Blizzard and High Wind in Alaska, April 2 to 4, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
540 AM AKDT SAT APR 2 2011

.ANALYSIS AND UPPER LEVELS...
A SHORTWAVE TROUGH OVER SOUTHCENTRAL AK IS ROTATING EAST AND
ENHANCING SOME OF THE SNOW SHOWERS FROM THE SUSITNA VALLEY DOWN
TOWARDS PRINCE WILLIAM SOUND. UPPER-RIDGING IS BUILDING THROUGH THE
EASTERN GULF AND SE AK AHEAD OF A DEEP LOW AROUND 200 MILES SOUTHEAST
OF DUTCH HARBOR. THE LOW IS SPREADING WIDESPREAD GALE TO STORM FORCE
WINDS ACROSS THE EASTERN BERING AND ALEUTIAN CHAIN...ALONG WITH A
SLUG OF RAIN/SNOW. AN ASSOCIATED FRONT IS NOSING INTO THE
SOUTHWESTERN GULF...BEGINNING TO SPREAD RAIN ACROSS KODIAK ISLAND AS
IT ADVANCES NORTHEAST. FURTHER WEST...A BROAD UPPER-LVL LOW OVER THE
WESTERN BERING IS DRIFTING SOUTH AND FILLING...WITH IT'S RESIDUAL
ENERGY HELPING TO DEEPEN THE AFOREMENTIONED LOW SOUTH OF THE
ALEUTIAN CHAIN.

.MODEL DISCUSSION...
MODELS ACCEPTABLY CAPTURE THE MAIN WEATHER FEATURES THROUGH EARLY
NEXT WEEK. MODELS SHOW THE STRONG LOW SOUTH OF THE CHAIN ADVANCING
EAST TOWARDS THE SOUTHCENTRAL GULF OF AK ON MON. THE NAM APPEARS TO
BRING THE FRONT IN THE GULF A BIT FURTHER NORTH THAN THE OTHER
SOLUTIONS...AND THUS DEPICTS CONSIDERABLY STRONGER GAP WINDS THROUGH
TURNAGAIN ARM/PORTAGE VALLEY. THE GFS WAS EMPLOYED IN THE MORNING
FORECAST PACKAGE DUE TO REASONABLE CONSISTENCY AND CONTINUITY...WITH
EXTENDED PARTS OF THE FORECAST PERIOD TRENDING WITH HPC GUIDANCE.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
IN THE SUSITNA VALLEY EAST OF THE PARKS HIGHWAY...SNOW SHOWERS WILL
TAPER OFF THIS MORNING AS A SHORTWAVE ROTATES AWAY...WHILE WEAK
ISENTROPIC LIFT AHEAD OF THE NEXT SYSTEM WILL KEEP A STEADY LIGHT
SNOW CONTINUING WEST OF THE PARKS HIGHWAY. SHOWERS ACROSS THE
SOUTHERN KENAI PENINSULA AND PRINCE WILLIAM SOUND WILL GIVE WAY TO
STEADIER RAIN AS THE STRONG FRONT WORKS IT'S WAY NORTHEAST THROUGH
SUNDAY. MILD TEMPERATURES AT SEA LEVEL LOOK TO SUPPORT ALL
RAIN...THOUGH WET SNOW MIXING IN AT HIGHER ELEVATIONS AND THROUGH
PASSES IS EXPECTED. A STRENGTHENING PRESSURE GRADIENT WILL SUPPORT
STRONG EAST WINDS THROUGH THE FAVORED LOCATIONS SUCH AS TURNAGAIN ARM
AND PORTAGE VALLEY NOT TO MENTION MUCH OF THE GULF. WINDS TO SUBSIDE
LATE SUNDAY/EARLY MONDAY AS THE FRONT WEAKENS NEAR THE COAST. A TRUE
FRONTAL PASSAGE INTO SOUTHCENTRAL IS NOT EXPECTED AS THE PARENT LOW
SLIPS SOUTH OF KODIAK ISLAND INTO CENTRAL AND SOUTHERN REACHES OF THE
GULF OF AK ON MONDAY. WITH THE PERSISTENT STRONG DOWNSLOPING WINDS
AND THE FRONTAL LIFT REMAINING WELL SOUTH...EXPECT RELATIVELY
DRY WEATHER ACROSS THE ANCHORAGE BOWL AND PORTIONS OF THE MATANUSKA
VALLEY WITH THIS SYSTEM.

