Small Craft Advisory 332, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
447 PM AKDT WED APR 15 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS A VERTICALLY STACKED LOW OVER THE NORTHWEST GULF OF
ALASKA WITH A TRAILING UPPER LEVEL TROUGH OVER THE ALASKA
PENINSULA. MOST OF THE PRECIPITATION WITH THESE SYSTEMS IS
CURRENTLY LIMITED TO AREAS NEAR THE COAST. THERE IS AN UPPER LOW
SOUTH OF THE WESTERN ALEUTAINS MOVING QUICKLY EASTWARD. ITS
ASSOCIATED SURFACE LOW IS TO THE SOUTH OF THE UPPER LOW AND IS
STILL DEEPENING. WEAK HIGH PRESSURE IS OVER THE BERING SEA
STRETCHING EAST OVER CENTRAL ALASKA. THE MAIN JET STREAM CONTINUES
TO BE STRONG AND FAIRLY ZONAL OVER THE NORTH PACIFIC ALONG ABOUT
45 DEGREES NORTH LATITUDE.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN VERY GOOD AGREEMENT. WE GENERALLY PREFER THE
HIGH RESOLUTION MODELS EARLY (NAM AND GEM REGIONAL) DUE TO THEIR
BETTER HANDLING OF SMALL SCALE DETAILS THEN MORE TOWARDS THE
ECMWF. THE MAIN DIFFERENCES INVOLVE PRECIPITATION TYPE AND
AMOUNT. THIS LOWERS THE CONFIDENCE A BIT BUT IT IS STILL A BIT
ABOVE NORMAL TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
WIDESPREAD PRECIPITATION ALONG THE GULF COAST WILL BEGIN TO
SPREAD ACROSS THE MOUNTAINS TO INTERIOR PORTIONS OF SOUTH CENTRAL
AK LATE TONIGHT INTO THURSDAY AS THE LOW OVER THE GULF PUSHES
INLAND OVER THE KENAI PENINSULA AND TRACKS INTO THE SUSITNA
VALLEY. THE AMOUNT OF COLD AIR ASSOCIATED WITH THIS SYSTEM WILL BE
SOMEWHAT LIMITED KEEPING THE PRECIPITATION TYPE MOSTLY RAIN WITH
SNOW MIXING IN AT TIMES THROUGH THURSDAY MORNING. PRESSURE RISES
BEHIND THE DEPARTING LOW WILL LEAD TO THE DEVELOPMENT OF STRONG
GAP WINDS THURSDAY AFTERNOON LASTING THROUGH THURSDAY NIGHT. A
WEAK UPPER TROUGH LIFTING NORTH THROUGH THE GULF OF ALASKA WILL
BRING ANOTHER CHANCE FOR PRECIPITATION ON THURSDAY NIGHT WITH ANY
PRECIPITATION CHANGING OVER TO ALL SNOW AS COLDER AIR FILTERS BACK
INTO THE REGION. SHOWERS WILL THEN LINGER THROUGH FRIDAY AHEAD OF
THE NEXT SYSTEM TRACKING INTO THE GULF FRIDAY NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE LOW JUST EAST OF KODIAK ISLAND WILL MOVE INTO THE KENAI
PENINSULA BY LATE WEDNESDAY EVENING. THIS SYSTEM WILL MOVE
FARTHER INLAND INTO MATSU VALLEY BY THURSDAY BEFORE DISSIPATING
BY FRIDAY. THIS WILL RESULT IN CONTINUED DRIER CONDITIONS WITH
THE NORTHERLY WINDS. THERE WILL BE SCATTERED SNOW SHOWERS ALONG
THE ALEUTIAN RANGE/ALASKA PENINSULA. THE EASTERN INTERIOR OF THE
LOWER KUSKOKWIM VALLEY WILL HAVE SCATTERED SNOW SHOWERS EXCEPT
FOR NUMEROUS SNOW SHOWERS BY THURSDAY EVENING WITH THE REMNANTS OF
THE LOW PRESSURE SYSTEM DISSIPATING. BY FRIDAY AFTERNOON A WEATHER
FRONT ASSOCIATED WITH A NORTH PACIFIC LOW WILL BE POSITIONED
THROUGH THE BRISTOL BAY INTERIOR. THIS FRONT WILL BRING WARM
TEMPERATURES HEADING INTO THE WEEKEND. AS THIS FRONT TRACKS
NORTHWARD BY SATURDAY MORNING IT WILL BE IN THE KUSKOKWIM DELTA
REGION. THIS WILL BRING GUSTY NORTHERLY WINDS FROM BETHEL TO THE
COASTLINE AND ACCOMPANIED BY A LARGE SWATH OF MOISTURE. THE
SYNOPTIC CONDITIONS ARE SETTING UP FOR THE POTENTIAL FOR BLOWING
SNOW ADVISORY FOR THE KUSKOKWIM DELTA BY SATURDAY MORNING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BRISTOL BAY REGION AND THE EASTERN ALEUTIAN CHAIN WILL HAVE
NORTHERLY WINDS WITH ISOLATED SNOW AND RAIN SHOWERS THIS EVENING.
