Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 011554
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
854 AM MST SUN MAR 1 2015

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM STRENGTHENING 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 TODAY AND TONIGHT...THEN
BECOMING WIDESPREAD MONDAY TO GO ALONG WITH COOLER TEMPERATURES.
PRECIPITATION CHANCES WILL LESSEN MIDWEEK WITH DRY CONDITIONS AND
WARMER TEMPERATURES BY THE END OF THE WEEK.

&&

.DISCUSSION...THE UPPER LOW IS CURRENTLY SPINNING NEAR THE CENTRAL
CALIFORNIA COAST AND GRADUALLY MOVING TO THE SOUTH. A WELL
ESTABLISHED PLUME OF MOISTURE CAN BE SEEN ON IR IMAGERY EXTENDING
FROM WELL OFF THE CALIFORNIA COAST INTO NRN BAJA/SRN CALIFORNIA AND
THEN EASTWARD INTO THE LOWER COLORADO RIVER VALLEY AND THE NORTHERN
HALF OF THE STATE. MEANWHILE...MOST OF SOUTHEAST ARIZONA FROM TUCSON
EASTWARD IS UNDER MOSTLY CLEAR SKIES WITH THE BULK OF THE CLOUDINESS
TO THE WEST OF WEST OF TUCSON AND ACROSS FAR NORTHERN PORTIONS OF
THE FORECAST AREA. AS THE UPPER LOW DIGS TO THE SOUTH AND THE
MOISTURE PLUME BECOME MORE NORTH TO SOUTH ORIENTED...MOST OF THE
SHOWERS WILL REMAIN TO THE NORTH AND WEST OF THE FORECAST AREA
TODAY. THUS...HAVE MADE SOME ADJUSTMENTS TO THE FORECAST FOR TODAY
TO FURTHER REDUCE CLOUD COVERAGE AND PRECIPITATION CHANCES FROM
TUCSON EASTWARD INCLUDING OVER THE HIGHER TERRAIN. WINDS WILL BE
BREEZY THIS AFTERNOON AS WELL...BUT NOT QUITE AS STRONG AS WHAT
OCCURRED YESTERDAY. REMAINDER OF THE FORECAST REMAINS
UNCHANGED...SEE PREVIOUS DISCUSSION BELOW FOR ADDITIONAL
INFORMATION.

&&

.AVIATION...VALID THRU 02/18Z.
SCT-BKN CLOUDS 5-7 KFT AGL WITH SCT-BKN LYRS ABV.  HIGHER LEVEL
CLOUDS BECOMING BKN-OVC AFT 02/03Z.  ISOLD -SHRA MNLY W AND N KTUS
WITH MTN TOPS OBSCD.  WINDS S 6-12 KTS INCREASING TO SW 10-20 KTS
AFT 01/16Z THEN EASING TO 8-13 KTS AFT 02/03Z.  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...WATER VAPOR IMAGERY SHOWS THE UPPER LOW SPINNING
JUST OFFSHORE OF THE SOUTH CENTRAL CALIFORNIA COAST THIS MORNING. IR
SATELLITE IMAGERY SHOWS EXTENSIVE CLOUDINESS ASSOCIATED WITH THIS
SYSTEM SPREADING TO THE NORTHEAST ACROSS EXTREME SOUTHERN
CALIFORNIA...AND MUCH OF ARIZONA...AS WELL AS AREAS FARTHER TO THE
NORTHEAST INCLUDING PARTS OF UTAH...COLORADO AND NORTHWEST NEW
MEXICO. CLOSER TO HOME...SKIES ACROSS MY FORECAST AREA STILL MOSTLY
CLEAR WITH THE EXCEPTION OF THE NORTHERN FRINGES OF MY FORECAST
AREA. RADAR MOSAIC CONTINUES TO DETECT SHOWERS OVER NORTH CENTRAL
ARIZONA AND MOVING TO THE NORTHEAST BETWEEN PRESCOTT...FLAGSTAFF AND
TUBA CITY.

