Small Craft Advisory 244, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
439 PM AKDT WED MAR 18 2015

.ANALYSIS AND UPPER LEVELS...

THE OVERALL WEATHER PATTERN REMAINS UNCHANGED FROM YESTERDAY AND
FEATURES A ROBUST UPPER LOW SOUTH OF THE ALEUTIANS ANCHORING A
LONGWAVE TROUGH THAT SPANS MOST OF THE NORTH PACIFIC. SOUTHERN
ALASKA REMAINS ON THE DOWNSTREAM/"WARM" SIDE OF THIS TROUGH...WITH
SOUTHERLY/SOUTHEASTERLY FLOW BRINGING WARM AIR ALOFT AND A PARADE
OF EMBEDDED SHORTWAVE FEATURES TO THE AREA. THE PRIMARY SHORTWAVE
FEATURE YESTERDAY WAS A SHORTWAVE RIDGE...WHICH RESULTED IN CLEAR
SKIES AND ALLOWED TEMPERATURES TO SOAR TO NEAR 50 DEGREES AROUND
PARTS OF COOK INLET. TODAY...A SERIES OF CLOSELY-SPACES SHORTWAVE
TROUGHS ARE IMPACTING THE REGION WITH CLOUDS AND PRECIPITATION.
THANKS TO THE PERSISTENT SOUTHEAST FLOW...MOST OF THE PRECIP IS
FALLING OUT ALONG THE GULF COAST (IN THE FORM OF RAIN)...WITH ONLY
OCCASIONAL SPRINKLES/RAIN SHOWERS FOR INLAND LOCATIONS.

THE SAME HOLDS TRUE OVER THE SOUTHWEST MAINLAND AND ALASKA
PENINSULA AS THE SENSIBLE WEATHER CONTINUES TO BE DRIVEN BY THESE
WEAKENING SHORTWAVE FEATURES MOVING THROUGH FROM EAST TO WEST. A
ROUND OF SHOWERS MOVED THROUGH THE BRISTOL BAY ZONE EARLY THIS
MORNING AND IS NOW FALLING APART ACROSS THE DELTA. MEANWHILE...THE
NEXT UPSTREAM DISTURBANCE IS PREPARING TO IMPACT KODIAK ISLAND AND
WILL MOVE ACROSS THE ALASKA RANGE INTO THE BRISTOL BAY AREA THIS
EVENING.

IN THE BERING SEA/ALEUTIAN REGION...THE WARM FRONT THAT PUSHED
WESTWARD THROUGH THE AREA YESTERDAY HAS STALLED AS EXPECTED OVER
THE CENTRAL ALEUTIANS. THUS...STIFF NORTHERLY WINDS AND HEAVY SNOW
SHOWERS CONTINUE TODAY FROM ADAK TO ATKA...WITH THE RAIN/SNOW LINE
INCHING ONLY SLOWLY WESTWARD FROM DUTCH HARBOR.

&&

.MODEL DISCUSSION...

