Gale Warning 695, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
210 PM AKDT WED OCT 16 2013

.ANALYSIS AND UPPER LEVELS...

THE GENERAL LARGE SCALE SYNOPTIC PATTERN CONSISTS OF A HIGH AMPLITUDE
TROUGH/RIDGE PATTERN OVER THE REGION...WITH THEIR RESPECTIVE AXES
CENTERED OVER THE EASTERN BERING SEA/EASTERN ALASKA. EMBEDDED WITHIN
THE LARGER SYNOPTIC WAVE PATTERN ARE NUMEROUS SMALLER SCALE WAVE
DISTURBANCES. THE TWO MOST NOTABLE FEATURES ARE A DEEP SHORTWAVE
TROUGH CURRENTLY TRACKING JUST SOUTH OF THE CENTRAL ALEUTIAN CHAIN
ALONG THE WESTERN PERIPHERY OF THE TROUGH...AND A CLOSED CIRCULATION
IN THE NORTH PACIFIC NEAR 45N. A WELL DEFINED PLUME OF WARM AND MOIST
AIR ON SATELLITE ASSOCIATED WITH THE CLOSED LOW IS CURRENTLY LIFTING
INTO THE WESTERN GULF OF ALASKA...AND THIS WILL IMPACT KODIAK...THE
KENAI AND GULF COASTS...AND MUCH OF SOUTHWEST ALASKA WITH STEADY
RAINFALL THROUGH THURSDAY.

THE OTHER BIG STORY IS A POWERFUL LOW...THE FORMER REMNANTS OF
TYPHOON WIPHA...WHICH WILL BEGIN IMPACTING PORTIONS OF THE WESTERN
ALEUTIAN MARINE ZONES WITH HURRICANE FORCE WINDS LATE THURSDAY. THIS
LOW WILL SLOWLY WEAKEN AS IT TRACKS ACROSS THE ALEUTIAN CHAIN THROUGH
FRIDAY.

.MODEL DISCUSSION...

THE NUMERICAL GUIDANCE IS IN GREAT AGREEMENT WITH THE LARGE SCALE
SYNOPTIC PATTERN HEADING INTO EARLY NEXT WEEK. AND WHILE THEY DIVERGE
SLIGHTLY LATE MONDAY INTO TUESDAY WITH SMALLER SCALE WAVE
FEATURES...THEY REMAIN IN VERY GOOD AGREEMENT WELL INTO MIDWEEK AS
MUCH OF THE REGION REMAINS UNDER THE INFLUENCE OF A WELL DEFINED
TROUGH/RIDGE PATTERN (SEE EXTENDED DISCUSSION). IN THE SHORTER
TERM...THE LARGEST DISCREPANCIES REVOLVE AROUND THE TIMING OF A WAVE
DISTURBANCE CURRENTLY IN THE GULF OF ALASKA...AND THE ASSOCIATED
FRONTAL PASSAGE LATE TOMORROW INTO FRIDAY ACROSS SOUTHERN ALASKA. ALL
THE GLOBAL MODELS ARE IN FAIR AGREEMENT WITH AN ARRIVAL 3 TO 6 HOURS
SLOWER THAN THE NAM...SO THE GFS AND ECMWF WERE FAVORED ACROSS
SOUTHERN ALASKA...WHILE THE GFS WAS FAVORED FOR THE HURRICANE FORCE
TYPHOON REMNANTS ACROSS THE BERING SEA.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
LIGHT RAIN AND SHOWERS ARE BEGINNING TO TRACK UP COOK INLET INTO THE
SUSITNA VALLEY THIS AFTERNOON...WITH STEADIER RAIN ALONG THE KENAI
COAST DOWN TO KODIAK. MOST INTERIOR LOCATIONS...INCLUDING
ANCHORAGE...WILL SEE SOME DEGREE OF DOWNSLOPE SHADOWING THROUGH
THURSDAY AFTERNOON...WITH SPORADIC SHOWERS INSTEAD OF PERSISTENT
LIGHT RAIN. BREEZY SOUTHEAST WINDS ACROSS THE ANCHORAGE BOWL WILL
PERSIST THROUGH LATE THIS AFTERNOON BEFORE SLACKENING OFF AND TURNING
NORTHEAST OVERNIGHT. ALONG TURNAGAIN ARM AND HIGHER
ELEVATIONS...SOUTHEAST WINDS WILL STEADILY INCREASE THROUGH EARLY
TOMORROW AHEAD OF THE NEXT WAVE...PEAKING LATE TOMORROW EVENING
BEFORE WEAKENING OVERNIGHT. AS THE FRONT PASSES THROUGH THURSDAY
NIGHT...BRIEF GUSTY SOUTHEAST WINDS 20 TO 40 MPH WILL SWEEP THROUGH
ANCHORAGE...WITH A SHOT OF STEADIER AND HEAVIER RAIN. ANOTHER FRONT
WILL APPROACH SOUTHCENTRAL LATE FRIDAY INTO SATURDAY.

