Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 211639
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
939 AM MST SUN SEP 21 2014

.SYNOPSIS...
LOW PRESSURE WILL MOVE FROM SOUTHERN CALIFORNIA INTO NEVADA TODAY.
THIS SYSTEM WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS TO
NORTHERN ARIZONA...THOUGH CLEARING SKIES SHOULD MOVE INTO WESTERN
ARIZONA BY THIS AFTERNOON. HIGH PRESSURE OVER THE REGION FROM MONDAY
THROUGH THURSDAY WILL DELIVER MAINLY DRY WEATHER AND WARMER DAYTIME
TEMPERATURES.

&&

.DISCUSSION...
WILL CONTINUE TO MONITOR STORM DEVELOPMENT DURING THE MORNING
HOURS AND MAKE ADJUSTMENTS TO POP FIELDS AS NECESSARY...THOUGH
CURRENT GRIDS/FORECASTS LOOK TO HANDLE THE SHORT-TERM SITUATION
PRETTY WELL AT THIS TIME. DRYING CONDITIONS LOOK TO FILL IN BEHIND
THE TROUGH PASSAGE TONIGHT AND MONDAY.

&&

.PREVIOUS DISCUSSION /230 AM MST/...
LOW PRESSURE WAS CENTERED OVER CENTRAL CALIFORNIA EARLY THIS
MORNING...ACCELERATING NORTHEASTWARD TOWARD NEVADA. AN AREA OF
WEAK UPWARD MOTION WILL REMAIN OVER NORTHERN ARIZONA RESULTING IN
THE BEST CONCENTRATION OF STORMS MAINLY NORTH OF INTERSTATE-40.
HOWEVER...STORM CONCENTRATION WILL ALSO BE HIGHER OVER THE WHITE
MOUNTAINS AREA OF FAR EAST CENTRAL ARIZONA WHERE DEEPER MOISTURE
WILL LEND ITSELF TO DECENT INSTABILITY WITH DAYTIME HEATING. THE
FLOW WILL SHIFT TO A MORE SOUTHWESTERLY DIRECTION THROUGH THE DAY
WITH GRADUAL DRYING...ESPECIALLY OVER WESTERN TO CENTRAL PORTIONS
OF ARIZONA. WE WILL UPDATE THE FORECAST AS NEEDED FOR ANY OBSERVED
DRYING.

MONDAY THROUGH THURSDAY...WARM HIGH PRESSURE BUILDS INTO THE
DESERT SOUTHWEST WITH A DRIER WESTERLY FLOW. A VERY STABLE AIR
MASS OVERHEAD WILL SHARPLY LIMIT DAYTIME CONVECTION WITH FAIR
NIGHTS EXPECTED.

FRIDAY AND SATURDAY...MODELS SHOW THAT A STORM SYSTEM FROM THE
WEST WILL LIKELY INTERACT WITH LINGERING MOISTURE OVER ARIZONA
FOR A CHANCE OF SHOWERS AND THUNDERSTORMS. AT THIS TIME...TIMING
IS THE MAIN DIFFERENCE BETWEEN THE ENSEMBLE OF MODELS. WE`LL KEEP
YOU POSTED.

&&

.AVIATION...
FOR THE 18Z PACKAGE...SCT SHRA AND TSRA WILL DEVELOP ACROSS
PORTIONS OF NO. AZ WITH THE BEST CHANCES OF STORMS NO. AND EAST
OF A LINE FROM KGCN-KFLG-KPAN-KSOW. TO THE SO. AND WEST OF THIS
LINE...DRIER AIR HAS MOVED IN WITH ISOLD CHANCES OF SHRA/TSRA.
EXPECT MOSTLY VFR CONDITIONS...WITH WDLY SCT IFR/MVFR AND ERRATIC
SFC WIND GUSTS 30 TO 40 KTS NEAR THE STRONGER TSRA. AVIATION
DISCUSSION NOT UPDATED FOR AMENDMENTS.

&&

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

&&

$$

PUBLIC.........KD/MCCOLLUM
AVIATION.......TC

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF






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