Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 281003
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
303 AM MST WED JAN 28 2015

.SYNOPSIS...DRY CONDITIONS WITH WELL ABOVE NORMAL DAYTIME
TEMPERATURES THROUGH THURSDAY. VALLEY RAIN AND MOUNTAIN SNOW WILL
THEN OCCUR BEGINNING THURSDAY NIGHT AND CONTINUING THROUGH SATURDAY
AS A STORM SYSTEM MOVES ACROSS THE AREA. EXPECT MUCH COOLER DAYTIME
TEMPERATURES WITH THIS SYSTEM. DRY CONDITIONS WILL RETURN EARLY NEXT
WEEK ALONG WITH A WARMING TREND.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 28/00Z UPPER-AIR PLOTS SHOW
RIDGING MOVING BY TO OUR EAST AS A PACIFIC STORM SYSTEM APPROACHES
THE WEST COAST. WE WILL BE DRY THROUGH MUCH OF THURSDAY WITH SOME
HIGH CLOUDINESS MOVING BY FROM TIME TO TIME. THE MAIN STORY WITH
THIS FORECAST PACKAGE WITH BE THE MAJOR STORM SYSTEM THAT WILL
PRODUCE CONSIDERABLE PRECIPITATION AMOUNTS AS IT MOVES ACROSS THE
DESERT SOUTHWEST.

MODELS INDICATE THAT THIS SYSTEM WILL BE MOVING INTO THE WEST COAST
LATE THURSDAY WITH ABUNDANT MOISTURE OUT AHEAD OF THE TROUGH AXIS
MAKING ITS WAY INTO ARIZONA DURING THE DAY ON THURSDAY. ISOLATED
SHOWERS WILL BEGIN TO DEVELOP THURSDAY AFTERNOON...MAINLY OVER THE
HIGHER TERRAIN EAST OF TUCSON. BY THURSDAY EVENING THE LOW WILL
BEGIN TO DEVELOP INTO A CLOSED LOW OVER THE GREAT BASIN...WITH THE
ASSOCIATED TROUGH AXIS EXTENDING SOUTH THROUGH SOUTHERN CALIFORNIA
AND JUST WEST OF THE BAJA PENINSULA. DEEP MOISTURE WILL ALREADY BE
OVER MUCH OF THE DESERT SOUTHWEST BY THAT TIME...INCLUDING MUCH OF
ARIZONA...PARTS OF NEW MEXICO...AS WELL AS PARTS OF UTAH AND NEVADA.
PW`S ARE PROGGED TO INCREASE TO MORE THAN AN INCH EARLY FRIDAY AND
EVEN AROUND 1.25 INCHES ACROSS THE FAR WESTERN DESERTS OF SOUTHWEST
ARIZONA.

QPF AMOUNTS WITH THIS SYSTEM ARE EXPECTED TO BE LARGE WITH WPC`S DAY
3 FORECAST VALID FROM 12Z FRI THRU 12Z SAT SHOWING A LARGE SWATH OF
AMOUNTS IN EXCESS OF 0.75 INCHES COVERING MOST OF MY FORECAST
AREA...WITH HIGHER AMOUNTS OVER THE MOUNTAIN RANGES. LESSER AMOUNTS
OUT WEST NEAR AJO...BUT STILL BETWEEN 0.25 AND 0.50 INCHES IN THIS
24 HOUR PERIOD. OF COURSE QPF AMOUNTS WILL END UP BEING EVEN LARGER
THAN THIS GIVEN THAT THIS STORM WILL IMPACT SOUTHEAST ARIZONA FOR
ABOUT 48 HOURS (EARLY THURSDAY EVENING THROUGH LATE SATURDAY
AFTERNOON).

AMOUNTS FOR DESERT AND VALLEY LOCATIONS COULD RANGE FROM AROUND 1.25
TO 1.50 INCHES BY THE TIME ALL IS SAID AND DONE. AS A RESULT...SNOW
AMOUNTS WILL ALSO BE CONSIDERABLE. AT THIS TIME THE BEST THREAT FOR
HEAVY SNOW WILL OCCUR OVER THE WHITE MOUNTAINS OF NORTHERN GREENLEE
COUNTY OVER EAST CENTRAL ARIZONA. NEXT IN LINE WILL BE THE PINALENO
MOUNTAINS (MT. GRAHAM) OF SOUTH CENTRAL GRAHAM COUNTY AND THE SANTA
CATALINA MOUNTAINS (MT. LEMMON) AND RINCON MOUNTAINS.

