Blizzard in Alaska, April 25 to 26, 2006

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 AM ADT TUE APR 25 2006

.DISCUSSION...

ANALYSIS...A VERY COLD UPPER LOW IS DROPPING SOUTHWARD ACROSS THE
CENTRAL BERING SEA. SURFACE LOW IS NOT DIRECTLY UNDERNEATH THE UPPER
LOW SO THERE IS SOME VERTICAL TILT BUT SYSTEM SHOULD BECOME VERTICAL
BY LATER TODAY. SATELLITE IMAGERY ALSO INDICATES MULTIPLE LOW CENTERS
DEVELOPING WITHIN THE BROADER UPPER CIRCULATION. WILL WATCH TO SEE
IF ANY OF THESE DEVELOPS OR JUST ROTATES AROUND THE UPPER CENTER. THE
SURFACE ARCTIC COLD FRONT HAS MOVED THROUGH THE PRIBILOFS AND PAST
BUOY 46073 AND IS HEADED TOWARD THE ALEUTIANS. QUICKSCAT WINDS SHOW
THERE IS ABOUT A 45 DEGREE WIND SHIFT ALONG THE FRONT. BEHIND THE
FRONT IS SOME EXTREMELY COLD AIR THAT ORIGINATED IN THE RUSSIAN
ARCTIC. MODELS INDICATE 850 TEMPERATURES DOWN TO -20 DEGREES CELSIUS.
THE COMBINATION OF PRESSURE GRADIENT AND COLD ADVECTION IS RESULTING
IN STORM FORCE WINDS BEHIND THE COLD FRONT. BUOY 46035 HAS SEEN GUSTS
TO 54KT AND TEMPERATURES DOWN TO 18 DEGREES FAHRENHEIT. THE PRIBILOFS
HAVE BOTTOMED OUT AT 1/4 MILE VISIBILITY A COUPLE TIMES AND A BLOWING
SNOW ADVISORY IS CURRENTLY IN EFFECT. THIS IS DEFINITELY A WINTER
AIR MASS. AS THIS COLD AIR GETS CHANNELED THROUGH THE ALEUTIANS THERE
WILL BE SOME MUCH HIGHER WIND GUSTS.

OVER SOUTHCENTRAL...RADAR SHOWS RAIN AND SNOW FROM NORTHERN COOK
INLET UP THE SUSITNA VALLEY AND SHOWERS ACROSS PRINCE WILLIAM SOUND.
THIS IS IN THE WAKE OF THE LOW THAT MOVED INLAND MONDAY AND IS NOW IN
THE INTERIOR. PRECIPITATION IS CHANGING FROM RAIN TO SNOW IN MOST
PLACES AS COLDER AIR FILTERS INTO THE REGION. SOME GUSTY SOUTHERLY
WINDS ARE NOTED ACROSS SOUTHCENTRAL...MAINLY DUE TO THE RISING
PRESSURES AS A RIDGE OF HIGH PRESSURE BEGINS TO BUILD ALONG THE NORTH
GULF COAST.

MODEL ANALYSIS...MODELS ARE FAIRLY CONSISTENT IN THE SHORT-TERM. NAM
DOES SHOW BETTER INDICATION OF MULTIPLE LOW CENTERS IN THE BERING BUT
THE GFS IS MORE ACCURATE WITH THE DEPTH OF THE LOW. SO WILL USE A
COMBINATION OF THE TWO MODELS AS THE LOWS TRACKS SOUTHWARD TODAY AND
WEDNESDAY. MODEL SOLUTIONS DIVERGE IN THE EAST AT ABOUT 72 HOURS WHEN
A LOW MOVING AROUND EAST SIDE OF UPPER CENTER MOVES INTO THE GULF.
WILL GO WITH THE GFS SOLUTION FOR NOW.

