Small Craft Advisory 546, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
448 AM AKDT SAT JUL 4 2015

.ANALYSIS...
UPPER LEVELS... THE CLOSED HIGH PRESSURE AT 500 MB REMAINS OVER
THE EASTERN SIBERIAN AREA WITH AN UPPER LEVEL LOW POSITIONED NEAR
HOOPER BAY THIS MORNING. UPSTREAM THERE IS A CLOSED LOW JUST NORTH
OF ADAK WITH AN ASSOCIATED TROUGH EXTENDING EASTWARD THROUGH THE
PRIBILOF ISLANDS INTO THE EASTERN ALEUTAINS. THIS SYNOPTIC FEATURE
IS REFLECT AT THE SURFACE WITH A 997 MB LOW PRESSURE SYSTEMS JUST
SOUTH OF ADAK AND ANOTHER 997 MB LOW SOUTH OF THE DUTCH HARBOR
AREA. THESE SYSTEMS ARE GETTING SUPPORT FROM A STRONG 130 KNOT
NORTHWESTERLY MERIDIONAL JET STREAK LOCATED JUST SOUTH OF THE
WESTERN ALEUTIAN CHAIN. THE SATELLITE IMAGERY IS SHOWING A LARGE
SWATH OF MOISTURE OVER THE CENTRAL/EASTERN ALEUTIANS STREAMING
INTO THE BERING SEA. A WEATHER FRONT ASSOCIATED WITH THE
AFOREMENTIONED SYSTEM IS MOVING THROUGH THE EASTERN
ALEUTIANS...SOUTHERN PORTION OF ALASKA PENINSULA AND THE LOWER
SOUTHWESTERN GULF REGION THIS MORNING. WHILE...THE EASTERN GULF
THROUGH THE SOUTHCENTRAL REGION IS UNDER THE INFLUENCE OF THE
RIDGE OF HIGH PRESSURE. THIS RIDGE IS POSITIONED OVER THE
SOUTHEASTERN ALASKA EXTENDING INTO THE ANCHORAGE BOWL AREA.

&&

.MODEL DISCUSSION...
THE MODELS CONTINUE TO REMAIN IN GOOD AGREEMENT THROUGH THE
WEEKEND. THEY MERGE THE TWO NORTH PACIFIC LOWS OVER THE CENTRAL
TO EASTERN ALEUTIANS AS ONE LOW BY SATURDAY. WHILE...ANOTHER
NORTH PACIFIC LOW SOUTH OF DUTCH HARBOR WILL TRACK NORTHWARD AND
PHASE IN WITH THE PREVIOUS LOW OVER THE CENTRAL ALEUTIANS BY
SUNDAY. THIS SYSTEM WILL THEN TRACK ACROSS THE CHAIN INTO THE
CENTRAL BERING SEA BY MONDAY. WHILE...THE HIGH PRESSURE OVER
THE EASTERN GULF WILL BEGIN TO REGRESS AND THEN RETROGRADES
BACK OVER THE NORTHERN GULF AS WE HEAD INTO THE EARLY PART OF
NEXT WEEK. THE NAM WAS THE PREFERRED MODEL OF CHOICE FOR THE
HANDLING OF THE SYNOPTIC DETAILS. THE FORECAST CONFIDENCE
REMAINS HIGH THROUGH THE WEEKEND.

&&

.FIRE WEATHER...
THE SOUTHWEST ALASKA REGION WILL HAVE WETTING RAINS THROUGH THE
WEEKEND WITH THE ARRIVAL OF A WEATHER FRONT THIS MORNING. THE
RADAR IMAGERY IS SHOWING A BAND OF RAIN OVER THE SOUTHERN END OF
THE ALASKA PENINSULA TRACKING NORTHWARD. ASSOCIATED WITH THE FRONT
WILL BE GUSTY EAST TO SOUTHEASTERLY WINDS. THE HUMIDITIES WILL
REBOUND NICELY WITH THE ABUNDANT MOISTURE HEADING INTO THE
WEEKEND.

