Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 022216
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 PM MST SAT MAY 2 2015

.SYNOPSIS...SOUTHEAST ARIZONA WILL EXPERIENCE COOLER TEMPERATURES
TOMORROW INTO NEXT WEEK. A WEAK WEATHER DISTURBANCE MOVING ACROSS THE
AREA WILL RESULT IN A SLIGHT CHANCE OF LIGHT SHOWERS AND THUNDERSTORMS
FROM TUCSON EAST THE NEXT COUPLE OF DAYS. A STRONGER PACIFIC STORM SYSTEM
WILL THEN MOVE ACROSS THE AREA MONDAY...RESULTING IN A BETTER CHANCE FOR
SHOWERS AND THUNDERSTORMS ACROSS THE MAJORITY OF THE AREA MONDAY INTO
TUESDAY.

&&

.DISCUSSION...THE UPPER WEATHER PATTERN IS DEFINED BY A RIDGE OF HIGH
PRESSURE ACROSS NEW MEXICO/WEST TEXAS...A TROUGH OF LOW PRESSURE
DEVELOPING IN THE EASTERN PACIFIC...AND A WEAKER SHORTWAVE ON THE
EASTERN PERIPHERY OF THIS TROUGH IN THE NORTHERN BAJA. IT IS THIS
FEATURE THAT IS BEGINING TO IMPACT THE WEATHER ACROSS SOUTHEAST ARIZONA
THIS AFTERNOON.

THE LATEST VISIBLE AND WATER VAPOR IMAGERY INDICATES THAT SHOWERS AND
THUNDERSTORMS ARE DEVELOPING ALONG AND AHEAD OF THIS FEATURE EXTENDING
FROM DOUGLASS...TO GREEN VALLEY TO THE CENTRAL DIAHANN ATOM NATION/WEST
OF THREE POINTS/. THE 12Z KTWC UPPER AIR SOUNDING INDICATED AN INCREASE
IN MID-LEVEL MOISTURE WITH 0.58 INCHES OF PRECIPITABLE WATER.
HOWEVER...MODEST AMOUNTS OF DRY AIR WERE STILL PRESENT IN THE LOWER
LAYERS. THIS DRIER AIR IN THE LOWER LEVELS WILL KEEP POPS/RAINFALL
AMOUNTS FAIRLY LOW IN THE VALLEYS. THE HIGH BASED NATURE OF THE STORMS
AND THE PRESENCE OF DRY AIR IN THE LOWER LEVELS WILL INCREASE THE RISK
THAT DOWNDRAFTS MAY RESULT IN GUSTY AND ERRATIC WINDS. THIS WILL CREATE
THE POTENTIAL FOR LOCALIZED BLOWING DUST ISSUES.

THIS WEAK SHORTWAVE WILL EJECT NORTHEAST THROUGH THE FORECAST AREA
SUNDAY/SUNDAY NIGHT AS THE MAIN UPPER TROUGH THEN MOVES INTO SOUTHERN
CALIFORNIA. THE SOUTHERLY FLOW AHEAD OF THIS FEATURE WILL IMPORT DEEPER
MOISTURE INTO THE STATE AT THE SAME TIME THE UPPER DIFLUENCE INTENSIFIES
ACROSS SOUTH-CENTRAL ARIZONA. THE BEST DYNAMICS SHIFT INTO CENTRAL AND
NORTHERN ARIZONA MONDAY AFTERNOON. THE BEST CHANCE FOR SHOWERS AND
THUNDERSTORMS ACROSS SOUTHEAST ARIZONA WILL BE EARLY MONDAY MORNING
INTO MONDAY EVENING. PRECIPITATION AMOUNTS WILL BE SOMEWHAT LOW WITH THIS
EVENT /A QUARTER TO THIRD INCH WITH ISOLATED LOCATIONS UP TO THREE
QUARTERS OF AN INCH IN THE HIGHER TERRAIN/. THIS SYSTEM FINALLY MOVES OUT
OF THE STATE TUESDAY WITH DECREASING POPS THROUGH THE DAY.

MEDIUM RANGE MODELS ARE ALL IN GOOD AGREEMENT WITH AN AMPLIFIED RIDGE
DEVELOPING IN THE EASTERN PACIFIC. I AM CONFIDENT THAT A DEEP TROUGH WILL
DEVELOP ALONG THE WEST COAST THE SECOND HALF OF THE WORK WEEK...BUT NOT
CONFIDENT THAT THIS WILL RESULT IN ANY PRECIPITATION FOR OUR AREA.
THIS PATTERN WILL LIKELY ONLY RESULT IN STRONGER WINDS.

&&

.AVIATION...VALID THRU 04/06Z. ISOLATED TO SCATTERED -TSRA/-SHRA
WILL OCCUR EAST OF A LINE FROM KOLS TO KCGZ TIL 03/03Z...POSSIBLY
PERSISTING OVERNIGHT IN THE WHITE MOUNTAINS NE OF KSAD. -SHRA/-TSRA
WILL LIMITED TO AREAS NE OF KTUS SUNDAY AFTN. -SHRA/TSRA WILL HAVE
HIGH BASES 8-12 KFT ABOVE VALLEY FLOORS AND MAY BE ACCOMPANIED BY
WIND GUSTS TO 40 KTS AND BLDU. OTHERWISE...SURFACE WINDS THROUGH
SUNSET AND AGAIN SUNDAY AFTERNOON WILL BE SWLY/WLY AT 10-18 KTS WITH
GUSTS TO 25 KTS... DIMINISHING OVERNIGHT. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT GUSTY WEST AND SOUTHWEST AFTERNOON WINDS THIS
WEEKEND ALONG WITH ISOLATED TO SCATTERED MAINLY AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS FROM TUCSON EASTWARD. SHOWERS AND
STORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS BUT CHANCES FOR
RECEIVING MORE THAN A TENTH OF AN INCH OF RAINFALL ARE LOW. THE
CHANCE FOR WETTER STORMS SHOULD INCREASE MONDAY AS A WEAK LOW
PRESSURE SYSTEM APPROACHES FROM THE WEST BRINGING HIGHER HUMIDITIES
AND COOLER TEMPERATURES. A CHANCE OF SHOWERS AND THUNDERSTORMS
CONTINUES TUESDAY INTO WEDNESDAY NORTHEAST OF TUCSON. DRY CONDITIONS
WILL THEN PREVAIL THURSDAY AND FRIDAY ALONG WITH AN UPTICK IN
AFTERNOON WINDS AS A MORE SIGNIFICANT WEATHER SYSTEM TAKES SHAPE
ACROSS THE GREAT BASIN AREA TO OUR NORTH.

&&

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

&&

$$

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