Small Craft Advisory 1079, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
555 AM AST FRI DEC 21 2007

.ANALYSIS AND UPPER LEVELS...
TWO LOWS IN OUR FORECAST DOMAIN IN THE LOWER 970S PROVIDING PLENTY OF
CHALLENGES TO THE FORECAST. MAIN COLD CORE UPPER LOW OVER
NORTHWESTERN ALASKA IS SHIFTING ITS ENERGY SOUTHWEST TOWARD THE
EASTERN BERING SEA WHERE IT WILL BE ABSORBED BY A VERTICALLY STACKED
LOW CURRENTLY OVER THE CENTRAL ALEUTIANS. THE NEW LOW WILL SETTLE
NEAR THE NORTON SOUND BY EARLY NEXT WEEK. THIS WILL INSURE COLD AIR
REMAINS OVER OUR DOMAIN AS SURFACE LOWS ARE SENT EAST INTO JUNEAUS
FORECAST AREA.

.MODEL DISCUSSION...
CONFIDENCE IS GROWING IN THE FORECAST AS GFS AND UKMET IN AGREEMENT
AND SHOW SOME RUN TO RUN CONSISTENCY. NAM NOT INITIALIZING WELL WITH
THE LOCATION OF GULF LOW. STUCK WITH THE LATEST RUN OF THE GFS. WITH
LITTLE CHANGES MADE TO THE PREVIOUS FORECAST...HAD TO MAKE SOME
UPDATES IN THE MID AND LONG RANGE FORECAST TO REFLECT THIS LATEST
RUN.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
IMMEDIATE CONCERN THIS MORNING IS CHANCE OF SNOW TODAY AGAIN IN
ANCHORAGE. THE LOW IS TRACKING A BIT FURTHER WEST AND BELIEVE THIS
WILL ALLOW FOR A BETTER CHANCE OF SNOW IN ANCHORAGE THIS AFTERNOON.
KENAI RADAR ECHOES SHOWING SOME SNOW...BUT NOTHING MAKING IT TO THE
GROUND YET. THERE IS NEUTRAL TEMPERATURE ADVECTION AS THE TROUGH AXIS
ROTATES THROUGH SOUTHCENTRAL LATE THIS AFTERNOON BUT WHEN
TEMPERATURES ARE ALREADY THIS COLD...BELIEVE IT WILL NOT TAKE MUCH
DYNAMICS TO SQUEEZE SNOW OUT OF THE ATMOSPHERE...AS EVIDENCED BY THE
SNOW THURSDAY AFTERNOON. THINKING SNOW ACCUMULATION WILL GENERALLY BE
LIGHT AS THE SYSTEM MOVES RAPIDLY INLAND AND DISSIPATES. FOG WILL
LIKELY RETURN TO MANY AREAS TONIGHT WITH FRESH SNOWFALL AND LIGHT
WINDS.

WEST OF THE ALASKA RANGE...
NORTH-SOUTH AXIS OF SNOW FALLING WEST OF THE ALASKA RANGE FROM KING
SALMON NORTH TO MCGRATH. BELIEVE THIS IS A RESULT OF A TROWAL ON THE
NORTHWESTERN SIDE OF THE MATURE LOW. THIS FEATURE...BEST SEEN
UTILIZING 700 MB EQUIVALENT POTENTIAL TEMPERATURE...HAS MOVED VERY
LITTLE OVERNIGHT SO HAVE SEEN A PROLONGED PERIOD OF LIGHT SNOW IN
THIS REGION. LIGHT SNOW WILL CONTINUE TODAY AS THE LOW MOVES NORTH
AND THE TROWAL SLOWLY DISSIPATES.

KUSKOKWIM DELTA SEEING ADVISORY LEVEL WIND CHILLS AS ARCTIC AIR MASS
IS BEING DRAWN SOUTH AND WEST TOWARD THE COAST. A FEW STATIONS
INCLUDING BETHEL ASOS HAVE WIND CHILL READINGS CURRENTLY 35 TO 40
BELOW ZERO. ALTHOUGH WINDS WILL REMAIN MODERATE TODAY...SOME WARMER
AIR ALOFT WILL EVENTUALLY MAKE IT TO THE SURFACE. WARMER AIR IS A
RELATIVE TERM AS TEMPERATURES WILL STILL REMAIN BELOW CLIMATOLOGICAL
NORMS.

VERTICALLY STACKED LOW ENTERS BRISTOL BAY LATE TONIGHT SENDING SNOW
NORTHWARD INTO THE LOWER KUSKOKWIM VALLEY. THE LOW WILL SLOWLY WEAKEN
AS IT DRIFTS NORTH TOWARD NORTON SOUND EARLY IN THE WEEK. ON THE BACK
SIDE OF THE LOW WILL BE A REINFORCING SHOT OF COLD AIR AND PLENTY OF
SNOW SHOWERS.

BERING SEA WILL REMAIN COLD AND WINDY WITH NUMEROUS SNOW SHOWERS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 195
MARINE...STORM WARNING ZONE 120.
         GALE WARNING ZONES 125 130 155 172 175 179 180.
         HEAVY FREEZING SPRAY WARNING ZONES 130 140 160 180 185.
FIRE WEATHER...NONE.

AB DEC 07