THE MODELS REMAIN IN OUTSTANDING SYNOPTIC/LARGE-SCALE AGREEMENT.
AND IN FACT...MODELS ARE ALSO IN UNUSUALLY GOOD AGREEMENT ON THE
TIMING AND STRENGTH OF MOST OF THE MINOR SHORTWAVES MOVING THROUGH
THE OVERALL PATTERN OVER THE NEXT FEW DAYS. THE ONE EXCEPTION IS
THE GFS THAT IS A BIT FASTER THAN THE CONSENSUS WITH A SFC LOW AND
MID-LEVEL SHORTWAVE APPROACHING KODIAK ISLAND THURSDAY EVENING.
THE MAIN THING THIS WOULD IMPACT IS THE START TIME FOR RAIN ACROSS
KODIAK ISLAND. FOR FORECAST PREPARATION TODAY...BOTH DOMAINS WERE
ABLE TO MAKE USE OF THE HI-RES GEM-REGIONAL WITH INCREASING
INFLUENCE/CONTRIBUTION FROM THE GLOBAL ECMWF FOR THE END OF THE
WEEK.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2...THU AND
FRI)...NOT MUCH CHANGE TO THE PATTERN EXPECTED OVER THE NEXT FEW
DAYS. THE BROAD UPPER LEVEL LOW CONTINUES TO MEANDER SOUTH OF
DUTCH HARBOR ALLOWING WEAK FRONT AFTER WEAK FRONT TO MOVE FROM THE
NORTH PACIFIC TO THE NORTH GULF COAST. ONE FRONT HAS ALREADY MOVED
ONSHORE AND PRODUCED LITTLE TO NO PRECIPITATION FOR INLAND
AREAS...WITH KACHEMAK BAY ONLY PICKING UP A FEW HUNDREDTHS. THE
NEXT FRONT IS WEAKENING AS IT DRIFTS NORTH THROUGH THE GULF
TONIGHT. THIS WILL ONLY SERVE TO REINFORCE PRECIPITATION ALONG THE
COAST. BUT LIGHT TO MODERATE SOUTHEAST FLOW WILL KEEP THINGS
MOSTLY DRY AND RELATIVELY WARM FOR INLAND LOCATIONS. KODIAK ISLAND WILL
ENDURE THE WORST CONDITIONS FROM THESE FRONTS AS WARM AND MOIST
EAST TO NORTHEAST FLOW WILL PUSH RAIN AND FOG INTO THE CITY. IN
BETWEEN THESE FRONTS ARE EMBEDDED SHORT WAVE RIDGES. ONE SUCH
RIDGE WILL PASS THROUGH MUCH OF THE AREA THURSDAY AFTERNOON. THIS
WILL BRING A FEW BREAKS IN THE CLOUDS AND HELP TO NUDGE HIGH
TEMPERATURES UP A FEW DEGREES FROM WEDNESDAY'S FOR INLAND LOCALES.
THE NEXT FRONT IN THE SERIES WILL ACTUALLY TRACK FURTHER TO THE
SOUTHWEST OVERNIGHT THURSDAY INTO FRIDAY. THIS MEANS PRECIPITATION
SHOULD ONLY REACH AS FAR NORTHEAST AS SEWARD AND KACHEMAK BAY AS
THE LOW PASSES SOUTH OF KODIAK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
YET ANOTHER SHORTWAVE TRAVERSING OVER THE SOUTHWEST MAINLAND WILL
BRING WET SNOW MIXED WITH RAIN FROM WESTERN BRISTOL BAY...THAT
WILL SPREAD NORTHWARD INTO THE KUSKOKWIM DELTA THIS AFTERNOON.
WITH A WARM NOSE EXTENDING TO 3000 FT ON THIS MORNINGS BETHEL
SOUNDING...PRECIP SHOULD INITIALLY BEGIN AS RAIN OVER THE DELTA...BUT
THEN BECOME A RAIN/SNOW MIX THIS AFTERNOON AS THE ENVIRONMENT WET
BULBS. SURFACE TEMPERATURES DURING THIS TIME WILL BE RISING TO
ABOVE FREEZING AT THIS SAME TIME...SO A ISOLATED AREAS OF FREEZING
RAIN ARE POSSIBLE IN THE LATE MORNING AND EARLY AFTERNOON. THESE
AREAS ARE NOT EXPECTED TO BE LONG LIVED OR WIDESPREAD ENOUGH TO
REQUIRE AN ADVISORY. AFTER A BRIEF BREAK OVER BRISTOL BAY THIS
EVENING...A FINAL SHORTWAVE WILL MOVE OVER THE SAME AREA AND
BRING RAIN/SNOW BACK TO THE AREA INTO THURSDAY MORNING. RIDGING