THE SOUTHCENTRAL ALASKA REGION WILL HAVE THE RIDGE OF HIGH
PRESSURE GRADUALLY REGRESS GIVING WAY TO THE ARRIVAL OF THE
WEATHER FRONT IN THE LOWER SOUTHWESTERN GULF THIS MORNING. THE
MOISTURE WILL TRACK FROM KODIAK ISLAND INTO THE NORTHERN GULF AND
UP THROUGH THE COOK INLET BY THIS AFTERNOON. THE PRESSURE GRADIENT
WILL STRENGTHEN AND THERE WILL GUSTY EASTERLY WINDS THROUGH THE
BARREN ISLANDS EASTWARD. THE SATELLITE IMAGERY IS SHOWING A LARGE
SWATH OF MOISTURE ENTERING THE NORTHERN GULF THIS MORNING. THE
FRONT WILL BRING COOLER TEMPERATURES ACCOMPANIED BY MORE STABLE
CONDITIONS IN THE REGION. THE RIDGE WILL TRY TO BUILD BACK INTO
THE REGION ON SUNDAY WITH SLIGHTLY WARMER TEMPERATURES. THIS WILL
BE SHORT LIVED DUE TO THE NEXT SHORTWAVE PUSHING THROUGH THE
SOUTHCENTRAL ALASKA REGION BY MONDAY HELPING THE HUMIDITIES TO
REBOUND. LOOK FOR GUSTY GAP WINDS ALONG THE TURNAGAIN ARM...KNIK
RIVER VALLEY AND THE COPPER RIVER BASIN ASSOCIATED WITH THE FRONT
FOR SATURDAY AFTERNOON/EVENING HOURS. LOOK FOR THE SAME SCENARIO
FOR THE WINDS ON MONDAY WITH THE ARRIVAL OF THE NEXT SYNOPTIC
WEATHER FRONT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A WEAK FRONT IS PUSHING THROUGH THE GULF AND MAKING ITS WAY TO THE
KENAI PENINSULA. BY THE AFTERNOON IT WILL MAKE IT INTO PRINCE
WILLIAM SOUND AND THEN PUSH INLAND. HOWEVER...THE MAJORITY OF THE
RAIN WILL STAY ALONG THE GULF COAST WITH THE LEE SIDE OF THE
COASTAL RANGES SEEING DOWNSLOPING. THERE WILL BE SOME SHOWER
ACTIVITY THAT DOES MAKE IT INTO THE MORE INLAND LOCATIONS
PRIMARILY OVERNIGHT TONIGHT. THEN ON SUNDAY HIGH PRESSURE WILL
BUILD IN OVER THE AREA BRINGING SOME CLEARER SKIES TO THE
SOUTHCENTRAL WHILE KEEPING THE MAJORITY OF THE RAIN DOWN BY
KODIAK AND SOUTHERN PORTIONS OF THE KENAI PENINSULA.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FIRST OF TWO FRONTAL SYSTEMS TO IMPACT SOUTHWEST ALASKA IS
MOVING ASHORE ALONG THE ALASKA PENINSULA AND INTO BRISTOL BAY
THIS MORNING AND WILL CONTINUE TO PUSH NORTHWARD TO THE KUSKOKWIM
DELTA BY THIS AFTERNOON BEFORE CLEARING THE AREA EARLY SUNDAY
MORNING. RAINFALL TOTALS WILL BE THE HIGHEST ALONG THE USUAL
UPSLOPE TERRAIN FEATURES WITH SOME DOWNSLOPING ON THE WESTERN
SLOPES OF THE KILBUCKS AND ALEUTIAN RANGES. RAIN WILL TAPER OFF
INTO A MIX OF STRATIFORM RAIN AND SHOWERS IN THE EARLY MORNING
HOURS ON SUNDAY. THE NEXT FRONT WILL BEGIN TO MOVE INTO THE
ALASKA PENINSULA AND THE SOUTHERN AREAS OF BRISTOL BAY ON SUNDAY
MORNING BEFORE FOLLOWING THE SAME PATH AS TODAYS FRONT.

THERE IS A DEEP SOUTHERLY FLOW WITH THESE SYSTEMS WITH THE NAFES
ENSEMBLE PRECIPITABLE WATER VALUES AVERAGING MORE THAN THREE
STANDARD DEVIATIONS ABOVE NORMAL THROUGH THE PERIOD. THIS...
COMBINED WITH STRONG SOUTHERLY FLOW AT THE UPPER LEVELS...WILL
LEAD TO AREAS OF MODERATE TO POTENTIALLY HEAVY RAINFALL AT TIMES
ESPECIALLY ALONG THE MOUNTAIN AREAS TO THE NORTH AND WEST OF
DILLINGHAM. THE HEAVIEST AMOUNTS OF RAINFALL ARE EXPECTED WITH THE
SECOND FRONT ON SUNDAY.

