Heavy Freezing Spray Warning 32, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
410 PM AKST MON JAN 9 2012

.ANALYSIS AND UPPER LEVELS...SURFACE HIGH PRESSURE IS PROVIDING MUCH
OF MAINLAND ALASKA WITH VERY COLD BUT PLEASANT WEATHER TODAY. THIS IS
IN ADVANCE OF A LARGE STORM DEVELOPING SOUTH OF THE ALASKA PENINSULA.
THIS SYSTEM ALREADY BROUGHT BLIZZARD CONDITIONS FROM THE CENTRAL
ALEUTIANS TO THE ALASKA PENINSULA. SNOW AND WIND WILL CONTINUE TO
SPREAD NORTH AND EAST AND WILL AFFECT SOUTHWEST ALASKA AND
SOUTHCENTRAL OVER THE NEXT 24 HOURS. AN IMPRESSIVE PLUME OF MOISTURE
IS ASSOCIATED WITH THIS SYSTEM REACHING BACK TO THE SUBTROPICS.
SATELLITE ESTIMATES PUTS THE REGION AT OVER 200 PERCENT AVERAGE
PRECIPITABLE WATER FOR THIS TIME OF YEAR.

.MODEL DISCUSSION...THE FORECAST MODELS ARE SHOWING CONSISTENCY AND
GOOD CONTINUITY FROM RUN TO RUN WHICH IS ADDING CONFIDENCE TO OUR
ONGOING FORECAST. OVERALL...THE ECMWF WAS SLIGHTLY FAVORED OVER THE
OTHER OPERATIONAL MODELS BUT THIS WILL RESULT IN VERY FEW CHANGES TO
THE FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...CLEAR SKIES AND COLD TEMPERATURES WILL QUICKLY
GIVE WAY TO INCREASING CLOUDS THIS EVENING ACROSS SOUTHCENTRAL
ALASKA. SNOW WILL SPREAD ACROSS THE COASTAL REGIONS AND THE TYPICAL
UPSLOPE MOUNTAIN RANGES OVER THE INTERIOR. A BRIEF PERIOD OF
OVERRUNNING MOISTURE MAY BRING WESTERN KENAI PENINSULA AND ANCHORAGE
LIGHT SNOW BUT OVERALL WE ARE EXPECTING VERY LITTLE IF ANY
PRECIPITATION THROUGH TUESDAY.

THAT WILL NOT BE THE CASE AROUND PRINCE WILLIAM SOUND. PRECIPITATION
WILL BE VERY HEAVY AT TIMES THANKS IN LARGE PART TO THE
AFOREMENTIONED SUBTROPICAL FETCH STREAMING NORTHWARD. MANY PLACES
WILL START OFF COLD ENOUGH THAT PRECIPITATION WILL FALL IN THE FORM
OF SNOW. COUPLED WITH THE STRONG WINDS...WE ARE EXPECTING BLIZZARD
CONDITIONS FOR MANY COMMUNITIES AROUND PRINCE WILLIAM SOUND.

PRINCE WILLIAM SOUND WILL SEE VERY HIGH QPF FROM THIS EVENT...SO WILL
ADVERTISE AT LEAST A FOOT OF SNOW STORM TOTAL FOR MANY AREAS AT OR
NEAR SEA LEVEL. HIGHER AMOUNTS ARE LIKELY IN THE MOUNTAINS. MORE
SNOW...POSSIBLY RAIN...WILL CONTINUE DURING THE WEEK ADDING TO THE
ASTRONOMICAL SEASONAL SNOWFALL TOTALS IN THE REGION.

THE TIGHT PRESSURE GRADIENT ACROSS THE CHUGACH RANGE WILL ALSO BRING
THE FIRST HIGH WIND EVENT TO TURNAGAIN ARM AND THE HIGHER ELEVATIONS
ABOVE ANCHORAGE SINCE DECEMBER 20TH. THIS EVENT WILL BE DIFFERENT
THAN THE DECEMBER WIND EVENTS SINCE COLD AIR IS WELL ESTABLISHED OVER
SOUTHCENTRAL ALASKA. THE STRONG WINDS WILL REACH THE HIGHER
ELEVATIONS AND ALONG TURNAGAIN ARM BUT WILL NOT REACH THE LOWER
ELEVATIONS.

