Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 280337
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
837 PM MST SAT DEC 27 2014

.SYNOPSIS...
COLD AND DRY WEATHER CONDITIONS WILL CONTINUE THROUGH MONDAY.
WIND SPEEDS WILL TREND HIGHER ON MONDAY AND TUESDAY AHEAD OF A
POTENTIALLY SIGNIFICANT WINTER STORM EXPECTED TO MOVE ACROSS THE
SOUTHWEST REGION FROM TUESDAY THROUGH THURSDAY. THE MOST LIKELY
TRACK OF THIS STORM WILL BRING AREAS OF RAIN AND SNOW TO NORTHERN
ARIZONA WITH THE PEAK INTENSITY FORECAST FOR WEDNESDAY AND
THURSDAY.

&&

.DISCUSSION...QUIET WEATHER PREVAILS THIS EVENING IN THE WAKE OF
YESTERDAYS TROUGH WHICH HAS NOW MOVED EAST OF THE STATE. HIGH
CLOUDS ARE APPROACHING FROM THE NORTH AND WILL CONTINUE TO
INCREASE TONIGHT INTO SUNDAY. TEMPERATURES ARE CURRENTLY RUNNING A
FEW DEGREES COOLER THAN LAST NIGHT AT THIS TIME IN MOST LOCATIONS
AND EXPECT SIMILAR OVERNIGHT LOWS AGAIN TONIGHT. HAVE ADJUSTED
MINIMUM TEMPERATURES FORECASTS DOWN ACCORDINGLY.

&&

.PREVIOUS DISCUSSION /340 PM MST/...
COLD AND DRY WEATHER CONDITIONS WILL CONTINUE THROUGH
MONDAY WITH INCREASING HIGH CIRRUS CLOUDS MOVING IN FROM THE NORTH.
LOOKING OUT INTO THE LONG RANGE FORECAST OUR COMPUTER MODELS
CONTINUE TO SHOW A CUT OFF LOW MOVING THROUGH OUR REGION NEXT WEEK
BRINGING US OUR NEXT BEST CHANCE FOR PRECIPITATION. STRONG WINDS
AHEAD OF THE SYSTEM MAY BRING OROGRAPHIC SHOWERS AS THE WIND WRINGS
OUT MOISTURE OVER THE WINDWARD SLOPES OF THE HIGH TERRAIN STARTING
AS EARLY AS TUESDAY. FOR THE AFTERNOON FORECAST WE INCREASED OUR
CHANCES FOR MEASURABLE RAIN AND SNOW FOR WEDNESDAY AND THURSDAY BY
20 PERCENT IN LINE WITH OUR EXPECTED PEAK SHOWER ACTIVITY DURING
THIS EVENT.

FORECASTING SNOW LEVELS...RAIN AND SNOW AMOUNTS WILL NEED TO WAIT
UNTIL THE SYSTEM GETS CLOSER AS THERE ARE SEVERAL CHALLENGES WITH
THIS UPCOMING STORM FORECAST. FIRST...THIS CUT OFF LOW IS A SMALLER
SYSTEM THAT WILL BE CUT OFF FROM THE MAIN STEERING FLOW AND THUS THE
MODELS HAVE A HARDER TIME DIALING IN ON DETAILED IMPACTS. SECOND...
WHILE THE EUROPEAN AND AMERICAN OPERATIONAL MODELS ARE IN FAIR
AGREEMENT ON TIMING AND TRACK OTHER MODELS SUCH AS THE CANADIAN SHOW
RATHER LARGE DEPARTURES IN SOLUTIONS FOR THE MID WEEK TIME PERIOD.
FORECASTING FOR THESE CUT OFF SYSTEMS ALWAYS DEMANDS USING AN
ENSEMBLE APPROACH TO HELP GAUGE POTENTIAL FOR CHANGES IN THE STORM
TRACK/INTENSITY. TODAY`S 27/12Z AMERICAN GFS ENSEMBLE MODEL FOR
EXAMPLE SHOWS A 1000 MILE SPREAD IN THE POSITION OF THE CENTER OF
THIS LOW BY WEDNESDAY MORNING RESULTING IN A LARGER THAN NORMAL
UNCERTAINTY ON IMPACTS FOR NORTHERN ARIZONA.

FOR NOW WE WAIT TO SEE HOW THIS NEXT WINTER STORM EVOLVES OVER THE
NEXT FEW DAYS. EXPECT TO SEE MORE DETAILED IMPACTS INCLUDED IN OUR
NORTHERN ARIZONA FORECAST IN THE NEXT 24 TO 48 HOURS. KEEP WATCHING
OUR WEB PAGE FOR FREQUENT UPDATES ON THIS DEVELOPING STORM.

&&

.AVIATION...
FOR THE 06Z PACKAGE...A DRY NORTHWEST FLOW WILL BRING VFR
CONDITIONS AND LIGHT WINDS UNDER VARIABLE HIGH CLOUDS OVER THE
NEXT 24 HOURS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

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

&&

$$

PUBLIC.........MCS/MCCOLLUM
AVIATION.......MCS/BOHLIN

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF





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