Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 261608
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
908 AM MST TUE AUG 26 2014

.SYNOPSIS...DEEPER MOISTURE IN PLACE ACROSS SOUTHEAST ARIZONA WILL
RESULT IN SHOWERS AND THUNDERSTORMS...SOME WITH VERY HEAVY
RAINFALL...THROUGHOUT TODAY. IMPROVING WEATHER CAN THEN BE EXPECTED
WEDNESDAY...WITH DAYTIME TEMPERATURES REBOUNDING TO SLIGHTLY ABOVE
NORMAL READINGS BY THE WEEKEND.

.DISCUSSION...THE COMBINATION OF ELEVATED ATMOSPHERIC
MOISTURE...INSTABILITY...AND AN APPROACHING MID/UPPER TROUGH WILL
LEAD TO AN ACTIVE WEATHER DAY FOR PORTIONS OF SOUTHEAST ARIZONA.
WATER VAPOR IMAGERY IS DEPICTING THE APPROACHING TROUGH NOW
DIGGING EASTWARD ACROSS SOUTHERN CALIFORNIA AND NEVADA. AHEAD OF
THIS TROUGH...SOUTH TO SOUTHWEST FLOW IS FUNNELING AN AIRMASS WITH
NEAR TO ABOVE NORMAL PRECIPITABLE WATER VALUES. A WEAK DISTURBANCE
MOVED AROUND THE BASE OF THE TROUGH AND TRIGGERED SOME
OVERNIGHT/EARLY MORNING CONVECTION OVER THE AREA. THIS FEATURE IS
NOW PROGRESSING TO THE NORTHEAST INTO NEW MEXICO AND MORNING
CONVECTION HAS WANED AREA-WIDE. THE 12Z KTUS SOUNDING INDICATES
THAT A MOIST AND GENERALLY UNSTABLE AIRMASS IS IN PLACE FOR
SOUTHEAST ARIZONA. THE AIRMASS ALSO IS NEARLY SATURATED UP THROUGH
500MB...MEANING STORMS THAT DEVELOP WILL LIKELY BE VERY EFFICIENT
RAIN PRODUCERS. ANOTHER INFLUENTIAL ASPECT OF THE SOUNDING IS
LIGHT WIND FLOW THROUGH THE BOTTOM 6KM OF THE ATMOSPHERIC COLUMN.
THIS COULD MAKE FOR SLOW MOVING STORMS...AT LEAST INITIALLY.

THERE WILL BE A DISTINCT TRANSITION AS THE TROUGH APPROACHES AND
PASSES THROUGH OVER THE NEXT 24 HOURS. CONVECTION WILL LIKELY
TRIGGER OVER AND AROUND TERRAIN INITIALLY...BEFORE INCREASING MID-
LEVEL SOUTHWESTERLY FLOW INCREASES AND BEGINS TO FOCUS CONVECTION
TO THE NORTH. THROUGHOUT THE EVENT TODAY THE BEST DYNAMICS WILL
REMAIN NORTH OF SOUTHEAST ARIZONA...WITH AN EMPHASIS ON NORTHERN
ARIZONA AND SOUTHERN UTAH.

MID/LONG RANGE MODELS ARE IN GOOD AGREEMENT THAT AFTER THE TROUGH
PROGRESSES THROUGH OVERNIGHT INTO WEDNESDAY A DRIER AND MORE
STABLE AIRMASS WILL FILTER IN AND REALLY DRY OUT OUR WEATHER
PATTERN THROUGH THE REST OF THE WEEK.


&&

.AVIATION...
A VERY MOIST AIRMASS IN PLACE ACROSS SOUTHEAST ARIZONA WILL RESULT
IN WIDESPREAD SHRA/ISOLATED -TSRA ACROSS MOST OF SOUTHEAST ARIZONA
THROUGH THIS EVENING.  EXPECT SCT-BKN 8-12KFT AGL WITH LCL MVFR
CONDS NEAR STRONGEST SHRA/TS.  SFC WINDS VARIABLE AND LESS THEN 10
KTS...EXCEPT VICINITY TSRA WHERE GUSTS TO 45 MPH ARE POSSIBLE.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DEEP MOISTURE IN PLACE ACROSS SOUTHEAST ARIZONA
WILL RESULT IN WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS...SOME
WITH VERY HEAVY RAINFALL TODAY.  A DRYING TREND WILL GET STARTED
WEDNESDAY WITH MUCH LESS CONVECTION EXPECTED AND SLIGHTLY WARMER
TEMPERATURES.  THURSDAY THROUGH THE WEEKEND...THE DRYING WILL
CONTINUE TO THE POINT THAT CONVECTION IS NOT EXPECTED AND
TEMPERATURES WILL RISE TO OR SLIGHTLY ABOVE NORMAL LEVELS.


&&

.TWC WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 8 PM MST THIS EVENING FOR AZZ502>515.

&&

$$

DISCUSSION...CANTIN
AVIATION/FIRE WEATHER...CERNIGLIA

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






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