SNOWFALL AMOUNTS DURING THE ENTIRE 48 HOUR STORM TOTAL PERIOD WILL
LIKELY EXCEED 24 INCHES FOR THE WHITE MOUNTAINS...20 TO 24 INCHES
FOR MT. GRAHAM IN THE PINALENO MOUNTAINS AND 12 TO 18 INCHES FOR MT.
LEMMON IN THE SANTA CATALINA MOUNTAINS. THERE IS STILL SOME
UNCERTAINTY REGARDING STORM TOTALS FOR THE CHIRICAHUA MOUNTAINS AS
WELL AS THE REMAINING MOUNTAIN RANGES ACROSS SOUTHEAST ARIZONA NEAR
THE BORDER WITH MEXICO. FOR NOW WILL ISSUE A WINTER STORM WATCH FROM
EARLY FRIDAY MORNING THROUGH MIDDAY SATURDAY FOR THE ELEVATIONS
ABOVE 7000 FEET FOR GRAHAM AND GREENLEE COUNTIES AND THE SANTA
CATALINA MOUNTAINS AND RINCON MOUNTAINS OF EASTERN PIMA COUNTY. AS
MODELS SHED MORE LIGHT ON THIS APPROACHING SYSTEM THIS WATCH MAY BE
EXTENDED TO COVER MORE TERRITORY AND/OR BE UPGRADED IN THE NEXT DAY
OR SO.

THIS SYSTEM WILL FINALLY EXIT THE REGION LATE SATURDAY/EARLY SUNDAY
WITH RIDGING BUILDING IN BEHIND THE SYSTEM FOR WARMING TEMPERATURES
AND A RETURN TO DRY WEATHER. BEGINNING MONDAY...WEAK DISTURBANCES
WILL BRUSH BY TO OUR NORTH...RESULTING IN INTERMITTENT CLOUDINESS...
BUT WE SHOULD REMAIN DRY THROUGH NEXT TUESDAY.

FOR TUCSON...HIGH TEMPERATURES GENERALLY AROUND 10 DEGS ABOVE NORMAL
TODAY AND THURSDAY...THEN 5 TO 7 DEGS BELOW NORMAL FOR FRIDAY AND
SATURDAY. THEREAFTER...HIGHS WILL HOVER A COUPLE OF DEGREES EITHER
SIDE OF NORMAL. LOWS WILL RANGE FROM 10 TO 12 DEGS ABOVE NORMAL
THURSDAY AND FRIDAY MORNINGS...THEN 6 TO 8 DEGS ABOVE NORMAL FOR
SATURDAY. THEREAFTER...LOWS 1 TO 3 DEGS ABOVE NORMAL.

&&

.AVIATION...VALID THRU 29/12Z.
HIGH CLOUDS WILL BE ON THE INCREASE THROUGH THE PERIOD AND SHOULD
SLOWLY LOWER AS THE UPPER LEVEL TROUGH OFF THE BAJA COAST NEARS THE
FORECAST AREA. THERE IS SOME LOW/MID RESIDUAL MOISTURE IN PLACE THAT
COULD PRODUCE SOME CU DURING THE AFTERNOON HOURS. OTHERWISE...LIGHT
WINDS EXPECTED THROUGH THE PERIOD. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...BENIGN DAY AHEAD AS THE AREA REMAINS BETWEEN TWO
SYSTEMS. TOMORROW HIGH PRESSURE WILL BEGIN TO SETTLE INTO THE SOUTH
PLAINS OF TEXAS. THIS WILL TIGHTEN THE PRESSURE GRADIENT OUT EAST
WHICH WILL ELEVATE WINDS SOME EAST OF TUCSON...ESPECIALLY ACROSS THE
SAN SIMON VALLEY AND GILA RIVER VALLEY. THEN TOMORROW EVENING THE
SYSTEM CURRENTLY OFF THE BAJA COAST WILL PUSH MOISTURE INTO THE AREA
RESULTING IN A BEGINNING OF SHOWER ACTIVITY FOR THE AREA. THIS
SYSTEM WILL USHER IN DEEP MOISTURE FRIDAY MORNING INTO SATURDAY SO
EXPECT WETTING RAINS ACROSS MOST LOCATIONS...WITH SNOW ACROSS THE
HIGHER ELEVATIONS. THE SHOWER ACTIVITY WILL DIMINISH DURING THE
OVERNIGHT SATURDAY. MAX TEMPERATURES WILL DECREASE COMPARED TO LAST
SEVERAL DAYS ON FRIDAY AND GOING INTO THE WEEKEND. HOWEVER...MIN
TEMPERATURES WILL LIKELY REMAIN ABOUT THE SAME UNTIL SUNDAY ONCE
THINGS CLEAR OUT.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FROM LATE
      THURSDAY NIGHT THROUGH SATURDAY MORNING FOR AZZ510-511-514
      ABOVE 7000 FEET.

&&

$$

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PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...MEADOWS





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