Flash Flood Warning 8, NWS Flagstaff, AZ

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST THU AUG 09 2001

.SYNOPSIS...LOW PRESSURE OVER NEW MEXICO WILL CONTINUE TO BRING
SHOWERS AND THUNDERSTORMS TO MUCH OF NORTHERN ARIZONA TONIGHT. THE
LOW PRESSURE SYSTEM WILL BEGIN TO WEAKEN ON FRIDAY WITH HIGH
PRESSURE STRENGTHENING OVER SOUTHERN CALIFORNIA. THIS WILL ALLOW A
DRIER AND WARMER NORTHWEST FLOW TO DEVELOP ON FRIDAY AND 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...A MID TO UPPER TROUGH REMAINS OVER NEW MEXICO WITH AN
AN UPPER RIDGE CENTERED OVER NORTHERN BAJA CALIFORNIA. AS A
RESULT...A MOIST AND UNSTABLE NORTHEAST FLOW WILL CONTINUE FOR THE
NEXT 12- TO 24-HOURS. THERE WERE A FEW STRONG AND ORGANIZED
THUNDERSTORMS THIS AFTERNOON BUT MUCH OF THE AIR MASS ACROSS ARIZONA
REMAINED UNSTABLE AND UNTAPPED. FOR TONIGHT...WITH A LARGE AREA OF
THUNDERSTORMS DEVELOPING IN SOUTHERN UTAH AND FAR NORTHWEST ARIZONA
THIS AFTERNOON...EXPECT THIS AREA OF STORMS AND ASSOCIATED OUTFLOW
TO MOVE SOUTH AND SOUTHEASTWARD INTO COUNTY WARNING AREA TONIGHT FOR
PRETTY GOOD COVERAGE OF SHOWERS AND STORMS. ISOLATED SHOWERS AND STORMS
OVER THE NORTHEAST CORNER OF THE STATE. ON FRIDAY AND
SATURDAY...MODELS ARE INSISTING THAT THE UPPER RIDGE WILL SHIFT
NORTHWARD WITH A DRIER NORTH TO NORTHWEST FLOW DEVELOPING. THINK THE
NET RESULT WILL BE A DOWNTURN IN ACTIVITY INTO SATURDAY WITH A MORE
DIURNAL NATURE TO THUNDERSTORMS. PROBABLY STILL GO WITH A GENERAL
LOW END SCATTERED WORDING FOR FRIDAY AND SATURDAY OVER THE HIGHER
TERRAIN AND SOUTH AND SOUTHWEST OF THE RIM WITH ISOLATED STORMS
ELSEWHERE AS LOW-LEVEL MOISTURE WILL BE SLOW TO SCOUR OUT.

IN THE EXTENDED...EXTENDED MODELS ARE CONSISTENT IN KEEPING THE
SUBTROPICAL RIDGE AXIS LOCATED OVER THE SOUTHWEST UNITED STATES
THROUGH WELL INTO NEXT WEEK. IN ADDITION...NORTHWEST MEXICO WILL BE
IN A FAVORED LOCATION FOR THE DEVELOPMENT OF MESOSCALE CONVECTIVE
COMPLEXES WHICH SHOULD FAVOR A CONTINUED NORTHWARD PUSH OF MOISTURE
INTO ARIZONA. DAY TO DAY VARIATIONS IN THE LOCATION OF THE MID-LEVEL
CENTER OF ANTICYCLONIC CIRCULATION WILL MODULATE STORM ACTIVITY.
WILL LET THE STANDARD MONSOON FORECAST STAND THROUGH THE
EXTENDED.

MCCOLLUM

.FGZ...NONE.

AZZ004>018-037>040-091930-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 AM MST THU AUG 9 2001

...SCATTERED THUNDERSTORMS TODAY ACROSS NORTHERN ARIZONA WITH THE
POTENTIAL FOR HEAVY RAINFALL...

A NEARLY STATIONARY UPPER LEVEL WEATHER DISTURBANCE OVER NEW MEXICO
WILL CONTINUE TO PRODUCE A MOIST NORTHEAST FLOW ACROSS NORTHERN
ARIZONA TODAY. WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED.
THE MAIN THREAT FROM THESE STORMS WILL BE HEAVY RAIN...WITH
RAINFALL AMOUNTS OF 1 TO 3 INCHES POSSIBLE...AND THE
POTENTIAL FOR LOCALIZED FLASH FLOODING. FOR TODAY THE MOST INTENSE
STORMS ARE EXPECTED OVER THE LITTLE COLORADO RIVER VALLEY...THE
WHITE MOUNTAINS AND THE MOGOLLON RIM. FOR LATE THIS AFTERNOON AND
EVENING STRONGER STORMS SHOULD MOVE INTO THE AREA OF THE KAIBAB
PLATEAU...PAGE...THE GRAND CANYON AND THE COCONINO PLATEAU.