW FOR THE FIRST HALF OF
JULY.

STILL LOOKING AT HOTTER TEMPERATURES BY THE MIDDLE OF NEXT WEEK WITH
A VERY STRONG RIDGE BUILDING THROUGH THE DESERT SOUTHWEST. NEAR
RECORD LEVELS ARE POSSIBLE WEDNESDAY AND THURSDAY AS WE STILL
STRUGGLE WITH AVAILABLE MOISTURE. WE MIGHT END UP NEAR EXCESSIVE
HEAT LEVELS WITH BOTH ECMWF AND GFS THICKNESSES SUPPORTING
TEMPERATURES ABOVE 110 AT TUCSON WEDNESDAY AND THURSDAY. BY THURSDAY
OR FRIDAY THIS SHOULD HELP SET UP A DEEP MOISTURE SURGE AND KNOCK
THE TEMPERATURES BACK CLOSER TO CLIMO BY FRIDAY AND SATURDAY NEXT
WEEK.

&&

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

&&

$$

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

FRANCIS
PREVIOUS DISCUSSION...MEYER




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