FXUS65 KFGZ 071604
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
900 AM MST MON DEC 7 2009
.SYNOPSIS...A MAJOR WINTER STORM WILL AFFECT NORTHERN ARIZONA
THROUGH TUESDAY MORNING. SNOW LEVELS WILL RANGE FROM 5000 TO 6000
FEET...WITH HEAVY SNOW ACCUMULATIONS ABOVE 6000 FEET...ESPECIALLY
ALONG THE MOGOLLON RIM AND WHITE MOUNTAINS. AT LOWER ELEVATIONS
SOUTH OF THE RIM...EXPECT PERIODS OF MODERATE TO HEAVY RAIN. WEATHER
CONDITIONS SHOULD IMPROVE FROM NORTHWEST TO SOUTHEAST TUESDAY
AFTERNOON...WITH FAIR WEATHER THROUGH WEDNESDAY EVENING. UNSETTLED
WEATHER SHOULD RETURN THURSDAY THROUGH SUNDAY.
&&
.DISCUSSION...RADAR INDICATES WIDESPREAD SNOW AND RAIN OVER MUCH OF
NRN AZ...ESPECIALLY THE WESTERN ZONES. ACCUMULATING SNOW ALREADY
OCCURRING IN MANY LOCATIONS. WARM AND MOIST AIR HAS ALREADY ARRIVED
OVER THE SOUTHERN AND SOUTHWESTERN ZONES AND SNOW LEVELS HAVE ALREADY
MOVED UP TO AROUND 5500 FEET...AND WILL LIKELY CLIMB TO AROUND 6000
FEET THIS AFTERNOON.
HAVE MADE SOME MINOR UPDATES FOR THE SHORT TERM. THESE INCLUDE
BUMPING POPS TO 100 PERCENT IN MANY LOCATIONS...RAISING SNOW LEVELS
A BIT...AND CHANGING WX TYPE FROM SNOW TO RAIN FOR THESE LOCATIONS.
PREVIOUS DISCUSSION FROM MIDNIGHT SHIFT BELOW STILL COVERS THE
SITUATION WELL.
&&
.PREV DISCUSSION (400 AM)...MAJOR WINTER STORM EVENT BEGINNING TO
UNFOLD ACROSS NRN AZ. RADAR INDICATES PRECIP BEGINNING TO
DEVELOP...MUCH OF WHICH IS LIGHT AND ISN'T REACHING THE GROUND YET.
THE FIRST DECENT SNOW SHOWERS EARLY THIS MORNING EXPECTED TO START
IN THE FAVORED UPSLOPE AREA...THEN EXPAND IN COVERAGE AND INTENSITY
AS THE DAY PROGRESSES. THE HEAVIEST PRECIP STILL EXPECTED TO BEGIN
LATER THIS AFTERNOON THROUGH THE OVERNIGHT PERIOD. NOT MUCH CHANGE
IN THINKING REGARDING PRECIP TYPE...STILL LOOKS LIKE A MAJOR SNOW
EVENT FOR ELEVATIONS ABOVE 6000 FEET WITH 1-2 FEET OF SNOW EXPECTED
BY TUESDAY MORNING. FROM 5000-6000 FEET...EXPECT PRECIP TO START OFF
AS LIGHT SNOW THIS MORNING WITH LITTLE ACCUMULATION...THEN MIX WITH
AND CHANGE TO RAIN THIS AFTERNOON AS WARMER AIR ADVECTS IN FROM THE
SOUTHWEST. LATE TONIGHT LOCATIONS IN THIS ELEVATION RANGE WILL
SWITCH BACK TO SNOW AS COLDER AIR MOVES IN BEHIND THE TROUGH AXIS
WITH SEVERAL INCHES OF SNOW EXPECTED. THE EXCEPTION TO THIS
5000-6000 FEET RANGE THINKING IS ACROSS THE LCR...WHERE IT WILL BE
WARMER AND PRECIP WILL BE VERY SLOW TO START DUE TO DOWNSLOPE FLOW
INTO THE VALLEY. LOCATIONS IN THE LCR SUCH AS WINSLOW SHOULD REMAIN
DRY THROUGH THE MORNING...AND ANY PRECIP THAT SURVIVES THE DOWNSLOPE
SHOULD BE RAIN. BUT LATER OVERNIGHT WHEN FLOW TURNS MORE TO THE WEST
AND COLDER AIR MOVES IN...EXPECT A COUPLE HOURS OF PRECIP OVER THE
LCR WHICH WILL CHANGE TO SNOW AND PROVIDE PERHAPS AND INCH OR TWO OF
ACCUMULATION. FOR ELEVATIONS BELOW 5000 FEET...EXPECT A COUPLE
INCHES OF ALL RAIN.
