Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 192106
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST TUE AUG 19 2014

.SYNOPSIS...ABUNDANT MOISTURE COMBINED WITH AN APPROACHING UPPER LOW
WILL CONTINUE TO GENERATE NUMEROUS SHOWERS AND THUNDERSTORMS INTO
THE EVENING HOURS FROM TUCSON EASTWARD WITH LOCAL VERY HEAVY
RAINFALL.  A SLIGHTLY DRIER ATMOSPHERE AND LESS FORCING WILL ALLOW
FOR A MORE TYPICAL AMOUNT OF CONVECTION THE REMAINDER OF THE WEEK
WITH A VERY MODEST DRYING TREND INTO THIS WEEKEND.  BELOW NORMAL
DAYTIME TEMPERATURES WILL PREVAIL THROUGH THURSDAY FOLLOWED BY A
GRADUAL WARMING TREND LATER THIS WEEK.

&&

.DISCUSSION...THE UPPER LOW CONTINUES TO GRADUALLY APPROACH WITH
THE ASSOCIATED DYNAMICS HAVING MORE INFLUENCE OVER THE AREA.  THIS
WILL CONTINUE TO BE THE CASE INTO THE EVENING HOURS WITH A MOIST AND
UNSTABLE AIR MASS IN PLACE.  DRIER AIR IN THE MID LEVELS IS PUNCHING
INTO THE WESTERN PORTIONS OF THE AREA AND HAS LIMITED CONVECTION
THERE.  THE PRIMARY CONCERN WILL BE FOR THE TUCSON AREA EAST TO THE
NEW MEXICO BORDER THIS EVENING.

CONVERGENT STREAMERS HAVE DEVELOPED ON SATELLITE IMAGERY AND ON THE
DOPPLER RADAR JUST WEST OF TUCSON AND AIMED AT THE CITY WHERE
CONVECTION CONTINUES TO BLOSSOM OVER THE CITY WITH PERIODS OF HEAVY
RAIN.  PLENTY OF STANDING AND FLOWING WATER WITH AREA WASHES
RISING.  VARIOUS HI RES MODELS ALL POINT TO CONTINUED DEVELOPMENT
OVER/AROUND THE CITY THROUGH 7-8 PM THIS EVENING AND THIS WILL HAVE
TO BE WATCHED CLOSELY...ESPECIALLY WITH RESPECT TO HEAVY RAIN IN THE
CATALINAS AND RINCONS.  CURRENTLY HAVE AN URBAN AND SMALL STREAM
ADVISORY IN EFFECT FOR THE IMMEDIATE AREA.

PLENTY OF SHOWER ACTIVITY OVER COCHISE AND EASTERN PINAL COUNTIES AS
WELL WITH A FEW RURAL ROADS CLOSED DUE TO HIGH WATER.  THIS WILL
NEED TO WATCHED WELL INTO THE EVENING AS SHOWER ACTIVITY LIKELY TO
CONTINUE OVER EASTERN AREAS WELL INTO THE EVENING.

AS THE UPPER LOW CONTINUES TO APPROACH THE REGION IT WILL PUSH SOME
DRIER AIR IN OVERNIGHT FROM THE WEST BEHIND THE MAIN AREA OF SHOWERS
AND THUNDERSTORMS WHICH WILL RESULT IN A DECREASE IN THE CONVECTION
ACROSS THE REGION FROM WEST TO EAST.  AS A RESULT OF THE DRIER AIR
MOVING IN ALOFT AND LIMITED FORCING...THERE WILL BE LESS AREAL
COVERAGE OF STORMS ON WEDNESDAY...BUT THANKS TO PLENTY OF NEAR
SURFACE MOISTURE IT SHOULD REMAIN SOMEWHAT ACTIVE.  LIKELY SIMILAR
TO A TYPICAL AVERAGE MONSOON DAY WITH CONVECTION FIRING OFF THE
HIGHER TERRAIN AND DRIFTING TO THE NORTH-NORTHEAST.

