Heavy Freezing Spray Warning 146, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT SUN MAR 18 2012

.ANALYSIS AND UPPER LEVELS...ZONAL FLOW OVER THE FORECAST AREA IS
GIVING WAY TO A DIGGING UPPER LEVEL TROUGH DOWN THE COAST OF WESTERN
ALASKA. THIS TROUGH WILL MOVE EASTWARD TO THE ALCAN BORDER BY
WEDNESDAY AS A RIDGE BUILDS ALONG THE WESTERN COAST OF THE STATE AT
THAT TIME.
THE JET STREAM CAN BE SEEN ON IR SATELLITE WELL SOUTH OF THE STATE
AND NOT MOVING MUCH FARTHER NORTH THAN 50N.
AT THE SURFACE THERE IS A LARGE HIGH OVER THE WESTERN BERING SEA THAT
IS MOVING SLOWLY EASTWARD AND A BROAD AREA OF LOW PRESSURE OVER THE
GULF OF ALASKA. THE CENTER OF THIS GULF LOW CAN BE SEEN EAST OF
KODIAK ISLAND AND SHOWS UP WELL ON VISIBLE SATELLITE. THE TIGHT
PRESSURE GRADIENT BETWEEN THE LOW AND HIGH IS CONDUCIVE FOR COLD
ADVECTION AND GUSTY NORTHWEST WINDS FROM THE ALASKA PENINSULA THROUGH
THE CENTRAL ALEUTIAN ISLANDS.

.MODEL DISCUSSION...MODELS ARE DOING WELL FOR THE NEXT FEW DAYS.
THERE IS A NOTICEABLE CHANGE IN SOLUTIONS BETWEEN THE GFS/NAM AND
UKMET/ECMWF SOLUTIONS AROUND WEDNESDAY. THE GFS/NAM WANT TO QUICKLY
BREAK DOWN THE RIDGE IN THE EASTERN BERING SEA AND PUSH A LOW THROUGH
IT WHILE THE UKMET AND ECMWF KEEP THE RIDGE MOSTLY IN PLACE AND
DAMPEN THE ENERGY THAT PUSHES PAST IT. THIS SECOND SOLUTION OF THE
UKMET AND ECMWF LOOKS TO BE THE MORE REASONABLE ONE AND WILL BE USED
IN THE FORECASTS.

.SHORT TERM FORECAST...THE WEATHER OVER THE EASTERN PART OF THE
FORECAST AREA IS QUITE BENIGN TODAY WITH A FEW SNOW SHOWERS OVER
KODIAK ISLAND AND SOME MORE OFFSHORE FROM THE NORTH GULF COAST.
HOWEVER AS THE NIGHT PROGRESSES THERE WILL BE SUPPORT FOR THE
DEVELOPMENT OF AN INVERTED TROUGH OVER THE COOK INLET REGION. THIS
WILL BRING SOME SNOW SHOWERS TO THE NORTH GULF COAST AND INCREASE THE
CHANCE OF SOME SNOW SHOWERS MOVING INLAND TONIGHT.
SOUTHWEST ALASKA WILL REMAIN MOSTLY CLEAR AND COLD. SOME AREAS OF FOG
AND STRATUS MAY DEVELOP NEAR THE BERING SEA COAST BUT THE TIGHTENING
PRESSURE GRADIENT WILL INCREASE WINDS AND KEEP THE ATMOSPHERE BETTER
MIXED. WINDS CHILLS IN THE KUSKOKWIM DELTA WILL PROBABLY NOT REACH
WIND CHILL ADVISORY CRITERIA BUT WILL BE CLOSE...WITH WINDS CHILLS
EXPECTED TO REACH 35 BELOW IN SOME AREAS. THE BRISTOL BAY REGION WILL
LIKELY SEE LESS IN THE WAY OF WINDS AS THE INVERSION DEVELOPS AND
KEEPS THE STRONGER WINDS RIDING ALOFT OVER THE INVERSION. THIS WILL
KEEP AMBIENT TEMPERATURES COLDER BUT THE WIND CHILLS WILL NOT BE AS
BAD.

.LONG TERM FORECAST...THE WEATHER WILL BE SLOW TO CHANGE FROM THE
MIDDLE TO LATER PART OF THE WEEK AS THE MEAN POSITION OF THE UPPER
LEVEL RIDGE AND TROUGH WILL NOT CHANGE MUCH UNTIL WE APPROACH NEXT
WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 150 155 170 175 176.
         HEAVY FREEZING SPRAY 130 132 138 150 155 165 170 171.
FIRE WEATHER...NONE.

EZ MAR 12