Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 011648
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
948 AM MST TUE SEP 1 2015

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

&&

.UPDATE/DISCUSSION...
EXPECT LESS INTENSE STORMS OVERALL TODAY COMPARED WITH YESTERDAY
AS INSTABILITY HAS DECREASED. MOST STORMS FROM NEAR I-17/US 89
EASTWARD THIS AFTERNOON/EVENING WITH A FEW ISOLATED CELLS CAPABLE
OF VERY HEAVY RAINFALL RATES. MINOR UPDATES TO PRECIP CHANCES FOR
THIS AFTERNOON/EVENING HAVE BEEN SENT.

&&

.PREV DISCUSSION /330 AM MST/...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 18Z PACKAGE...EXPECT A ROUND OF SCATTERED TO
ISOLATED SHOWERS AND THUNERSTORMS TODAY. THE GREATEST COVERAGE IS
EXPECTED IN THE WHITE MOUNTAINS REGION...WITH DECREASING COVERAGE
WESTWARD. 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...TAYLOR/PETERSON
AVIATION...RICKEY


FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF


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