Weather Service Report


444 
FXUS65 KTWC 012100
AFDTWC

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

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM NEAR THE CALIFORNIA COAST 
WILL BRING STRONG AND GUSTY WINDS AGAIN MONDAY. PERIODS OF VALLEY 
RAIN AND MOUNTAIN SNOW ARE POSSIBLE MAINLY ACROSS THE HIGHER TERRAIN 
TO THE NORTH OF TUCSON TONIGHT...THEN BECOMING WIDESPREAD FROM WEST 
TO EAST MONDAY TO GO ALONG WITH COOLER TEMPERATURES. PRECIPITATION 
CHANCES WILL LESSEN CONSIDERABLY MIDWEEK WITH DRY CONDITIONS 
AREAWIDE AND WARMER TEMPERATURES BY THE END OF THE WEEK.

&&

.DISCUSSION...A MILD AND BREEZY AFTERNOON ACROSS SOUTHEAST ARIZONA 
WITH AREAS FROM TUCSON EASTWARD SEEING MOSTLY CLEAR SKIES WITH 
LOCATIONS TO THE WEST OF TUCSON SEEING PARTLY TO OCCASIONALLY MOSTLY 
CLOUDY SKIES. THIS IS ALL OUT AHEAD OF AN UPPER LOW THAT IS NOW JUST 
OFF THE CENTRAL/SOUTHERN CALIFORNIA COAST AND GRADUALLY MOVING TO 
THE SOUTH. A WELL ESTABLISHED PLUME OF MOISTURE CONTINUES THIS 
AFTERNOON FROM WELL OFF THE BAJA COAST INTO NRN BAJA/SRN CALIFORNIA 
AND THEN EASTWARD INTO THE LOWER COLORADO RIVER VALLEY AND NORTHERN 
PORTIONS OF ARIZONA. WITH THE TROUGH AXIS TRANSITIONING FROM WEST TO 
EAST MORE TOWARDS A NORTH-SOUTH AXIS...THAT IS KEEPING THE MOISTURE 
PLUME TO OUR WEST AND WILL CONTINUE TO DO SO THROUGH THIS EVENING 
WITH ONLY A SLIGHT CHANCE OF SHOWERS AND MOUNTAIN SNOW SHOWERS TO 
THE NORTH OF TUCSON THIS EVENING. 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. 

&&

.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.  

&&

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

&&

$$

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GL



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