Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 011030
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
330 AM MST TUE SEP 01 2015

.SYNOPSIS...THE MOST ACTIVE AREAS FOR SHOWER AND THUNDERSTORM
ACTIVITY WILL SHIFT A BIT EASTWARD OVER THE NEXT DAY OR TWO. STORM
ACTIVITY WILL BE MOST COMMON OVER APACHE COUNTY.

A DEEPENING LOW PRESSURE SYSTEM OVER THE PACIFIC NORTHWEST WILL
ENHANCE THE THREAT OF MOISTURE MOVING IN FROM THE SOUTH LATER THIS
WEEK AND INTO THE WEEKEND. DAILY SHOWER AND THUNDERSTORM ACTIVITY
WILL CONTINUE AS A RESULT...ESPECIALLY OVER THE EASTERN HALF OF THE
STATE.

&&

.DISCUSSION...THERE IS STILL SOME WEAK CONVECTION OVER NORTHERN
COCONINO COUNTY EARLY THIS MORNING...DUE TO LINGERING FORCING FROM A
S/WV MOVING THROUGH SOUTHERN NEVADA AND INTO UTAH. WATER VAPOR
IMAGERY SHOWS SOME SUBTLE RIDGING MOVING IN FROM THE SOUTHWEST AHEAD
OF A TROPICAL S/WV SOUTHWEST OF SAN DIEGO. THIS MAY SUPPRESS THE
WESTERN ZONES TODAY...MAYBE EVEN SOME OF THE CENTRAL ZONES.

THE DRYING WE HAVE BEEN WAITING FOR HAS NOT REALLY MATERIALIZED. A
FAIRLY SIGNIFICANT WEST-MOVING OUTFLOW (EVEN SEEN IN WATER VAPOR
IMAGERY) DEVELOPED OVER PHOENIX EARLIER IN THE NIGHT...FEATURES SUCH
AS THIS WILL PREVENT THE BOUNDARY LAYER FROM DRYING. BEHIND THE LOW
SOUTHWEST OF SAN DIEGO...MORE PRONOUNCED DRYING FROM THE WEST SHOULD
DEVELOP WEDNESDAY AND MAYBE THURSDAY.

DESPITE THIS...MANY GFS MEMBERS STILL INSIST THAT THE BACKING FLOW
FROM HGHT FALLS IN THE GREAT BASIN WILL DRAW MOISTURE INTO ARIZONA
LATE IN THE WEEK AND OVER THE WEEKEND. IN ADDITION...MANY MODELS ARE
ALSO FORECASTING SOME TROPICAL MOISTURE INTRUSION OVER THE WEEKEND.

IN SUMMARY...THERE IS TOO MUCH UNCERTAINTY TO REALLY DRY THINGS OUT
FROM WEST AS WAS ORIGINALLY PLANNED. ALTHOUGH ACTIVITY WILL DECREASE
OVER THE NEXT FEW DAYS...IT CANNOT BE TOTALLY RULED OUT. THE EASTERN
ZONES MAY NEVER SEE A DECREASE AT ALL...WHEN COMPARED TO THE LAST
FEW DAYS. THESE TRENDS ARE REFLECTED IN THE LATEST POP GRIDS.

&&

.AVIATION...FOR THE 12Z PACKAGE...ISOLATED SHOWERS THIS MORNING
BECOMING SCATTERED SHOWERS AND THUNDERSTORMS AROUND NOON. STORM
COVERAGE WILL DECREASE ACROSS NORTHWESTERN ARIZONA BY AFTERNOON AS
MORE STABLE AIR MOVES IN FROM THE WEST. IFR CONDITIONS AND ERRATIC
GUSTY WINDS UP TO 40 MPH ARE FORECAST NEAR THE STRONGER STORMS.
THUNDERSTORM COVERAGE WILL DIMINISH AROUND SUNSET. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

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

&&

$$

PUBLIC...PETERSON
AVIATION...BOHLIN


FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF



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