Small Craft Advisory 887, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
437 PM AKST SAT NOV 8 2014

.ANALYSIS AND UPPER LEVELS...THE VERY DEEP EXTRA-TROPICAL LOW BOTTOMED
OUT OVER THE SOUTHWESTERN BERING SEA SOMETIME LAST EVENING AND HAS
STARTED TO VERY SLOWLY WEAKEN. THERE ARE NO OBSERVATIONS TO RECORD
THE ACTUAL CENTRAL PRESSURE IN THAT AREA...BUT A DRIFTING BOUY
EAST OF THE LOW CENTER DROPPED TO 929.8MB LATE YESTERDAY AFTERNOON.
BASED ON THIS OBSERVATION THE CENTRAL PRESSURE WAS LIKELY SOMEWHERE
IN THE LOWER OR MID 920S. THE LOW WAS NEARLY STALLED FOR ABOUT 12
HOURS BUT IS NOW PROGRESSING SLOWLY EASTWARD PASSING JUST NORTH OF
THE WESTERN-MOST ALEUTIANS. A CORE OF STRONGER WINDS ON THE SOUTH
SIDE OF THE LOW HAS MOVED BACK INTO SHEMYA WITH GUSTS TO AROUND 70
MPH. THIS IS WELL BELOW THE 96 MPH OBSERVED YESTERDAY.

THE FRONTAL SYSTEM ASSOCIATED WITH THIS LOW HAS TRACKED ACROSS
THE BERING SEA AND IS NOW JUST OFF THE SOUTHWEST COAST. WINDS
ALONG THE FRONT HAVE WEAKENED SIGNIFICANTLY...NOW MAXING OUT AT
35 TO 40 KT...WHICH ARE VERY TYPICAL WINDS FOR THIS TIME OF YEAR.

MEANWHILE...AN UPPER LEVEL SHORT-WAVE TROUGH OUT AHEAD OF THIS
SYSTEM EXTENDS FROM SOUTHWEST ALASKA INTO THE WESTERN GULF WITH A
SURFACE LOW SOUTH OF THE KENAI PENINSULA. THERE IS A NARROW BAND
OF PRECIP RIGHT OUT AHEAD OF THE TROUGH. BASED ON RADAR DATA THE
PRECIP IS MOSTLY SHOWERY IN NATURE. STRONG EASTERLY FLOW ALONG THE
CHUGACH AND KENAI MOUNTAINS IS PRODUCING DOWNSLOPE DRYING WITH
PARTLY CLOUDY SKIES NOTED FROM THE WESTERN KENAI UP TO ANCHORAGE.

&&

.MODEL DISCUSSION...AS WOULD BE EXPECTED WITH A STRONG WELL
ESTABLISHED SYSTEM...THE MODELS ALL INITIALIZED WELL. THE GFS
SOLUTION FOR TRACK OF THE LOW QUICKLY DIVERGES FROM THE REST OF
THE MODELS AND WILL BE IGNORED. OTHERWISE MODELS ARE IN VERY GOOD
AGREEMENT WITH HANDLING OF LARGE SCALE FEATURES THROUGH MONDAY AND
FORECAST CONFIDENCE IS ABOVE NORMAL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA...
A WET PATTERN WILL CONTINUE THROUGH THE BEGINNING OF THE WEEK WITH
DEEP SOUTHERLY FLOW ESTABLISHED OVER SOUTHCENTRAL ALASKA AND A
SERIES OF FRONTS APPROACHING THE GULF COAST. THE BULK OF THE
PRECIPITATION WILL BE CONFINED TO THE GULF COAST AS STRONG
SOUTHEASTERLY MID LEVEL FLOW ACROSS THE CHUGACH RANGE KEEPS INLAND
AREAS LIMITED TO MAINLY TO SCATTERED SHOWERS. ONE EXCEPTION WILL
BE THIS EVENING AS A WEAK UPPER TROUGH LIFTS NORTHWARD THROUGH THE
AREA...BRINGING A BRIEF WINDOW OF MORE NUMEROUS SHOWERS TO
ANCHORAGE AND THE MAT-SU. SOME SNOW WILL MIX IN OVER INLAND
LOCATIONS BUT PRECIPITATION TYPE WILL BE MOSTLY RAIN OVER THE
COMING DAYS AS TEMPERATURES CONTINUE TO WARM IN SOUTHERLY
FLOW...WITH ANY LIGHT ACCUMULATIONS MOSTLY LIMITED TO HIGHER
ELEVATIONS SUCH AS TURNAGAIN AND THOMPSON PASSES. THE NEXT FRONT
APPROACHING THE COAST LATE SUNDAY WILL LEAD TO ANOTHER ROUND OF
STRONGER SOUTHEASTERLY WINDS THROUGH FAVORED AREAS SUCH AS
TURNAGAIN ARM. INLAND LOCATIONS WILL THEN SEE AN INCREASED CHANCE
OF PRECIPITATION ON MONDAY AS MID LEVEL FLOW BECOMES MORE
SOUTHERLY AND DOWNSLOPE FLOW WEAKENS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

