Gale Warning 806, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN NOV 17 2013

.ANALYSIS AND UPPER LEVELS...
A RIDGE OF HIGH PRESSURE OVER THE BERING SEA CONTINUES WITH A
LONGWAVE TROUGH CENTERED OVER THE AK PANHANDLE. BETWEEN THESE
FEATURES...DEEP LAYER NORTHERLY FLOW IS ALLOWING THE COLDEST AIR OF
THE SEASON SO FAR TO SPILL OVER MAINLAND ALASKA...WITH NUMEROUS
TEMPERATURE READINGS BELOW ZERO THIS MORNING FROM THE ANCHORAGE BOWL
NORTHWARD. GUSTY OUTFLOW WINDS CONTINUE THROUGH TERRAIN GAPS ALONG
THE GULF COAST...WITH THE STRONGEST WINDS OCCURRING AROUND VALDEZ.
MEANWHILE...A VERY SLOW-MOVING CUTOFF LOW OVER THE NORTH PACIFIC
CONTINUES TO BRING RAIN AND MODERATELY GUSTY WINDS TO THE WESTERN AND
CENTRAL ALEUTIANS.

.MODEL DISCUSSION...
MODEL AGREEMENT IS FAIRLY GOOD THROUGH THE FIRST 60 HOURS OR SO OF
THE FORECAST...BUT BEGINS TO DECREASE SIGNIFICANTLY AS THE BERING
RIDGE BREAKS DOWN AND SUBTROPICAL AIR ATTEMPTS TO SURGE BACK
NORTHWARD TOWARD SOUTHERN ALASKA BY MIDWEEK. THERE ARE MULTIPLE
PIECES OF ATMOSPHERIC ENERGY THAT WILL BE INTERACTING...AND MANY OF
THE KEY DETAILS OF THIS INTERACTION REMAIN UNCLEAR AT THIS POINT. THE
NAM IS THE ONLY MODEL THAT CAN BE COMPLETELY DISCOUNTED DUE TO AN
EXTREME OUTLIER EVOLUTION OF THE UPPER LOW THAT DROPS DOWN FROM THE
NORTH ON TUESDAY. THE EC/GEM/GFS ALL EVENTUALLY DEVELOP A MORE
SIGNIFICANT LOW IN THE EASTERN BERING TOWARD THE VERY END OF THE
SHORT TERM FORECAST PERIOD. THE ECMWF IS FAVORED OVERALL...BY VIRTUE
OF HAVING THE MOST COMMON GROUND AMONG THE THREE GLOBAL MODELS.

.SHORT TERM FORECAST...
MAINLAND...COLD AND CLEAR WILL CONTINUE TO BE THE STANDARD FOR THE
NEXT FEW DAYS. PRESSURE GRADIENTS WILL GRADUALLY RELAX THROUGH
TOMORROW AFTERNOON...ALLOWING GAP WINDS TO EVENTUALLY FOLLOW SUIT
AROUND VALDEZ AND THE OTHER FAVORED AREAS. WITH EACH PASSING DAY THE
COLD AIRMASS BECOMES MORE AND MORE ENTRENCHED...AND WHEN COMBINED
WITH WEAKENING WINDS MANY AREAS WILL SET NEW SEASONAL LOW TEMPERATURE
MARKS EACH OF THE NEXT FEW DAYS.

BERING SEA AND ALEUTIANS...LOITERING NORTH PACIFIC CUT-OFF LOW WILL
CONTINUE THE RAIN AND WIND OVER THE WESTERN HALF OF THE ALEUTIANS
THROUGH TUESDAY NIGHT. MEANWHILE...NORTHERLY FLOW AND COLD AIR WILL
CONTINUE TO BLEED INTO THE EASTERN BERING...INCREASING THE CHANCES
FOR SOME INSTABILITY SNOW SHOWERS ACROSS THE REGION. MODELS ARE
SUGGESTING AN UPPER LEVEL SHORTWAVE DROPPING DOWN FROM SIBERIA ON
TUESDAY NIGHT/WEDNESDAY. THIS HAS THE POTENTIAL TO BRING A MORE
WIDESPREAD...ALBEIT STILL GENERALLY LIGHT...SNOW EVENT ACROSS THE
EASTERN HALF OF THE AREA.

.LONG TERM FORECAST...
THE LONG RANGE MODELS SUGGEST A SHIFT BACK TO A MORE TYPICAL UPPER
LEVEL PATTERN CHARACTERIZED BY A LONGWAVE TROUGH OVER THE BERING AND
SOUTHWESTERLY FLOW ACROSS THE SOUTHERN MAINLAND. HOWEVER...AS
MENTIONED ABOVE...THE MODELS ARE STRUGGLING WITH THE DETAILS OF THE
TRANSITION TO THIS PATTERN. AS WARMER AIR AND THE CHANCE FOR
PRECIPITATION RETURNS TO THE SOUTHERN ALASKA IN THE LATTER HALF OF
THIS COMING WEEK...THE POTENTIAL FOR FREEZING RAIN WILL NEED TO BE
MONITORED IF ENOUGH SUBTROPICAL AIR IS ABLE TO BE PULLED NORTHWARD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 126 127 128 173 174 175 176 177 178
         HEAVY FREEZING SPRAY 121 140
FIRE WEATHER...NONE

AMD NOV 13