Small Craft Advisory 209, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
511 AM AKDT SUN MAR 8 2015

.ANALYSIS AND UPPER LEVELS...

PROGRESSIVE FLOW PERSISTS THIS MORNING WITH A BROAD UPPER TROUGH
EXTENDING BETWEEN RIDGES OVER EASTERN RUSSIA AND THE CANADIAN
ROCKIES. EMBEDDED WITHIN THIS TROUGH IS AN UPPER LOW NEAR THE
BERING STRAIT. A TROUGH IS ALSO SOUTHWEST OF ATTU. A 110 KT ZONAL
JET IS LOCATED OVER THE SOUTHERN BERING. AT THE SURFACE...THE JET
IS DRIVING THE LEADING EDGE OF A SURGE OF COLD AIR INTO SW AK WITH
SOME SNOW SHOWERS. A LOW SOUTH OF ATTU HAS A FRONT AFFECTING THE
WESTERN AND CENTRAL ALEUTIANS. HIGH PRESSURE MOVING INTO
SOUTHCENTRAL IS PARTIALLY CLEARING SKIES AND ALLOWING FOR WIDESPREAD
BELOW FREEZING TEMPERATURES.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT FOR THE NEXT FEW DAYS. THE
LEADING EDGE OF THE COLD SURGE WILL REACH THE ALASKA AND ALEUTIAN
RANGES THIS AFTERNOON AND FLOW INTO SOUTHCENTRAL TONIGHT AND SUN.
HIGH PRESSURE WILL BUILD OVER MAINLAND AK THROUGH MON NIGHT. AT
THE SAME TIME LOW PRESSURE WILL SET UP ALONG THE NORTH GULF COAST
AND LINGER INTO MON. THE RESULT WILL BE A STRONG PRESSURE
GRADIENT DEVELOPING ALONG THE COAST SETTING UP SIGNIFICANT GAP
FLOWS. MEANWHILE IN THE WEST...THE FRONT ASSOCIATED WITH THE LOW
SOUTH OF ATTU WILL AFFECT THE ENTIRE ALEUTIAN CHAIN THROUGH MON
NIGHT. THE FORECAST UTILIZES THE EC...WITH SOME GEM REGIONAL TO
CAPTURE GAP OUTFLOW DETAIL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

THE BIGGEST UNCERTAINTY TODAY DEALS WITH THE MOVEMENT OF A WEAK
UPPER LEVEL WAVE IN ADVANCE OF THE MAIN UPPER LEVEL LOW THAT WILL
MOVE THROUGH THE AREA TONIGHT. THERE HAS BEEN SOME CLOUD
DEVELOPMENT ALONG THE KENAI, CHUGACH, AND TALKEETNA MOUNTAINS
EARLY THIS MORNING REVEALING A GOOD AMOUNT OF MOISTURE IS STILL
IN THE AREA. THERE HAVE ALSO BEEN A FEW WEAK ECHOES ON RADAR AS
WELL. THIS DEVELOPMENT IS EARLIER THAN INDICATED ON MODELS WHICH
SHOWED THE CLOUDS AND A FEW SNOW SHOWERS DEVELOPING IN THE
AFTERNOON. AT THIS TIME IT DOES NOT LOOK LIKE THIS IS INDICATED
MORE THAN ISOLATED SNOW SHOWERS BUT THERE IS A SMALL CHANCE OF
MORE WIDESPREAD SNOW SHOWERS TODAY THAN INDICATED IN THE CURRENT
FORECASTS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TODAY THROUGH MONDAY)...

