Small Craft Advisory 914, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
115 PM AKST MON NOV 18 2013

.ANALYSIS AND UPPER LEVELS...
NORTHERLY FLOW CONTINUES TO BRING PROGRESSIVELY COLDER TEMPERATURES
TO NEARLY ALL LOCATIONS ACROSS THE MAINLAND. AN UPPER LOW MOVING
THROUGH THIS FLOW IS BRINGING SOME LIGHT SNOW TO THE INTERIOR OF THE
STATE THIS MORNING AND WILL BE HEADING INTO SOUTHERN ALASKA TOMORROW.
GAP WINDS CONTINUE TO BLOW...BUT ARE DIMINISHED SOMEWHAT FROM
YESTERDAY AT MOST LOCATIONS AS DROPPING PRESSURES IN THE INTERIOR
CAUSE THE COASTAL GRADIENTS TO RELAX.  OUT WEST...A CUT-OFF UPPER LOW
CONTINUES TO FESTER SOUTH OF THE ALEUTIAN CHAIN...MEANDERING EASTWARD
WITH MULTIPLE LOW CENTERS. THIS COMPLEX STORM CONTINUES TO BRING AN
AREA OF GALE-FORCE WINDS AND RAIN TO THE CENTRAL ALEUTIANS.

.MODEL DISCUSSION...
MODELS REMAIN IN PRETTY GOOD AGREEMENT THROUGH ABOUT 48 HOURS/TUE
NIGHT AT WHICH POINT THERE IS STILL GREAT DISAGREEMENT ABOUT THE
EVOLUTION THAT EVENTUALLY LEADS TO SOME KIND OF STORM SYSTEM IN THE
VICINITY OF THE ALASKA PENINSULA BY THE END OF THE WEEK. FORECAST
CONFIDENCE IS BELOW NORMAL AS SEVERAL MAJOR PIECES OF UPPER LEVEL
ENERGY WILL BE APPROACHING THE REGION AND INTERACTING AS THE WEEK
PROGRESSES. THIS MEANS THERE ARE A LOT OF MOVING PARTS TO THE
FORECAST FOR THE REST OF THE WEEK...WHICH INTRODUCES AN ADDITIONAL
MARGIN OF ERROR. BY FRIDAY ALL MODELS SHOW AN UPPER LOW DEVELOPING
OVER THE EASTERN BERING SEA. RIGHT NOW IT LOOKS LIKE THE KEY TO THE
TIMING AND PLACEMENT OF THIS DEVELOPMENT WILL BE THE STRENGTH OF A
SIGNIFICANT SHORTWAVE UNDERCUTTING THE HIGH-LATITUDE BERING RIDGE
OVER THE NEXT FEW DAYS. THE ECMWF IS THE STRONGEST WITH THE
SHORTWAVE...AND THUS DEVELOPS THE UPPER LOW FURTHER WEST AND THE
ENTIRE LONGWAVE TROUGH TAKES ON A MORE NEGATIVE TILT. THE NAM IS
DIFFERENT THAN ALL OTHER MODELS (LIKELY DUE TO MULTIPLE FEATURES
COMING IN FROM THE CORNERS OF THE MODEL DOMAIN) AND WAS QUICKLY
DISCARDED BEYOND 48 HOURS. THE GFS/GEM ARE BOTH MORE MODERATE WITH
THE STRENGTH OF THE SHORTWAVE AND THE RESULTING LOW POSITION...AND
HAVE ALSO BEEN THE MOST CONSISTENT DEPICTION OF LATE...AND WILL BE
USED TO LOOSELY GUIDE THE FORECAST FOR THE END OF THE WEEK.

.SHORT TERM FORECAST...
MAINLAND...SEVERAL MORE VERY COLD NIGHTS ARE ON TAP AS THE UPPER LOW
OVER THE INTERIOR USHERS IN A FINAL SLUG OF COLD AIR TO THE REGION.
TYPICALLY THESE TYPE OF UPPER FEATURES MOVING THROUGH A COLD AIRMASS
ARE VERY LIMITED IN AVAILABLE MOISTURE...SO MOST OF THE AREA WILL
SIMPLY SEE AN INCREASE IN CLOUDINESS ON TUESDAY. HOWEVER...SOME LIGHT
SNOW OR FLURRIES CANNOT BE COMPLETELY RULED OUT SO SOME MENTION OF
PRECIP WILL CONTINUE FOR MOST OF THE AREA OVER THE NEXT 36 HOURS. GAP
WINDS WILL CONTINUE TO VERY SLOWLY DIMINISH...ESPECIALLY WITH COLD
AIR DUMPING OFF THE LANDMASS CONTINUING TO REINFORCE LOWER PRESSURES
OVER THE NORTHERN GULF.

BERING SEA AND ALEUTIANS...A NEARLY-STATIONARY WEATHER FRONT WILL
CONTINUE TO CRAWL EASTWARD ALONG THE ALEUTIAN CHAIN THROUGH
THURSDAY...WITH THE BULK OF THE WIND AND RAIN BEING GRADUALLY PULLED
SOUTHWARD INTO THE PACIFIC. THIS WILL ALLOW SEASONABLY COLD AIR TO
CONTINUE TO GRADUALLY INFILTRATE MUCH OF THE BERING SEA AND CAUSE
WIDESPREAD CLOUDINESS TO GRADUALLY BECOME MORE CONVECTIVE IN NATURE.

.LONG TERM FORECAST...
REGARDLESS OF THE MODEL CHOSEN...CONFIDENCE IS HIGH THAT A WARM FRONT
WILL PUSH NORTHWARD INTO THE GULF OF ALASKA AT THE END OF THIS
WEEK...BRINGING SIGNIFICANTLY WARMER TEMPERATURES ALOFT ALONG WITH
GREATLY INCREASED CHANCES FOR PRECIPITATION. ITS TOO EARLY TO TELL IF
DOWNSLOPING WILL KEEP THE USUAL PLACES DRY...BUT THE GULF COASTLINE
LOOKS VERY LIKELY TO SEE SNOW TRANSITION TO A RAIN/SNOW MIX BY NEXT
WEEKEND AS ACTIVE WEATHER RETURNS TO THE REGION. OUT WEST...A
DEVELOPING LONGWAVE TROUGH WILL ALLOW COLD AIR AND SNOW SHOWERS TO
SPREAD ACROSS MOST OF THE AREA BY NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 127 175 176 177
         HEAVY FREEZING SPRAY 121 126 127 128 129
FIRE WEATHER...NONE

AMD NOV 13