Blizzard and Winter Storm in Alaska, November 5 to 6, 2011

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
643 AM AKDT SAT NOV 5 2011

.DISCUSSION...

...LOW PRESSURE SYSTEM NUMBER 1...
THE BIG BERING SEA LOW AND ITS OCCLUSION THAT CAME IN ON
THURSDAY...AND WHICH GRADUALLY WEAKENED ON FRIDAY...ARE NOW
FRAGMENTED OVER THE NORTHEAST CORNER OF THE ALASKA MAINLAND AND
HEADED INTO THE YUKON TERRITORY OF CANADA. THIS WEATHER SYSTEM
BROUGHT 11 INCHES OF SNOW TO GALENA IN THE WESTERN INTERIOR...AND
SEVERAL INCHES OF SNOW NEARLY EVERYWHERE IN NORTHERN ALASKA. BUT
THIS IS HISTORY.

...LOW PRESSURE SYSTEM NUMBER 2...
THE CURRENT GFS COMPUTER WEATHER FORECAST MODEL RUN PREDICTS A
BREAKOFF LOW / LOW PRESSURE SYSTEM NUMBER 2 / TO FORM THIS MORNING
ON AN OCCLUSION NOW IN THE CENTRAL BERING SEA. INDEED...THIS
PROCESS HAS ALREADY STARTED. THE BREAKOFF LOW IS EXPECTED TO REACH
KUSKOKWIM BAY SUNDAY MORNING AND THEN TO MOVE EASTWARD TO REACH
PRINCE WILLIAM SOUND SUNDAY NIGHT. THIS IS IN EXCELLENT AGREEMENT
WITH THE COMPUTER GUIDANCE TWO DAYS AGO.

WITH LOW PRESSURE SYSTEM NUMBER 2...GALE FORCE WINDS ARE FORECAST
FROM DALL POINT TO WALES INCLUDING NORTON SOUND BY THIS AFTERNOON.
THE WINDS WILL DIMINISH LATE TONIGHT OVER NORTON SOUND AND SUNDAY
EVENING OVER THE WATERS FROM DALL POINT TO BERING STRAIT INCLUDING
SAINT LAWRENCE ISLAND. DUE TO ICE FREE WATERS THERE...HEAVY
FREEZING SPRAY IS FORECAST. FINALLY...LOW PRESSURE SYSTEM NUMBER 2
IS FORECAST TO BRING 2 TO 5 INCHES OF SNOW TO THE YUKON
DELTA...THE LOWER YUKON VALLEY...AND THE UPPER KUSKOKWIM VALLEY
TONIGHT. THIS FORECAST HAS A GOOD CONFIDENCE FACTOR.

OVERALL...LOW PRESSURE SYSTEM NUMBER 2 WILL NOT BE AS STRONG AS
ITS PREDECESSOR...AND DEFINITIVELY WEAKER THAN ITS SUCCESSOR.

...LOW PRESSURE SYSTEM NUMBER 3...
THIS LOW PRESSURE SYSTEM IS THE ..REAL.. MATTER OF CONCERN FOR THE
NEXT SEVERAL DAYS...PARTICULARLY FOR TUESDAY AND
WEDNESDAY...NOVEMBER 8 AND 9. THE GFS AND EUROPEAN COMPUTER
WEATHER FORECAST MODELS ARE IN EXCELLENT AGREEMENT ON THE FORECAST
FOR MONDAY NIGHT. BOTH FORECAST A STORM WITH A CENTRAL PRESSURE
CLOSE TO 965 MILLIBARS NEAR 50 DEGREES NORTH LATITUDE AND 170
DEGREES EAST LONGITUDE FOR 3 AM AKST TUESDAY. THE EUROPEAN MODEL
FORECASTS A PATH OF THE LOW WEST OF THE PATH PREDICTED BY THE GFS
MODEL...BUT BOTH FORECAST IT TO BE EAST OF THE GULF OF ANADYR
TUESDAY EVENING. STORM FORCE SOUTH/SOUTHEAST WINDS ARE FORECAST
FOR ALL NORTHERN ALASKA COASTAL WATERS FROM DALL POINT UP TO POINT
HOPE FOR TUESDAY EVENING THROUGH WEDNESDAY MORNING.

LOW PRESSURE SYSTEM NUMBER 3 IS POTENTIALLY A DANGEROUS
STORM...NOT ONLY BECAUSE OF THE TERRIBLE MARINE WEATHER WHICH IT
MAY BRING...BUT MAINLY FOR ITS POTENTIAL TO CAUSE MAJOR COASTAL
FLOODING ON THE SOUTH COAST OF THE SEWARD PENINSULA...AT GAMBELL
AND ON THE CHUKCHI SEA COAST FROM CAPE KRUSENSTERN UP TO POINT
HOPE.

IT IS NOT YET REASONABLY CERTAIN THAT THIS FORECAST WILL VERIFY.
BUT THE CLOSE AGREEMENT BETWEEN THE U.S. AND EUROPEAN MODELS IS
CAUSE FOR CONCERN. ON THE OTHER HAND...SUCCESSIVE MODEL RUNS HAVE
COME UP WITH SIGNIFICANT DIFFERENCES IN THE FORECASTS FOR NEXT
TUESDAY ONWARD. SO...THE PROCESS NOW IS ONE OF WATCHFULNESS.

TO REPEAT...THE FORECAST FOR NEXT TUESDAY AND WEDNESDAY IS NOT YET
SUFFICIENTLY CERTAIN. BY MONDAY EVENING...THE OUTCOME WILL BE
COMING MUCH CLOSER INTO VIEW.

