Small Craft Advisory 527, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 PM AKDT FRI JUN 26 2015

.ANALYSIS AND UPPER LEVELS...
THE PATTERN CHANGE IN NOW IN HIGH GEAR AS THE UPPER LEVEL RIDGE
THAT HAS BEEN OVER THE STATE FOR NEARLY TWO WEEKS HAS BEEN PUSHED
INTO CANADA AS TWO UPPER LEVEL LOWS BECOME THE MAIN FEATURES OVER
THE REGION. THE FIRST LOW IS ONE THAT HAS BEEN CENTERED JUST
SOUTH OF THE GULF OF ALASKA FOR A FEW DAYS AND IS NOW MOVING
NORTHWARD INTO THE GULF. ANOTHER LOW IS DIGGING SOUTHWARD OVER THE
WEST COAST OF THE STATE AND INTO SOUTHWEST ALASKA. THESE TWO
FEATURES WILL COMBINE INTO ONE LOW TOMORROW WHICH WILL BE CENTERED
NEAR KAMISHAK BAY AND WILL ENCOMPASS MOST OF THE SOUTHERN PART OF
MAINLAND ALASKA.

AT THE SURFACE THERE IS A TROUGH EXTENDING INTO SOUTHWEST ALASKA
OUT OF THE INTERIOR. THIS CAN BE SEEN ON RADAR IN THE BRISTOL BAY
REGION WHERE THE NEARLY STATIONARY LINE OF SHOWERS HAS BEEN
LOCATED TODAY. A SURFACE HIGH ALONG THE NORTH GULF COAST HAS
INCREASED THE PRESSURE GRADIENT FROM THE EASTERN KENAI PENINSULA
THROUGH THE COPPER RIVER BASIN.

&&

.MODEL DISCUSSION...

MODELS ARE IN VERY GOOD AGREEMENT INTO EARLY NEXT WEEK WITH ALL
MAJOR SYNOPTIC FEATURES ALIGNED WELL. AS USUAL THERE ARE SOME DIFFERENCES
IN THE TIMING AND STRENGTH OF THE SHORT WAVES ROTATING AROUND THE
UPPER LEVEL LOW IN THE GULF BUT THIS SHOULD NOT BE A SIGNIFICANT
PROBLEM FOR THE FORECASTS.

&&

.FIRE WEATHER...
BOTH SOUTHCENTRAL AND SOUTHWEST ALASKA WILL HAVE IMPROVED
CONDITIONS THIS WEEKEND WITH HIGHER HUMIDITIES AND LOWER
TEMPERATURES THAN OCCURRED FOR MOST OF THE WEEK. SOUTHWEST ALASKA
WILL REMAIN UNDER A SOMEWHAT UNSTABLE ATMOSPHERE WITH SHOWERS
OCCURRING OVER THE REGION. THESE SHOWERS ARE VERY HIT OR MISS AS
TO WHETHER THEY IMPACT ANY OF THE FIRES. THE CHANCE OF GETTING HIT
BY A SHOWER AT ANY GIVEN LOCATION ARE NOT GREAT BUT THE PLACES
THAT DO GET SHOWERS MAY GET A WETTING RAIN.

SOUTHCENTRAL WILL SEE MOIST SOUTHEAST FLOW OFF THE GULF OF ALASKA
AND CLOUD COVER. AFTER THE SHORT WAVES MOVING THROUGH TODAY ARE
FINISHED THERE SHOULD JUST BE SOME AFTERNOON AND EVENING
SHOWERS...MAINLY OVER THE MOUNTAINS FOR THE WEEKEND. WHILE THIS
MEANS NO WIDESPREAD WETTING RAINS INLAND WHERE THE FIRES ARE...THE
CLOUDS WILL HELP KEEP TEMPERATURES DOWN AND RELATIVE HUMIDITY
VALUES UP.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
CURRENT DISTURBANCE IS MOVING ACROSS THE KENAI PENINSULA TOWARD
THE ALASKA RANGE AS PREDICTED...WITH THE NEXT DISTURBANCE ALREADY
VISIBLE ON MIDDLETON ISLAND NEXRAD HEADING TOWARD THE GULF COAST
FOR LATER THIS EVENING THROUGH TONIGHT. EXPECT ADDITIONAL
DISTURBANCES TO TREK ACROSS THE AREA THROUGH THE WEEKEND...AND
WITH COOLING TEMPERATURES ALOFT EXPECT MORE INSTABILITY AND
LOCALLY HEAVIER SHOWERS (AND EVEN A CLAP OR TWO OF THUNDER TOWARD
INTERIOR AREAS) DURING THE AFTERNOON AND EVENING HOURS.
ADDITIONALLY...A SMALL JET STREAK ENTRANCE REGION OVER THE CENTRAL
AND NORTHERN SUSITNA VALLEY MAY CONTRIBUTE TO A LOCALIZED HEAVIER
RAIN FALLING SATURDAY AFTERNOON AND EVENING. A MUCH STRONGER
SHORTWAVE MOVES ACROSS THE REGION LATE SATURDAY NIGHT INTO EARLY
SUNDAY...SETTING UP STRONGER ONSHORE FLOW AND HEAVIER RAINFALL
OVER THE WESTERN PRINCE WILLIAM SOUND REGION.

