Blizzard in Alaska, April 24, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
640 AM AKDT SUN APR 24 2011

.ANALYSIS AND UPPER LEVELS...A BROAD RIDGE EXTENDS ALONG THE WEST
COAST OF NORTH AMERICA AND CURVES TOWARDS THE CHUCKCHI SEA. AN UPPER
LEVEL LOW SOUTH OF CHIGNIK CONTAINS MULTIPLE EMBEDDED UPPER LEVEL
SHORTWAVES. FURTHER WEST AN UPPER LEVEL LOW COVERS MUCH OF THE WEST
BERING SEA. THE UPPER LEVEL JET REMAINS WELL TO THE SOUTH IN THE
NORTH PACIFIC. AS A RESULT...SYSTEMS ARE PROGRESSING RELATIVELY
SLOWLY.

.AT THE SURFACE...A BROAD SURFACE LOW IS BENEATH THE UPPER LEVEL LOW
SOUTH OF CHIGNIK. A SERIES OF WEAK FRONTS ARE PROGRESSING AROUND THIS
LOW.  ONE SUCH FRONT THAT STRETCHES ALONG BRISTOL BAY IS BRINGING
SHOWERS AND WIND ALONG THE COAST. A SECOND FRONT CONTINUES TO SLOWLY
FIZZLE ALONG THE NORTH GULF COAST AND BRING SHOWERS TO PRINCE WILLIAM
SOUND AND THE NORTH GULF COAST.

.MODEL DISCUSSION...MODELS CONTINUE TO SHOW GREAT AGREEMENT. A BLEND
OF THE GFS AND NAM WAS USED IN THE SHORT TERM TO BEST CAPTURE LOCAL
EFFECTS. IN THE LONG TERM...THE ECMWF WAS FAVORED DUE TO THE GOOD RUN
TO RUN CONSISTENCY OF THE MODEL AND AGREEMENT WITH ENSEMBLES.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...SHOWERS CONTINUE ALONG THE NORTH GULF COAST AND
PRINCE WILLIAM SOUND THIS MORNING BUT ARE BEGINNING TO TAPER. THE
COASTAL JET NEAR CORDOVA IS ALSO SHOWING SIGNS OF DISSIPATING AS THE
FRONT WEAKENS FURTHER. AT ANCHORAGE...THE WEST KENAI PENINSULA...AND
THE MATANUSKA VALLEY...DOWNSLOPING CONTINUES TO LIMIT PRECIPITATION.
UNSETTLED WEATHER WILL CONTINUE ALONG THE COAST AS THE NEXT SYSTEM
APPROACHES BY MONDAY MORNING.

.SOUTHWEST MAINLAND...RAIN AND SNOW SHOWERS WILL CONTINUE ACROSS MUCH
OF THE SOUTHWEST MAINLAND OVER THE NEXT FEW DAYS DUE TO THE PROXIMITY
OF A LOW NEAR CHIGNIK. A FRONT PROGRESSING ACROSS BRISTOL BAY IS
BRINGING SHOWERS AND WIND ESPECIALLY ALONG THE COAST.

.ALEUTIANS...THE LOW NEAR CHIGNIK CONTINUES TO SUPPORT STRONG WINDS
AND SNOW SHOWERS ACROSS THE EAST ALEUTIANS. MEANWHILE OUT WEST A WEAK
LOW NORTH OF SHEMYA IS BRINGING LIGHT SNOW TO THE WESTERN ALEUTIANS.
THIS SYSTEM IS EXPECTED TO PROGRESS EASTWARD AND BRING PRECIPITATION
TO THE CENTRAL ALEUTIANS TODAY.

.LONG TERM FORECAST...AN ACTIVE WEATHER PATTERN WILL CONTINUE ACROSS
THE REGION OVER THE NEXT WEEK.  AS A RESULT...UNSETTLED WEATHER WILL
CONTINUE WITH SOME BRIEF BREAKS BETWEEN SYSTEMS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE...138 140 155 170 172
         HEAVY FREEZING SPRAY...179 180
FIRE WEATHER...NONE.

ELN APR 11