Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 282128
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
228 PM MST TUE JUL 28 2015

.SYNOPSIS...EXPECT AN INCREASE IN THUNDERSTORMS...ESPECIALLY
WEDNESDAY AS DEEPER MOISTURE RETURNS. WE WILL THEN HAVE A DECREASING
THREAT FOR MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
INTO THE COMING WEEKEND.

&&

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A RIDGE CENTERED OVER THE
SOUTHERN PLAINS WITH A LOW PRESSURE SYSTEM OFF THE WEST COAST OF THE
SOUTHERN BAJA PENINSULA. BETWEEN THESE TWO SYSTEMS SOUTH TO
SOUTHEASTERLY FLOW WILL USHER IN ADDITIONAL MOISTURE BEGINNING TODAY
BUT CONTINUING THROUGH WEDNESDAY. A COUPLE OF DISTURBANCES ARE
EMBEDDED WITHIN THIS FLOW ALOFT OVER NORTHEAST MEXICO AND WEST
TEXAS...AS WELL AS OVER PORTIONS OF DURANGO AND SINALOA MEXICO AND
WILL EVENTUALLY ROTATE UP TOWARD SOUTHERN ARIZONA DURING THE NEXT 24
TO 36 HOURS OR SO AND SHOULD HELP TO ENHANCE ACTIVITY...ESPECIALLY
DURING THE DAY ON WEDNESDAY.

PRECIPITABLE WATER VALUES FROM VARIOUS SOURCES INDICATE THAT
READINGS CURRENTLY RANGE FROM 1.2 - 1.4 OVER EASTERN LOCALES...1.4 -
1.6 OVER CENTRAL ZONES AND 1.6 - 1.7 OVER THE FAR WESTERN DESERTS OF
PIMA COUNTY.

THE LATEST CIRA LPW IMAGE SHOWS VALUES WELL OVER 2 INCHES OVER
CENTRAL PORTIONS OF THE GULF OF CALIFORNIA. MODELS SHOW THIS
MOISTURE BEING TRANSPORTED TO THE NORTH NORTHWEST OVER EXTREME
SOUTHWESTERN ARIZONA DURING THE NEXT 24 HOURS OR SO. MEANWHILE PW`S
ARE ADVERTISED TO REMAIN AROUND THE 1.5 - 1.7 INCH RANGE FOR CENTRAL
ZONES...WITH VALUES TO THE EAST A BIT LOWER IN THE 1.3 - 1.5 INCH
RANGE. OVER THE WESTERN DESERTS AND FARTHER WEST...VALUES EXPECTED
TO INCREASE TO AROUND THE 2 INCH MARK ON WEDNESDAY.

IR AND VISIBLE SATELLITE IMAGERY SHOWS A SIGNIFICANT CUMULUS FIELD
THAT HAS DEVELOPED OVER MOSTLY SOUTHERN PORTIONS OF MY FORECAST
AREA...ESPECIALLY FROM NOGALES TO TUCSON AND WESTWARD ACROSS ALL OF
PIMA COUNTY...WITH A COUPLE OF ISOLATED CELLS NEAR AND SOUTHEAST OF
SANTA ROSA. MEANWHILE...ISOLATED SHOWERS AND THUNDERSTORMS HAVE BEEN
OCCURRING OVER PORTIONS OF COCHISE COUNTY AND INTO GRAHAM COUNTY.
EARLIER THIS AFTERNOON A STRONG STORM OVER THE CHIRICAHUA MOUNTAINS
OF EAST CENTRAL COCHISE COUNTY PRODUCED CONSIDERABLE RAIN...WITH THE
RUCKER CANYON GAUGE COLLECTING 1.85 INCHES IN THE PAST 3 HOURS.

BASED ON LATEST RUNS OF THE WRF/NAM AND GFS AS WELL AS HRRR...IT
LOOKS LIKE THE MAIN FOCUS FOR SHOWERS AND THUNDERSTORMS TODAY AND
ESPECIALLY ON WEDNESDAY WILL BE ALONG THE INTERNATIONAL BORDER AND
THE CENTRAL AND WESTERN SECTIONS OF PIMA COUNTY...WHICH INCLUDES THE
TOHONO O`ODHAM NATION. THEREFORE...LOOKING AT SCATTERED SHOWERS AND
THUNDERSTORMS...WITH NUMEROUS SHOWERS AND THUNDERSTORMS FOR THE
MOUNTAINS AS WELL AS AREAS ALONG THE INTERNATIONAL BORDER.

AS THE AFOREMENTIONED UPPER LOW OFF THE BAJA COAST CONTINUES TO MOVE
TO THE NORTH NORTHWEST ALONG THE WEST COAST...THE HIGH PRESSURE TO
OUR EAST WILL CONTINUE TO MEANDER ACROSS THE REGION THROUGH THE
REMAINDER OF THE FORECAST PERIOD...WITH A DECREASE IN ACTIVITY
THURSDAY...BUT ESPECIALLY BY FRIDAY AND THROUGH THE WEEKEND AS THE
HIGH MOVES TO A POSITION NEARLY OVERHEAD AND HIGH TEMPS ALSO
INCREASE AND REMAIN WARM THROUGH EARLY NEXT WEEK. WE COULD SEE A
SLIGHT INCREASE IN ACTIVITY EARLY NEXT WEEK AS MOISTURE INCREASES A
BIT AGAIN.

FOR TUCSON...HIGH TEMPS WILL BE 1 TO 3 DEGS BELOW NORMAL WEDNESDAY
AND THURSDAY...THEN SLIGHTLY ABOVE NORMAL FRIDAY. THEREAFTER...HIGHS
4 TO 6 DEGS ABOVE NORMAL...BUT THE WARMEST DAYS LIKELY WILL OCCUR
MONDAY AND TUESDAY OF NEXT WEEK. LOW TEMPS WILL GENERALLY RANGE FROM
3 TO 4 DEGS ABOVE NORMAL EACH MORNING.

&&

.AVIATION...VALID THRU 29/23Z.
SCT-BKN CLOUDS AT 6-10K FT AGL THRU 29/06Z. BETWEEN 29/06Z AND
29/15Z...SCT CLOUDS AT 8-14K FT AGL AND BKN-OVC CLOUDS AT 15-20K FT
AGL. AFT 29/15Z...SCT-BKN CLOUDS AT 5-9K FT AGL. ISOLD-SCT SHRA/TSRA
THRU 29/05Z...WITH SCT-NUMEROUS SHRA/TSRA DEVELOPING AGAIN AFT
29/18Z. MVFR CONDITIONS AND VRB WIND GUSTS TO 40 KTS POSSIBLE IN AND
AROUND THE STRONGER TSRA. OUTSIDE OF STORM INFLUENCES...SFC WINDS
WILL GENERALLY BE LESS THAN 12 KTS WITH A FEW HIGHER GUSTS IN THE
AFTERNOON/EARLY EVENING HOURS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...MOISTURE WILL CONTINUE TO INCREASE THIS WEEK...
RESULTING IN AN INCREASED CHANCE OF SHOWERS AND THUNDERSTORMS INTO
THURSDAY. STRONG OUTFLOW WINDS WILL BE POSSIBLE NEAR
THUNDERSTORMS...WITH WIND GUSTS BETWEEN 40 AND 45 MPH. OTHERWISE...
20-FT WINDS WILL GENERALLY BE TERRAIN DRIVEN AND LESS THAN 15
MPH...WITH SOME AFTERNOON AND EARLY EVENING BREEZINESS DUE TO THE
STRONG DAYTIME HEATING.

&&

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

&&

$$

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...ZELL

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



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