Small Craft Advisory 349, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
525 AM AKDT TUE APR 21 2015

.ANALYSIS AND UPPER LEVELS...
AT 500 MB THERE IS A CLOSED LOW OVER SAINT LAWRENCE ISLAND WITH
AN ASSOCIATED TROUGH EXTENDING THROUGH THE YUKON DELTA. SATELLITE
IMAGERY IS SHOWING A SWATH OF MOISTURE FROM THE PRIBILOFS
EXTENDING INTO THE KUSKOKWIM DELTA. THE SURFACE OBSERVATIONS HAVE
BEEN REPORTING SHOWERY SNOW SHOWERS FOR THE KUSKOKWIM DELTA WITH
LITTLE SNOW ACCUMULATION EXCEPT FOR A NARROW BAND OF SNOW SHOWERS
WEST OF BETHEL THIS MORNING. THE REST OF THE SOUTHERN BERING HAS
BROAD SOUTHWESTERLY FLOW AND EXTENDS INTO THE BRISTOL BAY
INTERIOR. THE EASTERN ALEUTIANS HAS A NEUTRAL TILTED TROUGH OVER
THE AREA AND HAS BEEN PRODUCING SCATTERED SNOW SHOWERS ALONG THE
CHAIN. WHILE THE WESTERN BERING/ALEUTIANS HAS AN AMPLIFIED RIDGE
OVER THE REGION WITH SATELLITE IMAGERY SHOWING A LARGE AREA OF
STRATUS UNDER THE UPPER LEVEL RIDGE.

THE GULF HAS BROAD SOUTHWESTERLY FLOW WITH A WEAK SHORTWAVE
PUSHING THROUGH THE COPPER RIVER BASIN. THE WATER VAPOR IMAGERY IS
SHOWING MOISTURE OVER THE NORTHERN GULF SPREADING INTO SOUTHCENTRAL
THIS MORNING. THE RADAR IMAGERY IS SHOWING SCATTERED SHOWERY
PRECIPITATION IN THE NORTHERN GULF AND PRINCE WILLIAM SOUND.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN PRETTY GOOD AGREEMENT WITH THE NEXT NORTH
PACIFIC LOW APPROACHING THE SOUTHWESTERN GULF. THE EC WAS TRACKING
THE LOW FARTHER SOUTH AND WAS WEAKER THAN THE OTHER MODELS. WITH
THE KAMCHATKA LOW APPROACHING THE WESTERN BERING SEA THE MODELS
WERE IN GOOD AGREEMENT WITH THE PLACEMENT AND STRENGTH OF THIS
SYSTEM. THE GFS/NAM WERE THE PREFERRED MODELS THROUGH THE SHORT
TERM FORECAST. THE FORECAST CONFIDENCE REMAINS ABOVE AVERAGE GOING
INTO THE MIDWEEK.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE COLD FRONT THAT MOVED THROUGH SOUTHCENTRAL YESTERDAY HAS NOW
MOVED INTO THE INTERIOR OF THE STATE. THIS HAS LEFT THE ATMOSPHERE
OVER SOUTHCENTRAL IN SOUTHWEST FLOW ALOFT AS WELL AS THERE BEING MUCH
COOLER TEMPERATURES ALOFT. THIS IS KEEPING SOME SNOW SHOWERS IN
THE REGION TODAY AND INTO TONIGHT. EVEN THOUGH TEMPERATURES WILL
WARM INTO THE 40S ACROSS MUCH OF THE AREA THE COLD AIR ALOFT
SHOULD KEEP ALMOST ALL OF THE PRECIPITATION AS SNOW.
A LOW SOUTH OF THE ALASKA PENINSULA WILL MOVE INTO THE GULF
TONIGHT AND BRING IN SOME RAINFALL AND STRONG WINDS TO KODIAK
ISLAND. THERE MAY BE SOME SNOW AT HIGHER ELEVATIONS ACROSS THE
ISLAND BUT TEMPERATURES WILL WARM UP FAST ENOUGH THERE SHOULD BE
LITTLE TO NO SNOW FOR SEA LEVEL AREAS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...TUE AND WED)...THE
UPPER LEVEL LOW NEAR NUNIVAK ISLAND WILL CONTINUE TO KEEP ACTIVE
WEATHER ACROSS MUCH OF THE AREA...BUT THERE WILL BE A SLOW
IMPROVEMENT IN CONDITIONS OVERALL. TO START THINGS OFF...THIS LOW
HAS CREATED A WEAK BOUNDARY ACROSS MUCH OF THE KUSKOKWIM DELTA
THIS MORNING. WITH COLD AIR TO THE WEST AND SLIGHTLY WARMER
SOUTHEAST WINDS TO THE EAST...THIS BOUNDARY HAS PROVIDED ENOUGH
LIFT TO WRING OUT SOME STEADY SNOW THROUGHOUT THE NIGHT. THERE
HAVE EVEN BEEN SOME HEAVIER SHOWERS ALONG THIS LINE THAT HAVE
PRODUCED LIMITED VISIBILITIES FOR BRIEF PERIODS. THIS LINE SHOULD
HOVER PRETTY CLOSE TO BETHEL FOR MUCH OF THE DAY BEFORE FINALLY
LIFTING NORTH. FOR THE REST OF THE AREA...ONSHORE FLOW AND COLD
AIR ALOFT WILL PERSIST TODAY. THIS WILL KEEP THE ATMOSPHERE
UNSTABLE ENOUGH TO ALLOW SHOWERS TO POP UP JUST ABOUT ANYWHERE. BY
WEDNESDAY...THE UPPER LEVEL LOW PULLS NORTH INTO THE BERING
STRAIT WHILE A NORTH PACIFIC LOW STARTS TO INFLUENCE THE PATTERN.
THIS NEW LOW STARTS TO PULL SOME OF THE FLOW AROUND TO THE
NORTHEAST THROUGH BRISTOL BAY...THIS COULD ALSO LEAD TO SOME WEAK
LOW LEVEL CONVERGENCE WITH THE NORTHERN PORTION OF THE AREA STILL
UNDER COLD SOUTHWEST FLOW. THIS WILL LIKELY RESULT IN SOME MORE
BANDING TYPE SNOW SHOWERS SETTING UP SOMEWHERE NORTH OF DILLINGHAM
STRETCHING TOWARD MCGRATH. ANY NOTE-WORTHY ACCUMULATIONS SHOULD BE
LIMITED TO LOCATIONS RIGHT UNDER THE NARROW BAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND
2...TUE AND WED)...NORTHWESTERLY FLOW SHOULD FINALLY RELINQUISH
ITS GRIP TODAY AND ALLOW A BRIEF RESPITE FROM THE COLD SHOWERS.
WEAK RIDING WILL MOVE IN FROM THE SOUTHWEST IN FRONT OF A
KAMCHATKA LOW. THE FRONT ASSOCIATED WITH THIS LOW SHOULD REACH THE
WESTERN ALEUTIANS BY THIS AFTERNOON AND BRING GALE FORCE
SOUTHERLIES TO THE AREA. THESE WINDS SHOULD THEN TRACK THROUGH THE
CHAIN REACHING THE EASTERN ALEUTIANS BY WEDNESDAY EVENING. THE
SOUTHERLY WINDS WILL ALSO HELP TO BRING UP SOME WARMER AIR WHICH
SHOULD ALLOW PLACES THAT HAVE BEEN SEEING PURELY SNOW SHOWERS TO
START TO SEE AT LEAST SOME RAIN MIX IN.

