Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 020416
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
915 PM MST SUN MAR 1 2015

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM NEAR CENTRAL AND SOUTHERN
CALIFORNIA WILL BRING WINDY CONDITIONS AS WELL AS PERIODS OF VALLEY
RAIN AND MOUNTAIN SNOW BY MID DAY MONDAY INTO MONDAY NIGHT.
PRECIPITATION CHANCES WILL LESSEN CONSIDERABLY FOR MIDWEEK WITH DRY
CONDITIONS AREAWIDE AND WARMER TEMPERATURES BY THE END OF THE WEEK.

&&

.DISCUSSION...SHOWERS SPREADING INTO THE YUMA AREA FROM THE WEST AND
SOUTHWEST THIS EVENING. INTERESTING MOISTURE TRENDS FROM THE GULF OF
CALIFORNIA INTO CENTRAL SONORA OVER THE PAST SEVERAL HOURS WITH 1
INCH VALUES NO CREEPING NORTH OF HERMOSILLO. STRONG SOUTHWESTERLY
UPSLOPE EFFECTS WILL PROBABLY START BRINGING A FEW MORE LIGHT
SHOWERS TONIGHT AS WE MIGHT SEE A LITTLE BIT DEEPER MOISTURE FOR THE
SOUTHERN CALIFORNIA SYSTEM TO WORK WITH WHEN THE INITIAL STRONGER
PIECE OF ENERGY PUSHES ACROSS ARIZONA MONDAY AND MONDAY NIGHT. WE
TWEAKED UP OUR MOUNTAIN STORM TOTAL PRECIP NUMBERS WITH ENOUGH SNOW
FOR A COUPLE OF HEADLINES. SOUTHERN MOUNTAINS ABOUT 1 TO 4 INCHES,
MT LEMMON AROUND 5 TO 8 INCHES, AND THE MOUNTAINS OF GRAHAM AND
GREENLEE COUNTIES ABOUT 10 TO 14 INCHES ABOVE 6500 OR 7000 FEET.
PLEASE SEE THE PREVIOUS DISCUSSION FOR ADDITIONAL DETAILS.

&&

.AVIATION...VALID THRU 03/00Z.
AN APPROACHING SLOW MOVING STORM SYSTEM WILL BE IMPACTING THE AREA
THRU MONDAY AFTERNOON OR 03/00Z. SCTD MID-LEVEL CLOUDS FROM KTUS W
WILL GRADUALLY BECOME BKN AND LOWER A BIT OVER THE NEXT 12-18 HRS.
ISOLD -SHRA EARLY THIS EVENING WELL W OF KTUS WILL GRADUALLY
INCREASE IN AREAL COVERAGE BETWEEN 02/05Z AND 02/12Z IN ADVANCE OF
APPROACHING COLD FRONT AND SLOWLY SPREAD E. ISOLD MVFR CONDS NR SHRA
AFT 02/10Z. CONFIDENCE STILL A LITTLE LOW ON TIMING OF -SHRA INTO
KTUS AND KOLS BUT DID PUT VCSH IN THE TAF STARTING AROUND 15Z-16Z.
AREAS E OF KTUS WILL SEE SCTD MID-HI LEVEL CLOUDS THRU 02/07Z WITH
MID-LEVEL CLOUD DECKS BCMG SCT-BKN THEREAFTER WITH ISOLD -SHRA DVLPG
AFT 02/12Z.

SFC WINDS SW 10-20 KTS THRU 02/03Z THEN DIMINISHING TO 5-12 KTS. S
WIND INCRG 10-25 KTS WITH HIGHER GUSTS MONDAY IN ADVANCE OF
APPROACHING COLD FRONT. THE STRONGEST WINDS AFTER 02/15Z WILL BE
FROM KTUS E. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A SLOWLY APPROACHING STORM SYSTEM JUST OFF THE
CENTRAL CALIFORNIA COAST WILL MAINTAIN BREEZY SW WINDS ACROSS THE
AREA TODAY AND EVEN SOMEWHAT STRONGER MONDAY AS A FRONT MOVES ACROSS
THE AREA. FAIRLY STRONG WINDS WILL CONTINUE THROUGH TONIGHT OVER
HIGHER TERRAIN. A FEW LIGHT SHOWERS ARE EXPECTED WEST AND NORTH OF
TUCSON TODAY AND TONIGHT WITH SHOWERS SPREADING ACROSS ALL AREAS
MONDAY THROUGH TUESDAY BEFORE DIMINISHING WEDNESDAY WITH DRY
CONDITIONS EXPECTED THEREAFTER. THE SHOWERS WILL BE IN THE FORM OF
SNOW ABOVE 8000 FT THROUGH MONDAY THEN DROPPING TO AROUND 6000 FEET
LATE MONDAY THROUGH WEDNESDAY.

