Small Craft Advisory 571, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
414 PM AKDT FRI JUL 17 2015

.ANALYSIS AND UPPER LEVELS...
THE MAIN LOW SITS OVER WESTERN ALASKA WITH ITS FRONT HAVING PUSHED
WELL INLAND. THE SOUTHWEST FLOW THAT HAS FOLLOWED BEHIND IS
BRINGING SHOWERS TO AREAS ALL OVER THE SOUTHERN HALF OF THE STATE.
THE REGION IS ALSO SEEING WINDS IN THE 20 TO 30 MPH RANGE WITH
AREAS IN CHANNELED TERRAIN GUSTING INTO THE 40S. OUT WEST ANOTHER
SYSTEM IS APPROACHING THE WESTERN ALEUTIANS FROM THE SOUTHWEST.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN DECENT AGREEMENT WITH THE PLACEMENT OF THE MAIN
FEATURES THROUGH THE MID TERM. THE PROBLEM IS WITH THE SHORTWAVES
MOVING AROUND THE LOWS. THE MAIN ISSUE IS WITH A WAVE SATURDAY
AFTERNOON THAT THE NAM HAS PUSHING DOWN INTO SOUTHCENTRAL WHILE
THE OTHER MODELS KEEP IT NORTH OF THE ALASKA RANGE WITH THE GFS
BEING THE FARTHEST NORTH. THE MORE NORTHERN SOLUTION OF THE EC
WAS PREFERRED FOR THIS FEATURE.

&&

.FIRE WEATHER...
SOUTHWEST FLOW FROM THE LOW OVER MAINLAND ALASKA WILL KEEP SHOWERS
OVER THE AREA THROUGH THE NIGHT KEEPING RH VALUES WELL ABOVE
CRITICAL LEVELS. LIGHT SHOWERS WILL THEN LINGER THROUGH SATURDAY
NIGHT. WINDS WILL BE SOUTHWESTERLY AROUND 20 TO 30 MPH THROUGH
THE EVENING AND WILL GRADUALLY DIMINISH TONIGHT. AREAS OF
CHANNELED TERRAIN AND ALONG THE COPPER RIVER WILL SEE WINDS CLOSER
TO 40 MPH THAT WILL BEGIN TO DIMINISH OVERNIGHT. WINDS ON SATURDAY
SHOULD STAY BELOW 25 MPH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A SERIES OF SHORTWAVES ROTATING AROUND THE BASE OF THE UPPER
LEVEL LOW TRACKING FURTHER INTO THE NORTHERN INTERIOR WILL HELP TO
BRING IN SOME COLDER AIR ALOFT...INCREASING INSTABILITY OVER PARTS
OF SOUTHCENTRAL WITH AMPLE AMOUNTS OF LOW LEVEL MOISTURE. ALONG
WITH GUSTY SOUTH TO SOUTHWEST LOW LEVEL FLOW (CAUSED BY HIGHER
PRESSURE FILLING IN BEHIND THE EXITING LOW TO THE NORTH)...AREAS
OF MODERATE TO HEAVY RAINFALL ARE EXPECTED TO PERSIST THROUGH
EARLY TOMORROW MORNING...ESPECIALLY FOR WEST FACING SLOPES
EXPERIENCING UPSLOPING. AREAS MOST LIKELY TO EXPERIENCE PERIODS
OF MODERATE TO HEAVY RAINFALL INCLUDE ANCHORAGE...THE MATANUSKA
VALLEY...THE SUSITNA VALLEY...AND EASTERN PRINCE WILLIAM SOUND.

