Small Craft Advisory 866, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
415 PM AKST MON NOV 4 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL PATTERN IS AMPLIFYING AS
A TROUGH DIGS SOUTHWARD INTO THE WESTERN BERING AND THE RIDGE BUILDS
IN THE EASTERN BERING SEA AND SOUTHWEST ALASKA. A STRONG 250 MB JET
IS ENHANCING THE DEVELOPMENT OF A SURFACE LOW THAT IS CURRENTLY
SOUTHWEST OF ATTU. THIS LOW WILL INTENSIFY AND MOVE INTO THE BERING
SEA TOMORROW NIGHT AND BECOME THE MAIN WEATHER FEATURE OVER THE STATE
UNTIL THE WEEKEND.
A MODERATE LOW IN THE NORTHERN GULF IS BEGINNING TO WEAKEN AND WILL
MOVE SOUTHWEST THROUGH TOMORROW NIGHT. AS THIS LOW MOVES
SOUTHEASTWARD AN UPPER LEVEL SHORT WAVE WILL MOVE THROUGH SOUTH
CENTRAL ALASKA TOMORROW.

MODEL DISCUSSION...
MODELS CONTINUE TO BE IN GOOD SYNOPTIC AGREEMENT REGARDING THE
LOW IN THE GULF AS WELL AS THE LOW APPROACHING THE WESTERN BERING.
REGARDING THE LOW APPROACHING THE WESTERN ALEUTIANS...THE
NAM/GFS/ECMWF ALL SEEM TO AGREE ON POSITIONING AND STRENGTH INITIALLY
AND THROUGH MOST OF THE SHORT TERM. EVEN THOUGH SOME VERY SLIGHT
DIFFERENCES EXIST AT THE END OF THE SHORT TERM...WITH THE NAM
CARRYING THE WEAKER SOLUTION AND THE ECMWF TAKING A SLIGHTLY SLOWER
AND SOUTHERLY POSITIONING WITH THE LOW OVER THE WESTERN BERING...THE
GFS AND ECMWF CONTINUE TO BE A PREFERRED MODEL CHOICES FOR THIS
SYSTEM.
CONFIDENCE CONTINUES TO BE HIGH REGARDING THE LOW APPROACHING THE
WESTERN ALEUTIANS. MODELS ARE PICKING UP ON FAVORABLE UPPER LEVEL JET
SUPPORT AND BAROCLINICITY THAT CONTINUE TO STRENGTHEN THIS LOW AS IT
MAKES IT WAY INTO THE WESTERN BERING THROUGH WED MORNING.
GFS/NAM/ECMWF 850 MB TEMPERATURES SHOW A SIGNIFICANT AMOUNT OF COLD
AIR WRAPPING INTO THE SYSTEM ON THE BACK END OF THE LOW...AS WELL AS
WARM MOIST AIR AHEAD OF THE SYSTEM BEING DRAWN IN FROM THE NORTHERN
PACIFIC. IN THE UPPER LEVELS...MODELS INDICATE AN UPPER LEVEL JET
WITH A 165 KT CORE ALONG THE SOUTHEAST SIDE OF THE SYSTEM THROUGH WED
MORNING.

.SHORT TERM FORECAST...
SOUTH CENTRAL...MOST OF THE PRECIPITATION WILL BE RAIN ALONG THE GULF
COAST OVERNIGHT WITH JUST A FEW RAIN AND SNOW SHOWERS SNEAKING THEIR
WAY INLAND. TOMORROW AN UPPER LEVEL TROUGH ASSOCIATED WITH WEAK COLD
ADVECTION WILL MOVE THROUGH SOUTH CENTRAL WHICH WILL BRING A MIX OF
RAINA ND SNOW SHOWERS TO THE AREA FROM COOK INLET NORTHWARD IN THE
MORNING...AND THEN TRANSITION TO SNOW SHOWERS IN THE AFTERNOON. THIS
COULD BE THE FIRST OFFICIAL SNOW ACCUMULATION FOR ANCHORAGE...THOUGH
AMOUNTS WOULD BE VERY LIGHT.

SOUTHWEST...
RAIN SHOWERS WILL CONTINUE TO TAPER OFF TONIGHT AND TRACK EASTWARD BY
TUESDAY MORNING AS A RIDGE OF HIGH PRESSURE MOVES INTO THE AREA
TUESDAY AFTERNOON BRINGING DRY CONDITIONS AND SEASONABLY STRONGER
NORTHWESTERLY FLOW TO SOUTHWEST ALASKA. HIGH PRESSURE WILL CONTINUE
OVER THE SOUTHWEST MAINLAND THROUGH LATE WEDNESDAY MORNING...THEN
PUSH EASTWARD AS A FRONTAL SYSTEM ASSOCIATED WITH A STRONG LOW BRINGS
WET AND WINDY CONDITIONS BACK TO THE SOUTHWEST MAINLAND WEDNESDAY
AFTERNOON THROUGH FRIDAY AFTERNOON. RAINY AND WINDY ARE CURRENTLY THE
EXPECTED PRE-FRONTAL CONDITIONS...WHERE MORE OF A WINTERY MIX CAN BE
EXPECTED AT THE MAIN POST-FRONTAL CONDITIONS.