&&

.PREV DISCUSSION...AS THE TROUGH AND ASSOCIATED PLUME OF MOISTURE
AND SURFACE COLD FRONT START TO MOVE EASTWARD LATE
TONIGHT...PRECIPITATION CHANCES WILL GRADUALLY INCREASE FOR FAR
WESTERN AREAS AND ACROSS THE HIGHER TERRAIN FROM TUCSON NORTHWARD.
PRECIPITATION AMOUNTS OVERNIGHT WILL BE MINIMAL THOUGH WITH THE BULK
EXPECTED MONDAY. SNOW LEVELS THROUGH TONIGHT WILL REMAIN AT
8000-9000 FEET.

THE SURFACE COLD FRONT WILL MOVE THROUGH THE AREA FROM WEST TO EAST
DURING THE DAY MONDAY...ACROSS THE WESTERN DESERTS DURING THE
MORNING...THROUGH THE CENTRAL SECTIONS OF THE FORECAST AREA
INCLUDING TUCSON DURING THE AFTERNOON AND THEN INTO EASTERN AREAS IN
THE EARLY EVENING. A 3 TO 7 HOUR PERIOD OF PRECIPITATION IS EXPECTED
ALONG WITH AND BEHIND THE FRONT AS IT MOVES THROUGH THE AREA. THE
NUMERICAL GUIDANCE IS FINALLY NOW IN GOOD AGREEMENT WITH ONLY MINOR
DIFFERENCES IN THE FRONTAL TIMING. WITH THE BEST ASCENT AND FORCING
TO THE NORTH AND WEST OF THE AREA...WE HAVE GONE AHEAD AND TWEAKED
QPF VALUES DOWN SLIGHTLY WITH ABOUT 0.20 TO 0.6 INCHES IN OUR
FORECAST AREA...WITH THE GREATEST AMOUNTS TO THE NORTH AND WEST OF
TUCSON WITH LESSER AMOUNTS TO THE SOUTH AND EAST. SNOW LEVELS WILL
START AT 8000-9000 FEET BUT LOWER TO 6000 FEET OR SO AFTER THE
FRONTAL PASSAGE. THE EXPECTATION IS FOR ABOUT 5 TO 9 INCHES OF SNOW
ABOVE 8000 FEET AND 3 TO 6 INCHES ABOVE 6500 FEET FOR THE MOUNTAINS
FROM TUCSON NORTH AND EASTWARD INCLUDING THE
CATALINA/RINCONS...PINALENOS AND WHITE MOUNTAINS. THE SKY ISLANDS TO
THE SOUTH AND EAST OF TUCSON WILL SEE LESS SNOW. THESE NUMBERS ARE
STILL ON THE MARGINAL SIDE FOR A WINTER WEATHER ADVISORY AND GIVEN
STILL SOME UNCERTAINTY ON SNOW AMOUNTS...WILL LET LATER SHIFTS
REEVALUATE NEED FOR ANY WINTER WEATHER HEADLINES. BREEZY TO WINDY
CONDITIONS ARE EXPECTED AHEAD OF THE COLD FRONT ON MONDAY WITH THE
STRONGEST WINDS SOUTH AND EAST OF TUCSON IN COCHISE COUNTY WHICH
WILL APPROACH ADVISORY LEVELS.

PRECIPITATION WILL TAPER OFF FOR EASTERN AREAS ON MONDAY NIGHT AS
THE COLD FRONT AND TROUGH AXIS ALOFT SHIFT TO THE EAST. THERE WILL
BE ANOTHER DISTURBANCE ALOFT DROPPING DOWN OFF THE CALIFORNIA COAST
INTO A CLOSED LOW WITH GREATER STREAM SEPARATION TUESDAY BUT THIS IS
EXPECTED TO STAY TO THE WEST OF OUR AREA ON TUESDAY.
THUS...SOUTHEAST ARIZONA LOOKS TO GENERALLY BE BETWEEN SYSTEMS WITH
ONLY SLIGHT CHANCE OF PRECIPITATION. THIS UPPER LOW WILL ATTEMPT TO
EJECT EASTWARD TUESDAY NIGHT INTO WEDNESDAY SO HAVE MAINTAINED
SLIGHT CHANCES OF PRECIPITATION INTO WEDNESDAY FOR EASTERN AREAS.
TEMPERATURES WILL REMAIN ON THE COOL SIDE STARTING MONDAY AND
CONTINUING THROUGH WEDNESDAY. THEREAFTER...BROAD WEAK TROUGHINESS
WILL REMAIN OVER THE REGION INTO THE END OF THE WORK WEEK BUT THE
ATMOSPHERE WILL BE DRYING OUT SO HAVE KEPT POPS BELOW MENTIONABLE
LEVELS WITH WARMING TEMPERATURES.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
     WINTER STORM WARNING 11 AM MST MONDAY TO 1 AM MST TUESDAY
     ABOVE 6500 FEET FOR AZZ510-511.

     WINTER WEATHER ADVISORY 11 AM MST MONDAY TO 1 AM MST TUESDAY
     ABOVE 6500 FEET FOR AZZ514.

&&

$$

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MEYER/GL





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