Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 260411
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
910 PM MST TUE NOV 25 2014

.SYNOPSIS...DRY CONDITIONS WILL PREVAIL THROUGH MONDAY. STRONG HIGH
PRESSURE ALOFT WILL RESULT IN A PRONOUNCED WARMING TREND WEDNESDAY
THROUGH FRIDAY...WITH ABOVE AVERAGE DAYTIME TEMPERATURES CONTINUING
THIS WEEKEND. A PACIFIC STORM SYSTEM WILL THEN BRING AN INCREASING
CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW NEXT TUESDAY.

&&

.DISCUSSION...CLEAR SKIES CONTINUE TO PREVAIL ACROSS MOST OF ARIZONA
AS OF 04Z WITH THE EXCEPTION OF PERHAPS SOME THIN CIRRUS OVER THE
NERN CORNER OF THE STATE. LATEST WV IMAGERY CONTINUES TO SHOW RIDGE
BUILDING IN OVER THE WESTERN CONUS THIS EVENING. AREA SFC TEMPS
RANGED FROM THE MID AND UPPER 30S ACROSS COCHISE COUNTIES AND THE
HIGHER ELEVATIONS TO THE LOW 50S ACROSS THE WESTERN DESERT AREAS.
AIR NEAR THE SURFACE REMAINS CONSIDERABLY DRY WITH DEWPOINTS IN THE
SINGLE DIGITS AT MOST LOCATIONS. THIS COMBINED WITH LIGHTER WINDS
OVERNIGHT WILL LIKELY ALLOW LOWS TO DIP A FEW DEGREES COOLER THAN
LAST NIGHT. STILL EXPECTING HIGH TEMPS TOMORROW TO BE 7-10 DEGREES
HIGHER THAN TODAY WITH THE RIDGE SLIDING EASTWARD. CURRENT FORECAST
LOOKS ON TRACK...SO NO UPDATES ARE PLANNED AT THIS TIME. FOR MORE
INFORMATION ON THE FORECAST PAST TONIGHT...PLEASE SEE THE PREVIOUS
DISCUSSION BELOW.

&&

.AVIATION...VALID THRU 27/06Z.
STRONG HIGH PRESSURE ALOFT NEAR THE SOUTHERN CALIFORNIA COAST WILL
MAINTAIN CLEAR SKIES OR PERHAPS A FEW CLOUDS ABOVE 20K FT AGL THRU
WEDNESDAY EVENING. SURFACE WIND WILL GENERALLY BE TERRAIN DRIVEN
AT LESS THAN 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL OCCUR THROUGH MONDAY. NORMAL
DIURNAL WIND TRENDS WILL PREVAIL DURING MUCH OF THE REST OF THE WEEK
AND INTO THIS WEEKEND. THE EXCEPTION WILL BE LOCALLY GUSTY EAST
WINDS ON THANKSGIVING DAY. EXPECT A PRONOUNCED WARMING TREND TO
OCCUR WEDNESDAY THROUGH FRIDAY FOLLOWED BY WELL ABOVE AVERAGE
DAYTIME TEMPERATURES THIS WEEKEND. THEREAFTER...A PACIFIC STORM
SYSTEM WILL THEN BRING AN INCREASING CHANCE OF VALLEY RAIN AND
MOUNTAIN SNOW NEXT TUESDAY.

&&

.PREV DISCUSSION...CLEAR SKIES WILL CONTINUE TONIGHT WITH ANY
CIRRIFORM CLOUDS OF SIGNIFICANCE TO REMAIN WELL NORTH OF THE AREA.
THE COMBINATION OF CLEAR SKIES...LIGHT WINDS...AND A VERY DRY REGIME
MAY PRODUCE COLDER TEMPS FOR SOME LOCALES LATE TONIGHT/EARLY WED
MORNING VERSUS LAST NIGHT. AM SOMEWHAT CONCERNED ABOUT THE POTENTIAL
FOR FREEZING TEMPS ACROSS THE TUCSON METRO AREA. BASED ON VARIOUS
25/12Z NWP GUIDANCE...APPEARS THAT ONLY A FEW LOCALES SHOULD
EXPERIENCE FREEZING TEMPS. THUS...GIVEN THAT WIDESPREAD FREEZING
TEMPS ARE NOT EXPECTED TO OCCUR...A FREEZE WARNING WILL NOT BE
ISSUED AT THIS TIME.

