Small Craft Advisory 567, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
508 AM AKDT THU JUL 16 2015

.ANALYSIS AND UPPER LEVELS...
THE VERTICALLY STACKED LOW CURRENTLY CENTERED SOUTH OF THE
EASTERN ALEUTIANS WILL BEGIN A SHARP CURVE TO THE NORTH TODAY AS A
STRONG JET STREAK CENTERED AROUND 41N ROUNDS THE BASE OF THE
LARGE SCALE UPPER LEVEL TROUGH OVER THE NORTH CENTRAL PACIFIC.
THIS WILL CAUSE THE UPPER TROUGH TO DEEPEN FURTHER AND THE RIDGE
OVER THE NORTHEASTERN PACIFIC AND GULF TO AMPLIFY...TURNING THE
FLOW ALOFT BETWEEN 170W AND 150W TO THE SOUTH-SOUTHWEST. THE
FETCH OF THIS STRENGTHEN JET WILL EXTEND FROM 40N UP INTO SOUTH
CENTRAL ALASKA RUNNING ACROSS THE FAR WESTERN GULF...SHELIKOF
STRAIT AND THE KENAI PENINSULA. THE NET RESULT WILL BE TO STEER
THE LOW PRESSURE CENTER INTO BRISTOL BAY AND PROPEL AN
UNSEASONABLY STRONG FRONTAL SYSTEM ACROSS THE GULF OF ALASKA AND
OVER SOUTHWEST AND SOUTHCENTRAL ALASKA BRINGING WINDY CONDITIONS
AND WIDESPREAD WETTING RAINS.

&&

.MODEL DISCUSSION...
MODELS IN FAIR AGREEMENT THROUGH THE SHORT TERM ALTHOUGH MORE
SIGNIFICANT DIFFERENCES START CREEPING IN WITH ALL THE LITTLE
WAVES AND TROUGHS BEHIND THE MAIN FRONT. THESE BECOME MORE
NOTICEABLE FRIDAY NIGHT AND SATURDAY IN HOW THE WAVE ENERGY IS
SPLIT UP IN THE DIFFUSE WESTERLY FLOW WHICH DEVELOPS OVER THE
AREA. MODELS BECOME MORE CONSISTENT AGAIN SATURDAY NIGHT INTO
SUNDAY AS A LARGE SCALE UPPER LEVEL RIDGE BUILDS OVER THE EASTERN
BERING AND MAINLAND ALASKA

&&

.FIRE WEATHER...
A LARGE FRONTAL SYSTEM WILL BRING WIDESPREAD WETTING RAIN TO
SOUTHWEST ALASKA AND COASTAL PORTIONS OF SOUTH CENTRAL ALASKA
TODAY AND THEN SPREAD INLAND TO COVER THE REMAINDER OF SOUTH
CENTRAL ALASKA TONIGHT. THIS COOL...WET AND WINDY PATTERN WILL
CONTINUE INTO FRIDAY WITH STEADY RAIN CHANGING OVER TO SHOWERS.
SHOWERS WILL EVENTUALLY TAPER OFF FROM SOUTHWEST TO NORTHEAST
SATURDAY AND SATURDAY NIGHT. ISOLATED WET THUNDERSTORM ARE
POSSIBLE ALONG THE TALKEETNA MOUNTAINS AND HIGHER ELEVATION
PORTIONS OF THE COPPER RIVER BASIN SATURDAY AFTERNOON AND EVENING.

AN UPPER LEVEL RIDGE BUILDING SUNDAY THROUGH TUESDAY WILL BRING
SEVERAL DAYS OF WARMER AND DRIER WEATHER BUT WITH THE ABUNDANT
PRECIPITATION AMOUNTS EXPECTED OVER THE NEXT SEVERAL DAYS...NO
FIRE WEATHER CONCERNS ARE ANTICIPATED.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UNSEASONABLY STRONG STORM WILL AFFECT SOUTHCENTRAL ALASKA
TODAY THROUGH TONIGHT BRINGING STRONG WINDS AND HEAVY RAIN TO
MUCH OF THE REGION. WINDS WILL PEAK AS A FRONTAL BOUNDARY PUSHES
ONSHORE ALONG THE NORTH GULF COAST THIS AFTERNOON THROUGH THIS
EVENING. WITH FRONTAL PASSAGE GUSTY WINDS WILL BEND INTO
ANCHORAGE...PALMER...AND THE COPPER RIVER BASIN. WINDS WILL
THEN DIMINISH A BIT...BUT GUSTY SOUTHERLIES WILL DOMINATE
THROUGH FRIDAY EVENING WITH PRESSURE RISES IN A WELL MIXED
BOUNDARY LAYER.

