Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 251700
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1000 AM MST MON AUG 25 2014

.SYNOPSIS...
SUBTROPICAL MOISTURE WILL MOVE NORTHWARD OVER NORTHERN
ARIZONA ON MONDAY AHEAD OF AN ADVANCING LOW PRESSURE TROUGH WITH
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS.  FROM LATE MONDAY
THROUGH TUESDAY...THE PASSING TROUGH WILL BRING NUMEROUS SHOWERS AND
THUNDERSTORMS TO THE STATE. SOME STRONG THUNDERSTORMS WILL BE
POSSIBLE...ALONG WITH THE THREAT OF HEAVY RAIN. THURSDAY ONWARD...A
DRYING NORTHWEST FLOW WILL DECREASE THUNDERSTORM CHANCES.

&&

.DISCUSSION...
ABUNDANT CLOUD COVER IS AFFECTING NORTHERN ARIZONA THIS MORNING.
WE ARE EXPECTING MOISTURE TO GRADUALLY INCREASE DURING THE DAY
WHILE A TROUGH MOVING INTO THE GREAT BASIN APPROACHES FROM THE
NORTHWEST. THESE CONDITIONS WILL BRING A CHANCE OF SHOWERS BY THIS
AFTERNOON...INCREASING SUBSTANTIALLY THIS EVENING AND OVERNIGHT.
THE CURRENT FORECAST FOR TODAY IS IN GOOD SHAPE WITH NO UPDATES
ANTICIPATED. WILL CONTINUE TO MONITOR THE DEVELOPING WEATHER
SYSTEM ANTICIPATED LATE TONIGHT THROUGH TUESDAY...FOR DETAILS
PLEASE SEE BELOW DISCUSSION.

&&

.PREVIOUS DISCUSSION /340 AM MST/...
TODAY THROUGH WEDNESDAY...A DEEP TROUGH OF LOW PRESSURE WILL
APPROACH ARIZONA FROM THE NORTHWEST...THIS SYSTEM WILL PULL A
DEEP SUBTROPICAL AIRMASS NORTHWARD ALONG WITH THE HELP OF A
TROPICAL SYSTEM PASSING TO THE WEST OF BAJA. 1.5 INCH PW AIR IS
FORECAST TO MOVE NORTHWARD INTO SOUTHERN ARIZONA WITH UP TO 1.0 INCH
PW AIR AS FAR NORTH AS THE MOGOLLON RIM. THIS MOIST AIR MASS IS
FORECAST TO BE LIFTED OROGRAPHICALLY INTO THE YAVAPAI AND NORTHERN
GILA COUNTY MOUNTAINS...COCONINO PLATEAU...MOGOLLON RIM AND WHITE
MOUNTAINS. THE MOISTURE...LARGE SCALE LIFT...AND OROGRAPHIC LIFT IS
FORECAST TO COME TOGETHER LATE MONDAY NIGHT INTO TUESDAY MORNING AND
THEN PEAK TUESDAY AFTERNOON/EVENING...THEN DECREASE RAPIDLY EARLY
WEDNESDAY MORNING AS THE COLD FRONT MOVES EAST INTO NEW MEXICO. THE
BEST CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BEGIN ON EARLY
TUESDAY MORNING...WINDS ALOFT ARE FORECAST TO STRENGTHEN. THE
COMBINATION OF STRENGTHENING WINDS AND INSTABILITY WILL BRING THE
THREAT OF STRONG THUNDERSTORMS...THAT COULD POTENTIALLY PRODUCE
SEVERE HAIL...STRONG WINDS...POSSIBLE ISOLATED TORNADOES...AND A
THREAT OF LOCALIZED HEAVY RAIN. THE LOCATION OF THE HEAVY RAIN
THREAT WILL LIKELY BE ALONG THE YAVAPAI AND NORTHERN GILA COUNTY
MOUNTAINS...COCONINO PLATEAU...MOGOLLON RIM...AND WHITE
MOUNTAINS...FROM VERY MOIST OROGRAPHIC UPSLOPE FLOW AND FROM
TRAINING SHOWERS AND THUNDERSTORMS IN A UNI-DIRECTIONAL FLOW
ENVIRONMENT. WE INTRODUCED HEAVY SHOWERS AND THUNDERSTORMS IN THE
FORECAST GRIDS FROM EARLY TUESDAY AND TUESDAY NIGHT. STAY TUNED
TODAY AND TOMORROW TO THE LOCAL WEATHER FORECAST...AS THIS COULD
BE A FAIRLY WIDESPREAD WET WEATHER EVENT.

BY LATE WEDNESDAY MORNING INTO THE AFTERNOON A DRY WEST TO NORTHWEST
FLOW WILL USHER IN A RAPID TRANSITION FROM NUMEROUS SHOWERS AND
THUNDERSTORMS TO ISOLATED ACTIVITY BY THE AFTERNOON.

 THURSDAY THROUGH SATURDAY...FORECAST MODELS INDICATE A DRY
NORTHWEST FLOW WILL CONTINUE BEHIND THE WEATHER DISTURBANCE WITH
DRY CONDITIONS...AND SLIGHTLY WARMER DAYTIME TEMPERATURES.

THERE IS THE POSSIBILITY THAT ANOTHER RELATIVELY STRONG TROUGH OF
LOW PRESSURE IS FORECAST TO MOVE ACROSS THE WESTERN STATES LATE NEXT
WEEKEND WITH A A DRY AND BREEZY WEST TO NORTHWEST FLOW...MODERATE
UNCERTAINTY AT THIS TIME IS ATTACHED TO THE LATE WEEKEND STORM
SYSTEM...AS WELL AS WHETHER MOISTURE WILL INTERACT WITH THIS SYSTEM
AS IT MOVES THROUGH THE SOUTHWEST STATES.

&&

.AVIATION...
FOR THE 18Z PACKAGE...SCT SC/CU TODAY WITH BASES FROM
4-7KFT AGL...AND HIGH CLOUD COVER PERSISTING. ISOLD SHRA/TSRA
DEVELOPING MID TO LATE AFTERNOON CONTINUING THROUGH THE EVENING
HOURS. SHOWER AND THUNDERSTORM ACTIVITY INCREASING IN COVERAGE
06Z-18Z TUE...WITH AREAS MVFR/LOCAL IFR CONDITIONS IN RAIN. AVIATION
DISCUSSION NOT UPDATED FOR AMENDMENTS.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC.........MCS
AVIATION.......JJ

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF





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