Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 021658
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1000 AM MST SAT MAY 2 2015

.SYNOPSIS...WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL FORM
ACROSS NORTHERN ARIZONA THIS WEEKEND...WITH THE BEST CHANCES
DURING THE AFTERNOON AND EVENING. AN UPPER LEVEL LOW WILL CROSS
OUR AREA MONDAY AND TUESDAY BRINGING HIGHER PRECIPITATION CHANCES
AND COOLER TEMPERATURES.
&&

.DISCUSSION...TEMPERATURES HAVE WARMED UP QUICKLY THIS MORNING,
ALREADY ABOVE SEASONAL NORMAL HIGHS AT 9 AM OVER THE MOUNTAINS.
DAYTIME HEATING COMBINED WITH COOLER MID-LEVEL TEMPERATURES FROM AN
APPROACHING SHORTWAVE SHOULD LEAD TO A BIT HIGHER COVERAGE OF SHOWER
AND THUNDERSTORM ACTIVITY THIS AFTERNOON AND EARLY EVENING...MAINLY
FROM THE MOGOLLON RIM AND WHITE MTNS NORTHWARD, THOUGH SOME ISOLATED
ACTIVITY CANT BE RULED OUT FARTHER SOUTH. MINOR UPDATE TO RAISE RAIN
CHANCES HAS BEEN SENT, REST OF FORECAST IN GOOD SHAPE - SEE
DISCUSSION BELOW.

.PREV DISCUSSION...(629 AM MST)...FORECAST SOUNDINGS INDICATE AN
APPROACHING UPPER LEVEL SHORTWAVE TROUGH WILL MAKE CONDITIONS A
LITTLE MORE MOIST IN THE LOW LEVELS AND A LITTLE COOLER ALOFT TODAY
AS COMPARED TO YESTERDAY. THE RESULTING INCREASE IN INSTABILITY WILL
CAUSE GREATER AREAL COVERAGE OF ISOLATED TO SCATTERED SHOWER AND
THUNDERSTORM ACTIVITY. THE BOUNDARY LAYER WILL STILL BE QUITE
DRY...SO MUCH OF THE RAIN THAT FALLS FROM THESE STORMS WILL
EVAPORATE BEFORE REACHING THE GROUND. THIS MEANS THE BEST CHANCE
OF MEASURABLE PRECIPITATION WILL BE OVER HIGHER TERRAIN. STRONG
OUTFLOW WINDS ARE POSSIBLE IN THE VICINITY OF SHOWERS AND
THUNDERSTORMS. SIMILAR CONDITIONS ARE EXPECTED ON SUNDAY. DAYTIME
TEMPERATURES ARE FORECAST TO BE SEVERAL DEGREES ABOVE NORMAL.

MONDAY AND TUESDAY...A LOW PRESSURE SYSTEM IS FORECAST TO CROSS
NORTHERN ARIZONA. THIS SYSTEM WILL COOL UPPER LEVEL TEMPERATURES
FURTHER...INCREASING INSTABILITY AND CAUSING GOOD CHANCES FOR
SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE REGION. THE GREATEST
RAINFALL IS EXPECTED TO FALL FROM THE MOGOLLON RIM SOUTH...NEAREST
THE LOW...WITH MANY LOCATIONS EXPERIENCING ANYWHERE FROM 0.20 TO
0.50 INCHES OF RAIN. DAYTIME TEMPERATURES ARE FORECAST TO DROP TO
NEAR NORMAL.

WEDNESDAY ONWARD...THE CHANCES FOR SHOWERS GREATLY DIMINISH ON
WEDNESDAY. HOWEVER...FORECAST SOUNDINGS INDICATE THERE MAY BE
ENOUGH INSTABILITY FOR ISOLATED SHOWER ACTIVITY. LONGER TERM
MODELS INDICATE ANOTHER LOW PRESSURE SYSTEM MAY AFFECT THE REGION
LATE NEXT WORK WEEK.
&&

.AVIATION...FOR THE 18Z PACKAGE...EXPECT SCT-BKN CLOUD BASES AOA
12KFT THROUGH THE PERIOD. TIL 02Z SUN AREAS OF HIGH BASED CONVECTION
TO DEVELOP...PRIMARILY ALONG THEN NORTH AND EAST OF THE MOGOLLON
RIM. ISOLD -SHRA/-TSRA IN THESE AREAS. HEAVIER SHOWERS MAY PRODUCE
BASES DOWN TO 5-7KFT AGL AND ERRATIC WIND GUSTS TO 40KTS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
&&

FIRE WEATHER...WARM CONDITIONS WILL CONTINUE TODAY...WITH ISOLATED
TO SCATTERED HIGH BASED CONVECTION EAST OF FLAGSTAFF. MOISTURE WILL
SLOWLY INCREASE SUNDAY AS A WEAK UPPER LOW APPROACHES THE AREA. THE
COVERAGE OF CONVECTION WILL ALSO INCREASE ON SUNDAY...WITH A FEW
DEGREES OF COOLING. DAYTIME SOUTHWEST WINDS OF 10 TO 20 MPH WINDS
ARE EXPECTED BOTH DAYS.

.MONDAY THROUGH WEDNESDAY...A WEAK LOW PRESSURE SYSTEM WILL MEANDER
THROUGH THE AREA DURING THIS PERIOD. EXPECT A COOLING TREND AND AN
INCREASED CHANCE OF SHOWERS AND HIGH-BASED THUNDERSTORMS DURING THIS
PERIOD. DESPITE THIS...MOST AREAS WILL STILL BE UNDER ONLY A LOW
POSSIBILITY OF ANY WETTING RAINFALL. WINDS WILL BE SOUTHWEST 10 TO
20 MPH EACH AFTERNOON...INCREASING TO 15 TO 25 MPH ON WEDNESDAY.
&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$

PUBLIC...JJ
AVIATION...DL
FIRE WEATHER...PETERSON


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