SOUTHWEST...
SNOW AND RAIN FROM THE EASTERN ALEUTIAN SYSTEM WILL OVERSPREAD THE
SOUTHWEST MAINLAND THE REMAINDER OF THIS WEEKEND. ACROSS BRISTOL
BAY...EXPECT STRONG EAST WINDS THROUGH CHANNELED TERRAIN TO DOWNSLOPE
AREAS ADJACENT TO THE ALEUTIAN RANGE TO PASSING SHOWERS...WITH THE
HEAVIEST AND STEADIEST PRECIPITATION MAINLY FROM DILLINGHAM NORTH AND
WEST. THROUGH THE KUSKOKWIM DELTA WHERE THE COLDEST AIR STILL RATHER
ENTRENCHED...PRECIPITATION WILL BE ALL SNOW. STRENGTHENING NORTHEAST
WINDS BRING THE THREAT OF BLIZZARD CONDITIONS TO AREAS ALONG THE
IMMEDIATE COAST THIS EVENING/TONIGHT. THE PATTERN REMAINS UNSETTLED
AS A SERIES OF DISTURBANCES MOVE IN ON THE HEELS OF THIS FIRST
SYSTEM. WITH THE FLOW BECOMING MORE ONSHORE...THE CHANCES OF
RAIN/SNOW WILL BE MODESTLY WIDESPREAD THROUGH EARLY NEXT WEEK.

BERING SEA/ALEUTIANS...
THE LOW WILL MOVE TOWARDS SAND POINT TONIGHT...AND TRACK TO THE
SOUTHWESTERN GULF OF MONDAY. IN THE INTERIM...THE STRONG PRESSURE
GRADIENT IS BRINGING STORM-FORCE WINDS TO MUCH OF THE AREA. COLD
ADVECTION FILTERING IN ON THE BACKSIDE OF THE LOW TO PRODUCE BLIZZARD
CONDITIONS TODAY FOR THE EASTERN ALEUTIANS. A COMBINATION OF
COLD-ADVECTION A STRONG PRESSURE GRADIENT AND MODEST PRESSURE RISES
MAY BRING HURRICANE FORCE WINDS SUNDAY OVER THE WESTERN AKPEN WHERE
A HIGH WIND WATCH HAS BEEN ISSUED. A DEVELOPING LOW NEAR JAPAN WILL
MOVE TOWARDS THE FAR WESTERN ALEUTIAN CHAIN SUNDAY AND BRING MORE
SNOW/RAIN AND SOLID GALE FORCE WINDS...WITH THE RESIDUAL MOISTURE AND
ENERGY TRACKING EAST ON MONDAY.

.LONG TERM FORECAST...
UPPER-LVL FLOW LOOKS TO REMAIN RATHER PROGRESSIVE THROUGH THE
EXTENDED FORECAST PERIOD. EXPECT THE STORM TRACK TO BRING ADDITIONAL
STORM SYSTEMS THROUGH THE BERING/ALEUTIAN CHAIN AND TOWARDS THE
MAINLAND THROUGH THE END OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...185
         BLIZZARD WATCH...155
         HIGH WIND WATCH...181
MARINE...STORM...120 130 132 150 155 165 170 171 172 179 351 352 414
         GALE...125 138 140 141 160 175 176 180 185 411 412 413
         HEAVY FREEZING SPRAY...179 185 414
FIRE WEATHER...NONE

JAM APR 11