Funnel Cloud in Arizona, August 10, 2001

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST FRI AUG 10 2001

.SYNOPSIS...A MOIST NORTHERLY FLOW WILL CONTINUE TO PRODUCE SHOWERS
AND THUNDERSTORMS OVER NORTHERN ARIZONA TONIGHT. THE LOW PRESSURE
SYSTEM OVER NEW MEXICO WILL DISSIPATE OVERNIGHT WITH HIGH PRESSURE
BUILDING OVER SOUTHERN CALIFORNIA AND WESTERN ARIZONA. THIS WILL ALLOW A
SOMEWHAT DRIER AND WARMER NORTHWEST FLOW TO DEVELOP ON SATURDAY.
HIGH PRESSURE WILL GRADUALLY SHIFT TO THE FOUR CORNERS AREA BY EARLY
NEXT WEEK WITH ENOUGH MOISTURE FOR A CONTINUING CHANCE OF SHOWERS
AND THUNDERSTORMS.

.DISCUSSION...UPPER TROUGH OVER NEW MEXICO WILL ESSENTIALLY
DISSIPATE OVERNIGHT WITH THE UPPER RIDGE OVER SOUTHERN CALIFORNIA
BEGINNING TO DOMINATE THE FLOW PATTERN. THE RIDGE WILL GRADUALLY
SHIFT TO THE FOUR CORNERS AREA BY SUNDAY. IN ANY CASE...A GENERAL
NORTHERLY FLOW SHOULD REMAIN THROUGH SATURDAY WITH TRAJECTORIES A
LITTLE MORE NORTHWESTERLY. THIS WILL RESULT IN SOME DRYING OVER THE
NORTHERN PORTIONS OF THE COUNTY WARNING AREA (CWA) ON SATURDAY.
HOWEVER...MOISTURE WILL REMAIN AMPLE OVER SOUTHERN PORTIONS OF THE CWA.
BY SUNDAY...AS RIDGE SHIFTS TO THE FOUR CORNERS...THE FLOW WILL TURN
MORE FROM THE SOUTHEAST WITH MODELS PROMISING THAT THE MOISTURE WILL
SHIFT TO THE NORTH. FOR TONIGHT...THINK THERE WILL BE ANOTHER ROUND
OF NOCTURNAL STORMS BUT WILL BE MORE FOCUSED OVER THE EASTERN HALF
OF THE LITTLE COLORADO RIVER VALLEY...THE EASTERN MOGOLLON
RIM...WHITE MOUNTAINS AND NORTHERN GILA COUNTY. THE AIR MASS IS
APPARENTLY VERY UNSTABLE ACROSS THIS AREA AND A FAIRLY SIGNIFICANT
AREA OF LOW INERTIAL STABILITY IN THE UPPER LEVELS WILL REMAIN INTO
THE NIGHT. DEEP MOISTURE REMAINS OVER PORTIONS OF YAVAPAI AND
COCONINO COUNTIES AND ANY STORMS THAT FORM WILL PRODUCE HEAVY RAIN.
FOR SATURDAY...WITH SOME DRYING OVER THE NORTH...WOULD EXPECT A MORE
DIURNAL TREND TO CONVECTION AND SOMEWHAT LESS ACTIVITY (ALTHOUGH IT
REMAINS MOIST AND MID LEVEL LAPSE RATES REMAIN FAVORABLE). OVER
CENTRAL AND SOUTHERN PORTIONS OF THE CWA EXPECT SCATTERED TO
NUMEROUS STORMS WITH DEEP MOISTURE REMAINING OVER THE AREA. FOR
SUNDAY MOISTURE NORTHWARD WITH SOME INCREASE IN ACTIVITY. DAYTIME
TEMPERATURES WILL BE WARMER THE NEXT TWO DAYS AS HIGH PRESSURE
BUILDS.

IN THE EXTENDED...SUBTROPICAL RIDGE AXIS REMAINS ENTRENCHED OVER THE
SOUTHWEST UNITED STATES WITH MOIST AIR FROM MEXICO CONTINUING TO
MOVE INTO ARIZONA. AS A RESULT...WILL CONTINUE THE CHANCE OF SHOWERS
AND THUNDERSTORMS THROUGH THE EXTENDED.

MCCOLLUM

.FGZ...FLASH FLOOD WATCH UNTIL 800 PM MST FOR SOUTHWEST COCONINO
       COUNTY AND ALL OF YAVAPAI COUNTY.