930
FXUS65 KFGZ 042136
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST SAT JUL 4 2009
SYNOPSIS
MOISTURE AND A UNSTABLE AIRMASS WILL HELP FUEL A CHANCE
OF SHOWERS AND THUNDERSTORMS THIS EVENING. A DRIER WESTERLY FLOW
WILL BEGIN TO DEVELOP BY SUNDAY WITH A DECREASE IN THE CHANCE OF
STORMS THROUGH MIDWEEK. A MOIST SOUTHERLY FLOW IS FORECAST TO RETURN
BY THE SECOND HALF OF NEXT WEEK WITH A DAY TO DAY INCREASE IN SHOWER
AND THUNDERSTORM ACTIVITY. SEASONABLE TEMPERATURES ARE EXPECTED
THROUGH THE PERIOD.
DISCUSSION
THERE IS SLIGHTLY DRIER AIR ACROSS NORTHERN ARIZONA
...THE AIRMASS WILL ALLOW FOR SCATTERED THUNDERSTORMS TO CONTINUE
INTO THE EVENING HOURS. TO THE NORTH OF THE MOGOLLON RIM THE LARGE
SCALE WESTERLY FLOW WILL HELP MOVE STORMS TO THE EAST...TO THE SOUTH
OF THE MOGOLLON RIM...YAVAPAI AND NORTHERN GILA COUNTIES...AND THE
WHITE MOUNTAINS OUTFLOW BOUNDARIES WILL CONTROL STORM MOVEMENT
PUSHING ACTIVITY TO THE SOUTH. THERE WILL BE THE POTENTIAL OF
EXCESSIVE RAINFALL AMOUNTS AND LOCALIZED FLOODING IN YAVAPAI AND
GILA COUNTIES...DUE TO A COMPONENT OF THE LARGE SCALE FLOW PUSHING
INTO THE OUTFLOW BOUNDARIES.
HIGH PRESSURE ALOFT WILL GRADUALLY TRANSITION TO THE WEST SOUTHWEST
OF ARIZONA INTO SUNDAY...AND DURING THE SAME TIME PERIOD A LOW
PRESSURE TROUGH WILL MOVE ALONG THE NORTHERN CALIFORNIA COAST. THIS
FLOW PATTERN WILL AID IN PUSHING A DRIER AND MORE STABLE AIRMASS
INTO NORTHERN ARIZONA THROUGH MIDWEEK. MODEL GUIDANCE DOES SUGGEST
AN EASTWARD SHIFT OF THE SUBTROPICAL HIGH LATER IN THE
WEEK...ALLOWING FOR THE RETURN OF A MOIST SOUTHERLY FLOW INTO
ARIZONA ALONG WITH THE INCREASE IN AFTERNOON AND EVENING
THUNDERSTORMS OVER THE HIGHER TERRAIN.
AVIATION...FOR THE 00Z PACKAGE
ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS WILL CONTINUE THROUGH THE EARLY EVENING HOURS ACROSS
NORTHERN ARIZONA. SCATTERED MVFR CONDITIONS ARE FORECAST NEAR HEAVY
SHOWERS AND THUNDERSTORMS. THUNDERSTORM AND SHOWER ACTIVITY WILL
DIMINISH AFTER SUNSET. AVIATION DISCUSSION NOT UPDATED FOR
AMENDMENTS.
FIRE WEATHER
HIGH PRESSURE CENTERED OVER SOUTHERN ARIZONA WILL
BRING MORE STABLE AIR FROM THE PACIFIC INTO ARIZONA OVER THE NEXT
FEW DAYS. THIS WILL MEAN A GRADUAL DECREASE IN THUNDERSTORM ACTIVITY
EACH DAY AS THE REMAINING LOW LEVEL MOISTURE MIXES OUT. ENOUGH
MOISTURE WILL REMAIN ACROSS NORTHERN ARIZONA TO PRODUCE ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS ON SUNDAY WITH A NOTICEABLE
DECREASE IN SHOWER ACTIVITY ON MONDAY.
TUESDAY THROUGH THURSDAY...HIGH PRESSURE IS FORECAST TO MOVE
SOUTHWEST OF ARIZONA AND A TROUGH WILL MOVE IN OFF THE WEST COAST TO
PRODUCE A DRIER WESTERLY FLOW ACROSS THE SOUTHWEST. THIS PATTERN
WILL LIKELY PRODUCE A BREAK IN THE THUNDERSTORM ACTIVITY ON TUESDAY.
THE HIGH CENTER IS EXPECTED TO MOVE EASTWARD BY THE MIDDLE OF NEXT
WEEK WHICH COULD TAP INTO THE DEEP MOISTURE OVER NORTHERN MEXICO AND
INCREASE OUR CHANCES FOR PRECIPITATION BY THE END OF THE WORK WEEK.
FGZ WATCHES/WARNINGS/ADVISORIES
NONE.
PUBLIC..................TC
AVIATION/FIRE WEATHER...BOHLIN
VISIT WEATHER.GOV/FLAGSTAFF FOR NORTHERN ARIZONA WEATHER
INFORMATION.
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