AER SHORT-TERM FORECAST...THE STEADY PRECIP OVER NORTHERN COOK INLET
AND SUSITNA VALLEY WILL DIMINISH THIS MORNING AS LOW IN THE INTERIOR
CONTINUES TO MOVE FARTHER AWAY. SCATTERED SHOWERS WILL CONTINUE
ACROSS SOUTHCENTRAL UNTIL UPPER TROUGH AXIS MOVES THROUGH TUESDAY
NIGHT. GUSTY SOUTH WINDS WILL ALSO DIMINISH THROUGH THE DAY AS
GRADIENT WEAKENS AND ISALLOBARIC MAX MOVES OFF TO THE NORTH. LOW
LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO BUILD ALONG THE NORTH
GULF COAST TODAY AND MOVE INLAND TONIGHT INTO WEDNESDAY. THIS WILL
HELP SHIFT FLOW AROUND TO THE NORTH AND CREATE A NICE DAY ACROSS MOST
OF SOUTHCENTRAL WEDNESDAY (EXCEPT KODIAK WHO WILL START TO FEEL
EFFECTS OF BERING LOW AS IT DROPS DOWN INTO THE PACIFIC). CLOUDS AND
PRECIP WILL BE ON THE INCREASE THURSDAY (MAINLY COASTAL AREAS) AS
UPPER LOW MOVES TO THE GULF AND NEW LOW MOVES NORTHWARD ACROSS THE
EASTERN GULF.

ALU SHORT-TERM FORECASTS...STRONGEST WINDS TODAY WILL BE IN A WIDE
SWATCH ACROSS THE CENTRAL BERING WEST OF 170. THESE WILL SPREAD
SOUTHWARD TO THE CENTRAL AND EASTERN ALEUTIANS LATER TODAY.
COMBINATION OF SNOW AND WIND WILL RESULT IN VERY LOW VISIBILITIES.
THERE IS A BLIZZARD WARNING OUT FOR PRIBILOFS TODAY - WILL ADJUST
THE TIMING TO BEGIN LATER TODAY BEHIND THE LOW CENTER. BLIZZARD
WATCH FOR THE EASTERN ALEUTIANS WILL BE UPGRADED TO A WARNING. FOR
THE CENTRAL ALEUTIANS HAVE DECIDED TO GO WITH A BLOWING SNOW ADVISORY

FOR ATKA EASTWARD. BECAUSE THIS AREA WILL SEE MAINLY SNOW SHOWERS
INSTEAD OF THE STEADY SNOW NEAR THE LOW CENTER THINK THE LOW
VISIBILITIES WILL BE MORE INFREQUENT. THE LOW CENTER WILL TRACK WEST
OF COLD BAY LATE TUESDAY NIGHT AND INTO THE PACIFIC WEDNESDAY. STRONG
WINDS WILL SPREAD OVER THE EASTERN BERING AND AKPENN BY LATE
WEDNESDAY. AS GET CLOSER MAY NEED TO CONSIDER A BLOWING SNOW ADVISORY
FOR THE AKPENN. TEMPERATURES ACROSS THE BERING AND ALEUTIANS FOR THE
NEXT FEW DAYS WILL BE AT FREEZING OR BELOW.

EXTENDED FORECASTS...COLD UPPER LOW WILL MOVE INTO THE CENTRAL GULF
BY THE END OF THE WEEK AND THEN LIFT NORTHWARD NEXT WEEK. WITH SUCH
COLD AIR ALOFT ATMOSPHERE WILL REMAIN QUITE UNSTABLE OVER THE
SOUTHERN MAINLAND AND ANY SUNSHINE WILL TRIGGER SHOWERS. SO EXPECT
A VERY SHOWERY REGIME TO PERSIST THROUGH THE EXTENDED PERIOD. WESTERN
BERING RIDGE WILL SLIDE EASTWARD AT WEEKS END AND NORTHERLY FLOW WILL
GRADUALLY DIMINISH FROM WEST TO EAST. GFS INDICATES RIDGE WILL START
TO BREAK DOWN NEXT WEEKEND AS A NEW LOW MOVES IN FROM THE SOUTHWEST.
GFS TENDS TO DO THIS TOO QUICKLY SO HAVE LOW CONFIDENCE IN THIS
SOLUTION. IN ANY CASE AFTER SEVERAL DAYS OF COLD NORTHERLY FLOW THE
BERING SEA REGION WILL BEGIN TO WARM UP AS WE HEAD INTO THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 185 195.
MARINE...STORMS 172.
         GALES 170 171 179 185.
         HEAVY FREEZING SPRAY 179 185.
FIRE WEATHER...NONE.

SEB APR 06