Small Craft Advisory 311, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 AM AKDT THU APR 9 2015

.ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL CLOSED LOW IS POSITIONED JUST WEST OF CAPE NEWENHAM
THIS MORNING. WITH A NEGATIVE TILTED TROUGH EXTENDING FROM THE
CLOSED LOW THROUGH THE ALASKA PENINSULA INTO THE LOWER
SOUTHWESTERN GULF REGION. THE RADAR IMAGERY IS SHOWING A LARGE
SWATH OF SNOW SHOWERS IN THE BRISTOL BAY INTERIOR MOVING SOUTH TO
NORTH. THIS COINCIDES WITH A VORTICITY LOBE MOVING INTO THE
BRISTOL BAY AREA THIS MORNING. SURFACE OBSERVATIONS ACROSS
INTERIOR BRISTOL BAY HAVE BEEN REPORTING LIGHT TO MODERATE SNOW
SHOWERS. THE HEAVIEST SNOWFALL WILL FALL ALONG THE ALEUTIAN
RANGE...BEING REINFORCED WITH OROGRAPHIC LIFT ALONG THE
MOUNTAINS. REFLECTED AT THE SURFACE THERE IS A GALE FORCE LOW
LOCATED IN KAMISHAK BAY WITH THE ASSOCIATED FRONTAL BOUNDARY IN
THE NORTHERN GULF. THIS IS BRINGING WARM TEMPERATURES TO THE
NORTHERN COASTAL AREAS WITH GALE FORCE SOUTHEASTERLY WINDS. THE
TEMPERATURES ALONG THE COASTAL AREAS ARE IN LOWER 40S WITH ALL
PRECIPITATION IN THE FORM OF RAIN AND WINTRY MIX INLAND AREAS. THE
SATELLITE IMAGERY REFLECTS A LARGE SWATH OF MOISTURE IN THE
WESTERN GULF SPREADING INTO SOUTHCENTRAL REGION AND SPILLING OVER
THE ALASKA PENINSULA AND ALEUTIAN RANGE.

THE BERING SIDE...THE GALE FORCE LOW IS POSITIONED IN THE BRISTOL
BAY AREA WITH STRONG GUSTY WINDS ON THE BACKSIDE FOR REST OF THE
BERING SEA. THE SATELLITE IMAGERY IS SHOWING THE HEAVIEST SNOW
SHOWERS FROM PRIBILOF ISLAND NORTHWARD...WHILE THE LOWER BERING
SEA AND ALEUTIAN CHAIN HAS MORE SCATTERED SNOW SHOWERS ACCOMPANIED
BY STRONG GUSTY WEST TO NORTHWESTERLY WINDS.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN GOOD AGREEMENT THIS MORNING WITH THE STORM
FORCE LOW AS IT MOVES INLAND INTO THE BRISTOL BAY REGION. THE
MODELS ARE HANDLING THE ASSOCIATED FRONTAL BOUNDARY IN THE
SOUTHWESTERN GULF AS IT MOVES TO THE NORTHERN GULF BY LATE
THURSDAY AFTERNOON. THE NAM WAS THE PREFERRED MODEL OF CHOICE FOR
THE SHORT TERM FORECAST PERIOD. THE FORECAST CONFIDENCE REMAINS
ABOVE AVERAGE HEADING INTO THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL LOW OVER THE SOUTHWEST COAST OF ALASKA WILL
PROGRESS EASTWARD...PUSHING ACROSS KODIAK ISLAND TONIGHT AND INTO
THE CENTRAL GULF BY FRIDAY AFTERNOON. A FRONT ASSOCIATED WITH THIS
LOW HAS JUST CLEARED TO THE NORTH OF KODIAK ISLAND AND WILL SLIDE
TO THE GULF COAST THIS AFTERNOON AND TO INLAND AREAS THIS
EVENING. THIS FRONT WILL THEN BREAK APART LATE TONIGHT. BY FRIDAY
AND FRIDAY NIGHT ALL OF SOUTH CENTRAL ALASKA WILL BE IN WEAK
CYCLONIC FLOW WITH LITTLE DYNAMICS AND NOT MUCH MOISTURE WITH NOT
REALLY ANY WEATHER FEATURES TO FOCUS ON. HOWEVER...THERE IS JUST
ENOUGH MOISTURE TO KEEP SOME LOW POPS OVER MOST AREAS. THE SHOWER
ACTIVITY...LIMITED AS IT WILL BE...MAY BE THERMALLY DRIVEN
(DIURNAL) AS WELL.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TODAY THROUGH FRI NIGHT)...

ALL SIGNS CONTINUE TO POINT TO A SHOWERY REGIME REMAINING IN PLACE
THROUGH THE SHORT-TERM. SNOW...HEAVY AT TIMES...HAS BEEN SEEN
THROUGHOUT THE BRISTOL BAY AREA OVERNIGHT AND THIS MORNING ALONG
THE LEADING EDGE OF THE FRONT ASSOCIATED WITH THE LOW IN THE
EASTERN BERING SEA. THIS FRONT IS EXPECTED TO SLOW DOWN/STALL
ACROSS THE NORTHERN PORTIONS OF THE BRISTOL BAY AREA AS CROSS
BARRIER WINDS BEGIN TO DIMINISH. THIS WILL SET UP PLACES LIKE
ILIAMNA AND PORT ALSWORTH TO SEE DECENT SNOW FALL THROUGH THE
EARLY AFTERNOON. STORM TOTAL SNOW AMOUNTS NORTH AND EAST OF KING
SALMON ARE EXPECTED TO BE IN THE 5 TO 8 INCH RANGE...HENCE THE
ISSUANCE OF A WINTER WEATHER ADVISORY PRIOR TO THE ISSUANCE OF THIS
FORECAST PACKAGE. ELSEWHERE...SNOW AND RAIN SHOWERS WILL BE COMMON
WITH JUST MINIMAL NEW SNOW ACCUMULATIONS.

