Dust Storm in Arizona, September 6, 2002

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST FRI SEP 6 2002

.SYNOPSIS...HIGH PRESSURE TO THE EAST AND A TROUGH ALONG THE WEST
COAST WILL CONTINUE TO PULL MOISTURE ACROSS SOUTHERN ARIZONA INTO
THE MIDDLE OF NEXT WEEK. THERE WILL BE THE CHANCE OF SHOWERS AND
THUNDERSTORMS THROUGH WEDNESDAY OF NEXT WEEK...WITH THE BEST
PRECIPITATION CHANCES OVER THE UPCOMING WEEKEND.

.DISCUSSION...KEMX RADAR SHOWING THUNDERSTORM DEVELOPMENT TAKING
PLACE OVER THE EASTERN TWO-THIRDS OF THE CWA...WITH THE STRONGEST
DEVELOPMENT TO THE WEST/NORTHWEST OF TUCSON IN DEEPER MOISTURE AXIS.
WATER VAPOR AND GOES PW IMAGERY INDICATE THE BEST MOISTURE FROM
TUCSON WEST WITH PW VALUES BETWEEN 1.2 AND 1.5 INCHES. SOMEWHAT
DRIER AIR RESIDES OVER THE EASTERN HALF OF THE CWA WITH PW VALUES
BETWEEN 0.70 AND ONE INCH. A LARGE AREA OF DEEP MOISTURE LIES TO OUR
SOUTH/SOUTHWEST (THE REMNANTS OF HERNAN). AS THE WEST COAST TROUGH
DIGS SOUTHWARD OVER THE NEXT 24 HOURS...SOUTHWEST FLOW OUT AHEAD OF
THIS SYSTEM PICKS UP THE DEEPER MOISTURE TO OUR SOUTH AND BRINGS IT
UP ACROSS SOUTHERN ARIZONA.

TROFINESS THEN EXPECTED TO HANG OVER THE WEST COAST INTO THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE CURRENTLY CENTERED OVER NEW MEXICO
SHIFTS EAST INTO THE TEXAS PANHANDLE. THIS STILL KEEPS THE DOOR OPEN
FOR MOISTURE TO MOVE ACROSS SOUTHERN ARIZONA FROM THE SOUTH AND
SOUTHEAST. MODEL RH CROSS SECTIONS INDICATE DEEP MOISTURE OVER THE
REGION THROUGH MONDAY THEN SOMEWHAT LESS MOISTURE TUESDAY AND
WEDNESDAY. THEREFORE...HAVE USED SCATTERED WORDING THROUGH SUNDAY
NIGHT (EXCEPT FAR WESTERN PIMA COUNTY) THEN CHANCE WORDING MONDAY
THROUGH WEDNESDAY. TEMPS WILL BE TRICKY NEXT COUPLE OF DAYS
DEPENDING UPON AMOUNT OF CLOUD COVER HANGING AROUND DURING THE
OVERNIGHT AND MORNING HOURS. MODEL GUIDANCE INDICATES BROKEN TO
OVERCAST SKIES INTO SUNDAY...WHICH WOULD HOLD DOWN AFTERNOON HIGHS
AND BOOST OVERNIGHT LOWS. FWC AND AVN GUIDANCE NUMBERS SHOW A BIG
VARIANCE FOR DAYTIME HIGHS AND HAVE LEANED TOWARDS FWC NUMBERS. WILL
GO WITH MOSTLY CLOUDY WORDING TONIGHT THROUGH SATURDAY NIGHT...
HOWEVER FEEL WE WILL CLEAR OUT SOME DURING THE OVERNIGHT AND EARLY
MORNING HOURS...WHICH WILL ALLOW FOR DECENT HEATING EARLY IN THE
DAY.

LATE IN THE EXTENDED (THURSDAY/FRIDAY)...ZONAL FLOW BEGINS TO TAKE
PLACE ACROSS THE REGION...WITH ANOTHER SYSTEM MOVING INTO THE
PACIFIC NORTHWEST. THIS WOULD LEAD TO ADDITION DRYING AND HAVE OPTED
FOR PARTLY CLOUDY WORDING OVER THE EASTERN HALF OF THE CWA AND
MOSTLY CLEAR WORDING OVER THE WESTERN HALF OF THE CWA.
ZELL

.TWC...NONE.

