Small Craft Advisory 893, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
450 AM AKST MON NOV 10 2014

.ANALYSIS AND UPPER LEVELS...

THE CENTRAL BERING SEA HAS AN UPPER LEVEL VERTICALLY STACKED LOW
WITH THE SURFACE LOW OF 960 MB NORTHWEST OF SAINT PAUL ISLAND. THE
SURFACE OBSERVATIONS ALONG THE WESTERN/CENTRAL ALEUTIANS CONTINUE
TO REPORT SHOWERY PRECIPITATION WITH GUSTY WESTERLY WINDS. ON THE
BACKSIDE OF THE LOW PRESSURE SYSTEM THERE IS A STRONG 170 KT JET
STREAK DIGGING INTO THE BASE OF THE LONGWAVE TROUGH. THIS TROUGH
EXTENDS SOUTHWARD THROUGH THE CENTRAL ALEUTIANS INTO THE PACIFIC
OCEAN AS FAR AS 35N. THERE IS AN AMPLIFIED UPPER LEVEL RIDGE
EXTENDING ALONG THE CALIFORNIA COASTLINE NORTHWARD THROUGH
SOUTHEAST ALASKA INTO THE YUKON TERRITORY. SOUTHWEST AND
SOUTHCENTRAL ALASKA WILL BE UNDER THE INFLUENCE OF STRONG
SOUTHERLY FLOW BETWEEN THE TWO AFOREMENTIONED SYNOPTIC FEATURES.
THIS SOUTHERLY FLOW COINCIDES WITH THE SOUTHWEST TO NORTHEAST
MERIDIONAL 110 KT JET STREAK LOCATED THROUGH THE GULF OF ALASKA.
THE SATELLITE IMAGERY IS SHOWING THE FRONTAL BOUNDARY MOVING
THROUGH THE NORTHERN GULF INTO THE INTERIOR OF SOUTHCENTRAL ALASKA
WITH WARMER TEMPERATURES. THE COASTAL TEMPERATURES ARE IN THE 40S
WITH THE INTERIOR TEMPERATURES IN THE MID 30S. DUE TO THE
CONTINUED SOUTHERLY FLOW THE SOUTHCENTRAL ALASKA REGION WILL
CONTINUE TO SEE A WARMING TREND. THE RADAR IS DEPICTING WIDESPREAD
RAIN ALONG THE NORTHERN GULF COASTLINES EXTENDING INTO PRINCE
WILLIAM SOUND AND THROUGH THE MAT-SU VALLEY.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN GOOD AGREEMENT THROUGH 48 HOURS AS THE LOW IN
THE BERING SEA CONTINUES TO SPIN DOWN. BY WEDNESDAY MORNING THE
MODELS ARE HAVING DIFFICULTY WITH THE PLACEMENT OF A LOW FORMING
OVER THE EASTERN ALEUTIANS. THE FORECAST CONFIDENCE CONTINUES TO
REMAIN ABOVE AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 3)...

THE SOUTHERLY FLOW WILL BE SETTING UP FOR THE NEXT SEVERAL
DAYS...THIS WILL ENHANCE THE MOISTURE BEING TRANSPORTED UP THROUGH
THE COOK INLET WITH THE ANCHORAGE BOWL AND THE MAT-SU VALLEY
GETTING LIGHT RAIN SHOWERS THIS MORNING. BY TUESDAY THERE WILL BE
ANOTHER FRONTAL BOUNDARY MOVING THROUGH THE WESTERN GULF PRODUCING
GALE FORCE SOUTHEASTERLY WINDS INTO THE BARREN ISLANDS THROUGH THE
NORTHERN GULF. THE MAJORITY OF THE PRECIPITATION WITH THIS FRONT
WILL BE ALONG THE NORTHERN COASTLINE AND WESTERN KENAI PENINSULA
EXTENDING INTO THE PRINCE WILLIAM SOUND AREA. THE UPPER LEVEL
RIDGE WILL BUILD ALONG THE NORTHERN GULF COASTLINE BY
TUESDAY...LOOK FOR THE GRADIENT TO INCREASE RESULTING IN STRONG
GUSTY TURNAGAIN ARM WINDS AND HIGHER ELEVATIONS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 3)...

