Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 190338
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
830 PM MST SAT OCT 18 2014

.SYNOPSIS...A WEAK SYSTEM WILL THEN BRING A CHANCE OF SHOWERS AND A
FEW THUNDERSTORMS MAINLY EAST OF TUCSON THROUGH THE EARLY PART OF
THE COMING WEEK.  HIGH PRESSURE WILL BRING DRIER CONDITIONS LATE IN
THE WEEK ALONG WITH SEVERAL DEGREES OF WARMING.

&&

.DISCUSSION...CLOUDS FORMING OVER SOUTHERN AZ UNDER AN AREA OF UPPER
LEVEL DIFFLUENCE WITH A FEW SHOWERS AND EVEN LIGHTNING STRIKES
INDICATED ACROSS GREENLEE AND EASTERN GRAHAM COUNTIES.  THESE
SHOWERS ARE VERY LIGHT AND ARE HEADED NORTH.  THE COMBINATION OF
WEAK LIFT AND SOME MID LEVEL MOISTURE WILL MAINTAIN THE SMALL THREAT
OF LIGHT SHOWERS AND ISOLATED T-STORMS NEAR THE NEW MEXICO BORDER
THROUGH THE NIGHT.

THIS DIFFLUENCE IS ASSOCIATED WITH AN UPPER LOW JUST OFF THE COAST
OF BAJA RIGHT AT 30N LAT THIS HOUR.  THIS FEATURE WILL CONTINUE TO
SLOWLY CLOSE OFF AND GRADUALLY WORK ITS WAY EAST ACROSS NORTHERN
MEXICO TO THE VICINITY OF THE AZ/NM BORDER BY MONDAY EVENING.  AS IT
DOES SO WE ARE IN THE PRIME LOCATION IN RELATION TO THE LOW FOR
PRECIPITATION IF IT WERE NOT SO MOISTURE STARVED WHICH WILL LIMIT
THE ABUNDANCE OF PRECIPITATION.  HOWEVER THAT SAID...THE TREND OF
THE MODELS IS A BIT WETTER WITH EACH RUN AND FROM A LOOK AT CURRENT
CONDITIONS I AGREE WITH THAT ASSESSMENT.  NAM INITIALIZED WELL AT
18Z AND AGAIN AT 00Z WITH COVERAGE OF THE FEW AREAS OF CONVECTION
THAT HAVE DEVELOPED THIS EVENING LENDING SOME CONFIDENCE TO RAISING
THE CHANCE OF PRECIP FOR SUNDAY AFTERNOON AND EVENING WHICH I DID.
THE RESULT WAS SOMEWHAT INCREASED COVERAGE OF THE SLIGHT CHANCE AND
CHANCE CATEGORIES.  WE ALSO MATCH UP A BIT BETTER WITH OUR
SURROUNDING OFFICES.  I ALSO GAVE AN UPWARD TWEAK TO THE POPS MONDAY
AFTERNOON EASTERN MOST ZONES BASED ON THE ABOVE MODEL REASONING AND
BETTER CONSISTENCY.

ON TUESDAY THE UPPER LOW OPENS UP AND IS ABSORBED IN A LONGER WAVE
TROUGH MOVING ACROSS THE WEST.  HOWEVER AT THAT TIME THERE REMAINS
ENOUGH MOISTURE ACROSS THE EASTERN MOST ZONES TO MAINTAIN A SLIGHT
CHANCE OF SHOWERS AND T-STORMS IN THE FORECAST.

BEYOND THAT AN UPPER LEVEL RIDGE IS EXPECTED TO BUILD ACROSS THE
REGION WED INTO AT LEAST THE EARLY PART OF NEXT WEEKEND RESULTING IN
MOSTLY CLEAR AND DRY CONDITIONS WITH SIGNIFICANTLY WARMER THAN
NORMAL HIGH TEMPERATURES.  CERNIGLIA

&&

.AVIATION...VALID THRU 20/06Z.
SKC-SCT CLOUDS MAINLY ABOVE 10K FT AGL SOUTH OF KTUS AND SCT-BKN
NORTH OF KTUS THROUGH 19/18Z AND THERE WILL BE ENOUGH MOISTURE FOR
ISOLD -SHRA/-TSRA EAST OF KTUS.  INCREASING CLOUDS AFT 19/18Z
BECOMING SCT-BKN AROUND 10K FT ALL AREAS WITH A CHANCE OF
-SHRA/-TSRA DEVELOPING FROM AROUND KTUS EASTWARD.  SFC WINDS
GENERALLY LESS THAN 10 KTS THROUGH SUNDAY EXCEPT SOUTHEAST WIND TO
15 KT EASTERN AREAS SUNDAY AFTERNOON.  GUSTY WINDS ARE POSSIBLE
IN/NEAR -TSRA ON SUNDAY. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...A TROUGH OF LOW PRESSURE MOVING INTO THE AREA IN
COMBINATION WITH ADEQUATE MOISTURE WILL RESULT IN A CHANCE OF
SHOWERS AND A FEW THUNDERSTORMS THROUGH TUESDAY OR
WEDNESDAY...MAINLY TUCSON EASTWARD.  DRY CONDITIONS WILL THEN OCCUR
AREA WIDE THE SECOND HALF OF THE WEEK WITH SIGNIFICANTLY ABOVE
NORMAL HIGH TEMPERATURES.  20-FOOT WINDS WILL GENERALLY BE DIURNAL
AND LESS THAN 15 MPH THIS WEEKEND AND INTO NEXT WEEK.  SOME GUSTY
WINDS ARE POSSIBLE NEAR ANY THUNDERSTORMS.

&&

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

$$

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