BERING SEA/ALEUTIANS...
HIGH WINDS AND RAINY CONDITIONS WILL BEGIN TO MOVE INTO THE WESTERN
ALEUTIANS LATE TONIGHT AS THE RAPIDLY INTENSIFYING LOW BEGINS TO MOVE
TOWARDS THE WESTERN ALEUTIANS AND NEARBY WATERS. AS THE LOW TRACKS
NORTHWARD INTO THE WESTERN BERING...THE STRONG WINDS ON THE FRONT END
OF THE SYSTEM AS WELL AS THE WINDS ALONG THE BACK END WILL CONTINUE
TO PRODUCE STRONG AND GUSTY WINDS OVER MUCH OF THE ALEUTIAN CHAIN
THROUGH THE END OF THE SHORT TERM. HIGH WIND WARNINGS HAVE BEEN
ISSUED TO COVER THE STRONG FRONTAL PASSAGE AHEAD OF THE LOW AS WELL
AS WITH THE CIRCULATION OF THE LOW ITSELF. WITH INCREASED CONFIDENCE
REGARDING FAVORABLE COLD AIR ADVECTION ON THE BACK END OF THIS
SYSTEM...HURRICANE FORCE WINDS ARE POSSIBLE NEAR THE WESTERN MOST
ALEUTIANS AT THE SAME TIME THAT THE LOW WILL BE REACHING PEAK
INTENSITY. LARGE SEA SWELL CAN ALSO BE EXPECTED WITH THIS
SYSTEM...THUS CONTRIBUTING TO AN INCREASED DANGER TO MARINERS AS WELL
THROUGH MIDWEEK.

.LONG TERM FORECAST...
STRONG WESTERLY FLOW WILL ENVELOP THE BERING SEA BY THURSDAY AND WILL
PUSH A WEAKENING FRONT EAST INTO THE SOUTHERN MAINLAND. THIS FRONT
WILL GENERATE PRECIPITATION ACROSS THE REGION AND RESULT IN THE NEXT
GOOD CHANCE OF RAIN AND/OR SNOW FOR PARTS OF SOUTHCENTRAL MAINLY FROM
THE MATANUSKA VALLEY SOUTH LATE THURSDAY.
THE STRONG WESTERLY WINDS ACROSS THE BERING SEA WILL BRING THE THREAT
OF HIGH SURF AND SOME COASTAL FLOODING FROM THE BRISTOL BAY COAST
NORTHWARD DURING THE SECOND HALF OF THE WEEK. ANOTHER CONCERN WITH
THIS SYSTEM IS THAT THE LARGE SEAS IN THE BERING SEA AND WEST TO
SOUTHWEST FLOW WILL PERSIST INTO EARLY NEXT WEEK WHICH WILL MAY CAUSE
WATER TO PILE UP ALONG THE COAST AND NOT QUICKLY RECEDE BACK INTO THE
BERING SEA. THIS SITUATION SHOULD BE MONITORED BY PERSONS WHO ARE
NEAR THE COAST OR HAVE PROPERTY VULNERABLE TO HIGH SURF OR COASTAL
INUNDATION.

HIGH PRESSURE ALOFT MOVES OVER THE REGION FROM THE WEST THIS
WEEKEND...THEN IS FOLLOWED BY A LARGE AMPLITUDE TROUGH THAT WILL MOVE
QUICKLY WEST TO EAST ACROSS THE STATE SUNDAY INTO MONDAY OF NEXT WEEK
AND BRING ANOTHER SHOT OF PRECIPITATION FOLLOWED BY A RETURN TO A
COLDER AIR MASS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 187 191.
         COASTAL FLOOD WATCH 155 161.
MARINE...HURRICANE FORCE 175 178.
         STORM 170 172 173 174 176 177 179 181 185.
         GALE 130 131 132 137 138 150 155 160 165 171 180.
FIRE WEATHER...NONE.

TP/EZ NOV 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
242 AM AKST TUE NOV 05 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0226 AM     NON-TSTM WND GST N SHEMYA                52.72N 174.12E
11/05/2013  M75 MPH                             AK   ASOS

            PASY WIND GUST TO 75 MPH.

&&

DSTRICKL