Blizzard in Alaska, January 14 to 15, 2007

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1252 PM AST SUN JAN 14 2007

.DISCUSSION...

ANALYSIS...IN THE UPPER LEVELS THERE IS A LARGE HEMISPHERIC
CIRCULATION CENTERED OVER EASTERN RUSSIA AND THE FAR WESTERN BERING
SEA...A SHORT-WAVE RIDGE OVER THE EASTERN BERING SEA...UPPER LOW
CENTER SOUTH OF THE AKPENN NEAR 50N 160W WITH TROUGH AXIS EXTENDING
NORTHWARD ACROSS SOUTHCENTRAL ALASKA TO ANOTHER LOW CENTER OVER
WEST-CENTRAL ALASKA...AND A HIGH AMPLITUDE SHORT-WAVE RIDGE FROM THE
EAST PACIFIC NORTHWARD INTO BRITISH COLUMBIA AND SOUTHEAST ALASKA.
THE JET CORE EXTENDS OUT OF ASIA BETWEEN 30N AND 35N LATITUDE AND
SPLITS AROUND 40N 175W. A DEVELOPING SURFACE LOW AND ASSOCIATED
TRIPLE POINT ARE TRACKING TOWARD THIS AREA OF DIVERGENCE AND TRIPLE
POINT DEVELOPMENT IS EXPECTED. ELSEWHERE AT THE SURFACE...THE BERING
SEA/ALEUTIANS/SOUTHWEST ALASKA ARE VERY CALM TODAY UNDER THE
INFLUENCE OF THE UPPER RIDGE WITH JUST A FEW SHOWERS AND AREAS OF
FOG. SOUTHCENTRAL ALASKA IS FEELING THE BRUNT OF A MODERATE LOW
WHICH IS CURRENTLY TRACKING JUST WEST OF MIDDLETON ISLAND. WITH THE
EXCEPTION OF SOUTHEAST PRINCE WILLIAM SOUND WHERE PRECIPITATION IS
FALLING AS RAIN ALL OTHER AREAS ARE RECEIVING SNOW. WATER VAPOR
IMAGERY SHOWS UPPER TROUGH AXIS MOVING OVER SOUTHERN COOK INLET WITH
VERY SLOW MOVEMENT NORTHEASTWARD. MEANWHILE LOW LEVEL EASTERLY FLOW
IS SPREADING MOISTURE OVER THE KENAI AND CHUGACH MOUNTAINS TO
ANCHORAGE AND THE MAT-SU. THIS HAS SET UP A DEFORMATION ZONE FROM
WESTERN PRINCE WILLIAM SOUND TO THE SUSITNA VALLEY. SNOWFALL HAS
GENERALLY BEEN LIGHT ON THE WEST SIDE OF THE MOUNTAINS WITH
OCCASIONAL INCREASES IN INTENSITY. SNOWFALL OVER WESTERN PRINCE
WILLIAM SOUND HAS BEEN HEAVY AT TIMES WITH UP TO 1 FOOT ACCUMULATION
IN SOME AREAS ALREADY. SNOW HAS ALSO BEEN FALLING STEADILY FROM
NORTHEAST PRINCE WILLIAM SOUND TO THE COPPER RIVER BASIN. LOCALIZED
WINDS ARE CAUSING BLOWING SNOW IN WHITTIER WHERE A BLIZZARD WARNING
IS IN EFFECT AND THOMPSON PASS WHERE A BLOWING SNOW ADVISORY IS IN
EFFECT.

MODEL ANALYSIS...MODELS HAVE BEEN HAVING TROUBLE WITH THE GULF LOW.
THE UKMET/GFS ARE CLOSEST TO REALITY AND WILL BE USED FOR THIS
FEATURE. ELSEWHERE...MODELS INITIALIZED WELL AND SHOW FAIR
CONSISTENCY IN THEIR SOLUTIONS. WILL CONTINUE TO USE GFS WITH NEXT
MAJOR LOW OUT WEST...ALTHOUGH DO NOT THINK GFS OR OTHER MODELS ARE
PICKING UP ON LIKELY TRIPLE POINT DEVELOPMENT.