WILL THEN BEGIN TO MOVE INTO THE AREA BEGINNING ON THURSDAY
EVENING...BRINGING CLEARING SKIES AND TEMPERATURES FALLING BACK
TO NEAR OR BELOW NORMAL BY FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE STATIONARY LOW JUST SOUTH OF THE ALEUTIANS CONTINUES TO DRIVE
THE WEATHER FOR THE ENTIRE REGION. A WEAK LOW THAT FORMED ON THE
EASTERN EDGE YESTERDAY WILL BRING GUSTY WINDS TO THE EASTERN
ALEUTIANS THROUGH EARLY THIS MORNING...BEFORE DIMINISHING BY MID
MORNING. TO THE WEST...SNOWFALL THAT HAS BEEN FALLING OVER THE
CENTRAL ALEUTIANS ALL NIGHT WILL SPREAD TO THE WEST AND MIX WITH
RAIN...BRINING AN INCH OR TWO OF ADDITIONAL ACCUMULATION TO MANY
AREAS BY THIS AFTERNOON. OVER THE PRIBILOF ISLANDS...THE WESTERN
EDGE OF THE SAME SHORTWAVE IMPACTING THE SOUTHWEST MAINLAND WILL
BRING SNOW SHOWERS BACK IN THE AREA FOR THIS AFTERNOON AND
EVENING. GUSTY NORTHEASTERLY WINDS WILL BRING AREAS A BLOWING SNOW
BACK TO THE AREA...BUT SHOULD NOT BE STRONG ENOUGH TO BRING YET
ANOTHER ROUND OF NEAR BLIZZARD CONDITIONS. THE NEARLY STATIONARY
LOW WILL FINALLY BEGIN TO DEPART THE AREA LATE TONIGHT...WHICH
WILL HELP FOR SHOWERS AND WINDS TO DIMINISH THROUGHOUT THE REGION
ON THURSDAY AND FRIDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE CLOSED UPPER LEVEL LOW REMAINS POSITIONED SOUTH OF THE
EASTERN ALEUTIANS BY FRIDAY BEFORE DROPPING FARTHER SOUTH INTO
THE PACIFIC THROUGH THE WEEKEND. THE EASTERN ALEUTIANS AND THE
BRISTOL BAY REGION WILL CONTINUE TO HAVE SHOWERY PRECIPITATION
ASSOCIATED WITH THE SURFACE LOW SOUTH OF KODIAK ISLAND. THIS WILL
RESULT IN MORE MOISTURE WITH WARMER TEMPERATURES ABOVE FREEZING
WITH ALL THE PRECIPITATION IN THE FORM OF RAIN FOR THE EASTERN
ALEUTIANS/BERING SEA FOR THE NEXT SEVERAL DAYS. THE MODELS ARE
STRUGGLING WITH THE SURFACE LOW ASSOCIATED WITH THE AFOREMENTIONED
UPPER LEVEL LOW FEATURE. THE WPC GUIDANCE FAVORED THE EC ENSEMBLES
DUE TO ITS CONSISTENCY...WHERE THE GFS ENSEMBLES WERE FLIP-
FLOPPING ON THE POSITION OF THE NORTH PACIFIC LOW. THIS WILL
RESULT IN CONTINUED NORTHEASTERLY FLOW THROUGH THE BERING SEA
THROUGH TUESDAY. THE GULF WILL HAVE A WEAK NORTH PACIFIC LOW ENTER
THE SOUTHEASTERN GULF BY FRIDAY AFTERNOON. THIS SYSTEM WILL TRACK
SOUTH OF YAKUTAT BY SATURDAY EVENING BEFORE DISSIPATING BY SUNDAY
MORNING. THIS WILL BRING CONTINUED WARMER TEMPERATURES TO
SOUTHCENTRAL HEADING INTO THE WEEKEND WITH RAIN REMAINING MAINLY
ALONG THE NORTHERN COAST. THE UPPER LEVEL RIDGE POSITIONED OVER
YUKON TERRITORY INTO THE BERING STRAIT WILL HELP TO KEEP SYSTEMS
FROM MOVING INTO THE INTERIOR AND KEEP WEATHER SYSTEMS ALONG THE
THE ALEUTIAN CHAIN AND ALONG THE SOUTHERN GULF REGION. THE
FORECAST CONFIDENCE REMAIN AVERAGE DUE TO THE UNCERTAINTY WITH THE
LOW SOUTH OF THE EASTERN ALEUTIANS AS IT MOVES SOUTHWARD.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 130 131 132 138 185.
         HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.

&&