STRONG LOW LEVEL SOUTHEASTERLY FLOW AHEAD OF THE FRONT WILL
PRODUCE SOME DOWNSLOPE DRYING NEAR THE SURFACE ALONG THE WEST
SIDE OF THE KENAI AND CHUGACH MOUNTAINS...BUT DEEP SOUTHERLY FLOW
ALOFT WITH TROPICAL MOISTURE TRANSPORT AND A POTENT UPPER LEVEL
WAVE MOVING UP THE INLET THIS EVENING WILL ENSURE THAT ALL AREAS
GET SOME RAIN. UPSLOPE AREAS OF THE SUSITNA VALLEY AND PRINCE
WILLIAM SOUND WILL SEE A PERIOD OF HEAVY RAIN. THE MEAN FLOW
BEHIND THE STRONG UPPER WAVE WILL SHIFT SOLIDLY TO SOUTHWEST ON
FRIDAY AS A SERIES OF WEAKER UPPER WAVES MOVE IN FROM SOUTHWEST
ALASKA. THIS WILL FAVOR HEAVY RAIN ALONG THE WESTERN SLOPES OF
THE TALKEETNA MOUNTAINS AS WELL AS EASTERN PRINCE WILLIAM SOUND.
CONDITIONS WILL FINALLY BEGIN TO DRY OUT A BIT FRIDAY NIGHT AS A
SHORT-WAVE RIDGE MOVES IN.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FRONT EXTENDING FROM THE SURFACE LOW NEAR DUTCH HARBOR THIS
MORNING WILL MOVE NORTH THROUGH THE DAY SPREADING RAIN TO THE
KUSKOKWIM DELTA AND VALLEY. GUSTY EAST WINDS ARE EXPECTED ALONG
THE FRONT WITH THE STRONGEST WINDS ACROSS THE ALEUTIAN RANGE
BETWEEN 40 TO 50 MPH. A RIDGE SHIFTS EAST ACROSS THE BERING
TONIGHT FORCING THE LOW AND FRONT TO LIFT ACROSS THE NORTHWEST
COAST. A TROUGH AXIS REMAINS OVER THE SOUTHWEST THROUGH FRIDAY
PROVIDING A FOCUS FOR CONTINUED RAIN DEVELOPMENT. WINDS TAPER DOWN
OVERNIGHT AND BECOME SOUTHERLY ON FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE SURFACE RIDGE ALONG THE WESTERN BERING KEEPS A TIGHT PRESSURE
GRADIENT ALONG MUCH OF THE BERING TODAY AS THE LOW NEAR DUTCH
HARBOR SLOWLY MOVES INTO THE EASTERN BERING. NORTHERLY FLOW WILL
BE GUSTY ACROSS THE SOUTHERN BERING UNTIL THE RIDGE SHIFTS EAST
TONIGHT WHEN THE NEXT TROUGH SWINGS TO THE WESTERN
ALEUTIANS/BERING. WINDS BACK OUT OF THE SOUTHWEST AS THE TROUGH
AXIS MOVES THROUGH. THE NEXT STRONG SYSTEM MOVES INTO THE WESTERN
ALEUTIANS FRIDAY NIGHT WITH GALE WINDS AND RAIN ALONG THE FRONT
BOUNDARY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...SAT THROUGH WED)...
THIS TIME PERIOD WILL FEATURE THE TAPERING OFF OF THE RAIN EVENT
FOR THE SOUTHERN HALF OF THE STATE AND A TRANSITION TO SOME DRIER
AND SUNNIER WEATHER. ON SATURDAY...THE UPPER LEVEL LOW WILL DRIFT
OFF TO THE NORTHEAST AND FALL APART OVER THE TANANA VALLEY. RAIN
WILL SLOWLY DIMINISH TO SHOWERS FROM SOUTHWEST TO NORTHEAST WITH
THE ALASKA RANGE AND EASTERN PRINCE WILLIAM SOUND HANGING ON TO
THE PRECIPITATION THE LONGEST. MEANWHILE...A NEW AREA OF LOW
PRESSURE WILL MOVE TOWARD THE WESTERN ALEUTIANS. THIS WILL BRING
ANOTHER ROUND OF WIND AND RAIN TO MUCH OF THE WESTERN BERING. BY
SUNDAY...MID AND UPPER LEVEL RIDGING STARTS TO NOSE OVER THE
MAINLAND FROM THE NORTH PACIFIC. AS IT DOES SO IT SHOULD START A
DRYING TREND THAT WILL LAST THROUGH THE EARLY PORTION OF NEXT
WEEK. THERE COULD BE ENOUGH LINGERING MOISTURE AND INSTABILITY TO
TRIGGER A FEW MOUNTAIN SHOWERS...BUT MOST LOCATIONS WILL SEE MORE
ABUNDANT SUNSHINE THAN THEY HAVE OVER THE PAST FEW WEEKS. THIS
SHOULD HELP TO PUSH TEMPERATURES UP A FEW DEGREES ABOVE NORMAL
WITH LOW 70S POSSIBLE THROUGHOUT MUCH OF COOK INLET MONDAY AND
TUESDAY. EVEN WITH WARMER AND DRIER CONDITIONS...FIRE WEATHER
CONCERNS SHOULD BE MITIGATED BY LIGHT WINDS AND THE MODERATE
AMOUNTS OF RAIN EXPECTED OVER THE NEXT COUPLE OF DAYS.

BY THE MIDDLE OF NEXT WEEK...MODELS REMAIN IN EXTREMELY GOOD
AGREEMENT (FOR DAY 7) IN SHOWING THE UPPER LEVEL LOW OVER THE
WESTERN BERING KNOCKING DOWN THE RIDGE OVER SOUTH CENTRAL. THIS
COULD OPEN THE DOOR FOR ANOTHER RAIN AND WIND EVENT FOR MUCH OF
THE MAINLAND. WE HAVE NOT BOUGHT INTO THIS SOLUTION COMPLETELY
YET AS THERE IS STILL RUN TO RUN INCONSISTENCIES IN HOW FAST THE
RIDGE WILL BREAK DOWN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 125 130 131
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JER
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...MSO