Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 260940
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 AM MST WED AUG 26 2015

.SYNOPSIS...EXPECT SCATTERED THUNDERSTORMS THROUGH THURSDAY.
ISOLATED TO SCATTERED THUNDERSTORMS WILL THEN PREVAIL MAINLY FROM
TUCSON EAST AND SOUTH FRIDAY INTO EARLY NEXT WEEK. ABOVE NORMAL
DAYTIME TEMPERATURES WILL ALSO OCCUR LATER THIS WEEK AND THIS
WEEKEND.

&&

.DISCUSSION...WATER VAPOR IMAGERY...26/00Z UPPER-AIR PLOTS AND
RECENT MODEL DATA ALL INDICATE THAT THE UPPER RIDGE IS CENTERED OVER
EASTERN ARIZONA AND MUCH OF NEW MEXICO. IR SATELLITE IMAGERY SHOWS A
LARGE AREA OF MID AND UPPER LEVEL CLOUDINESS THAT COVERS THE
SOUTHWESTERN QUADRANT OF THE NATION...WITH THE MOST EXTENSIVE CLOUDS
OVER UTAH...NE ARIZONA...WRN COLORADO AND NEW MEXICO...WITH
SCATTERED TO BROKEN MID LEVEL CLOUDS OVER CENTRAL AND EASTERN
PORTIONS OF MY FORECAST AREA. RADAR MOSAIC SHOWS SCATTERED SHOWERS
AND THUNDERSTORMS CONTINUING TO LIFT TO THE NORTH NORTHEAST ACROSS
NORTHEAST ARIZONA AND EXTENDING INTO WEST CENTRAL NEW MEXICO AND AS
FAR SOUTH AS SOUTHWESTERN NEW MEXICO.

IT WAS AN ACTIVE DAY YESTERDAY AFTERNOON AND EVENING AND THE 26/00Z
KTWC SOUNDING BEARS THIS OUT...WITH A PW OF 1.77 INCHES...A LIFTED
INDEX OF MINUS 6 AND CAPE OF AROUND 3000 J/KG. IT WILL BE CURIOUS TO
SEE WHAT THE 26/12Z KTWC SOUNDING REVEALS THIS MORNING. AIRMASS IS
STILL QUITE JUICY...WITH THE 0528Z SATELLITE DERIVED BLENDED TOTAL
PW IMAGERY SHOWING VALUES AROUND CENTRAL AND EASTERN PIMA COUNTY AS
WELL AS MUCH OF PINAL COUNTY IN THE 1.8-2.0 INCH RANGE. THE 0645Z
UNIV OF AZ GPS PW VALUE FOR TUCSON WAS AROUND 1.5 INCHES. WITH
ABUNDANT MOISTURE IN PLACE AND WITH SUFFICIENT INSTABILITY (MODELS
SHOWING LIFTED INDICES RANGING FROM AROUND MINUS 4 TO 6 THIS
AFTERNOON)...IT SHOULD BE A FAIRLY ACTIVE DAY WITH SCATTERED
THUNDERSTORMS ACROSS JUST ABOUT ALL OF THE FORECAST AREA THIS
AFTERNOON AND EVENING.

THE U OF A WRF/NAM & GFS BOTH SUGGEST THAT STORMS WILL POP OVER
CENTRAL AREAS TODAY AROUND MID AFTERNOON FROM AROUND NOGALES TO
TUCSON AND LIFT NORTH TO NORTHEAST...WITH LESSER ACTIVITY OVER BOTH
THE FAR WESTERN AND EASTERN LOCALES OF MY CWA. MOS POP NUMBERS
SUPPORT THIS AS WELL WITH THE MODEL OF CHOICE BEING THE NAM...WHILE
THE GFS CONTINUES TO DOWNPLAY THE THREAT. FOR EXAMPLE MOS POP VALUES
TODAY FOR TUCSON ARE 55% FROM NAM AND 23% FROM THE GFS. 26/00Z MOS
NUMBERS FROM THE EURO DID NOT COME IN TONIGHT...SO NO ADDITIONAL
LIGHT SHED FROM THAT MODEL. HOWEVER...JUST LOOKING AT MOISTURE
FIELDS...QPF AND GRIDDED POP FIELDS FROM THE EURO ALSO SUGGEST A
SIGNIFICANT THREAT FOR SHOWERS AND THUNDERSTORMS AGAIN TODAY. THAT
SAID...I GENERALLY IGNORED THE GFS MOS POP VALUES AND LEANED HEAVILY
TOWARD NAM.

BY THURSDAY THE RIDGE WILL SHIFT TO A POSITION THAT ORIENTS THE HIGH
GENERALLY WEST TO EAST ACROSS NORTHERN MEXICO...GIVING US A WEST TO
SOUTHWEST FLOW ALOFT. MOISTURE SHOULD DECREASE A BIT WITH MODELS
SHOWING PW`S RANGING FROM 1.3-1.6 INCHES. SO LOW END SCATTERED
ACTIVITY FOR MOST VALLEY LOCATIONS AND A BIT HIGHER FOR MOUNTAINS.

FOR FRIDAY THE RIDGE SHOULD BE NEARLY OVERHEAD FOR A WARMING OF MID
AND UPPER LEVELS AND LESSER MOISTURE TO WORK WITH...SO A SUPPRESSION
OF ACTIVITY. THAT SAID...ONLY LOOKING AT ISOLATED TO SCATTERED
STORMS MAINLY BETWEEN TUCSON AND THE NEW MEXICO BORDER. THIS
SCENARIO WILL GENERALLY CONTINUE THROUGH THE REMAINDER OF THE
FORECAST PERIOD...WHICH IS NEXT TUESDAY.

FOR TUCSON...HIGHS NEAR NORMAL TODAY...THEN ABOVE NORMAL THROUGH THE
REMAINDER OF THE FORECAST PERIOD...ALTHOUGH THE WARMEST DAYS WILL
OCCUR FRIDAY THROUGH THE WEEKEND WITH HIGHS AROUND 4 TO 6 DEGS ABOVE
NORMAL.

&&

.AVIATION...VALID THRU 27/12Z.
SCT-BKN LAYERED CLOUDS ABOVE 8 TO 12K FT. ISO TO SCT SHRA/TSRA WILL
AGAIN BE POSSIBLE NEAR MOST TERMINALS AFTER 26/22Z. BRIEF MVFR
CONDITIONS AND GUSTS TO 40-45 KTS WILL BE POSSIBLE IN AND AROUND
STRONGER STORMS. SHRA/TSRA ACTIVITY WILL DIMINISH AFTER 26/03Z.
OUTSIDE OF TSRA INFLUENCE...WINDS WILL GENERALLY BE UNDER 12 KTS
AND FOLLOW NORMAL DIURNAL TRENDS. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED THUNDERSTORMS WILL PREVAIL THROUGH
THURSDAY. SLIGHTLY DRIER CONDITIONS WILL THEN PRODUCE ISOLATED TO
SCATTERED THUNDERSTORMS FRIDAY INTO EARLY NEXT WEEK...WITH AN
EMPHASIS ON AREAS FROM TUCSON SOUTH AND EAST. A WARMING TREND WILL
OCCUR INTO SATURDAY WITH ABOVE NORMAL DAYTIME TEMPERATURES
CONTINUING EARLY NEXT WEEK.

&&

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

&&

$$

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...HUMPHREYS

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



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