SCATTERED SNOW SHOWERS CONTINUE ACROSS THE SOUTHERN HALF OF THE
BRISTOL BAY AREA THIS MORNING AS MOIST ONSHORE FLOW UPSLOPES
TOWARD THE ALEUTIAN RANGE. THESE SHOWERS WILL TAPER OFF IN THE
MORNING WHILE SNOW SHOWERS WILL RE-DEVELOP ACROSS THE WEST COAST
OF ALASKA THIS MORNING AND PUSH INLAND DURING THE DAY. A STOUT
UPPER LEVEL LOW WILL TAP INTO THE RESIDUAL MOISTURE LEFT BEHIND
FROM THE SYSTEM THAT PUSHED THROUGH THE AREA FRIDAY NIGHT/MONDAY
MORNING. THIS WILL BRING ANOTHER 1 TO 2 INCHES OF SNOW
ACCUMULATION TO MUCH OF THE AREA. IN ADDITION TO INCREASING SHOWER
ACTIVITY...WINDS WILL BEGIN TO RAMP UP LATE THIS MORNING WHICH
WILL CREATE BLOWING SNOW CONCERNS ACROSS THE KUSKOKWIM DELTA AND
THE WESTERN CAPES OF THE BRISTOL BAY AREA. VISIBILITIES WILL BE
REDUCED TO ONE MILE OR LESS AT TIMES ACROSS THE AFOREMENTIONED
AREAS BUT WILL BE BRIEF DUE TO THE SHOWERY NATURE OF THE
PRECIPITATION. SNOW WILL TAPER OFF THIS EVENING BUT WINDS WILL
TAKE A WHILE TO SLACKEN ACROSS SOUTHWEST ALASKA. THIS WILL LEAD TO
WIND CHILL VALUES FROM 10 BELOW TO 30 BELOW ACROSS THE AREA FROM
MIDNIGHT TONIGHT THROUGH EARLY MONDAY MORNING. WINDS WILL WEAKEN
ON MONDAY AND BRING AN END TO WIND CHILLS...ALTHOUGH WELL BELOW
NORMAL TEMPERATURES WILL PERSIST.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TODAY THROUGH MONDAY)...

MUCH OF THE BERING SEA WILL BE RELATIVELY TAME OVER THE NEXT
SEVERAL DAYS AND AN AREA OF HIGH PRESSURE BEGINS TO BUILD ACROSS
THE NORTHERN TWO-THIRDS OF THE BERING SEA. SCATTERED SNOW SHOWERS
WILL BE SEEN OVER THE EASTERN ALEUTIANS ALONG THE EASTERN PERIPHERY
OF THE RIDGE THROUGH MONDAY. TOWARD THE WESTERN ALEUTIANS...A VERY
WET AND WINDY PATTERN IS SHAPING UP AS AN AREA OF LOW PRESSURE
FROM THE NORTH PACIFIC MOVES SOUTH OF SHEMYA. THIS LOW WILL CLASH
WITH THE RIDGE BUILDING OVER THE BERING SEA TO CREATE A VERY
COMPACT PRESSURE GRADIENT OVER THE WESTERN ALEUTIANS THAT WILL
BRING STORM FORCE WINDS TO THE COASTAL WATERS AND WIND GUSTS
UPWARDS TO 70 MPH BETWEEN SHEMYA AND ADAK. HEAVY SNOW AND RAIN
WILL FALL ACROSS THE WESTERN ALEUTIANS OVER THE NEXT 60 HOURS WITH
NEAR BLIZZARD CONDITIONS POSSIBLE ALONG THE SMALLER ISLANDS
BETWEEN SHEMYA AND ADAK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AS THE LOW OVER THE NORTH GULF COAST DRIFTS EAST AND WEAKENS
TUESDAY...OUTFLOW WINDS ALONG THE GULF COAST WILL ALSO SLOWLY
DIMINISH INTO THE MIDDLE OF NEXT WEEK. OFFSHORE FLOW AND RIDGING
WILL ALSO TAKE OVER MUCH OF THE SOUTHERN MAINLAND THROUGH THE
MIDDLE OF NEXT WEEK WHICH WILL KEEP CONDITIONS DRY UNDER CLEAR
SKIES THROUGHOUT THE AREA. OVER THE BERING...THE NORTH PACIFIC LOW
ENTERING THE WESTERN ALEUTIANS ON SUNDAY WILL BRING CONTINUED
GALE FORCE WINDS ALONG WITH SNOW MIXING WITH RAIN TO THE CENTRAL
ALEUTIANS THROUGH TUESDAY. THIS LOW WILL THEN RETURN TO THE NORTH
PACIFIC ON WEDNESDAY AND BECOME ABSORBED IN A COMPLEX LOW THAT WILL
BECOME THE FOCAL POINT FOR THE WEATHER OVER THE SOUTHERN MAINLAND
LATE NEXT WEEK.

