Small Craft Advisory 343, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
628 PM AKDT THU APR 24 2014

.UPDATE...

A FEW INSTABILITY RAIN SHOWERS HAVE POPPED UP OVER THE MATANUSKA
VALLEY THIS EVENING. STEERING FLOW ALOFT APPRECIABLY WEAK THOUGH
SOME DRIFTING/MOVEMENT TO THE NORTH CAN BE EXPECTED. EXPECTING
THESE FEW SHOWERS TO DISSIPATE QUICKLY WITH THE LOSS OF DAYTIME
HEATING.

FURTHER SOUTH...CIRCULATION SNEAKING JUST WEST OF MIDDLETON ISLAND
APPEARS A BIT STRONGER THAN MODELS WOULD SUGGEST. MAIN SUBSTANCE
OF THIS DEVELOPMENT IS THAT PRECIPITATION MAY BE A BIT MORE
WIDESPREAD TONIGHT OVER THE SOUTHERN TO EASTERN KENAI PENINSULA.
PRECIPITATION ACROSS THERE IS EXPECTED TO BE MAINLY RAIN...THOUGH
A BIT OF WET NON ACCUMULATING SNOW IS POSSIBLE THROUGH PASSES
OVERNIGHT.

&&

UPDATE...JAM

.PREV DISCUSSION... /ISSUED 305 PM AKDT THU APR 24 2014/

ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW ARE OVER THE
ALASKA CANADIAN BORDER MOVING INTO THE EASTERN INTERIOR AS IT
BECOMES A TROUGH THAT WILL EXTEND ACROSS THE INTERIOR NORTH OF THE
ALASKA RANGE. THE WEAK LOW AT BOTH THE SURFACE AND ALOFT OVER THE
KODIAK ISLAND AREA WILL DRIFT NORTH AS IT DISSIPATES. THE BIG
ALEUTIAN BERING SEA LOW IS NEARLY VERTICALLY STACKED OVER THE
CENTRAL ALEUTIANS WITH A FRONT EXTENDING THROUGH THE WEST CENTRAL
ALEUTIANS IN AN ARC JUST SOUTH OF THE PRIBILOF ISLANDS TO THE
WESTERN END OF THE ALASKA PENINSULA.

MODEL DISCUSSION...
THE MODELS INITIALIZED WELL AND HAVE A GOOD HANDLE ON THE CURRENT
SCENARIO. OVERALL SYNOPTIC LEVEL AGREEMENT IS GOOD THROUGH THE
WEEKEND. THE SHORT TERM SOLUTION FOR THE LOW IN THE EASTERN
INTERIOR IS WORKING OUT WELL AND THE MAIN IMPACT FOR THE ANCHORAGE
AREA OF RESPONSIBILITY IS THE INCREASED CLOUD COVER AND THREAT FOR
SHOWERS IN THE COPPER RIVER BASIN THROUGH TONIGHT. THE BULK OF THE
SHOWERY ACTIVITY SHOULD HOWEVER REMAIN NORTH OF THE WRANGELL
MOUNTAINS AND ALASKA RANGE. THE LOW OVER THE CENTRAL ALEUTIANS IS
PROGGED TO TRACK EAST STALLING OVER THE SAND POINT AREA LATE
FRIDAY NIGHT. THE FRONT ELONGATES EAST IN THE GULF OF ALASKA
SPREADING RAIN ACROSS KODIAK ISLAND THEN TO THE NORTH GULF COAST
AND PRINCE WILLIAM SOUND THROUGH THE WEEKEND.

SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE THREAT FOR SHOWERS IN THE COPPER RIVER BASIN IS CONFINED TO
NORTH OF THE WRANGELL MOUNTAINS TONIGHT. AFTER THE SURFACE LOW
MOVES NORTH OF THE ALASKA RANGE EXPECT THE SOUTH WIND FLOW TO
DEVELOP ACROSS THE COPPER RIVER BASIN ESPECIALLY BETWEEN EUREKA
AND GLENNALLEN. EXPECT CONDITIONS TO REMAIN ON THE DRIER SIDE
ACROSS THE COOK INLET AND SUSITNA VALLEY AREAS ALTHOUGH CLOUDS
WILL INCREASE IN COOK INLET AS THE FRONT APPROACHES FRIDAY. THE
PRESSURE GRADIENT WILL INCREASE IN ADVANCE OF THE INCOMING FRONT
AND WE WILL SEE THE TYPICAL GUSTY HILLSIDE AND TURNAGAIN ARM WINDS
TONIGHT THROUGH SATURDAY.