SOUTHCENTRAL FORECAST...DETERMINING THE END OF SNOWFALL FOR ANCHORAGE
AND THE MAT-SU IS A BIT TRICKY. THE UPPER TROUGH AXIS OVER SOUTHERN
COOK INLET LOOKS LIKE IT WILL MOVE THROUGH THIS EVENING.
HOWEVER...ANOTHER SHORT-WAVE TROUGH ROTATING AROUND THE UPPER LOW
OVER WESTERN ALASKA WILL APPROACH LATER TONIGHT WHILE THE UPPER LOW
SLOWLY SINKS SOUTHEASTWARD TOWARD SOUTHCENTRAL. SO...THIS SECOND
SHORT-WAVE MAY HELP PROLONG THE SNOW THROUGH AT LEAST THE EVENING
HOURS. IN ANY CASE...SNOW WILL REMAIN MAINLY LIGHT AND LITTLE
ACCUMULATION IS EXPECTED. MODERATE TO HEAVY SNOW WILL CONTINUE INTO
THE EVENING FOR WESTERN PRINCE WILLIAM SOUND AND SHOULD BEGIN TO
DIMINISH AS THE LOW MOVE SINLAND LATER THIS EVENING. THE BLIZZARD
WARNING FOR WHITTIER IS SET TO EXPIRE AT 4 PM THIS AFTERNOON...THIS
MAY HAVE TO BE EXTENDED BEWCAUSE WINDS WILL INCREASE AS THE LOW MOVES
INTO THE SOUND AND COLD AIR BEGINS TO FILTER IN FROM THE WEST. SO
EVEN IF THE SNOW DIMINISHES OR ENDS THE WINDS MAY BE STRONG ENOUGH
TO PRODUCE BLIZZARD CONDITIONS. THEREFORE...WILL EXTEND THE BLIZZARD
WARNING THROUGH TONIGHT. WITH A LOW TRACK ACROSS THE COPPER RIVER
BASIN LOOK FOR SNOW TO CONTINUE OVERNIGHT AND GRADUALLY TAPER OFF
FROM SOUTH TO NORTH. WITH ANOTHER SHORT-WAVE MOVING ACROSS
SOUTHCENTRAL EXPECT A RESIDUAL LOW TO FORM IN VICINITY OF PRINCE
WILLIAM SOUND TONIGHT...MODELS DEPICT THIS OCCURRING NEAR CORDOVA.
THE SECOND TROUGH AXIS WILL MOVE ACROSS SOUTHCENTRAL MONDAY PUSHING
THE RESIDUAL SURFACE LOW EASTWARD AND CLEARING OUT MOST OF THE
REGION. AS PER THE NORM GUSTY WINDS WILL CONTINUE THROUGH THE
SHORT-TERM FOR WESTERN AND NORTHERN GULF THROUGH CHANNELED AREAS
DUE TO COLD ADVECTION AND PRESSURE RISES. THERE WILL ONLY BE A BRIEF
BREAK AS A FRONT MOVES TO KODIAK ISLAND TUESDAY AFTERNOON AND
SOUTHCENTRAL TUESDAY NIGHT. IT LOOKS LIKE IT WILL BE FAST MOVING AND
PRODUCE ONLY A QUICK SHOT OF PRECIP.

BERING SEA/ALEUTIANS/AKPENN/SOUTHWEST ALASKA FORECAST...DEVELOPING
LOW OUT WEST WILL MOVE TO THE CENTRAL ALEUTIANS LATE MONDAY AS
FRONTAL SYSTEM MOVES NORTH AND EAST ACROSS ALEUTIANS. AS MENTIONED
EARLIER WILL HAVE TO WATCH FOR TRIPLE POINT LOW DEVELOPMENT DUE TO
FAVORABLE UPPER DIVERGENCE. ASSUMING A MAJOR TRIPLE POINT DOES NOT
DEVELOP OCCLUDED FRONT WILL STRETCH OUT AS IT MOVES NORTH AND EAST
INTO THE EASTERN BERING AND SOUTHWEST ALASKA DUE TO PARENT LOW
REMAINING NEARLY STATIONARY BACK OVER THE CENTRAL ALEUTIANS. EXPECT
MAX GALES ALONG THE FRONT INITIALLY THEN WEAKENING AS IT MOVES
PROGRESSES NORTH AND EAST. THERE IS ENOUGH WARM AIR BEING FORCED
NORTHWARD THAT MAIN PRECIP TYPE ALONG THE ALEUTIANS/AKPENN WILL BE
RAIN. HOWEVER AS FRONT OCCLUDES AND REACHES SOUTHWEST ALASKA AND
PRIBILOFS PRECIP WILL LIKELY BE SNOW. DOES NOT LOOK LIKE NEED TO
WORRY ABOUT BLOWING SNOW OR BLIZZARD AT THIS POINT...BUT WILL
REEVALUATE THIS AT A LATER TIME FOR SOUTHWEST ALASKA AND THE PRIBS.
AS WE HEAD THROUGH THE WEEK UPPER LOW CIRCULATION SETS UP VICINITY
OF WESTERN ALEUTIANS SO STORM TRACK WILL BRING LOWS NORTHWARD INTO
THE EASTERN BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING ZONE 125 FOR WHITTIER.
MARINE...GALES 130 150 155 160 165 170 171 172 175 176 179 185.
         HEAVY FREEZING SPRAY...121 129 130.

SEB JAN 07