THE RECENT SNOWFALL IN ANCHORAGE COULD LEAD TO REDUCED VISIBILITY IN
BLOWING SNOW WHERE THE WINDS INCREASE LATE THIS EVENING THROUGH
TUESDAY. SINCE SNOW WILL LIKELY NOT BE FALLING...VISIBILITY WILL ONLY
BE REDUCED TO SNOW BEING PICKED UP AND BLOWN AROUND. THERE IS STILL
SOME UNCERTAINTY AS TO THE EXTENT OF THE BLOWING SNOW AND HOW POOR
THE CONDITIONS WILL BE...SO AT THIS TIME WILL NOT BE ISSUING ANY
WARNINGS OR ADVISORIES RELATED TO THE BLOWING SNOW...ONLY MENTIONING
THE POSSIBILITY IN THE PUBLIC FORECAST.

WE WILL BE INCREASING THE CHANCES OF SNOW FOR ANCHORAGE BEGINNING
WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT. A VERY PROMISING SETUP
FOR SIGNIFICANT SNOWFALL LOOKS MORE AND MORE LIKELY DURING THIS TIME
FRAME. STILL QUITE A WAY OUT SO TOO EARLY TO ESTIMATE ACCUMULATION
BUT THE POTENTIAL IS THERE FOR ANOTHER ADVISORY LEVEL STORM.

SOUTHWEST ALASKA...SNOW IS SPREADING INLAND EARLY THIS AFTERNOON WITH
BLIZZARD CONDITIONS LIKELY OVER MUCH OF THE SOUTHWESTERN COASTAL AND
INTERIOR REGIONS. MODERATE TO HEAVY SNOW WILL ACCOMPANY THE GUSTY
WINDS THROUGH EARLY TUESDAY MORNING AS THE LOW MOVES NEAR THE ALASKA
PENINSULA. A DEFORMATION BAND WILL DEVELOP AS THE UPPER TROUGH
APPROACHES FROM THE WEST. THE COMBINATION OF THE APPROACHING TROUGH
AND OVERRUNNING MOISTURE WILL RESULT IN ANOTHER ROUND OF MODERATE TO
HEAVY SNOW ACROSS SOUTHWEST ALASKA TUESDAY NIGHT THROUGH EARLY
WEDNESDAY MORNING. HIGH PRESSURE AND COLD AIR WILL SETTLE OVER THE
REGION LATER IN THE WEEK.

BERING SEA/ALEUTIANS...OUT WEST THE BLIZZARD CONDITIONS WILL LAST
LONGEST OVER THE CENTRAL ALEUTIANS WHERE A NARROW BAND OF MOISTURE
CONTINUES TO FOCUS OVER THIS AREA. EVENTUALLY...THE LOW DIGS SOUTH
AND EAST BRINGING AN END TO THE STEADY PRECIPITATION ALLOWING FOR A
MORE TYPICAL COLD ADVECTION SNOW SHOWER PATTERN TO PREVAIL. HIGH
PRESSURE BUILDS OVER THE BERING SEA MID WEEK WHICH LOOKS TO BE A HIGH
AMPLITUDE BLOCKING RIDGE THAT COULD BE IN THIS VICINITY FOR AN
EXTENDED AMOUNT OF TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 125 131 135 155 161 187
         HIGH WIND WARNING 101
MARINE...STORM WARNING...120 125 130 132 140 150 172
         GALE WARNING...129 138 141 155 160 165 171 171 175 179 180
                        171 179 180.
         HEAVY FREEZING SPRAY WARNING...130 140
FIRE WEATHER...NONE.

AB JAN 12