BEYOND THAT THE OPERATIONAL MODELS ARE COMING IN LINE WITH THE UPPER
LOW OVER SOUTHERN CALIFORNIA...AT LEAST MORE IN LINE.  THE GFS IS
STILL THE SLOWER MODEL BUT ITS COMING AROUND TO THE OTHER SOLUTIONS.
WITH THE IDEA OF LEANING SLOWER...THE LOW WOULD LIFT NE THROUGH
CENTRAL AND/OR NORTHERN ARIZONA THURSDAY NIGHT INTO EARLY FRIDAY.
THIS COULD MAKE FOR AN INTERESTING THURSDAY AFTERNOON AND EVENING.
I TWEAKED POPS UP A BIT THAT TIME FRAME BUT THEY MAY END UP HIGHER
YET FOR THAT TIME PERIOD.  BELOW NORMAL HIGH TEMPERATURES EXPECTED
THROUGH AT LEAST THURSDAY THANKS TO THE ENHANCED CONVECTION.

DRIER AIR MOVES INTO NORTHERN AREAS FRIDAY ONWARD WITH DEEP MOISTURE
HANGING NEAR THE INTERNATIONAL BORDER AND SOUTH OF THERE AS WESTERLY
FLOW DEVELOPS OVER THE STATE.  WITH THAT THOUGHT WILL LIKELY HAVE A
DECENT DOWNTURN IN THE CONVECTION OVER THE REGION WITH THE POSSIBLE
EXCEPTION OF ALONG THE BORDER AREA.  THE RELATIVE LACK OF CONVECTION
WILL ALLOW AFTERNOON TEMPERATURES TO RETURN TO NORMAL LEVELS ACROSS
THE REGION SATURDAY ONWARD.  CERNIGLIA

&&

.AVIATION...VALID THRU 21/00Z.
EXPECT SCATTERED TO NUMEROUS SHOWERS PERSISTING INTO TONIGHT...WITH
COVERAGE LESSENING OVERNIGHT. MVFR VISIBILITIES AND WIND GUSTS OF
45-50 KTS WILL OCCUR WITH THE STRONGER TSRA. CLOUD DECKS WILL MAINLY
BE AT 6-12K FT AGL. OUTSIDE OF THUNDERSTORM OUTFLOWS...SURFACE WIND
WILL GENERALLY BE LESS THAN 10 KTS. SCATTERED THUNDERSTORMS AND
SHOWERS POSSIBLE AGAIN STARTING LATE MORNING WEDNESDAY. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
&&

.FIRE WEATHER...SCATTERED TO NUMEROUS THUNDERSTORMS WILL CONTINUE
INTO TONIGHT AND START AGAIN LATE MORNING WEDNESDAY...AS AMPLE
MOISTURE REMAINS IN PLACE ACROSS SOUTHEASTERN ARIZONA. THE STRONGER
THUNDERSTORMS WILL PRODUCE HEAVY RAINFALL LEADING TO THE POSSIBILITY
OF LOCALIZED FLOODING...AS WELL AS STRONG...GUSTY AND ERRATIC WINDS.
EXPECT SOMEWHAT LESS COVERAGE OF THUNDERSTORMS DURING THE LATTER
PART OF THE WEEK AND NEXT WEEK. HOWEVER...MOISTURE WILL BE
SUFFICIENT FOR ISOLATED TO SCATTERED MAINLY AFTERNOON AND EVENING
THUNDERSTORMS. OUTSIDE OF THE THUNDERSTORM OUTFLOWS...20-FOOT WINDS
WILL EXHIBIT NORMAL DIURNAL TRENDS AND WILL BE MOSTLY LESS THAN 15
MPH.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 FLASH FLOOD WATCH TODAY FROM 12 NOON UNTIL 11 PM FOR MOST OF SE AZ.

&&

$$

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