Small Craft Advisory 57, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AST SUN JAN 20 2008

.MODEL DISCUSSION...
MODEL RUNS WERE IN GOOD AGREEMENT AND CONSISTENT WITH PREVIOUS RUNS
IN THE SHORT TERM.  AFTER ABOUT 84 HOURS THE SOLUTIONS DIVERGE
DRASTICALLY.  GFS AND NAM HAVE SIMILAR POSITIONS ON THE LOW MOVING
INTO THE BERING BUT GFS IS SIGNIFICANTLY STRONGER...WHILE LATER THE
ECMWF SOLUTION BEGINS TO MIRROR THE GFS BUT DOES NOT PICK UP THE
SECONDARY LOWS.  ALTHOUGH THE GFS WAS CHOSEN AS THE MOST LIKELY
SOLUTION THE SOLUTION FOR THE END OF THE PERIOD HAS BEEN HIGHLY
VARIABLE FOR THE PAST FEW DAYS AND CONFIDENCE IN THE LONG TERM
FORECAST IS NOT HIGH.

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN STILL LOOKS VERY SIMILAR TO THE PREVIOUS COUPLE
OF DAYS.  THE STRONG SOUTHERLY JET IS FLOWING ALONG THE WEST COAST
WITH THE UPPER LEVEL RIDGE IN PLACE OVER THE GULF OF ALASKA.  THIS IS
BRINGING AN INCREASINGLY TIGHT GRADIENT TO THE MAINLAND AND STRONG
SURFACE WINDS ARE A PERSISTENT PROBLEM IN MANY OF THE ZONES.  A
COMBINATION OF DOWNSLOPING AND WARM AIR ADVECTION CONTINUES TO WARM
THE AIR COLUMN AND TEMPERATURES ARE UNSEASONABLY WARM PARTICULARLY
ALONG THE WEST COAST.  AS THE FRONT CURRENTLY POSITIONED WEST OF THE
ALASKA RANGE PROGRESSES EASTWARD PRECIP WILL MOVE ACROSS THE REGION
BUT SLOWLY.

.SHORT TERM FORECAST...
EAST OF THE ALASKA RANGE...THE FRONT IS APPROACHING FROM THE WEST AND
TIGHTENING THE GRADIENT AS IT DOES SO.  MEANWHILE A WEAKER SHORTWAVE
IS EXPECTED TO MOVE THROUGH THE PATTERN TODAY...THESE TWO FACTORS
COMBINED ARE CAUSING WARNING LEVEL WINDS IN THE TURNAGAIN ARM THIS
MORNING AND THESE WILL CONTINUE THROUGH THE AFTERNOON.  WHILE WARM
TEMPERATURES AND DOWNSLOPING ARE PREVENTING SIGNIFICANT SNOWFALL FROM
REACHING THE KENAI PENINSULA AND THE ANCHORAGE BOWL IN THE SUSITNA
VALLEY THE COLD AIR IS STILL IN PLACE.  OVER RUNNING AND THE SLOW
MOVEMENT OF THE FRONT IS EXPECTED TO BRING ADVISORY LEVEL SNOWS TO
THE SUSITNA VALLEY TODAY.  AS THIS FRONT SLOWLY MOVES WESTWARD IT
WILL BRING A SIMILAR AMOUNT OF SNOW TO VALDEZ AS WELL BUT THE WARM
AIR WILL BRING RAIN EVERYWHERE ELSE.

WEST OF THE ALASKA RANGE...WINDS ARE BEGINNING TO TAPER OFF ALONG THE
WEST COAST AS THE JET AND THE FRONT SLOWLY MOVE WESTWARD.  ALTHOUGH
WINDS ARE STILL GUSTY IN THE KUSKOKWIM VALLEY THIS MORNING THEY
SHOULD TAPER OFF BY AFTERNOON THERE AS WELL.  THE REGION WILL HAVE A
BRIEF RESPITE FROM THE WINDS THIS AFTERNOON BUT BY MONDAY MORNING THE
NEXT LOW IS ALREADY APPROACHING FROM THE SOUTH.  THE ALEUTIANS WILL
BEGIN TO SEE STORM WARNINGS AT THIS TIME WITH THE WEST COAST
BEGINNING TO EXPERIENCE STRONG WINDS AGAIN MONDAY AFTERNOON.

.LONG TERM FORECAST...
WEATHER PATTERN THROUGH THE MIDDLE OF THE WEEK LOOKS VERY SIMILAR TO
WHAT HAS HAPPENED OVER THIS PAST WEEKEND.  AS THE SURFACE LOW MOVES
UP TOWARD THE ARCTIC HOWEVER THE UPPER LEVEL TROUGH SHIFTS EASTWARD
SLIGHTLY AND THE FLOW BECOMES MORE WESTERLY ALOFT.  THIS POSITIONS A
RIDGE OVER THE BERING AND BRINGS COLD AIR AGAIN TO THE MAINLAND...IT
STILL LOOKS LIKE A SNOW EVENT SETTING UP FOR THE SOUTHCENTRAL REGION
FOR THE TUESDAY NIGHT WEDNESDAY TIMEFRAME WITH THE CAVEAT THAT
CONFIDENCE LEVEL IN THE THE LONG RANGE MODELS IS NOT HIGH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101
         SNOW ADVISORY 145
MARINE...GALES 120 125 130 138 140 141 150 160 165
               171 172 179 180 185
         STORM 155 170
FIRE WEATHER...NONE

LEWF JAN 08