AS FOR WINDS...SO FAR WE'VE SEEN STRONG WINDS DOWNWIND OF THE
MOGOLLON RIM AND PARTICULARLY ON THE EAST SIDE OF FLAGSTAFF AND
DONEY PARK AREA WHERE GUSTS UP TO 60 MPH HAVE OCCURRED SEVERAL HOURS
AGO. THIS SYSTEM WILL REMAIN QUITE WINDY WITH STRONGEST WINDS ALONG
THE MOGOLLON RIM AND ESPECIALLY DOWNWIND OF THE RIM.
AS FOR WATCHES...WARNINGS...AND ADVISORIES...BLIZZARD WARNING IS IN
EFFECT FOR THE MOGOLLON RIM DUE TO STRONG WINDS AND HEAVY SNOW WITH
REDUCED VISIBILITIES. THE BLIZZARD CONDITIONS ARE EXPECTED TONIGHT.
A WINTER STORM WARNING FOR HEAVY SNOW ACCUMULATIONS ABOVE 5000 FEET.
AS MENTIONED ABOVE...WHEN THE COLDER AIR MOVES IN TONIGHT...COULD
SEE A QUICK COUPLE INCHES ACROSS THE LCR WITH SOME ICY CONDITIONS
DUE TO WATER ON ROADWAYS FREEZING...THUS WILL CANCEL THE WINTER
STORM WARNING FOR ZONES 5 AND 12>14 AND REPLACE WITH A WINTER
WEATHER ADVISORY STARTING LATE TONIGHT. FINALLY...WILL ISSUE A WIND
ADVISORY FOR THE LCR AND ZONE 5 FOR TODAY THROUGH TUESDAY GIVEN
AFOREMENTIONED STRONG WINDS...AND WILL CLOSELY MONITOR WINDS AS THEY
COME UP TODAY AND WILL BE READY TO UPGRADE TO A HIGH WIND WARNING IF
NEEDED. SEE W/W/A SECTION BELOW FOR MORE DETAILS REGARDING TIMING OF
THESE PRODUCTS.
&&
.AVIATION...FOR THE 18Z PACKAGE...A STRONG WINTER STORM WILL MOVE
ACROSS NORTHERN ARIZONA OVER THE NEXT 24 HOURS WITH WIDESPREAD RAIN
AND SNOW. SNOW LEVELS 5000-6000 FEET. TIL 00Z SFC WINDS FROM THE SW
15 TO 35 KT...AFT 00Z SW 20-40 KT GUSTS TO 50KT. ASIDE FROM THE
LITTLE COLORADO RIVER VALLEY...THERE WILL BE COMPLETE MVFR
CONDITIONS WITH WIDESPREAD IFR. COLD FRONT MOVING INTO NW AZ AROUND
00-06Z TUES...WITH IFR CONDITIONS SPREADING INTO THE LITTLE COLORADO
RIVER VALLEY. AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...
...BLIZZARD WARNING IN EFFECT FROM 8 AM MONDAY TO NOON MST TUESDAY
AZZ015-016...
...WINTER STORM WARNING IN EFFECT FROM 8 AM MONDAY TO NOON MST
TUESDAY FOR AREAS ABOVE 5000 AZZ004-006>011-018-038...
..WINTER STORM WARNING IN EFFECT FROM 5 PM MONDAY TO NOON MST
TUESDAY AZZ017...
...WINTER WEATHER ADVISORY NOW IN EFFECT TUESDAY MORNING FOR AREAS
ABOVE 5000 FEET AZZ005-012>14...
...WIND ADVISORY IN EFFECT 10 AM MST THROUGH MID DAY TUESDAY
AZZ005-012>14.
&&
$$
PUBLIC..................DB/NP
AVIATION/FIRE WEATHER...41
VISIT WEATHER.GOV/FLAGSTAFF FOR NORTHERN ARIZONA WEATHER INFORMATION.