UPSTREAM THERE IS A WEAK RIDGE OVER THE CENTRAL ALEUTIANS/BERING
SEA THAT WILL MOVE INTO THE EASTERN BERING SEA THROUGH THURSDAY.
FARTHER UPSTREAM JUST SOUTH OF THE WESTERN ALEUTIANS IS A STORM
FORCE LOW. THIS SYSTEM WILL TRACK EASTWARD RUNNING PARALLEL TO
THE ALEUTIAN CHAIN. BY THURSDAY THIS LOW WILL BE LOCATED SOUTH OF
NIKOLSKI. RESULTING IN GUSTY GALE FORCE EASTERLY WINDS TO THE
CENTRAL ALEUTIANS ACCOMPANIED BY A LARGE SWATH OF MOISTURE. BY
FRIDAY EVENING THIS SYSTEM WILL BE LOCATED SOUTH OF DUTCH HARBOR.
AN ASSOCIATED FRONTAL BOUNDARY WILL BE LOCATED THROUGH THE
EASTERN BERING SEA AND INTO THE BRISTOL BAY INTERIOR. THIS WILL
PRODUCE GUSTY NORTHEAST WINDS AND SHIFT MORE NORTHERLY BY
SATURDAY MORNING. THIS WILL RESULT IN TEMPERATURES ABOVE FREEZING
IN FRONT OF THE LOW OVER THE EASTERN ALEUTIANS. THERE WILL BE
COOLER TEMPERATURES ON THE BACKSIDE OF THE LOW WITH A WINTRY MIX
OF RAIN/SNOW OVER THE CENTRAL ALEUTIANS. THE COLDER TEMPERATURES
WILL BE FARTHER NORTH INTO THE CENTRAL BERING. THE SYNOPTIC
FEATURES ARE ALIGNING UP FOR THE POTENTIAL FOR BLOWING SNOW
ADVISORY OR BLIZZARD WARNING WITH THE COLDER TEMPERATURES A LARGE
PLUME OF MOISTURE AND GUSTY NORTHERLY WINDS BY SATURDAY MORNING
FOR THE PRIBILOF ISLANDS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE DEEP LOW SOUTH OF THE ALEUTIANS WILL TURN NORTH SATURDAY AND
MOVE UP ALONG THE WEST COAST OF THE STATE. THIS WILL BRING IN
CONTINUED WARM SOUTHERLY FLOW TO THE SOUTHCENTRAL INTO MONDAY WHEN
THE SURFACE LOW DISSIPATES. ON THE WESTERN SIDE OF THE LOW OVER
THE BERING COLD NORTHERLY FLOW WILL DOMINATE. MODEL GUIDANCE IS IN
DECENT AGREEMENT WITH THIS OVERALL SYNOPTIC PATTERN.
HOWEVER THERE ARE DIFFERENCES WITH HOW ELONGATED THE LOW BECOMES
ALONG THE WEST COAST WHICH WILL IMPACT THE STRENGTH OF THE WINDS
CIRCULATING AROUND THE LOW ESPECIALLY ON THE SOUTHERN SIDE NEAR
BRISTOL BAY. A MORE CONSOLIDATED LOW CENTER IS THE PREFERRED
CHOICE WITH THIS SYSTEM.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

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