OVER THE SOUTHERN TIP OF THE ALASKA PENINSULA TOWARD COLD BAY AND
KING COVE...A STRONG WIND EVENT APPEARS TO BE IN THE MAKING. AS
THE LOW IN THE EASTERN BERING PUSHES INLAND THIS MORNING...A VERY
COMPACT PRESSURE GRADIENT WILL BE OBSERVED. THIS HAS LED TO WINDS
ALREADY GUSTING IN THE 40 TO 50 MPH RANGE. HOWEVER...PRESSURE
RISES ON THE BACK SIDE OF THE LOW (ISALLOBARIC FLOW) WILL BE
COUPLED WITH A SHORTWAVE PUSHING ACROSS THE ALASKA PENINSULA. THIS
SHOULD FAVOR WINDS GUSTING IN THE 60 TO 65 MPH RANGE AND REMAIN
JUST BELOW HIGH WIND CRITERIA. IF THE WINDS WERE MORE NORTHWESTERLY
THAN WESTERLY...THIS COULD HAVE BEEN A POTENTIAL HIGH WIND EVENT.

&&

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

NORTHWEST FLOW ALOFT WILL CONTINUE TO USHER IN A COLD AIR MASS
BEING ADVECTED FROM SIBERIA. THIS SHOULD CONTINUE THE SHOWERY
REGIME AS HAS BEEN OBSERVED VIA SATELLITE IMAGES OVERNIGHT. THE
BERING SIDE OF THE ALEUTIAN ISLANDS WILL SEE SOME OF THE SNOW
SHOWERS UPSLOPE ALONG THE TERRAIN WHICH COULD LEAD TO SOME STEADY
SNOW AND MINOR SNOW ACCUMULATIONS. OTHER THAN THAT...WINDS WILL
BEGIN TO DIMINISH AS THE LOW PUSHES INLAND THIS AFTERNOON AND NO
LARGER FEATURES ARE EXPECTED THROUGH THE REMAINDER OF THE SHORT-
TERM.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

A ZONAL TRANS PACIFIC JET WILL BEGIN TO BUCKLE SAT NIGHT...CAUSING
A PATTERN CHANGE THAT WILL AFFECT THE FORECAST AREA AT LEAST
THROUGH THE MIDDLE OF NEXT WEEK. CYCLONIC FLOW OVER MAINLAND AK
WILL GIVE WAY TO A BUILDING RIDGE OVER THE WEST COAST OF NORTH
AMERICA BEGINNING TUE. A DEEPENING TROUGH WILL AFFECT THE
ALEUTIANS SUN THROUGH WED. AT THE SURFACE...A LOW OVER THE
NORTHERN GULF WILL WEAKEN IN PLACE...DISSIPATING MON NIGHT WHEN
SURFACE RIDGING BUILDS INTO THE AREA. NORTHWEST FLOW OVER THE
BERING WILL SLOWLY WEAKEN THROUGH SUN. A LOW SOUTH OF THE WESTERN
ALEUTIANS ON MON WILL BRING A FRONT NEAR THE ALEUTIANS AND AKPEN
THROUGH WED.

ZONAL FLOW WITH UNCERTAIN TIMING OF WAVES IS BEST HANDLED BY AN
ENSEMBLE APPROACH...AND THE FORECAST INITIALLY UTILIZES THE EC AND
THEN RAPIDLY YIELDS TO THE WPC SOLUTION.

THE BERING AND ALEUTIANS CAN EXPECT RAIN AND SNOW SHOWERS...
DIMINISHING ON MON. THIS WILL BE FOLLOWED BY A ROUND OF SNOW
CHANGING TO RAIN...ASSOCIATED WITH THE FRONT APPROACHING THE AREA
THROUGH WED. AT FIRST SHOWERY CONDITIONS WILL PERSIST OVER
SOUTHCENTRAL AND COASTAL LOCATIONS. RAIN WILL BE DOMINANT ALONG
THE COAST WITH A MIX CROSSING THE MOUNTAIN RANGES...WITH SNOW MORE
COMMON AT NIGHT. DRYING WILL THEN OCCUR TUE INTO WED.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FOR SNOW 161.
MARINE...GALE WARNINGS 119 120 125 130 131 132 150 155 160 165
         170 171 172 173 174 176 177 178 179 180.
         HEAVY FREEZING SPRAY WARNINGS 180 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
119 PM AKDT THU APR 09 2015

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

0116 PM     SNOW             NEW STUYAHOK            59.45N 157.31W
04/09/2015  E4.0 INCH                           AK   COUNTY OFFICIAL

            3-4 INCHES OF SNOW ESTIMATED IN TOWN. STILL SNOWING.

0116 PM     SNOW             KOLIGANEK               59.73N 157.28W
04/09/2015  E7.0 INCH                           AK   PUBLIC

            6 TO 8 INCHES OF WET SNOW HAS FALLEN SO FAR. STILL
            SNOWING.

&&

JPW

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
142 PM AKDT THU APR 09 2015

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

0140 PM     SNOW             IGIUGIG                 59.33N 155.88W
04/09/2015  E4.0 INCH                           AK   PUBLIC

            3 TO 4 INCHES OF SNOW HAVE FALLEN.

&&

JPW