Blizzard and Heavy Snow in Alaska, April 6 to 7, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
445 PM AKDT TUE APR 5 2011

.ANALYSIS AND UPPER LEVELS...VERY PROGRESSIVE PATTERN RIGHT NOW OVER
THE FORECAST AREA WITH A NEARLY ZONAL FLOW AROUND THE NORTHERN
HEMISPHERE. THE ONLY BUMP IN THE FLOW IS THE STRONG LOW DEVELOPING IN
THE NORTHWEST PACIFIC. A VERY STRONG JET CORE (170KT) IS ACCOMPANYING
THIS LOW DEVELOPMENT. A SHORT WAVE RIDGE IS OVER THE EASTERN BERING
WITH A JET CORE OF 130KT. THERE IS ALSO A SHORT WAVE TROUGH MOVING
THROUGH THE NORTON SOUND AREA AND INTO THE MAINLAND. THIS FEATURE
WILL MERGE WITH ANOTHER SHORT WAVE TROUGH LIFTING THROUGH SOUTHWEST
AND SOUTH CENTRAL ALASKA. THERE IS PLENTY OF LIFT WITH THESE TWO
SHORT WAVE TROUGHS TO BRING SNOW TO MUCH OF THE MAINLAND TODAY. THE
HEAVIEST PRECIPITATION CURRENTLY IS OVER THE ANCHORAGE AREA WITH
REPORTS UP TO 5 INCHES. AT THE SURFACE WE HAVE AN AREA OF LOW
PRESSURE OVER THE MAINLAND EXTENDING INTO TO GULF OF ALASKA. A
DEVELOPING LOW PRESSURE SYSTEM IS MOVING TOWARD THE WESTERN ALEUTIANS
AS WELL WITH SOME PRECIPITATION STARTING TO FALL.

.MODEL DISCUSSION...SYNOPTICALLY THE MODELS ARE IN DARN GOOD
AGREEMENT THROUGH SATURDAY. EVEN THE CENTRAL PRESSURES ARE ONLY OFF
BY A FEW MILLIBARS. NAM DOES NOT GET AS DEEP AS THE EC AND GFS IN
THIS SITUATION.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...A SHORT WAVE TROUGH IS LIFTING THROUGH SOUTH
CENTRAL TONIGHT. THIS WILL KEEP SNOW AND SNOW SHOWERS OVER THE AREA
THROUGH TONIGHT. RAPID DRYING AND INCREASINGLY STABLE ENVIRONMENT TO
MOVE INTO THE AREA BEHIND THIS TROUGH BY EARLY MORNING. A WEAKENING
LOW PRESSURE SYSTEM TO REMAIN IN THE GULF OF ALASKA ALONG THE NORTH
COAST THROUGH THE PANHANDLE. WITH HIGH PRESSURE BUILDING OVER THE
WEST TONIGHT AND REMAINING INTO THE MORNING...EXPECT SOME MODERATE TO
STRONG WINDS THROUGH THE BARREN ISLANDS AND KODIAK ISLAND AREA. THESE
WINDS WILL DIMINISH AS THE LOW WEAKENS FURTHER AND A DEEP LOW
PRESSURE SYSTEM MOVES INTO THE BERING SEA TOMORROW. THE ASSOCIATED
FRONT FROM THE BERING LOW TO REACH KODIAK WEDNESDAY EVENING AND INTO
ANCHORAGE BY THURSDAY MORNING. GOOD WARMING WITH THIS SYSTEM
INITIALLY AND A GOOD PUSH OF MOISTURE. WITH THE FRONT...WE CAN EXPECT
STRONG WINDS TO PUSH THROUGH TURNAGAIN ARM AND PRINCE WILLIAM SOUND
THURSDAY. MAY HAVE TO THINK ABOUT A HIGH WIND WATCH FOR THE AREA IF
IT LOOKS THE SAME TONIGHT. THE LOW STACKS AND FILLS OVER THE MAINLAND
THURSDAY NIGHT WITH SNOW WITH COASTAL RAIN AND INLAND SNOW SHOWERS
PERSISTING INTO FRIDAY. THE LOW DROPS INTO THE GULF SATURDAY WITH
SHOWERS REMAINING.