WINDS WILL CONTINUE TO INCREASE OVER MUCH OF THE AREA TODAY AS THE
PRESSURE GRADIENT TIGHTENS OVER THE REGION. THE STRONGEST GUSTS
WILL BE AROUND THE KAMISHAK GAP AND ALONG THE WESTERN CAPES OF
BRISTOL BAY NORTHWARD ALONG THE KUSKOKWIM COAST AS GALE FORCE
WINDS DEVELOP SUNDAY OVER THE ADJACENT COASTAL WATERS. EXPECT
WINDS TO DECREASE LATE SUNDAY NIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE FIRST OF TWO FRONTS TO IMPACT THE REGION IS CURRENTLY PUSHING
ENTERING THE THE EASTERN ALEUTIANS AND THE ALASKA PENINSULA THIS
MORNING. THIS FRONT WILL MOVE RAPIDLY TO THE NORTH-CENTRAL BERING
SEA BY EARLY SUNDAY MORNING WITH THE SECOND FRONT MOVING INTO THE
EASTERN ALEUTIANS AND THE ALASKA PENINSULA SUNDAY MORNING.

THERE IS A DEEP SOUTHERLY FLOW WITH THESE SYSTEMS...SO AS WITH
SOUTHWEST ALASKA...THIS WILL LEAD TO AREAS OF MODERATE TO
POTENTIALLY HEAVY RAINFALL AT TIMES. EXPECT THE HIGHEST RAINFALL
TOTALS ALONG THE PACIFIC SIDE OF THE EASTERN ALEUTIANS ISLANDS
AND THE ALASKA PENINSULA WHERE THE HIGHER TERRAIN WILL HELP TO
PRODUCE HIGHER RAINFALL RATES. THE HEAVIEST AMOUNTS OF RAINFALL
ARE EXPECTED WITH THE SECOND FRONT ON SUNDAY.

WINDS WILL INCREASE OVER THE EASTERN HALF OF THE AREA AS THE
PRESSURE GRADIENT TIGHTENS THROUGH SUNDAY WITH GALE FORCE WINDS
EXPECTED OVER THE EASTERN BERING AND THE COASTAL WATERS EAST OF
UNALASKA. WINDS OVER THE CENTRAL ALEUTIANS WILL REMAIN LIGHT TODAY
BUT WILL BEGIN TO INCREASE ON SUNDAY.
&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A LARGE VERTICALLY STACKED LOW TRACKING ACROSS THE ALEUTIANS AND
INTO THE BERING LATE SUNDAY WILL REMAIN THE DOMINANT FEATURE IN
THAT AREA THROUGH MUCH OF NEXT WEEK. THE UPPER LEVEL RIDGE
EXTENDING ACROSS SOUTH CENTRAL ALASKA WILL CONTINUE TO SHARPEN
THROUGH SUNDAY NIGHT THEN SHIFT GRADUALLY EAST MONDAY BEFORE
BREAKING DOWN MONDAY NIGHT AND TUESDAY. SOUTHEASTERLY GAP WINDS
COULD GET FAIRLY STRONG MONDAY AFTERNOON AND EVENING AS THE
STRENGTHENING OF THE SURFACE RIDGING AND ONSHORE FLOW FROM THE
NORTHERN GULF COINCIDES WITH DIURNAL HEATING INLAND AND A SHIFTING
OF THE THERMAL TROUGH FURTHER NORTH IN INTERIOR ALASKA. THE LARGER
CHANNELED AREAS SUCH AS TURNAGAIN ARM...THE KNIK RIVER VALLEY AND
COPPER RIVER VALLEY WILL LIKELY SEE THE STRONGEST WINDS HOWEVER
BREEZY CONDITIONS ARE ALSO POSSIBLE IN MANY OF THE SMALLER
SOUTHEAST TO NORTHWEST RUNNING VALLEYS AS WELL.

INITIALLY THE HIGH AMPLITUDE UPPER LEVEL RIDGE WILL KEEP THE
INCOMING BERING FRONTAL SYSTEMS CONFINED TO SOUTHWEST ALASKA.
HOWEVER...AS THE RIDGE SHIFTS EAST AND THEN FLATTENS...PRECIPITATION
AND COOLER WEATHER WILL BE ABLE TO SPREAD FURTHER EAST INTO SOUTH
CENTRAL ALASKA MONDAY NIGHT AND TUESDAY. ADDITIONAL SHORTWAVE
TROUGHS ROTATING AROUND THE LARGE LOW OVER THE BERING WILL
CONTINUE TO PUSH ENOUGH MOISTURE ACROSS SOUTHWEST AND SOUTH
CENTRAL ALASKA TO BRING CHANCES OF RAIN TO MUCH OF THE AREA
THROUGH THE END OF THE WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...120 130 131 138 150 160 165 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PLD
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RF
LONG TERM...JR