THIS COMPLEX LOW REMAINS A CHALLENGE IN THE LONG TERM FORECAST AS
THERE HAS BEEN LITTLE IF ANY IMPROVEMENT IN THE MODEL AGREEMENT
SINCE YESTERDAY. THE GFS CONTINUES TO BE MORE AGGRESSIVE WITH AN
ARCTIC TROUGH THAT DEVELOPS OVER THE MAINLAND ON WEDNESDAY...AND
AS A RESULT IS MUCH DEEPER WITH THIS COMPLEX LOW AS IT MOVES INTO
THE GULF ON THU-FRI. ON THE OTHER SIDE OF THE COIN...THE EC CONTINUES
TO BE WEAKER WITH THE ARCTIC TROUGH...DEEPER WITH A LOW IN THE
BERING SEA...AND MUCH FURTHER EAST WITH THE GULF LOW WITH RIDGING
OVER THE MAINLAND. AFTER COORDINATION WITH WPC THIS MORNING IT WAS
DETERMINED THAT THE EC WILL BE THE PREFERRED SOLUTION IN THE LONG
TERM FOR THE TIME BEING AS THE GFS IS PROBABLY TOO DEEP WITH
ARCTIC TROUGH WITH A BUILDING NORTHEAST PACIFIC RIDGE. WITH LARGE
VARIABILITY IN THE MODELS...CONFIDENCE IN THE LONG TERM FORECAST
BEYOND THURSDAY IS QUITE LOW.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...
 GALES...120 127 129 132 150 173 175 176
 STORMS...130 131 177 178
 HVY FRZG SPRY...130 131 137-139 150 160 165 179-181 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DEK/CC

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
1022 AM AKDT SUN MAR 08 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1200 AM     SNOW             CANTWELL                63.37N 148.92W
03/07/2015  E5.0 INCH                           AK   LAW ENFORCEMENT

            4 TO 5 INCHES OF ESTIMATED STORM TOTAL ACCUMULATION
            REPORTED BY STATE TROOPERS NEAR CANTWELL. STILL SNOWING
            AS OF MIDNIGHT.

0402 AM     SNOW             TRAPPER CREEK           62.24N 150.42W
03/07/2015  M12.0 INCH                          AK   DEPT OF HIGHWAYS

            12 INCHES OF SNOW ON THE PARKS HIGHWAY FROM TALKEETNA
            SPUR ROAD TO MILEPOST 163.

0700 AM     SNOW             7 S TALKEETNA           62.24N 150.09W
03/07/2015  M6.5 INCH                           AK   COCORAHS

0532 PM     SNOW             8 SE EAGLE RIVER        61.24N 149.40W
03/07/2015  M2.7 INCH                           AK   NWS EMPLOYEE

            2.7 INCHES OF NEW SNOW SINCE 5PM FRI. HEAVIEST FELL
            BETWEEN NOON AND 2PM TODAY.

0559 PM     SNOW             8 NW HOMER              59.72N 151.68W
03/07/2015  M2.0 INCH                           AK   TRAINED SPOTTER

            STORM TOTAL SNOWFALL

0559 PM     SNOW             PAXSON                  63.09N 145.61W
03/07/2015  M12.0 INCH                          AK   DEPT OF HIGHWAYS

            STORM TOTAL SNOWFALL. MIDNIGHT TO 6PM 3/7.

0559 PM     SNOW             41 NNE TALKEETNA        62.88N 149.59W
03/07/2015  M16.0 INCH                          AK   TRAINED SPOTTER

            FINAL SNOWFALL TOTAL MEASURED THIS AFTERNOON.

&&

JPW

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1047 AM AKDT SUN MAR 8 2015

AKZ111-090430-
MATANUSKA VALLEY-
INCLUDING THE CITIES OF...PALMER...WASILLA...SUTTON...CHICKALOON
1047 AM AKDT SUN MAR 8 2015

...AVALANCHE DANGER FOR HATCHER PASS...

AN AVALANCHE WARNING IS IN EFFECT AT HATCHER PASS FROM SATURDAY,
MARCH 7,2015 AT 20:00 TO SUNDAY, MARCH 8, 2015 AT 20:00.

THE AVALANCHE HAZARD IS RATED HIGH ACCORDING TO THE NORTH AMERICAN
PUBLIC AVALANCHE DANGER SCALE.

VERY DANGEROUS AVALANCHE CONDITIONS. TRAVEL IN AVALANCHE TERRAIN
NOT RECOMMENDED. NATURAL AVALANCHES LIKELY, HUMAN TRIGGERED
AVALANCHES VERY LIKELY. LARGE AVALANCHES IN MANY AREAS; OR VERY
LARGE AVALANCHES IN SPECIFIC AREAS.

FOR MORE INFORMATION: HTTP://WWW.HATCHERPASSAVALANCHECENTER.ORG

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1125 AM AKDT SUN MAR 08 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1123 AM     SNOW             15 NE TALKEETNA         62.49N 149.76W
03/08/2015  M13.0 INCH                          AK   PUBLIC

            SNOW TOTAL FROM MAR 7TH.

&&

JPW