THE AIRMASS CONTINUES TO MOISTEN WITH YESTERDAY EVENINGS KTWC
SOUNDING SHOWING A PRECIPITABLE WATER VALUE OF 0.80 INCHES...WHICH
WAS NEARLY DOUBLE FROM 24 HOURS EARLIER. DEWPOINT TEMPERATURES
CURRENTLY IN THE 40S...AND THESE READINGS ARE GENERALLY 3 TO 7 DEGS
WARMER/WETTER THAN 24 HOURS AGO. THAT SAID...WE SHOULD GRADUALLY SEE
CONDITIONS DETERIORATE THROUGHOUT THE DAY WITH THE BEST THREAT FOR
PRECIPITATION OVER THE NORTHERN PORTIONS OF MY FORECAST AREA TOWARD
THE YUMA AND PHOENIX AREAS...AS WELL AS MOUNTAIN TOP LOCATIONS.

BY LATE TONIGHT AND EARLY MONDAY THE TROUGH AXIS WILL BECOME
ORIENTED FROM NORTH TO SOUTH ACROSS NEVADA AND INTO SOUTHERN
CALIFORNIA AS OPPOSED TO ITS CURRENT SETUP...WHICH IS GENERALLY EAST
NORTHEAST TO WEST SOUTHWEST ACROSS SOUTHERN NEVADA ACROSS SOUTH
CENTRAL CALIFORNIA AND THE ADJACENT COASTAL WATERS.

AS THE SYSTEM PIVOTS THROUGH EARLY MONDAY...MOISTURE WILL BE
TRANSPORTED NORTHEAST INTO PARTS OF SOUTHERN CALIFORNIA AND WESTERN
AND NORTHWESTERN ARIZONA...WITH ASSOCIATED CONVECTION LINING UP
AHEAD OF THE TROUGH AXIS. SO...FOR TODAY EXPECT TO SEE A FAIRLY
STEEP GRADIENT OF BOTH MOISTURE AND PRECIP CHANCES WITH ONLY
ISOLATED TO LOW END SCATTERED ACTIVITY OVER THE MOUNTAINS OF EXTREME
SOUTHEAST ARIZONA TO ISOLATED TO SCATTERED ACTIVITY TOWARDS AJO AND
NUMEROUS SHOWERS OVER THE WHITE MOUNTAINS OF NORTHERN GREENLEE
COUNTY.

FOR THE PAST SEVERAL DAYS THE MODELS HAVE GRADUALLY BEEN SLOWING
THIS SYSTEM DOWN AND THIS MORNING IS NO DIFFERENT. MODELS SUGGEST
THAT THE BEST TIMING FOR THE BULK OF THE SHOWERS TO MOVE THROUGH MY
FORECAST AREA WILL BE DURING THE LATE AFTERNOON HOURS MONDAY AND
EXTENDING INTO THE EVENING HOURS MONDAY. AT THAT TIME EXPECTING TO
SEE NUMEROUS SHOWERS ALONG WITH THE POTENTIAL FOR ISOLATED
THUNDERSTORMS ACROSS MOST OF THE AREA...WITH CATEGORICAL POPS FOR
THE MOUNTAINS.

IN ADDITION TO THE MODELS SLOWLY THE SYSTEM DOWN...A STRONG UPPER
LEVEL JET IS EXPECTED TO STREAK ACROSS WEST CENTRAL AND NORTHEAST
ARIZONA...WITH THE BEST FORCING FOR HEAVY PRECIPITATION EXPECTED TO
OCCUR ACROSS NORTH CENTRAL ARIZONA ON MONDAY. FOR MY AREA...MODEL
QPF`S HAVE DECREASED...SO NOW LOOKING AT GENERALLY A THIRD TO A HALF
INCH OF LIQUID PRECIP ACROSS DESERTS AND VALLEYS WITH ISOLATED
AMOUNTS OF A HALF TO THREE QUARTERS OF AN INCH TOWARD THE NORTH.