SOUTHWEST/AKPEN...
THE MAIN STORY WILL BE A WELL DEFINED STREAM OF SUBTROPICAL MOISTURE
WHICH WILL REMAIN OVER SOUTHWEST THROUGH THURSDAY...SUPPORTING STEADY
RAIN OVER ALL OF SOUTHWEST ALASKA EAST OF THE KUSKOKWIM DELTA. A WEAK
FRONT WILL BRING AN END TO PERSISTENT AND GUSTY SOUTH SOUTHEASTERLY
WINDS LATE THURSDAY INTO EARLY FRIDAY BEFORE ANOTHER FRONT TRACKS IN
FROM THE EASTERN BERING FRIDAY INTO SATURDAY...BRINGING MORE RAIN AND
SHOWERS AND GUSTY SOUTHEAST WINDS.

BERING SEA/ALEUTIANS...
A POWERFUL STORM/HURRICANE FORCE LOW WILL BEGIN IMPACTING THE WESTERN
ALEUTIANS TONIGHT...THEN SLOWLY WEAKEN AND TRACK EASTWARD ACROSS THE
CHAIN THROUGH FRIDAY. THE STRONGEST CORE OF HURRICANE FORCE WINDS ARE
EXPECTED TO REMAIN JUST SOUTH OF SHEMYA TONIGHT...ALTHOUGH STORM
FORCE WINDS WILL IMPACT PARTS OF THE WESTERN AND CENTRAL ALEUTIANS
BEFORE THE STORM WEAKENS AS IT TRACKS EAST. RAIN AND SHOWERS WILL
IMPACT THE REGION THROUGH THE WEEKEND.

.LONG TERM FORECAST...

SATURDAY AND BEYOND...THERE IS HIGH CONFIDENCE THAT A BROAD TROUGH
WILL STRETCH ACROSS THE BERING SEA INTO SOUTHERN ALASKA...WITH RAIN
AND SHOWERS ENCOMPASSING ALL OF SOUTHERN ALASKA AND THE BERING SEA.
WEAK WAVE DISTURBANCES EMBEDDED WITHIN THE FLOW ARE DIFFICULT TO TIME
AT THIS JUNCTURE...BUT MOST INTERIOR LOCATIONS ACROSS SOUTHCENTRAL
WILL TEND TO REMAIN SHOWERY...WITH CONTINUED ABOVE NORMAL
TEMPERATURES. BY THE END OF THE WEEK...MEDIUM RANGE GLOBAL GUIDANCE
INCLUDING THE GFS...ECMWF...AND GFS ENSEMBLE BEGIN TO HINT AT A
HIGHLY ANOMALOUS AND DEEP TROUGH FORMING OVER THE NORTHERN
PACIFIC...WITH A HIGH AMPLITUDE RIDGE FORMING OVER MUCH OF ALASKA.
SHOULD THIS PATTERN EVOLUTION UNFOLD...AND THERE IS INCREASING
CONFIDENCE IT WILL...THIS WILL LIKELY YIELD SUBSTANTIAL WARM
TEMPERATURE ANOMALIES OVER MUCH OF ALASKA...AND THE POTENTIAL FOR A
DEEP AND POWERFUL LOW TO FORM AND TRACK INTO THE BERING SEA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 119 120 125 129 130 131 132 150 155 165 170 172 173 175
              179.
         STORM 174 176.
         HURRICANE 177 178.
FIRE WEATHER...NONE.

AHSENMACHER OCT 13