Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 271607
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
905 AM MST TUE JAN 27 2015

.SYNOPSIS...A FEW LINGERING SHOWERS WILL OCCUR MAINLY NORTH OF
TUCSON INTO EARLY THIS AFTERNOON. DRY CONDITIONS WILL THEN PREVAIL
THROUGH WEDNESDAY NIGHT. A STRONGER STORM SYSTEM HOLDS THE POTENTIAL
TO BRING SIGNIFICANT VALLEY RAIN AND MOUNTAIN SNOW STARTING THURSDAY
NIGHT AND CONTINUING INTO THIS WEEKEND.

&&

.DISCUSSION...SCATTERED SHOWERS WERE MOVING NWD ACROSS SOUTH CENTRAL/
SE PINAL COUNTY AT THIS TIME. OTHER ISOLATED SHOWERS WERE ALSO
OCCURRING ACROSS THE TOHONO O`ODHAM NATION WEST OF TUCSON.
OTHERWISE...MOSTLY CLEAR SKIES WERE ONGOING NEAR THE NEW MEXICO
BORDER...AND CLOUDY SKIES PREVAILED ACROSS WRN PIMA COUNTY. A LOW
PRESSURE SYSTEM WAS CENTERED OVER SRN CALIFORNIA WITH MID-LEVEL
TROUGH AXIS EXTENDING SEWD INTO SE AZ. THE UPPER LOW WILL FILL AND
LIFT NEWD INTO THE GREAT BASIN LATER TODAY. MEANWHILE...THE MID-LEVEL
TROUGH AXIS WILL MOVE WELL NE OF THE AREA. THE BULK OF THE SHOWERS
WILL END DURING THE NEXT FEW HOURS...ALTHOUGH A FEW SHOWERS MAY YET
OCCUR INTO THIS AFTERNOON NORTH OF TUCSON. ANY PRECIP IS EXPECTED TO
END BY THIS EVENING FOLLOWED BY DRY CONDITIONS TONIGHT THRU WED
NIGHT. THE FOCUS OF ATTENTION WILL THEN TURN TOWARD A STRONGER LOW
PRESSURE SYSTEM TO DEVELOP OVER THE SWRN CONUS THUR NIGHT AND FRI.
THIS SYSTEM HAS THE POTENTIAL TO BRING SIGNIFICANT VALLEY RAIN AND
MOUNTAIN SNOW INTO THIS WEEKEND. FOR MORE INFORMATION REGARDING THIS
SYSTEM...PLEASE REFER TO THE PREVIOUS DISCUSSION SECTION BELOW.

&&

.AVIATION...VALID THRU 28/18Z.
SCATTERED -SHRA WILL OCCUR MAINLY WEST TO NORTH OF KTUS INTO EARLY
THIS AFTERNOON...WITH ANY SHOWERS TO END BY 28/00Z. OTHERWISE...
CLOUD DECKS INTO WEDNESDAY MORNING WILL GENERALLY BE AROUND
5-9K FT AGL. SURFACE WIND WILL BE LESS THAN 10 KTS THRU THE PERIOD.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A FEW SHOWERS WILL OCCUR INTO EARLY THIS AFTERNOON
MAINLY WEST TO NORTH OF TUCSON. THEREAFTER...DRY CONDITIONS WILL
PREVAIL THROUGH WEDNESDAY NIGHT. A STRONGER STORM SYSTEM WILL THEN
BRING A GOOD CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW LATE THURSDAY
INTO THIS WEEKEND. GUSTY SOUTHEAST WINDS MAY OCCUR THURSDAY
AFTERNOON AND THURSDAY NIGHT AHEAD OF THIS SYSTEM...ESPECIALLY EAST
OF TUCSON.

