Small Craft Advisory 314, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
514 AM AKDT FRI APR 10 2015

.ANALYSIS AND UPPER LEVELS...

THE REGIONAL UPPER AIR PATTERN IS BEING DOMINATED BY A 150 KT
NORTH PACIFIC JET STREAM STRETCHING ACROSS THE PACIFIC OCEAN. THIS
ENHANCED UPPER LEVEL JET STREAM IS BEING AIDED BY A LARGE POOL OF
COLD AIR ORIGINATING FROM THE NORTHERN BERING SEA AND EASTERN
SIBERIA. NORTHWEST FLOW IS ENCOMPASSING A LARGE PORTION OF THE
BERING SEA...WITH THE COLD AIR ALOFT AIDING DEEP INSTABILITY AND
STRONG MARITIME CONVECTIVE SHOWERS OVER MOST OF THE BERING AND
ALEUTIAN CHAIN. ALONG THE LEFT EXIT OF THE NPAC JET STREAM IS AN
ELONGATED UPPER LEVEL LOW ACROSS THE GULF OF ALASKA...WITH THE
CENTER NEAR THE BARREN ISLANDS. WATER VAPOR SATELLITE IMAGERY
DEPICTS MOISTURE ASSOCIATED WITH THE WARM CONVEYOR BELT ALOFT
WRAPPING INTO SOUTHERN ALASKA. THE FRONT ASSOCIATED WITH THE LOW
HAS OCCLUDED...EVIDENCED BY WEAKENING EAST-SOUTHEAST WINDS ACROSS
THE GULF OF ALASKA. AS USUAL...THE GULF LOW WILL WEAKEN AND STALL
OVER THE GULF...WITH MOISTURE AND CLOUDS WRAPPING AROUND THE
RESIDUAL LOW INTO THE WEEKEND.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH THE LARGE SCALE PATTERN
HEADING INTO EARLY NEXT WEEK BEFORE THEY DIVERGE WITH THE TRACK OF
A STRONG LOW SOUTH OF THE ALEUTIAN CHAIN. THE LARGEST SHORT TERM
DISCREPANCIES ARE ASSOCIATED WITH PRECIPITATION PATTERNS OVER THE
MAINLAND AS THE CURRENT LOW IN THE NORTHERN GULF TRACKS EAST AND
WEAKENS. THESE DISCREPANCIES ARE NORMAL IN SUCH PATTERNS...AND AS
A RESULT...DO NOT LEND TO LESS UNCERTAINTY IN THE OVERALL PATTERN.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE UPPER LOW OVER THE NORTHWEST GULF OF ALASKA WILL SLOWLY DRIFT
EAST AND WEAKEN THROUGH SATURDAY AFTERNOON. AN ASSOCIATED EAST TO
WEST ORIENTED FRONT THAT IS CURRENTLY JUST INLAND FROM THE GULF
COAST WILL SLOWLY DRIFT NORTH AND DISSIPATE BY THIS AFTERNOON. THE
GULF LOW WILL TRANSITION INTO A WEAK FRONT AND BEGIN TO MOVE
ONSHORE OF THE GULF COAST SATURDAY NIGHT. THIS IS IN RESPONSE TO
ANOTHER UPPER LOW APPROACHING FROM THE WEST THAT BEGINS TO PUSH
INTO THE GULF NEAR KODIAK ISLAND. IN GENERAL SOUTH CENTRAL ALASKA
WILL REMAIN IN WEAK CYCLONIC FLOW WITH SOME RESIDUAL MOISTURE AND
FAIRLY COLD AIR ALOFT THROUGH SATURDAY NIGHT. THIS WILL RESULT IN
SOME SHOWERS...POSSIBLY DIURNALLY ENHANCED...WITHOUT ANY REAL
FOCAL POINTS FOR PRECIPITATION.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...FRI AND
SAT)...THE PATTERN WILL BE DOMINATED BY COLDER AIR AND SNOW
SHOWERS WRAPPING INTO THE AREA FROM THE NORTHWEST. THE AREA OF LOW
PRESSURE NEAR THE COOK INLET WILL DRIFT EVER SO SLIGHTLY TO THE
EAST THROUGH THE DAY. THIS SHOULD LEAD TO WINDS AND PRECIPITATION
SLOWLY WINDING DOWN LATER TONIGHT. BUT THROUGH THE DAY...WE WILL