WITH THE PASSAGE OF EACH DISTURBANCE...BUILDING SURFACE RIDGING
ALONG THE GULF COAST WILL INCREASE WINDS THROUGH TERRAIN GAPS SUCH
AS THE COPPER RIVER BASIN AND TURNAGAIN ARM THROUGH THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE REMNANTS OF THE DEFORMATION BAND AND A WEAK THERMAL TROUGH
WILL BRING SHOWERS AND THUNDERSTORMS TO THE KUSKOKWIM VALLEY AGAIN
THIS EVENING. HOWEVER...SINCE CLOUD COVER THIS AFTERNOON WAS MORE
PERSISTENT THAN EXPECTED WILL NOT DEVELOP UNTIL THE EARLY EVENING
HOURS AND NOT BE AS WIDESPREAD AS INITIALLY THOUGHT. TO THE WEST
OF THIS THERMAL TROUGH...AN UPPER LEVEL LOW DIVING INTO THE BERING
WILL MERGE WITH ANOTHER TROUGH NEAR KODIAK ISLAND AND STALL OVER
THE EASTERN BERING. THIS WILL BRING CONTINUED CLOUDY AND SHOWERY
WEATHER TO MUCH OF THE SOUTHWEST MAINLAND THROUGH THE WEEKEND.
DIURNAL THUNDERSTORMS WILL ALSO DEVELOP DURING THIS
TIME...ESPECIALLY ON SATURDAY AFTERNOON/EVENING OVER THE KUSKOKWIM
VALLEY WHERE A SHORTWAVE WILL INTERACT WITH THE THERMAL TROUGH.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE LOW DIVING SOUTHWARD INTO THE BERING WILL BRING RAIN SHOWERS
AND NEAR GALE FORCE WINDS TO THE PRIBILOFS AND EASTERN BERING
OVERNIGHT TONIGHT. THIS WILL THEN WEAKEN SLIGHTLY AS IT PROGRESSES
TOWARDS THE AKPEN AND EASTERN ALEUTIANS...THOUGH THEY WILL STILL
EXPERIENCE GUSTY NORTHWESTERLY WINDS AND RAIN SHOWERS FOR MUCH OF
THE DAY TOMORROW. TO THE WEST OF THIS LOW...RIDGING WILL PREVAIL
OVER THE WESTERN BERING...KEEPING WINDS GENERALLY LIGHT AND
FOG/STRATUS IN THE AREA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

BEGINNING THE EXTENDED PERIOD FORECAST SUNDAY NIGHT...A CLOSED
UPPER LEVEL LOW IN THE VICINITY OF KODIAK ISLAND WILL BE THE MAIN
IMPACTFUL FEATURE OF INTEREST FOR THE REGION. THIS LOW WILL KEEP
MOISTURE...CLOUDS...AND COOLER WEATHER OVER MUCH OF THE REGION
THROUGH THE DAY TUESDAY. PRECIPITATION WILL GENERALLY BE IN THE
FORM OF SHOWERS WITH PERIODS OF LIGHTER RAIN ALONG THE NORTHERN
GULF COAST. DIFFICULTY IN ASCERTAINING WEAK EMBEDDED SHORTWAVE TROUGHS
WITHIN THE CLOSED LOW MEANS THAT DIURNAL HEATING AND INSTABILITY
WILL BE DIFFICULT TO DIAGNOSE AT THIS TIME...BUT THERE MAY BE
ENOUGH HEATING FOR ISOLATED THUNDERSTORMS ACROSS THE MORE
FAVORABLE LOCATIONS ALONG THE TALKEETNA MOUNTAINS AND PORTIONS OF
THE ALASKA RANGE. UNCERTAINTY QUICKLY RISES LATE TUESDAY AS A
CENTRAL PACIFIC LOW...WITH AN ASSOCIATED SUBTROPICAL WARM
FRONT...MERGES WITH THE LEFTOVER REMNANT UPPER LOW NEAR KODIAK
ISLAND. HOWEVER...THE LATEST SUITE OF GLOBAL NUMERICAL GUIDANCE
HAS CLUSTERED AROUND A GENERAL SOLUTION WHICH PHASES THE PACIFIC
LOW WITH THE KODIAK LOW...EVENTUALLY DRIVING A STOUT WARM FRONT
INTO THE GULF OF ALASKA WEDNESDAY AND THURSDAY. SHOULD THIS
PATTERN EMERGE AS CURRENTLY PROGGED...ESPECIALLY BY THE 12Z AND
18Z GFS SOLUTIONS...A STRONG GALE FORCE FRONT MAY MOVE UP TOWARD
THE NORTH GULF COAST...WITH AN IMPRESSIVE SLUG OF PRECIPITATION
IMPACTING COASTAL AND INLAND LOCATIONS. HOWEVER...DUE TO THE POOR
MODEL RUN CONSISTENCY WITH LARGE DEVIATIONS NOTED WITHIN THE
ENSEMBLE GUIDANCE...A VERY GENERALIZED WPC BLEND WAS FAVORED FOR
THE TIME BEING. UNCERTAINTY CONTINUES TOWARD THE END OF THE
WEEK...BUT THE GENERAL PATTERN LOOKS TO FAVOR TROUGHING OVER THE
EASTERN BERING SEA...AND SOUTH TO SOUTHWEST FLOW OVER MOST OF
SOUTHERN ALASKA...KEEPING A SLIGHTLY COOLER...POSSIBLY WETTER...AND
CLOUDIER PATTERN IN PLACE. OF COURSE...BY THAT FAR OUT...THERE
TENDS TO BE INTERMITTENT DRIER AND NICER DAYS IN BETWEEN...BUT
THAT IS DIFFICULT IF NOT IMPOSSIBLE TO FORECAST IN THESE PATTERNS
AT THAT TIME RANGE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...JA