Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 191012
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
310 AM MST TUE AUG 19 2014

.SYNOPSIS...AMPLE MOISTURE WILL PROVIDE SCATTERED TO NUMEROUS
THUNDERSTORMS THROUGH MIDWEEK. SOME STORMS WILL PRODUCE GUSTY WINDS
AND HEAVY RAINFALL. A VERY MODEST DRYING TREND WILL THEN OCCUR
DURING THE LATTER PART OF THE WEEK AND INTO THIS WEEKEND. HOWEVER...
ENOUGH MOISTURE WILL EXIST FOR ISOLATED TO SCATTERED THUNDERSTORMS.
BELOW NORMAL DAYTIME TEMPERATURES WILL PREVAIL THROUGH WEDNESDAY
FOLLOWED BY A GRADUAL WARMING TREND LATER THIS WEEK.

&&

.DISCUSSION...ISOLATED SHOWERS AND THUNDERSTORMS WERE OCCURRING
ACROSS ERN SECTIONS OF THE FORECAST AREA AS OF 3 AM. OUT WEST...A
FEW STORMS WERE TRYING TO DEVELOP AS DYNAMICS START TO INCREASE IN
ADVANCE OF APPROACHING UPPER LEVEL LOW....WHICH WAS CENTERED JUST
WEST OF FRISCO AND MOVING S. BY THIS EVENING...THIS LOW WILL BE
CENTERED NEAR THE LA BASIN. INCREASING UPPER DIFFLUENCE AHEAD OF
THIS FEATURE WILL COMBINE WITH A VERY MOIST ATMOSPHERE TO GENERATE
WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS ACROSS SE ARIZONA.
HEAVY RAIN IS LIKELY WITH SOME OF THE STRONGER STORMS AND WITH SOME
AREAS RECORDING PRETTY GOOD RAINFALL AMOUNTS OVER THE PAST FOUR
DAYS...FEEL THAT THE THREAT IS UP FOR FLASH FLOODING. WITH THAT
SAID I HAVE DECIDED TO HOIST A FLASH FLOOD WATCH FOR MOST OF SE
ARIZONA FROM 12 NOON UNTIL 11 PM.

SOME DRIER AIR WILL PUSH IN OVERNIGHT FROM THE WEST BEHIND THE MAIN
AREA OF SHOWERS AND THUNDERSTORMS. WITH THE UPPER LOW NEAR SAN DIEGO
AND SLIGHTLY DRIER AIR OVER THE AREA...WILL SEE LESS AREAL COVERAGE
OF STORMS ON WEDNESDAY...BUT STILL RATHER ACTIVE.

OPERATIONAL MODELS STILL HAVING ISSUES ON WHEN OR IF THE SRN CA
UPPER LOW WILL LIFT THRU THE STATE...GFS ON THU/ECMWF ON FRI...OR
SIT OFFSHORE INTO THE WEEKEND ALA THE CANADIAN. FOR NOW DIDN`T MAKE
MUCH CHANGE TO THE INHERITED FORECAST STARTING THU INTO THE WEEKEND
WHICH MAINTAINS ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS.

BELOW NORMAL HIGHS TODAY THROUGH THURSDAY THAN WARMER INTO THE
WEEKEND.

&&

.AVIATION...VALID THRU 20/12Z.
EXPECT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS DEVELOPING
THIS AFTERNOON...PERSISTING INTO THE EVENING HOURS TONIGHT. 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 THRU WEDNESDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED TO NUMEROUS THUNDERSTORMS WILL OCCUR
THROUGH WEDNESDAY AS AMPLE MOISTURE REMAINS ACROSS SOUTHEASTERN
ARIZONA. THE STRONGER THUNDERSTORMS WILL PRODUCE 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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