SOUTHWEST ALASKA... THE INCOMING ALEUTIAN LOW AND ASSOCIATED
FRONT WILL CONTINUE TO PRODUCE STRONGER PRE FRONTAL WINDS ALONG
THE ALASKA PENINSULA THROUGH FRIDAY. POST FRONTALLY THE WIND WILL
DROP OFF OVER THE DUTCH HARBOR AREA TONIGHT AND REMAIN LIGHTER
THROUGH FRIDAY. WINDS WILL INCREASE AND BE GUSTY OUT OF THE
NORTHWEST AROUND THE BACK SIDE OF THE LOW AS IT TRACKS TO THE EAST
INTO THE GULF. CLOUDS WILL OVER SPREAD THE BRISTOL BAY REGION
FRIDAY. THE STRONG CROSS BARRIER FLOW ACROSS THE ALEUTIAN
MOUNTAINS SHOULD LIMIT THE COVERAGE OF THE RAIN IN THE ZONE AS WE
SHOULD SEE THE TYPICAL DOWN SLOPE RAIN SHADOW NEAR KING SALMON.
RAIN WILL BE MINIMAL OVER THE LOWER KUSKOKWIM VALLEY INTO THE
KUSKOKWIM DELTA AS THE FRONT SHOULD REMAIN FAR ENOUGH SOUTH THAT
THESE AREAS WILL BE ON THE FRINGE OF THE PRECIPITATION SHIELD. AS
THE LOW SLIDES EAST THROUGH THE WEEKEND A LEE SIDE TROUGH FORMS
WEST OF THE ALASKA RANGE AND WE WILL LIKELY SEE A LOW FORM IN THIS
TROUGH. THEREFORE EXPECT AN INCREASED CHANCE FOR PRECIPITATION CAN
BE EXPECTED.

BERING SEA/ALEUTIANS...
AS PREVIOUSLY DISCUSSED THE LOW NOW NEAR THE CENTRAL ALEUTIANS
WILL TRACK EAST. COLDER AIR WRAPS AROUND THIS LOW INTO THE WESTERN
AND CENTRAL ALEUTIANS TONIGHT AND FRIDAY. THIS WILL RESULT IN SNOW
MIXING IN WITH THE RAIN SHOWERS FOR THE WESTERN AND CENTRAL
ALEUTIANS THAT WILL PERSIST INTO SATURDAY. A WEAK RIDGE OF HIGH
PRESSURE BUILDS INTO THE WESTERN BERING SEA AS THIS LOW EXITS TO
THE EAST THAT SHOULD DECREASE OR END THE SHOW ACTIVITY SATURDAY
NIGHT AND SUNDAY. THE FRONT WITH THIS STORM SHOULD REMAIN SOUTH OF
THE PRIBILOFS. EAST FLOW AHEAD OF THE FRONT WILL CONTINUE TO
SPREAD CLOUDS ACROSS THE PRIBILOF ISLANDS WITH PERIODS OF LIGHT
RAIN LIKELY ESPECIALLY FOR ST GEORGE. THE FLOW WILL COME AROUND TO
NORTH BY SATURDAY MORNING RESULTING IN MORE SHOWERY PRECIPITATION.

LONG TERM FORECAST...
THE LOW COMING OFF KAMCHATKA MONDAY WILL REMAIN IN THE NORTHERN
BERING SEA THROUGH THURSDAY WITH A TROUGH EXTENDING TO A LOW IN
THE GULF OF ALASKA. LATE NEXT WEEK A RIDGE POKES INTO THE
MAINLAND. HOWEVER THE PERSISTENT SOUTHWEST FLOW INTO THE MAINLAND
SHOULD KEEP CONDITIONS ON THE MORE CLOUDY AND COOL SIDE THROUGH
NEXT WEEK.

AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...GALE...119 120 130 131 132 136 137 138 150 155 170 174
                176 351 352 414
FIRE WEATHER...NONE

SAM APR 14