&&

.LONG TERM FORECAST (WEDNESDAY NIGHT THROUGH MONDAY)...
AFTER THE GALE FORCE LOW OVER THE GULF DISSIPATES AND DEPARTS THE
AREA WEDNESDAY EVENING...A WEAKENING BERING SEA FRONT WILL ENTER
THE SOUTHWEST MAINLAND...BRINGING RAIN AND SNOW TO THE AREA FOR
THURSDAY. THIS FRONT WILL ENTER THE GULF AS IT CONTINUES TO WEAKEN
ON FRIDAY AND BRING RAIN MAINLY TO THE GULF COAST...WHILE
SOUTHCENTRAL WILL REMAIN CLOUDY BUT DRY.

STARTING THIS WEEKEND THERE IS VERY GOOD MODEL AGREEMENT THAT THE
UPPER LOW ASSOCIATED WITH THE AFOREMENTIONED BERING FRONT WILL
DRAG THE JET WELL SOUTH OF THE STATE...ALLOWING FOR RIDGING TO
BUILD IN FROM THE CENTRAL BERING INTO THE INTERIOR. THIS LOOKS TO
BRING A MUCH LESS AMPLIFIED PATTERN TO MOST OF THE STATE THAT
SHOULD PERSIST INTO EARLY NEXT WEEK. THIS PATTERN WILL LIMIT
PRECIPITATION IN THE AREA MOSTLY TO DIURNAL SHOWERS AS
TEMPERATURES RETURN TO ABOVE NORMAL.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 131 132 136-138 150 155 170 172-178.
FIRE WEATHER...NONE.

&&

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