Small Craft Advisory 438, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM ADT MON MAY 19 2008

.MODEL DISCUSSION...MODELS ARE DOING WELL IN THE FIRST 60 TO 72
HOURS. NO LARGE DIFFERENCES UP THROUGH THEN. THE GFS MODEL CONTINUES
TO INCREASE THE STRENGTH OF THE LOW MOVING NEAR THE ALASKA PENINSULA
LATE THURSDAY AND FRIDAY. THIS IS OF SOME CONCERN SINCE THE ECMWF IS
NOT DOING THIS. HOWEVER THE ECMWF IS ALSO VERY INCONSISTENT BETWEEN
RUNS DURING THIS TIME FRAME AND DOES NOT GIVE MUCH OF AN ALTERNATIVE
TO THE GFS SOLUTION. WILL KEEP FORECASTS GENERALLY THE SAME FOR THAT
TIME PERIOD WHICH IS SIMILAR TO YESTERDAYS 00Z RUN OF THE GFS.

.ANALYSIS AND UPPER LEVELS...LARGE UPPER LEVEL TROUGH OVER THE
EASTERN ALEUTIANS AND BERING SEA WILL REMAIN LARGELY IN PLACE FOR THE
NEXT FEW DAYS. A SURFACE LOW DEVELOPING UNDER THIS TROUGH WILL MOVE
SOUTHEAST OF DUTCH HARBOR TUESDAY AND THEN ELONGATE THROUGH BRISTOL
BAY AND CONNECT WITH A THERMAL TROUGH WEDNESDAY IN THE INTERIOR. THIS
WILL INCREASE AFTERNOON CONVECTIVE ACTIVITY IN THE KUSKOKWIM VALLEY
AS WELL AS THE SUSITNA VALLEY AND COPPER RIVER BASIN AT THAT TIME.
A RIDGE OVER THE WESTERN GULF OF ALASKA COMBINED WITH A LOW NEAR THE
QUEEN CHARLOTTE ISLANDS IS CAUSING A TROUGH TO DEVELOP ALONG THE
SOUTHEAST ALASKA COAST THE IS EXTENDING INTO THE NORTH GULF COAST.
THE GRADIENT WITH THIS FEATURE IS STRONGER THAN WAS PREVIOUSLY
THOUGHT AND IS CAUSING NORTHERLY WINDS THROUGH BAYS AND PASSES ALONG
THE NORTH GULF COAST AND PRINCE WILLIAM SOUND. IT IS OVER RIDING THE
SEA BREEZE EFFECT TODAY.

.SHORT TERM FORECAST...CONVECTION ALREADY BEGINNING OVER THE NORTHERN
COPPER RIVER BASIN TODAY AS EVIDENCED ON VISIBLE SATELLITE. THIS AREA
ALONG WITH THE SUSITNA VALLEY AND KUSKOKWIM VALLEY MAY SEE AN
ISOLATED THUNDERSTORM THIS AFTERNOON OR EVENING. AS STATED ABOVE
THESE AREAS ARE MORE LIKELY TO SEE THUNDERSTORMS TOMORROW AS THE
ATMOSPHERE BECOMES MORE UNSTABLE. EXPECT SOME SCATTERED SHOWERS IN
THESE AREAS TODAY AND TOMORROW.
NORTHERLY WINDS ALONG THE NORTH GULF COAST WILL PERSIST THROUGH
TONIGHT AND THEN DIMINISH AND SOME TOMORROW. THE DECREASE IN PRESSURE
GRADIENT SHOULD ALLOW THE NORMAL SEA BREEZES TO KICK IN TOMORROW.

.LONG TERM FORECAST...UNCERTAINTY REMAINS FOR THE LONG TERM AS THE
MODELS ARE NOT IN GOOD AGREEMENT WITH EACH OTHER OR THEMSELVES LATE
IN THE WEEK. BEST GUESS IS THAT THE GFS HAS A DECENT HANDLE ON A LOW
MOVING TO THE ALASKA PENINSULA/KODIAK AREA FRIDAY BUT THE GFS LOOKS
LIKE IT IS TOO STRONG AT THIS TIME. WILL KEEP WATCHING THIS SYSTEM AS
IT DEVELOPS AND SEE IF A BETTER FEEL FOR THIS SYSTEM CAN BE
ASCERTAINED IN THE NEXT DAY OR SO.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 170.
FIRE WEATHER...NONE.

MAY 08