A WEAKENING SURFACE LOW IN THE GULF OF ALASKA CONTINUES TO BRING
SOME SHOWERS TO THE KUSKOKWIM VALLEY THIS EVENING. THE LOW WILL
WEAKEN AS AN UPPER LEVEL DISTURBANCE LIFTS OVER THE KUSKOKWIM
VALLEY TONIGHT AHEAD OF THE STRONG FRONT IMPACTING THE WEST COAST
OF ALASKA CURRENTLY. RAIN AND SNOW ARE POSSIBLE NORTH OF ANIAK TO
SPARRAVOHN LINE TONIGHT. OTHER AREAS WILL REMAIN RAIN OVERNIGHT.
THE FRONT WILL SHIFT INLAND OVERNIGHT. THE FRONTS STRENGTH WILL
REMAIN WITH GOOD MID AND UPPER LEVEL SUPPORT THROUGH TOMORROW
NIGHT. LOCALLY STRONG WINDS ARE DEVELOPING ALONG THE WEST COAST
AND ALEUTIAN RANGE AND LAST THROUGH SUNDAY NIGHT. WINDS WILL DIMINISH
MONDAY AS THE LOW IN THE BERING SEA CONTINUES TO WEAKEN SLOWLY.
DUE TO THE WARMTH OF THE SYSTEM...RAIN SHOWERS WILL CONTINUE TO
SPILL INTO SOUTHWEST ALASKA THROUGH MONDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE IMMENSE LOW ACROSS THE BERING SEA WILL SLOWLY WEAKEN AND TRACK
EAST SOUTHEAST THROUGH SUNDAY. STRONG WINDS AROUND 50 KNOTS WILL
CONTINUE AROUND THE CORE OF THE LOW THROUGH TOMORROW MORNING. THE
LOW WILL CONTINUE TO WEAKEN AND WRAP UP IN THE WESTERN BERING SEA
THROUGH MONDAY. WINDS WITH THE SYSTEM WILL DIMINISH TO 35 TO 40
KNOTS AND BE THROUGHOUT THE BERING SEA. THE STORM IS WRAPPED IN
WARMER AIR AND ALMOST THE ENTIRE BERING SEA AND ALEUTIANS WILL
ONLY EXPERIENCE RAIN. SOME COLD AIR WILL FILTER INTO THE WESTERN
ALEUTIANS MONDAY BEHIND THE LOW BRINGING A CHANCE OF SNOW BACK TO
THE REGION. COLDER AIR WILL CONTINUE TO FILTER INTO THE WESTERN
BERING SEA TUESDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A VERTICALLY STACKED LOW OVER THE NORTHERN BERING WILL CONTINUE
TO WEAKEN THROUGH WEDNESDAY MORNING...AS THE UPPER LEVEL TROUGH
CONTINUES TO ELONGATE AND DIVE SOUTH INTO THE NORTH PACIFIC.
FURTHER EAST...AN AMPLIFYING RIDGE BEGINS TO BUILD FROM THE
PANHANDLE THROUGH THE ALCAN BORDER...AND PERSISTS THROUGH THE
WEEKEND. THIS BLOCKING RIDGE WILL KEEP A SERIES OF WEAK BERING AND
NORTH PACIFIC LOWS CONFINED TO THE BERING SEA AND SOUTHWEST
MAINLAND. MODELS HAVE ALL BEEN CAPTURING THIS FEATURE WELL OVER
THE PAST FEW DAYS...CONTINUING TO INCREASE CONFIDENCE IN CLEARING
OVER SOUTHCENTRAL AND THE GULF COAST WITH A WARMING AND DRYING
TREND THROUGH THE LATER PART OF THE WEEK. WE BEGIN TO LOSE
CERTAINTY AT THIS POINT...AS MODEL AGREEMENT BEGINS TO WANE BY
FRIDAY WHEN A SIBERIAN LOW MERGES INTO THE TROUGH OVER THE
BERING.

OVER THE BERING SEA AND WESTERN GULF...EXPECT CLOUDY AND SHOWERY
CONDITIONS TO CONTINUE THROUGH MID WEEK WITH WINDS SLOWLY
DIMINISHING THROUGH EARLY NEXT WEEK. GALE FORCE WINDS FROM THE
BERING LOW WILL BEGIN TO DIMINISH ON MONDAY...EXCEPT NEAR THE
WESTERN BERING/ALEUTIANS WHERE THEY ARE EXPECTED TO CONTINUE INTO
TUESDAY. THE WESTERN ALEUTIANS WILL SEE A QUICK BREAK FROM THE
WINDS AND PRECIP ON WEDNESDAY...AS WEAK RIDGING PASSES THROUGH
FROM THE WEST. HOWEVER...A FRONTAL SYSTEM WILL QUICKLY APPROACH
THE WESTERN ALEUTIANS FROM THE WEST BY THURSDAY...BRINGING PRECIP
AND GUSTY WINDS BACK TO THE AREA THROUGH THE BEGINNING OF THE
WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 120 130 131 132 136 150 155 160 165 170 172 173 174
               175 176 179 180 181 185 351 352 411 412 413 414.
         STORMS 177 178

FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SB
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JN
LONG TERM...TP