AZZ019-029>035-070700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1145 AM MST FRI SEP 6 2002

.SYNOPSIS...VERY SIMILAR TO YESTERDAY. MOISTURE HAS INCREASED ACROSS
WESTERN PORTIONS OF SOUTHEAST ARIZONA AND DECREASED OVER EASTERN
PORTIONS OF THE AREA. PROBABILITIES FOR PRECIPITATION GREATER THAN 1
INCH AND SEVERE THUNDERSTORMS BOTH REMAIN BELOW CLIMATOLOGY.

.DISCUSSION...SIMILAR SITUATION FOR SOUTHEAST ARIZONA TODAY AS
COMPARED TO YESTERDAY. KTUS 12Z SOUNDING SHOWS A LITTLE DRIER
PROFILE (WITH PW VALUES OF 1.25 INCHES) AND RELATIVELY DRY LOWER
LEVELS. SURFACE DEWPOINTS ARE IN THE 50S OVER THE EASTERN HALF OF
THE CWA AND IN THE 60S OVER WESTERN HALF. WATER VAPOR AND GOES PW
IMAGERY SHOW BEST MOISTURE FROM ABOUT TUCSON WEST...WITH SOME DRYING
NOTED OVER COCHISE...GRAHAM AND GREENLEE COUNTIES.

ALTHOUGH MOISTURE IS DECENT...NOT MUCH IN THE WAY OF FORCING OR
DYNAMICS TO GET THINGS ROLLING THIS AFTERNOON. THEREFORE...WILL HAVE
TO RELY ON DAYTIME HEATING AND TOPOGRAPHY. EXPECT THE BEST CHANCES
FOR STORMS THIS AFTERNOON FROM TUCSON WEST. THE STORMS SHOULD BE
RATHER HIGH BASED...AS HAS BEEN THE CASE IN THE PREVIOUS COUPLE OF
DAYS. THE CHANCE FOR SHOWERS AND STORMS WILL CONTINUE OVERNIGHT...AS
BETTER MOISTURE MOVES INTO THE AREA FROM THE WEST AND MINOR IMPULSES
IN THE FLOW MOVE THROUGH WITH THE REMNANTS OF HERNAN. STEERING FLOW
WILL BE TO THE NORTH-NORTHEAST AT 10 TO 15 MPH.

AZZ019-029>035-070700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1145 AM MST FRI SEP 6 2002

.SYNOPSIS...VERY SIMILAR TO YESTERDAY. MOISTURE HAS INCREASED ACROSS
WESTERN PORTIONS OF SOUTHEAST ARIZONA AND DECREASED OVER EASTERN
PORTIONS OF THE AREA. PROBABILITIES FOR PRECIPITATION GREATER THAN 1
INCH AND SEVERE THUNDERSTORMS BOTH REMAIN BELOW CLIMATOLOGY.

.DISCUSSION...SIMILAR SITUATION FOR SOUTHEAST ARIZONA TODAY AS
COMPARED TO YESTERDAY. KTUS 12Z SOUNDING SHOWS A LITTLE DRIER
PROFILE (WITH PW VALUES OF 1.25 INCHES) AND RELATIVELY DRY LOWER
LEVELS. SURFACE DEWPOINTS ARE IN THE 50S OVER THE EASTERN HALF OF
THE CWA AND IN THE 60S OVER WESTERN HALF. WATER VAPOR AND GOES PW
IMAGERY SHOW BEST MOISTURE FROM ABOUT TUCSON WEST...WITH SOME DRYING
NOTED OVER COCHISE...GRAHAM AND GREENLEE COUNTIES.

ALTHOUGH MOISTURE IS DECENT...NOT MUCH IN THE WAY OF FORCING OR
DYNAMICS TO GET THINGS ROLLING THIS AFTERNOON. THEREFORE...WILL HAVE
TO RELY ON DAYTIME HEATING AND TOPOGRAPHY. EXPECT THE BEST CHANCES
FOR STORMS THIS AFTERNOON FROM TUCSON WEST. THE STORMS SHOULD BE
RATHER HIGH BASED...AS HAS BEEN THE CASE IN THE PREVIOUS COUPLE OF
DAYS. THE CHANCE FOR SHOWERS AND STORMS WILL CONTINUE OVERNIGHT...AS
BETTER MOISTURE MOVES INTO THE AREA FROM THE WEST AND MINOR IMPULSES
IN THE FLOW MOVE THROUGH WITH THE REMNANTS OF HERNAN. STEERING FLOW
WILL BE TO THE NORTH-NORTHEAST AT 10 TO 15 MPH.