Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 272245
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
345 PM MST THU NOV 27 2014

.SYNOPSIS...EXPECT DRY CONDITIONS WITH WARM DAYTIME TEMPERATURES
INTO EARLY NEXT WEEK. A WEAKENING PACIFIC STORM SYSTEM MOVING NORTH
OF THE AREA MAY THEN BRING A FEW VALLEY RAIN AND MOUNTAIN SNOW
SHOWERS AROUND THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...HIGH PRESSURE ALOFT WAS CENTERED WEST OF THE BAJA
CALIFORNIA SPUR NEAR 25N/120W...AND A RIDGE AXIS EXTENDED NEWD INTO
THE NRN ROCKIES THIS AFTERNOON. THE UPPER RIDGE OVER THE SWRN CONUS
WILL FLATTEN BY SAT AS A SERIES OF SHORTWAVE TROUGHS MOVE EWD ACROSS
THE PACIFIC NW AND NRN ROCKIES. EXPECT CLEAR SKIES OR MOSTLY CLEAR
SKIES TONIGHT INTO FRI. LOCALLY GUSTY EAST WINDS WILL CONTINUE INTO
FRI...THEN SURFACE WINDS WILL DIMINISH FRI AFTERNOON AS THE SURFACE
PRESSURE GRADIENT LOOSENS. CLEAR SKIES ARE ON TAP FRI NIGHT-SAT.
MOSTLY CLEAR SKIES SHOULD OCCUR SAT NIGHT-MON UNDER WLY/SWLY FLOW
ALOFT. INCREASING MOISTURE ABOVE 500 MB IN SWLY FLOW ALOFT WILL
RESULT IN PARTLY CLOUDY TO MOSTLY CLOUDY SKIES MON NIGHT-TUE.

FORECAST CONFIDENCE FOR TUE NIGHT-THUR REMAINS LOW REGARDING PRECIP
POTENTIAL FOR THIS FORECAST AREA. A LOW PRESSURE SYSTEM IS PROGGED
VIA THE 27/12Z GFS/ECMWF TO BE CENTERED WEST OF THE CENTRAL CALIF
COAST NEAR 33N/133W TUE EVENING. THE PROGRESSION OF THIS SYSTEM INTO
THE WRN CONUS AND SUBSEQUENT LOWER-LEVEL MOISTURE TRANSPORT ACROSS
SE AZ DURING THE MIDDLE OF NEXT WEEK REMAINS IN CONSIDERABLE DOUBT.
THE GFS WAS FASTER VERSUS THE ECWMF IN DEPICTING LIGHT QPF/S TO
OCCUR ACROSS NRN PORTIONS TUE NIGHT AND WED MORNING. MEANWHILE...THE
ECMWF DEPICTED LIGHT QPF/S TO OCCUR ACROSS NRN PORTIONS LATE WED
NIGHT INTO THUR.

GIVEN THE CONTINUED INABILITY FOR THE MEDIUM RANGE MODELS TO PROVIDE
CLARITY REGARDING PRECIP POTENTIAL...HAVE OPTED TO MAKE ONLY VERY
MINOR ADJUSTMENTS TO THE GRIDDED DATA POPS FOR TUE NIGHT-THUR.
THUS...THE OFFICIAL FORECAST DEPICTS A SLIGHT CHANCE OF SHOWERS
AREA-WIDE TUE NIGHT-WED NIGHT...AND A SLIGHT CHANCE OF SHOWERS
MOSTLY ACROSS THE HIGHER TERRAIN EAST OF TUCSON NEXT THUR.

HIGH TEMPS FRI SHOULD BE QUITE SIMILAR TO TEMPS ACHIEVED THIS
AFTERNOON...AND WILL AVERAGE NEARLY 5-10 DEGS F ABOVE NORMAL. EXPECT
A COUPLE OF DEGS OR SO OF DAILY COOLING THIS WEEKEND...THEN NO
SIGNIFICANT CHANGE IN HIGH TEMPS MON. HIGH TEMPS TUE ARE FORECAST TO
BE ABOUT 2-5 DEGS F COOLER VERSUS MON...THEN DAYTIME TEMPS WILL
GRADUALLY COOL AND TREND CLOSE TO NORMAL NEXT THUR.

&&

.AVIATION...VALID THRU 29/00Z.
A WEAKENING HIGH PRESSURE RIDGE ALOFT WILL PROVIDE CLEAR SKIES TO
PERHAPS SCATTERED CLOUDS ABOVE 20K FT AGL THRU FRIDAY AFTERNOON.
SURFACE WIND INTO FRIDAY MORNING WILL BE ELY/SELY 5-15 KTS WITH
OCCASIONAL GUSTS TO AROUND 25 KTS. SURFACE WIND FRIDAY AFTERNOON
WILL THEN DIMINISH TO LESS THAN 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT DRY CONDITIONS WITH ABOVE NORMAL DAYTIME
TEMPERATURES THROUGH TUESDAY. THERE IS A SLIGHT CHANCE OF SHOWERS
ACROSS TUESDAY NIGHT THROUGH THURSDAY AS A WEAKENING PACIFIC STORM
SYSTEM MOVES NORTH OF THE AREA. LOCALLY GUSTY EAST WINDS WILL
CONTINUE INTO FRIDAY MORNING. THEREAFTER...NORMAL DIURNAL WIND
TRENDS WILL PREVAIL INTO EARLY NEXT WEEK.

&&

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

&&

$$

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FRANCIS




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