LOW PRESSURE SYSTEM NUMBER 3 IS FORECAST TO LOOK VERY MUCH LIKE
THE STORM THAT CAUSED THE GREAT BERING SEA COASTAL FLOOD OF
NOVEMBER 11 1974. THE 1974 STORM CAUSED MAJOR COASTAL FLOODING ON
THE SOUTH COAST OF NORTON SOUND AND MINOR COASTAL FLOODING TO
KOTZEBUE SOUND UP TOWARD POINT HOPE.

THERE ARE SEVERAL DIFFERENCES...

FIRST...IN 1974 THERE WAS CONSIDERABLE SHORE ICE IN NORTON SOUND
AND THE SOUTHEAST CHUKCHI SEA WAS MOSTLY ICE COVERED. THIS YEAR
THESE WATERS ARE LARGELY ICE FREE. ON THE PLUS SIDE...THE SOUTH
COAST OF THE SEWARD PENINSULA WILL NOT HAVE LARGE CHUNKS OF ICE
THAT COULD BATTER THE COAST THIS TIME. ON THE MINUS SIDE...THE
CHUKCHI SEA COAST WILL HAVE LITTLE ICE TO BLOCK INCOMING SEAS.
FURTHER...SHORELINE EROSION OVER THE PAST 37 YEARS HAS LEFT LARGE
STRETCHES OF COAST MORE VULNERABLE TO STORMS OVER THE NEARBY
OCEAN. THE CHUKCHI SEA COAST FROM CAPE KRUSENSTERN TO POINT HOPE
IS THE FOCUS THIS TIME.

THERE WILL BE A COUPLE OF DAYS OF COLD OFFSHORE WIND ON THE
NORTHWEST COAST...STARTING TODAY. FREEZEUP THERE IS POISED TO
RAPIDLY PROGRESS. THIS WILL PROVIDE SOME INCREASED ICE NEAR
SHORE...BUT MOSTLY IN KOTZEBUE SOUND AND NORTON BAY. ANOTHER WEEKS
TIME WOULD MAKE A POSITIVE DIFFERENCE...BUT THIS WILL CLEARLY NOT
BE AVAILED THIS TIME.

SECOND...ON THE PLUS SIDE...THE OCEAN TIDES IN THIS CASE ARE NOT
QUITE AS HIGH AS THEY WERE IN THE STORM ON NOVEMBER 11 1974. SINCE
THE MAGNITUDE OF TIDES FROM DALL POINT UP TO POINT HOPE IS ONLY 1
TO 3 FEET...THIS IS NOT A MAJOR FACTOR. FOR NEXT TUESDAY AND
WEDNESDAY...THE HIGH AND LOW TIDES AT NOME ARE FORECAST TO BE
1.2 FEET AND 0.3 FEET. THIS IS CLOSE TO AVERAGE. IN 1974...MAXIMUM
MONTHLY TIDES CAME AT THE SAME TIME AS THE STORM.

THIS TIME...FULL MOON IS ON THURSDAY NOVEMBER 10. OCEAN TIDES
NEAR THE TIMES OF FULL MOON OR NEW MOON ARE NEAR AVERAGE OR ABOVE
AVERAGE. AT FIRST QUARTER OR LAST QUARTER THE MAGNITUDE OF TIDES
IS USUALLY AT A MINIMUM. THE BOTTOM LINE HERE IS THAT THE OCEAN
TIDE COMPONENT OF COASTAL WATER LEVELS THIS TIME WILL ONLY BE A
FOOT OR FOOT AND A HALF LESS THAN ON NOVEMBER 11 1974.

THIRD...THE COASTAL FLOODING ON NOVEMBER 11 1974 OCCURRED AT MID
DAY AT NOME AND LATE AFTERNOON IN KOTZEBUE SOUND. IF...IF THE GFS
AND EUROPEAN MODEL FORECASTS ARE CLOSE TO TRUE...THIS UPCOMING
EVENT WILL OCCUR AT NIGHT.

AGAIN...IT IS STILL TOO EARLY TO RAISE THE WELKIN...BUT BRIGHT
EYES ARE LOOKING SOUTHWEST.

EARLY MORNING POLAR ORBITING SATELLITE IMAGERY SHOWS CONSIDERABLE
CLEARING OVER THE INTERIOR EXCEPT THE SOUTHEAST CORNER / ZONE
224...INCLUDING EAGLE AND TOK / AS WELL AS THE NORTH SLOPES OF THE
ALASKA RANGE. THERE IS EXTENSIVE CLEAR SKY OVER NORTON SOUND...FROM
NORTH OF SAINT LAWRENCE ISLAND UP THROUGH BERING STRAIT AND MUCH
OF THE CHUKCHI SEA COAST. WELL DEFINED SCATTERED SNOW SHOWERS ARE
AGAIN PRESENT OVER COASTAL WATERS FROM POINT HOPE TO POINT BARROW.
IT IS STILL OVERCAST EAST OF BARROW...BUT OFFSHORE WINDS LATER
TODAY ARE EXPECTED TO CLEAR LARGE PORTIONS OF ALASKAS ARCTIC
SLOPE.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...ON DAY 4 / TUESDAY
NOVEMBER 8 / STORM FORCE WINDS AND POSSIBLE COASTAL FLOOD FROM
DALL POINT TO BERING STRAIT...INCLUDING THE SOUTH COAST OF THE
SEWARD PENINSULA...AND ALSO THE COAST FROM CAPE KRUSENSTERN UP TO
POINT HOPE. SEE DISCUSSION OF LOW PRESSURE SYSTEM NUMBER 3
ABOVE...FIFTH PARAGRAPH ONWARD.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
HEAVY FREEZING SPRAY WARNING FOR PKZ200-PKZ210-PKZ220.

SMALL CRAFT ADVISORY FOR PKZ200-PKZ210.

GALE WARNING FOR PKZ200-PKZ210.
&&

TF NOV 11