SOUTHWEST ALASKA...SHORT WAVE TROUGH TO LIFT THROUGH THE AREA EARLY
THIS EVENING ENDING ANY CURRENT SNOW SHOWER ACTIVITY. COLD AIR TO
REMAIN IN PLACE AHEAD OF THE STRONG FRONT COMING IN TOMORROW. THIS
FRONT IS ASSOCIATED WITH A BOMBING LOW WHICH IS EXPECTED TO DROP FROM
986 MB CURRENTLY TO 941 MB TOMORROW AFTERNOON. A STRONG JET TO HELP
THE FRONT ALONG TOMORROW. THIS FRONT WILL PRODUCE STRONG WINDS OF 35
TO 50 MPH BY TOMORROW EVENING AND POSSIBLY PUSH ICE ONSHORE IN
BRISTOL BAY AND ICE SHOVES IN THE KUSKOKWIM DELTA AREA. IN
ADDITION...THE STRONG WINDS WILL BRING SOME BEACH EROSION. THE WINDS
WILL CONTINUE ONSHORE THROUGH THURSDAY.  WITH THE COLD AIR IN PLACE
THE FRONT WILL PUSH THROUGH AND PRODUCE BLIZZARD CONDITIONS ACROSS
THE PRIBILOF ISLANDS LATE TONIGHT INTO THE EARLY MORNING. THIS
SCENARIO MAY BE REPLAYED ALONG THE WEST COAST STARTING TOMORROW
AFTERNOON FROM BRISTOL BAY THROUGH THE KUSKOKWIM DELTA. THE SNOW WILL
CHANGE OVER TO RAIN ALONG THE SOUTHERN BRISTOL BAY RATHER QUICKLY
WEDNESDAY NIGHT BUT FURTHER INLAND AND NORTHWEST OF DILLINGHAM...SNOW
WILL BE SLOWER TO TURN OVER. SNOW WILL NOT START IN THE KUSKOKWIM
VALLEY TIL WEDNESDAY NIGHT AS THE FRONT PUSHES INLAND.  WINDS WILL
BEGIN TO DIE DOWN THURSDAY AS THE LOW FILLS AS IT MAKES ITS WAY
INLAND. THE LOW WILL EVENTUALLY PUSH INTO THE GULF SATURDAY. RAIN AND
SNOW SHOWERS WILL CONTINUE THROUGH THAT PERIOD.

BERING SEA/ALEUTIANS...GREAT SUPPORT ALOFT FOR A DEVELOPING LOW
PRESSURE SYSTEM TONIGHT. THIS LOW WILL BE LARGE A CREATE ALL KINDS OF
STRONG WINDS AND BLIZZARD CONDITIONS. GOOD COLD AIR IN PLACE OVER THE
EASTERN BERING INCLUDING THE PRIBILOFS. THE ASSOCIATED FRONT WITH THE
LOW WILL PRODUCE WINDS OF 70 TO 85 MPH IN THE CENTRAL AND EASTERN
ALEUTIANS STARTING LATE TONIGHT. THESE STRONG WINDS COULD REACH INTO
THE ALASKA PENINSULA TOMORROW NIGHT. WITH THE COLD AIR IN PLACE AND A
STRONG FRONT MOVING NORTH...THE COLD AIR WILL BE DEEP ENOUGH FOR SOME
BLIZZARD CONDITIONS TO REMAIN WITH THE FRONT ACROSS THE BERING AND
THROUGH THE PRIBILOF ISLANDS LATE TONIGHT INTO TOMORROW MORNING. THE
REMAINDER OF THE CENTRAL AND EASTERN ALEUTIANS SHOULD WARM
CONSIDERABLY FAST WITH THE FRONT. RAPID COOLING BEHIND THE FRONT FOR
SOME STRONG NORTHWEST WINDS AS WELL ACROSS THE BERING SEA WRAPPING
AROUND THE LOW. STRONG WINDS TO CONTINUE WITH THE LOW THROUGH
THURSDAY. STRONG NORTHWEST FLOW TO REMAIN THROUGH FRIDAY AS THE LOW
FILLS INLAND FRIDAY NIGHT AND INTO THE GULF ON SATURDAY.

.LONG TERM FORECAST...THE BERING LOW EVENTUALLY MOVES INTO THE GULF
SATURDAY WITH ANOTHER MUCH WEAKER LOW MOVING INTO THE BERING. THIS
LOW TO FILL INTO THE GULF AS WELL BY MONDAY KICKING OUT THE OTHER
ONE. HIGH PRESSURE TO MOVE OVER THE CENTRAL BERING MONDAY AND TUESDAY
WITH A LOW DEVELOPING OVER THE KAMCHATKA REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 155 195
         HIGH WIND WARNING 185 187
         BLIZZARD WATCH 161
         HIGH WIND WATCH 181
MARINE...HURRICANE FORCE WIND WARNING...172 175 185 411 412 413 414.
         STORM WARNING...150 155 160 165 170 171 176 179 180.
         GALE WARNING...130 132 138 351 352.
         HEAVY FREEZING SPRAY WARNING...160 179 185 412.
FIRE WEATHER...NONE.

JN APR 11