Severe Thunderstorm Warning 96, NWS Flagstaff, AZ

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
940 AM MST THU SEP 13 2001

.SYNOPSIS...AN AREA OF LOW PRESSURE OVER NORTHERN CALIFORNIA AND
HIGH PRESSURE OVER MEXICO WILL CONTINUE TO PRODUCE A MOIST
SOUTHERLY FLOW ACROSS ARIZONA TODAY. LOOK FOR AN INCREASE IN SHOWERS
AND THUNDERSTORMS THIS AFTERNOON...MORE NUMEROUS ALONG AND
SOUTHEAST OF A LINE FROM CANYON DE CHELLY NATIONAL MONUMENT TO
SEDONA. A FEW THUNDERSTORMS COULD PRODUCE LOCALLY HEAVY RAIN AND
RAPID RUN OFF. THE MOIST AND UNSTABLE FLOW WILL CONTINUE THROUGH THE
WEEKEND...AND INTO THE EARLY OF NEXT WEEK. BY MID WEEK A WESTERLY
FLOW ALOFT WILL BRING DRIER WEATHER TO NORTHERN ARIZONA.

.DISCUSSION...LAPSE RATES AROUND 7.0 TO 7.5 DEGREE C/KM BETWEEN 700
TO 500 MB OVER NORTHWEST ARIZONA TRANSITIONING TO 5.5 DEGREE C/KM
OVER THE WHITE MOUNTAINS THIS MORNING. PRECIP WATER IS THE LEAST
OVER THE NORTHWEST PER WATER VAPOR AND AROUND .75 INCHES AT
FLAGSTAFF... INCREASING TO AROUND AN INCH OVER THE WHITE MOUNTAINS.
SHEAR VECTOR IS THE WEAKEST OVER THE WHITES AND STRONGEST OVER THE
KAIBAB PLATEAU. THERE WILL BE THE POSSIBILITY TODAY FOR ISOLATED
STRONG STORMS TO THE NORTHWEST OF FLAGSTAFF IN THE BETTER
INSTABILITY AND SHEAR. ALONG AND SOUTH OF A LINE FROM WINDOW ROCK TO
PAYSON LOCALLY HEAVY RAIN CONTRIBUTED TO HIGH PRECIP WATER...SLOW
MOVING STORMS AND WEAK LARGE SCALE ASCENT...LAPSE RATES CLOSE TO
MOIST ADIABATIC THIS AFTERNOON...SO NOT EXPECTING STRONG STORMS IN
THIS AREA. CHANCES OF PRECIP TODAY LOOK GOOD...WILL UPDATE ZONES TO
ADD WORDING IN THE ZONES FOR LOCALLY HEAVY FROM WINDOW ROCK INTO THE
EASTERN MOGOLLON RIM...WHITE MOUNTAIN AND NORTHERN GILA COUNTY
ZONES.

.FGZ...NONE.

AZZ004>018-037>040-131930-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1015 AM MST THU SEP 13 2001

...SCATTERED THUNDERSTORMS OVER NORTHERN ARIZONA TODAY...
...A FEW STORMS WILL PRODUCE LOCALLY HEAVY RAIN WHICH COULD PRODUCE
   RAPID RUNOFF INTO SOME OF THE DRY WASHES...

AN AREA OF LOW PRESSURE OVER NORTHERN CALIFORNIA AND HIGH PRESSURE
OVER MEXICO WILL CONTINUE TO PRODUCE A MOIST SOUTHERLY FLOW ACROSS
ARIZONA TODAY. LOOK FOR AN INCREASE IN SHOWERS AND THUNDERSTORMS
THIS AFTERNOON...MORE NUMEROUS ALONG AND SOUTHEAST OF A LINE FROM
CANYON DE CHELLY NATIONAL MONUMENT TO SEDONA. A FEW THUNDERSTORMS
COULD PRODUCE LOCALLY HEAVY RAIN...ON THE ORDER OF ONE TO THREE
INCHES IN A SHORT PERIOD OF TIME...ALONG WITH RAPID RUNOFF INTO
NORMALLY DRY WASHES AND SLOT CANYONS. EXPECT GUSTY WINDS BETWEEN 20
TO 40 MPH FROM SOME OF THE THUNDERSTORMS AS WELL.

AZZ004>018-037>040-141930-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1105 AM MST THU SEP 13 2001

...FLASH FLOOD WATCH THROUGH THIS EVENING ALONG AND SOUTH OF A LINE
   FROM WINDOW ROCK TO SELIGMAN...
...SOME THUNDERSTORM WILL PRODUCE LOCALLY HEAVY RAIN WHICH COULD
    PRODUCE RAPID RUNOFF INTO SOME OF THE DRY WASHES...
...A FEW THUNDERSTORMS WITH LARGE HAIL AND GUSTY WINDS...

HIGH PRESSURE CIRCULATION JUST SOUTHWEST OF THE BIG BEND REGION IN
TEXAS WILL CONTINUE TO PRODUCE A MOIST SOUTHERLY FLOW ACROSS ARIZONA
TODAY. LOOK FOR AN INCREASE IN SHOWERS AND THUNDERSTORMS BY LATE
MORNING...BECOMING MORE NUMEROUS DURING THE AFTERNOON. THE MAIN AREA
OF CONCERN FOR HEAVY RAIN RUNS ALONG AND SOUTH OF A LINE FROM
WINDOW ROCK TO FLAGSTAFF TO SELIGMAN. IN THIS AREA...SOME
THUNDERSTORMS WILL PRODUCE LOCALLY HEAVY RAIN...ON THE ORDER OF TWO
TO THREE INCHES IN A SHORT PERIOD OF TIME...ALONG WITH RAPID RUNOFF
INTO NORMALLY DRY WASHES. THUNDERSTORMS NORTH OF THE WINDOW ROCK TO
SELIGMAN LINE HAVE THE POTENTIAL TO PRODUCE RAINFALL AMOUNTS OF 1 TO
2 INCHES. SLOT CANYONS WILL ESPECIALLY BE PRONE TO FLOODING IF THE
CONDITIONS ARE RIGHT. EXPECT A FEW THUNDERSTORMS WITH LARGE HAIL AND
GUSTY WINDS BETWEEN 20 TO 40 MPH FROM SOME OF THE THUNDERSTORMS AS
WELL.