THE UPPER RIDGE WILL MOVE EWD INTO THE WRN CONUS WED...THEN FLATTEN
OVER THE AREA THUR. CLEAR SKIES OR MOSTLY CLEAR SKIES WILL OCCUR WED-
THUR...AND LOCALLY GUSTY ELY WINDS SHOULD RETURN LATE WED NIGHT-THUR
IN RESPONSE TO A FAIRLY TIGHT SURFACE PRESSURE GRADIENT. LIGHTER
WINDS WILL PREVAIL FRI AS THE SURFACE PRESSURE GRADIENT LOOSENS.
EXPECT SUNNY SKIES OR MOSTLY SUNNY SKIES SAT AS THE UPPER FLOW
BECOMES INCREASINGLY SWLY AHEAD OF A DEEPENING TROUGH OVER THE ERN
PACIFIC. A SHORTWAVE RIDGE WILL MOVE EWD ACROSS SE AZ SUN IN
RESPONSE TO THE DEEPENING ERN PACIFIC LOW PRESSURE SYSTEM. PRECIP-
FREE CONDITIONS WILL CONTINUE MON...ALTHOUGH CLOUDS SHOULD INCREASE
IN MODERATE-TO-STRONG SWLY FLOW ALOFT.

THEREAFTER...THE 25/12Z OPERATIONAL GFS/ECMWF EXHIBITED DIFFERENCES
REGARDING THE PRECIP POTENTIAL BY TUE. ALTHOUGH BOTH SOLUTIONS
DEPICTED FAIRLY SIGNIFICANT QPF/S...THE OPERATIONAL GFS WAS FASTER
WITH THE PROGRESSION OF THE UPPER TROUGH AS WELL AS MORE TEMPERED
WITH AMOUNTS VERSUS THE ECMWF. THE ECMWF WAS QUITE SIMILAR TO THE
GFS 13 KM SOLUTION...AND THESE TWO SOLUTIONS WERE PREFERRED FOR THIS
FORECAST PACKAGE. FOR MON NIGHT-TUE...HAVE NOTED THE INCREASING
INTEGRATED VAPOR TRANSPORT INDICATING THE POTENTIAL FOR AN
ATMOSPHERIC RIVER EVENT IMPACTING SE AZ.

AT ANY RATE...HAVE OPTED FOR A SLIGHT CHANCE OF SHOWERS MAINLY FROM
TUCSON WWD MON NIGHT...THEN CHANCE-CATEGORY POPS AREA-WIDE TUE.
ALTHOUGH THESE POPS MAY SEEM TO BE FAIRLY LOW AT THIS TIME...WILL
NOT BE SURPRISED TO SEE POPS INCREASED MARKEDLY DURING THE NEXT
SEVERAL FORECAST SHIFTS...ESPECIALLY ASSUMING STRONG RUN-TO-RUN
MODEL CONTINUITY. PLENTY OF TIME TO REFINE DETAIL REGARDING
QPF/S...SNOW LEVELS AND ACCUMULATIONS.

A PRONOUNCED WARMING TREND WILL OCCUR WED...WITH HIGH TEMPS TO BE
NEARLY 10 DEGS F WARMER VERSUS THIS AFTERNOON. THE WARMING TREND
WILL CONTINUE THANKSGIVING DAY AND FRI FOLLOWED BY CONTINUED ABOVE
NORMAL DAYTIME TEMPS SAT-MON. MARKEDLY COOLER TEMPS ASSOCIATED WITH
THE LOW PRESSURE SYSTEM WILL THEN OCCUR TUE.

&&

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

&&

$$

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

DISCUSSION...FRENCH
PREVIOUS DISCUSSION...FRANCIS




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