ISOLATED TO SCATTERED SHOWERS WILL LINGER OVER THE REGION TODAY IN
THE WAKE OF THE STRONG FRONT THAT IS NOW TRACKING INTO
SOUTHCENTRAL ALASKA. GUSTY SOUTHEAST WINDS WILL CONTINUE AS THE
PRESSURE GRADIENT REMAINS MODERATE. THE BIG STORY THEN SHIFTS TO A
STRONG PACIFIC WARM FRONT EXPECTED TO IMPACT THE REGION BEGINNING
TONIGHT THROUGH WEDNESDAY. THIS SYSTEM WILL SPREAD COPIOUS AMOUNTS
OF PRECIPITATION (POSSIBLY MIXED WITH SNOW ACROSS PORTIONS OF THE
LOWER KUSKOKWIM VALLEY AND KUSKOKWIM DELTA TUESDAY NIGHT) AS IT
MOVES FROM EAST TO WEST. IN ADDITION...VERY STRONG SOUTHEAST WINDS
WILL DEVELOP ACROSS PORTIONS OF BRISTOL BAY AND ALONG AND NEAR THE
ALASKA RANGE...WITH THE POTENTIAL FOR 65+ MPH GUSTS. THE LOW WILL
TRACK OFF TO THE NORTHEAST WEDNESDAY...BUT THE THREAT FOR RAIN
WILL CONTINUE INTO THURSDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 3)...

SHOWERS WILL SLOWLY TAPER OFF THROUGH WEDNESDAY AS THE LARGE
CLOSED LOW OVER THE NORTHWEST BERING CONTINUES TO WEAKEN. COLDER
AIR WILL MOVE OVER THE WESTERN AND CENTRAL ALEUTIANS ON THE
BACKSIDE OF THE LOW WITH THE POTENTIAL FOR SNOW TO MIX IN WITH THE
RAIN SHOWERS. A PACIFIC WARM FRONT WILL MOVE INTO THE EASTERN
BERING TUESDAY EVENING INTO WEDNESDAY...BUT WILL ONLY IMPACT THE
FAR EASTERN ALEUTIANS WITH RAIN AND GUSTY SOUTHEAST WINDS.

&&

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

A HIGH LATITUDE BLOCKING PATTERN WILL BE OBSERVED MIDWEEK THROUGH
THE UPCOMING WEEKEND. AMPLIFIED LONGWAVE RIDGING WILL EXTEND
ACROSS THE ALASKA PANHANDLE NORTHWARD NEARLY TO THE NORTH POLE.
MEANWHILE AN AMPLIFIED TROUGH OVER THE BERING SEA AND NORTH
PACIFIC (DUE IN LARGE PART TO POWERFUL STORM SYSTEM OVER THE
BERING SEA LAST WEEK) WILL CONTINUE TO CLASH WITH THE AFOREMENTIONED
RIDGE OVER THE ALASKA MAINLAND. MULTIPLE SHORTWAVES WILL PUSH
THROUGH THE AMPLIFIED TROUGH BUT STRUGGLE TO MAKE MUCH EASTWARD
PROGRESS WITH HIGH PRESSURE THOROUGHLY ENTRENCHED. BY THIS
WEEKEND...A DEEPENING VERTICALLY STACKED LOW IN THE NORTH PACIFIC
SOUTH OF COLD BAY WILL BEGIN TO SLOWLY PUSH THE BLOCKING HIGH
EASTWARD (BUT NOT BY MUCH). MODEL AGREEMENT IS POOR IN THE
PLACEMENT AND EVOLUTION OF THIS VERTICALLY STACKED LOW AND THE
OVERALL IMPACT IT HAS ON THE HIGH LATITUDE BLOCKING PATTERN.
HOWEVER...ALL GUIDANCE SUGGESTS THAT SOME OF THE SHORTWAVE ENERGY
PUSHING ACROSS THE UPPER LEVEL TROUGH WILL PUSH ACROSS
SOUTHCENTRAL/SOUTHWEST ALASKA WHICH WILL IN TURN INCREASE
PRECIPITATION CHANCES.

THE MULTIPLE SHORTWAVES IN THE AMPLIFIED TROUGH OVER THE NORTH
PACIFIC AND BERING SEA WILL CREATE MULTIPLE AREAS OF WEAK LOW
PRESSURE THAT THE MODELS ARE HAVING A DIFFICULTY RESOLVING THIS
FAR OUR. HOWEVER...ALL GUIDANCE HINTS AT THESE LOWS TAPPING INTO
WARMER AIR FROM THE SUBTROPICS. WHILE THE ACTUAL LOW PRESSURE
CENTERS WILL NOT MAKE MUCH PROGRESS TOWARD THE ALASKA MAINLAND DUE
TO THE BLOCKING HIGH...THE WARMER AIR FROM THE SUBTROPICS WILL
STILL BE ADVECTED INTO THE MAINLAND...WITH 850 MB TEMPERATURES
RANGING IN THE 0 TO +5 CELSIUS RANGE (AVERAGE 850 MB TEMP FOR
THIS TIME OF THE YEAR IS ABOUT -4 TO -6 CELSIUS). THIS WILL LEAD
TO AN OVERALL WARMER THAN AVERAGE PERIOD LEADING INTO NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE...119 120 131 175 176 177 178 179 185.
FIRE WEATHER...NONE.

&&

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