Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 161631
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 PM MST TUE DEC 16 2014

.SYNOPSIS...
EXPECT CONSIDERABLE CLOUDINESS TODAY IN ADVANCE OF AN APPROACHING
STORM. THIS STORM SYSTEM WILL MOVE INTO NORTHERN ARIZONA LATE THIS
EVENING AND EXIT THURSDAY AFTERNOON BRINGING GOOD CHANCES FOR RAIN
AND SNOW...WITH ACCUMULATING SNOW ABOVE ABOUT 5500 FEET. DRY
WEATHER RETURNS FOR FRIDAY.
&&

.DISCUSSION...CURRENT FORECAST FOR THE TODAY PERIOD...MINOR
ADJUSTMENT FOR CLOUD COVER HAVE BEEN MADE. A FAIRLY GOOD BREAK IN
CLOUD COVER BETWEEN SYSTEMS...EASTERN AZ ONE SYSTEM AND THE SOUTHERN
CAL/WEST OF BAJA SECOND SYSTEM. ACTIVE AREA OF TSTORMS OFF OF BAJA
IN AN AREA OF COLD AIR ALOFT. GFS TRACKS THIS AREA OF INSTABILITY
EASTWARD...WEAKENING RAPIDLY AS COLD POOL SHEARS EASTWARD IN
WESTERLY FLOW.

WE WILL BE LOOKING AT LATEST MODEL TRENDS IN QPF (MODEL
PRECIPITATION OUTPUT) FOR THE WEDNESDAY AND THURSDAY TIME PERIOD.
LAST NIGHTS OPERATIONAL AND ENSEMBLE MODEL OUTPUT CUT BACK ON QPF
MODERATELY... SOME OF THE SHORTWAVE ENERGY WITH THIS SYSTEM IS
NOW FORECAST TO TRACK ACROSS SOUTHERN AZ AND NORTHERN MEXICO.
CURRENTLY THE GREATEST IMPACTS WITH THIS SYSTEM WILL OCCUR AROUND
RUSH HOUR 4-7 PM ON WEDNESDAY FOR THE FLAGSTAFF/PRESCOTT/GRAND
CANYON AREAS AND THEN LATER FARTHER EAST INTO THE EASTERN RIM AND
WHITES.
&&

.PREVIOUS DISCUSSION /350 AM MST/...CONSIDERABLE MID-TO-UPPER LEVEL
CLOUDINESS IS IN PLACE ACROSS NORTHERN ARIZONA EARLY THIS
MORNING...AND WILL LIKELY PERSIST FOR MUCH OF THE DAY. AS WE HEAD
INTO LATE THIS EVENING AND OVERNIGHT...THE FIRST IN A SERIES OF
SHORTWAVE TROUGHS WILL MOVE ACROSS THE NORTHLAND. CONDITIONS WILL
TURN COLDER AND A GENERAL UNSETTLED PERIOD WITH CHANCES FOR RAIN AND
SNOW SHOWERS WILL CONTINUE THROUGH THURSDAY AFTERNOON. THE BEST
CHANCES FOR WIDESPREAD SHOWERS LOOKS TO BE FROM MID-DAY WEDNESDAY
THROUGH EARLY THURSDAY FOR MOST LOCATIONS. SNOW LEVELS WILL BE
BETWEEN 5000 AND 6000 FEET DURING THE BULK OF THE EVENT.

MODEL QPF AMOUNTS GENERALLY RANGE FROM 0.15"-0.40" IN THE
OPERATIONAL GFS & ECMWF WITH NAM VALUES HIGHER AS TYPICALLY SEEN
THIS TIME OF YEAR. HAVE REDUCED SNOWFALL TOTALS SLIGHTLY IN THE
FORECAST...AND WE`LL SEE HOW MODEL AND OBSERVED TRENDS DEVELOP
TODAY.

FRIDAY IS LOOKING DRY AND WARMER...AND EXTENDED RANGE MODEL HAVE
ALSO TRENDED DRIER FOR THE COMING WEEKEND.
&&

.AVIATION...
FOR THE 18Z PACKAGE...THROUGH 06Z WEDS PRIMARILY VFR CONDITIONS ARE
EXPECTED WITH SFC WINDS S-SW 5-15 KT. LOCAL TERRAIN OBSCURATIONS IN
CLOUDS POSSIBLE ALONG THE MOGOLLON RIM. THERE IS A SLIGHT CHANCE OF
SHOWER WEST OF A KPGA-KPRC LINE BTWN 00Z AND 06Z.

FROM 06Z WEDS-18Z WEDS...AN UPPER LEVEL WEATHER DISTURBANCE WILL
BRING MIXED MVFR AND IFR CONDITIONS IN FROM WEST TO EAST. WIDESPREAD
RAIN AND SNOW ARE EXPECTED...WITH SNOW LEVELS FALLING TO 5K FT OVER
THE KAIBAB PLATEAU TO 6K FEET IN THE WHITE MTNS. THESE CONDITIONS TO
CONTINUE THROUGH WEDNESDAY EVENING. AVIATION DISCUSSION NOT UPDATED
FOR AMENDMENTS.
&&

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

$$

PUBLIC.........TC
AVIATION.......DL

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF











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