SNOW AMOUNTS NOT EXPECTED TO BE AS HIGH AS PREVIOUSLY THOUGHT. THE
FORECAST IS NOW INDICATING THE BEST THREAT FOR SNOW TO OCCUR OVER
THE WHITE MOUNTAINS OF NORTHERN GREENLEE COUNTY...WITH PERHAPS 8 TO
NEAR 12 INCHES OF SNOW DURING THE ENTIRE DURATION OF THE STORM...
WHICH IS THROUGH THE DAY ON TUESDAY. THIS RANGE OF SNOW AMOUNTS
FALLS WITHIN THE MIDDLE TO HIGH END OF ADVISORY CRITERIA. THE
PINALENO MOUNTAINS OF SOUTH CENTRAL GRAHAM COUNTY...WHICH INCLUDES
MT. GRAHAM...AS WELL AS THE SANTA CATALINA MOUNTAINS OF EASTERN PIMA
COUNTY ARE ONLY EXPECTED TO SEE PERHAPS 6 TO 10 INCHES OF
SNOW...WHICH FALLS WITHIN THE LOW TO MIDDLE RANGE OF AN ADVISORY.
THAT SAID...AFTER COORDINATION WITH SURROUNDING OFFICES HAVE DECIDED
TO HOLD OFF ON ISSUING ANY WINTER WEATHER HEADLINES AT THIS TIME...
GIVEN THE WAY THE MODELS HAVE CONTINUALLY BACKED OFF ON THE
INTENSITY OF THIS STORM (AT LEAST FOR MY FORECAST AREA). THE BOTTOM
LINE IS TO STAY TUNED AND VISIT OUR WEB PAGE FREQUENTLY SINCE A
WINTER WEATHER HEADLINE FOR THE MOUNTAINS TO THE NORTHEAST OF TUCSON
AS WELL AS EAST CENTRAL ARIZONA MAY BE REQUIRED DURING THE NEXT 12
TO 24 HOURS.

THE MODELS KICK THE INITIAL SYSTEM TO THE NORTHEAST LATE
MONDAY/EARLY TUESDAY IN A MUCH WEAKENED STATE. MEANWHILE...A
SECONDARY SYSTEM WILL SWING ACROSS ARIZONA AND BAJA THROUGH LATE
WEDNESDAY...BUT MODELS SHOW THIS WEAK UPPER LOW LINGERING ACROSS
SOUTHERN ARIZONA/NORTHERN MEXICO THROUGH LATE IN THE WEEK...ALTHOUGH
ANY MOISTURE ASSOCIATED WITH THIS SYSTEM SHOULD REMAIN TO THE EAST
AND SOUTHEAST OF ARIZONA...SO DRY WEATHER IS EXPECTED AFTER
WEDNESDAY.

FOR TUCSON...HIGH TEMPERATURES ARE EXPECTED TO BE SLIGHTLY ABOVE
NORMAL TODAY...THEN SEVERAL DEGREES BELOW NORMAL MONDAY THROUGH
THURSDAY...ALTHOUGH THE COOLEST DAYS WILL OCCUR TUESDAY AND
WEDNESDAY WHEN HIGHS WILL BE AROUND 7 TO 9 DEGS BELOW NORMAL. NEAR
NORMAL HIGHS EXPECTED FRIDAY AND A FEW DEGS ABOVE NORMAL FOR
SATURDAY. LOW TEMPS AROUND 10 TO 12 DEGS ABOVE NORMAL MONDAY
MORNING...THEN NEAR NORMAL TUESDAY AND 2 TO 4 DEGS BELOW NORMAL
WEDNESDAY AND THURSDAY. THEREAFTER...LOWS NEAR TO SLIGHTLY ABOVE
NORMAL.

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

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

DISCUSSION...GL
PREV DISCUSSION...MOLLERE
AVIATION/FIRE WEATHER...CERNIGLIA








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