&&

.PREV DISCUSSION...AS THIS SYSTEM EXITS TO OUR NORTH WE WILL SEE A
COUPLE OF DAYS OF DRY WEATHER WEDNESDAY AND THURSDAY BEFORE ANOTHER
STRONGER PACIFIC SYSTEM BEGINS TO IMPACT SOUTHEAST ARIZONA LATE
THURSDAY THROUGH THE WEEKEND. MODELS ARE INDICATING THAT THIS NEXT
SYSTEM WILL BE MUCH STRONGER THAN THE ONE CURRENTLY EXITING TO OUR
NORTH. THIS SYSTEM WILL MOVE INTO CENTRAL CALIFORNIA EARLY THURSDAY
WITH THE TROUGH AXIS EXTENDING SOUTHWEST INTO THE PACIFIC WATERS
WEST OF BAJA. PLENTY OF MOISTURE WILL BEGIN STREAMING NORTHEAST
AHEAD OF THE SYSTEM OVER THE DESERT SOUTHWEST AND BY EARLY TO MIDDAY
FRIDAY THE SYSTEM WILL DEVELOP INTO A CLOSED LOW OVER SOUTHERN
NEVADA AND SOUTHERN CALIFORNIA. DEEP MOISTURE AND LIFT IS EXPECTED
TO ACCOMPANY THIS STORM AS EVIDENCED BY TIME HEIGHT SECTIONS. QPF
VALUES WITH THIS STORM ARE EXPECTED TO BE SIGNIFICANT WITH WPC`S
3-DAY QPF FORECAST VALID FROM 12Z THU THROUGH 12Z FRI SHOWING
WIDESPREAD VALUES OF 0.50-0.75 INCHES...WITH A SMALLER AREA OF
AMOUNTS RANGING 0.75-1.0 INCHES OVER MY EASTERN ZONES AS WELL AS
OVER THE HIGHER TERRAIN OF THE MOGOLLON RIM. THE DAY 4-5 FORECAST
VALID FROM 12Z FRI THRU 12Z SUNDAY SHOWS WIDESPREAD AMOUNTS OF
0.50-0.75 INCHES FOR CENTRAL AND EASTERN ZONES WITH PERHAPS 0.75-1.0
INCHES OVER THE HIGHER TERRAIN. MY QPF FORECAST FROM LATE THURSDAY
AFTERNOON THROUGH LATE FRIDAY EVENING (30 HOURS)...SHOWS QPF`S FOR
DESERT/VALLEYS OF THE CENTRAL AND EASTERN ZONES RANGING FROM AROUND
0.6-0.9 INCHES WITH MOUNTAIN LOCATIONS PERHAPS SEEING WATER
EQUIVALENT AMOUNTS RANGING FROM 1.0-1.4 INCHES. QPF`S OVER THE
WESTERN DESERTS...WEST OF TUCSON EXPECTED TO RANGE FROM AROUND
0.2-0.6 INCHES.

SNOW LEVELS ARE EXPECTED TO BOTTOM OUT AT AROUND 6000 FEET BY LATE
SATURDAY INTO EARLY SUNDAY. THE BULK OF THE PRECIPITATION WITH THIS
SYSTEM EXPECTED TO OCCUR FROM THURSDAY EVENING THROUGH MUCH OF THE
DAY FRIDAY...WITH SHOWERS DECREASING SLIGHTLY ON SATURDAY AND
ESPECIALLY BY SUNDAY AS THE TROUGH AXIS WILL EXTEND FROM NORTHERN
NEW MEXICO THROUGH CHIHUAHUA MEXICO. MY SNOW AMOUNT FORECAST FOR THE
PERIOD LATE THURSDAY THROUGH LATE FRIDAY SHOWS AMOUNTS RANGING FROM
AROUND 8 TO 10 INCHES FOR THE WHITE MOUNTAINS OF NORTHERN GREENLEE
COUNTY AND THE PINALENO`S OF SOUTH CENTRAL GRAHAM COUNTY...WITH MUCH
LESSER SNOW AMOUNTS FOR THE CATALINA`S AND MOUNTAINS RANGES FARTHER
SOUTH AND EAST. CATALINA`S AND RINCONS ONLY EXPECTED TO SEE PERHAPS
UP TO 6 INCHES. THESE NUMBERS FALL WITHIN ADVISORY CRITERIA...BUT IT
IS TOO EARLY FOR SUCH HEADLINES AT THIS TIME. WE WILL CONTINUE TO
FINE TUNE THE QPF/SNOW FORECAST BETWEEN NOW AND THE ARRIVAL OF THE
STORM...SO STAY TUNED.

FOR TUCSON...HIGH TEMPS GENERALLY 6 TO 8 DEGS ABOVE NORMAL TODAY
THROUGH THURSDAY...THEN 5 TO 7 DEGS BELOW NORMAL FRIDAY AND
SATURDAY. SLIGHTLY BELOW NORMAL HIGHS EXPECTED SUNDAY AND NEAR
NORMAL FOR MONDAY. LOW TEMPS WILL BE ABOVE NORMAL THROUGHOUT THE
FORECAST PERIOD...BUT THE WARMEST MORNINGS WILL OCCUR THURSDAY AND
FRIDAY.

&&

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

&&

$$

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

FRANCIS
PREVIOUS DISCUSSION...MOLLERE




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