Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 292226
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
325 PM MST THU JAN 29 2015

.SYNOPSIS...A STORM SYSTEM WILL BRING VALLEY RAIN AND MOUNTAIN SNOW
ESPECIALLY TONIGHT INTO SATURDAY. MINOR FLOODING MAY OCCUR DUE TO
PERIODS OF HEAVY RAINFALL. THE MOST SIGNIFICANT SNOWFALL WILL BE
ABOVE 8000 FEET...OR ACROSS THE HIGHEST PEAKS. EXPECT MUCH COOLER
DAYTIME TEMPERATURES FRIDAY INTO THIS WEEKEND. DRY CONDITIONS WITH A
WARMING TREND WILL THEN OCCUR EARLY NEXT WEEK.

&&

.DISCUSSION...UPPER LEVEL TROUGH WAS ADJACENT THE CALIFORNIA/BAJA
CALIFORNIA COASTS WITH 568 DM LOW CENTERED NEAR 29N/120W THIS
AFTERNOON. THE UPPER TROUGH WILL MOVE EWD INTO THE SWRN CONUS
TONIGHT AND REMAIN QUASI-STATIONARY INTO SAT. ABUNDANT MOISTURE WILL
MOVE INTO THE AREA...WITH TOTAL PRECIP WATER VALUES PERHAPS NEARING
1.20 INCHES BY SAT. SHOWERS WILL INCREASE IN COVERAGE EARLY THIS
EVENING...THEN NUMEROUS SHOWERS PRODUCING POTENTIALLY LOCALLY HEAVY
RAINFALL WILL OCCUR LATER TONIGHT AND CONTINUING FRI. THERE IS A
SLIGHT CHANCE OF THUNDERSTORMS FRI AFTERNOON/EVENING DUE TO WEAK
INSTABILITY WITH MUCAPE AOB 300 J/KG.

RAINFALL INTENSITY SHOULD DECREASE PERHAPS AS EARLY AS FRI
EVENING...BUT MORE LIKELY LATE FRI NIGHT AND ESPECIALLY SAT.
HOWEVER...AMPLE MOISTURE CONTINUING ACROSS THE AREA IN COMBINATION
WITH WEAK SYNOPTIC SCALE ASCENT DUE TO THE PRESENCE OF THE UPPER LOW
WILL LEAD TO WIDESPREAD SHOWER COVERAGE. A SLIGHT CHANCE OF
THUNDERSTORMS WILL CONTINUE SAT AFTERNOON DUE TO AN ENVIRONMENT OF
WEAK AOB 300 J/KG MUCAPE. THE UPPER LOW THAT IS PROGGED TO BE
CENTERED OVER THE LOWER COLORADO RIVER VALLEY MIDDAY SAT IS PROGGED
TO MOVE SWD INTO THE NRN GULF OF CALIFORNIA SAT NIGHT...THEN MOVE
SLOWLY SEWD ACROSS SONORA MEXICO SUN. THERE SHOULD BE ENOUGH
MOISTURE TO MAINTAIN A SLIGHT CHANCE OF SHOWERS FROM TUCSON EWD/SWD
SUN.

STORM TOTAL LIQUID AMOUNTS ARE FORECAST TO GENERALLY RANGE FROM 0.50
TO 1.50 INCHES IN THE VALLEYS...WITH SOME AMOUNTS IN EXCESS OF 2.00
INCHES POSSIBLE. LIQUID AMOUNTS ACROSS THE MOUNTAINS WILL GENERALLY
RANGE FROM 1.00 - 2.00 INCHES. HOWEVER...LIQUID AMOUNTS IN EXCESS OF
2 INCHES SHOULD OCCUR ACROSS SOME MOUNTAINS...PARTICULARLY FROM THE
CATALINA/RINCON MOUNTAINS NEAR TUCSON NEWD TO THE WHITE MOUNTAINS.

SNOW LEVELS FRI MORNING WILL BE AROUND 9000 FEET. SNOW LEVELS WILL
THEN LOWER TO AROUND 8000 FEET FRIDAY EVENING...AND CONTINUE TO
LOWER TO NEAR 7500 FEET BY MIDDAY SATURDAY. STORM TOTAL SNOW
ACCUMULATIONS SHOULD APPROACH OR EVEN EXCEED 2 FEET IN THE WHITE
MOUNTAINS ABOVE 7000 FEET...WITH 18-22 INCHES OF SNOWFALL ABOVE 7000
FEET FURTHER SWWD ACROSS THE PINALENO MOUNTAINS INCLUDING MOUNT
GRAHAM. STORM TOTAL SNOW ACCUMULATIONS ARE FORECAST TO RANGE BETWEEN
12-16 INCHES ACROSS THE CATALINA/RINCON MOUNTAINS ABOVE 7000 FEET.

DRY CONDITIONS WILL THEN PREVAIL SUN NIGHT-THUR. MUCH COOLER TEMPS
WILL OCCUR FRI AND SAT...WITH HIGH TEMPS ACROSS THE AREA TO AVERAGE
ABOUT 5-10 DEGS F BELOW NORMAL. A WARMING TREND WILL THEN OCCUR
SUN-THUR.

&&

.AVIATION...VALID THRU 31/00Z.
A PACIFIC LOW PRESSURE SYSTEM WILL MOVE EASTWARD INTO SOUTHEAST
ARIZONA INTO FRIDAY. THIS SYSTEM WILL BRING A SIGNIFICANT AMOUNT AND
MOISTURE RESULTING IN WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW.
THERE IS ALSO A SLIGHT CHANCE OF THUNDERSTORMS ACROSS MUCH OF THE
AREA FRIDAY AFTERNOON. CLOUD DECKS EARLY THIS EVENING WILL GENERALLY
BE AT 6-10K FT AGL...THEN LOWER TO GENERALLY 2-3K FT AGL BY FRIDAY
MORNING. HIGHER TERRAIN WILL BE OBSCURED FRIDAY IN CLOUDS AND
PRECIPITATION. SURFACE WIND WILL GENERALLY BE SELY/SLY AT 5-15 KTS
THRU THE PERIOD. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW
TONIGHT INTO SATURDAY. THE MOST SIGNIFICANT SNOWFALL WILL OCCUR
ACROSS THE HIGHEST PEAKS OF THE WHITE MOUNTAINS...MOUNT GRAHAM...AND
THE CATALINA AND RINCON MOUNTAINS NEAR TUCSON. A FEW LINGERING
SHOWERS WILL OCCUR MAINLY EAST TO SOUTH OF TUCSON SUNDAY...THEN DRY
CONDITIONS WILL PREVAIL SUNDAY NIGHT THROUGH THURSDAY.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    WINTER STORM WARNING FROM 5 AM FRIDAY TO NOON MST SATURDAY FOR
    AZZ510-511 ABOVE 7000 FEET.

    WINTER STORM WARNING FROM 11 AM FRIDAY TO NOON MST SATURDAY FOR
    AZZ514 ABOVE 7000 FEET.

&&

$$

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FRANCIS




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