THE UPPER LEVEL TROUGH WILL BEGIN TO EXIT TO THE EAST ON SATURDAY
WHICH GENERALLY SUPPORTS A WARMING AND DRYING TREND. HOWEVER...THE
MODELS ARE HINTING AT ONE LAST UPPER WAVE MOVING THROUGH BEFORE A
FAIRLY STRONG UPPER LEVEL RIDGE BEGINS TO BUILD INTO THE REGION
SUNDAY. THUS SATURDAY STILL LOOKS FAIRLY CLOUDY WITH A CHANCE OF
SHOWERS...ESPECIALLY OVER INTERIOR SOUTHCENTRAL.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
RAIN WILL TAPER OFF TO SCATTERED SHOWERS THROUGH SATURDAY AS THE
UPPER LOW OVER THE WESTERN MAINLAND MOVES INTO THE INTERIOR
TONIGHT AND MOIST SOUTHWEST FLOW OVER THE AREA BECOMES MORE
WESTERLY. THE DRYING TREND WILL CONTINUE ON SUNDAY AS HIGH
PRESSURE BEGINS TO BUILD OVERHEAD FROM THE EASTERN BERING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A FRONT MOVING OVER THE WESTERN ALEUTIANS TONIGHT WILL MAKE SLOW
EASTWARD PROGRESS TOWARDS THE CENTRAL ALEUTIANS THROUGH SATURDAY
NIGHT AS A NORTH PACIFIC LOW TRACKS TO A POSITION NEAR ATTU. THIS
FRONT WILL BRING RAIN AND GALE FORCE WINDS TO THE WESTERN HALF OF
THE BERING THROUGH SUNDAY WHILE LOW CLOUDS AND FOG PREVAIL OVER THE
EASTERN BERING BENEATH HIGH PRESSURE.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...THE SOUTHWEST ALASKA
REGION WILL HAVE AN UPPER LEVEL RIDGE POSITIONED THROUGH THE AREA
EXTENDING INTO THE BERING STRAIT. THIS RIDGE WILL MOVE INTO THE
SOUTHCENTRAL AREA BY MONDAY. THIS RIDGE WILL GRADUALLY SLIDE TO
THE SOUTHEAST INTO THE GULF. THE RIDGE WILL ALLOW FOR DRIER
CONDITIONS WITH SUNNY SKIES THROUGH TUESDAY. BY WEDNESDAY MOISTURE
FROM THE BRISTOL BAY INTERIOR WILL STREAM INTO THE SOUTHCENTRAL
ALASKA AREA. THIS MOISTURE IS BEING DRIVEN BY A VERTICALLY STACKED
CLOSED LOW POSITIONED OVER THE KUSKOKWIM DELTA. THIS FEATURE WILL
BE ACCOMPANIED BY A STRONG SOUTHWESTERLY 120 KNOT MERIDIONAL JET
STREAM COMING OUT OF THE BASE OF THE UPPER LEVEL LOW TRACKING NEAR
KODIAK ISLAND INTO THE LOWER GULF. THE PRECIPITATION WILL MOVE
FROM THE SOUTH TO NORTH DIRECTION UP THROUGH THE COOK INLET INTO
THE INTERIOR AND THE PRINCE WILLIAM SOUND REGION HEADING INTO THE
THURSDAY TIME FRAME. WHILE...THE BERING SEA AND THE SOUTHWEST
ALASKA REGION WILL CONTINUE TO HAVE THE EFFECTS OF THIS LOW
PRESSURE THROUGH NEXT WEEK. THIS SYSTEM WILL MOVE INLAND NEAR THE
KUSKOKWIM DELTA BY MIDWEEK BEFORE EVENTUALLY MOVE INTO THE YUKON
TERRITORY BY LATE THURSDAY. THERE WILL BE SHOWERY PRECIPITATION
WITH STRATUS AND FOG THROUGHOUT THE BERING SEA AND THE SOUTHWEST
ALASKA AREA THIS FEATURE MOVES THROUGH WEEK. THE MODELS HAVE SOME
DISAGREEMENT WITH THE LOW OVER THE BERING BUT PHASE THE
DIFFERENCES TO REFLECT A BROAD AREA OF LOW PRESSURE THROUGH NEXT
WEEK.
&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 175 176 177 178.
FIRE WEATHER...NONE.

&&

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