STILL SEE SOME GUSTY WINDS...ESPECIALLY ALONG THE KUSKOKWIM DELTA
COAST AND THE ALASKA PENINSULA. THIS COUPLED WITH THE HEAVIER
SHOWERS THAT ARE SHOWING UP ON RADAR COULD LEAD TO BRIEF PERIODS
OF REDUCED VISIBILITY IN BLOWING SNOW. ACCUMULATIONS SHOULD BE
LIMITED THOUGH AS MOST OF THE FEATURES ARE TRANSIENT AND DO NOT
APPEAR TO BE STALLING OVER ANY ONE AREA. BY SATURDAY...THE ENTIRE
AREA WILL BE UNDER NORTH TO WEST FLOW. THIS SHOULD KEEP THE BEST
SNOW SHOWERS OVER THE BERING SIDE OF THE AKPEN AND THE NORTHWEST
FACING SLOPES OF THE ALEUTIAN AND ALASKA RANGES. COLD AIR
ADVECTION WILL CONTINUE THROUGH THE EARLY PART OF THE WEEKEND WITH
850MB TEMPS DROPPING ON THE ORDER OF 5 DEGREES C. THIS WILL KEEP
THE ATMOSPHERE RATHER UNSTABLE...ESPECIALLY WITH A FEW BREAKS OF
APRIL SUNSHINE...AND COULD MAKE FOR SOME GUSTY WINDS AND QUICK
BURSTS OF SNOW JUST ABOUT ANYWHERE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...FRI AND
SAT)...TWO WORDS DESCRIBE THE FORECAST...NORTHWEST FLOW. THE CLASSIC
FLOW REGIME WILL DOMINATE THIS TIME PERIOD. THE RESULTING SENSIBLE
WEATHER WILL BE GUSTY GALE-FORCE WINDS AND SOME SNOW
SHOWERS...ESPECIALLY ON THE BERING SIDE. MODELS DO AGREE THAT A
WEAK UPPER LEVEL DISTURBANCE WILL MOVE OFF THE KAMCHATKA PEN AND
INTO THE CENTRAL ALEUTIANS THROUGH SAT. THIS WILL ONLY SERVE TO
REINFORCE THE SHOWERY AND GUSTY PATTERN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE MID TERM WILL BEGIN WITH A BROAD UPPER LEVEL TROUGH
ENCOMPASSING MAINLAND ALASKA AS THE ZONAL JET CURRENTLY SITUATED
ALONG 50N BEGINS TO BUCKLE THIS WEEKEND. THIS WILL BRING SHOWERY
WEATHER TO MUCH OF THE REGION THROUGH SUNDAY...WITH A MIX OF RAIN
AND SNOW CONTINUING ALONG THE GULF COAST IN THE VICINITY OF A
SURFACE LOW OVER THE NORTHERN GULF AND MORE SPORADIC SHOWERY
CONDITIONS INLAND. SNOW SHOWERS WILL ALSO PERSIST ACROSS THE
BERING IN NORTHWEST FLOW ON THE BACK SIDE OF THE TROUGH.

SOUTHCENTRAL ALASKA WILL THEN UNDERGO A GRADUAL DRYING TREND
EARLY NEXT WEEK AS THE GULF LOW SLOWLY WEAKENS...WITH SHOWERS ALSO
DIMINISHING OVER MUCH OF THE BERING BUT CONTINUING ALONG THE
ALEUTIAN CHAIN AS A NORTH PACIFIC LOW PASSES JUST TO THE SOUTH.
WIDESPREAD PRECIPITATION LOOKS TO RETURN TO THE SOUTHERN MAINLAND
DURING THE MIDDLE OF NEXT WEEK AS THIS LOW TRACKS TOWARDS THE GULF
AND AN UPPER RIDGE BUILDS OVER THE WEST COAST OF NORTH AMERICA. IT
APPEARS THAT THE BULK OF THIS PRECIPITATION WOULD EVENTUALLY
TRANSITION TO RAIN AS WARMER AIR RETURNS TO SOUTHCENTRAL AK IN
SOUTHERLY FLOW ON THE WESTERN PERIPHERY OF THE RIDGE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE...130 132 138 150 155 160 165 170 172-178 180
         HEAVY FREEZING SPRAY...180 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO
LONG TERM...CB/MMC