Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 010323
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
822 PM MST MON AUG 31 2015

.SYNOPSIS...STORM ACTIVITY WILL DECREASE AND GENERALLY SHIFT TO THE
EAST ON TUESDAY AND WEDNESDAY...WITH THE GREATEST CHANCES OF
THUNDERSTORMS OVER THE HIGH TERRAIN OF EASTERN ARIZONA. INCREASING
TROPICAL MOISTURE MAY LEAD TO BETTER CHANCES FOR SHOWERS AND
THUNDERSTORMS LATE IN THE WORK WEEK AND INTO THE WEEKEND.

&&

.DISCUSSION...CONVECTION HAS DIMINISHED SIGNIFICANTLY THIS EVENING
OVER MOST OF THE CWA. THERE IS STILL ENOUGH INSTABILITY ALOFT FOR
WIDELY SCATTERED SHOWERS AND A FEW THUNDERSTORMS TO CONTINUE FOR THE
NEXT COUPLE HOURS...WITH ACTIVITY GENERALLY LIMITED TO THE AREA
SOUTH OF A KGCN-KRQE LINE. HAVE KEPT POPS HIGHEST NEAR THE SOUTHERN
BORDER OF THE CWA WHERE ONGOING CONVECTION TO THE SOUTH MAY EXCITE
FURTHER DEVELOPMENT LATER TONIGHT.

STILL ON TRACK FOR SOME DRYING FROM THE WEST TUESDAY AND
WEDNESDAY...AND A RETURN OF MOISTURE LATE IN THE WEEK. HAVE RAISED
POPS A BIT MORE FOR THURSDAY AND FRIDAY...WITH GREATER CONFIDENCE IN
THE RETURN OF STORM ACTIVITY AS PER THE ENSEMBLE MODEL SOLUTIONS.

&&

.PREV DISCUSSION /359 PM MST/...IT HAS BEEN A CONVECTIVELY ACTIVE
DAY ACROSS MOST NORTHERN ARIZONA. SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS DEVELOPED ACROSS THE REGION BY LATE MORNING. SEVERAL
STORMS PRODUCED VERY HEAVY RAINFALL AND THERE WAS ENOUGH
ENVIRONMENTAL SHEAR FOR A FEW ROTATING SUPERCELLS.

MOST MODEL GUIDANCE SUGGESTS SHOWER AND THUNDERSTORM ACTIVITY WILL
LARGELY DIMINISH THIS EVENING. THIS MAKES SENSE GIVEN THAT MOST
OF NORTHERN ARIZONA HAS ALREADY EXPERIENCED CONVECTIVE ACTIVITY.
THE EXCEPTION COULD BE IN SOUTHERN YAVAPAI COUNTY, BUT THERE
DOESN`T APPEAR TO BE ANY MESOSCALE MECHANISM IN PLACE AT THE
MOMENT TO GET ACTIVITY GOING THERE.

FOR TUESDAY AND WEDNESDAY...SHOWER AND THUNDERSTORM ACTIVITY IS
EXPECTED TO DECREASE AS THE ATMOSPHERE DRIES A BIT...MOSTLY ACROSS
THE WESTERN PORTIONS OF NORTHERN ARIZONA. SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED IN THE WHITE MOUNTAINS REGION WITH
ISOLATED OR NO ACTIVITY ELSEWHERE.

LONG RANGE GUIDANCE SUGGESTS ANOTHER SURGE OF MOISTURE WILL MOVE
INTO NORTHERN ARIZONA THURSDAY NIGHT INTO FRIDAY. SOUTHERLY WINDS
WILL INCREASE DURING THIS TIME PERIOD AS THE PRESSURE GRADIENT
STRENGTHENS BETWEEN A HIGH ACROSS EASTERN MEXICO/SOUTHERN TEXAS
AND A PACIFIC NORTHWEST TROUGH. THE GFS CONTINUES TO BE MORE
AGGRESSIVE THAN THE ECMWF WITH REGARDS TO THE AMOUNT OF MOISTURE
RETURN, SO TRENDS WILL HAVE TO BE MONITORED TO SEE WHICH SOLUTION
IS MORE LIKELY. STORMS THAT DO DEVELOP FRIDAY AFTERNOON MAY HAVE
MODEST SHEAR VALUES AND AT LEAST LIMITED CAPE TO WORK WITH, SO
SOME STRONG STORMS CANNOT BE RULED OUT.

AS WE HEAD INTO THE WEEKEND, BOTH THE GFS AND ECMWF ARE IN AGREEMENT
THAT A DRY WESTERLY FLOW WILL SPREAD ACROSS THE REGION GREATLY
REDUCING THE CHANCE FOR PRECIPITATION. THE BEST CHANCES FOR
AFTERNOON SHOWERS AND THUNDERSTORMS LOOK TO BE MOSTLY CONFINED TO
EASTERN ARIZONA SATURDAY AND SUNDAY.

&&

.AVIATION...FOR THE 06Z PACKAGE...ISOLD -TSRA WILL CONTINUE
OVERNIGHT...WITH MVFR CONDITIONS AND GUSTY WINDS WITH THE STRONGER
STORMS. ISOLD TO SCT -TSRA WILL DEVELOP OVER THE HIGHER TERRAIN AFT
17Z ON TUESDAY...WITH STORM MOST NUMEROUS SOUTHEAST OF A KPAN-KRQE
LINE. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

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

&&

$$

PUBLIC...BAK/RR
AVIATION...BAK

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF



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