Small Craft Advisory 378, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT SUN APR 22 2007

.MODEL DISCUSSION...MODELS CONTINUE TO HAVE A GOOD HANDLE ON LARGE
LOW SOUTH OF THE AKPENN. SOLUTIONS BEGIN TO DIVERGE AROUND 36 HOURS
AS A STRONG UPPER SHORT-WAVE ROUNDS THE EAST SIDE OF THE LOW...LIKELY
FORMING A SECONDARY SURFACE LOW SOMEWHERE TO THE EAST OF THE ORIGINAL
LOW. MODELS ALL INDICATE ELONGATION OF SURFACE LOW CENTER...BUT
DISAGREE ON NUMBER OF SURFACE LOWS AND EXACT PLACEMENT OF LOW(S).
PREFER THE GFS SOLUTION WHICH CLEARLY INDICATES TWO SURFACE LOWS.

MODELS CONTINUE TO TREND FASTER WITH NEXT LOW TRACKING SOUTH OF THE
ALEUTIANS MONDAY AND TUESDAY. WITH STRONG JET ALOFT LIKE THE IDEA OF
THIS FASTER SOLUTION. THE GFS IS THE FASTER THAN OTHER MODELS AS WELL
AS THE ENSEMBLE MEAN...BUT WITH THE FASTER TREND THINK THIS WILL WORK
OUT WELL. SO FORECASTS WILL TREND HEAVILY TOWARD THIS NEW SOLUTION.

.ANALYSIS AND UPPER LEVELS...A LARGE LOW COMPLEX IS SPINNING SOUTH
OF THE AKPENN. WATER VAPOR IMAGERY SHOWS SEVERAL VORT-MAXES EMBEDDED
WITHIN THE CYCLONIC FLOW...THE STRONGEST OF WHICH IS EAST OF THE LOW
CENTER MOVING NORTHWARD INTO THE GULF. THIS IS HELPING TO GENERATE
LOTS OF LIFT ACROSS THE SOUTH TO WEST GULF...WITH MOISTURE MAKING
SLOW PROGRESSION NORTHWARD. THE MOISTURE THEN ROTATES WESTWARD ACROSS
SOUTHWEST ALASKA AND THEN SOUTHWARD TO THE AKPENN AND EASTERN
ALEUTIANS. A TROUGH AXIS EXTENDS DUE SOUTH FROM THE LOW CENTER TO
NEAR 30N. A STRONG UPPER JET EXTENDS EASTWARD OUT OF ASIA BETWEEN 40N
AND 50N TO ABOUT 175W. THERE IS A BIT OF A BREAK ON THE WESTERN SIDE
OF THE TROUGH AND THEN ANOTHER JET STREAK EXTENDS FROM THE SOUTH TO
EAST SIDE OF THE UPPER TROUGH. THE NEAR ZONAL JET FROM THE WEST IS
SERVING TO PUSH THE TROUGH EASTWARD WHILE THE STRONGER FLOW ON THE
EAST SIDE OF THE TROUGH IS AMPLIFYING THE RIDGE OVER WESTERN NORTH
AMERICA AND PUSHING ENERGY NORTHWARD INTO THE GULF. BACK TO THE
WEST...A WEAK LOW IS RIDING THE JET EASTWARD AT ABOUT 48N. WEAK FLOW
ALOFT DOMINATES THE BERING SEA REGION AS UPPER TROUGH EXTENDS FROM
LOW CENTER WEST-NORTHWEST TO RUSSIA.

.SHORT TERM FORECAST...LARGE LOW COMPLEX WILL REMAIN SOUTH OF
AKPENN/KODIAK ISLAND THE NEXT COUPLE DAYS RESULTING IN PERSISTENT
AREAS OF RAIN FROM THE WESTERN GULF ACROSS SOUTHWEST ALASKA TO THE
AKPENN. FARTHER NORTH...MOISTURE WILL INCREASE TONIGHT AND MONDAY
AS SURFACE FRONT MOVES TO THE NORTH GULF COAST AND SHORT-WAVES ALOFT
ARE DRIVEN NORTHWARD ACROSS THE GULF AND THEN WESTWARD ACROSS
SOUTHWEST ALASKA. EXPECT MOST OF PRECIP TO REMAIN ALONG THE COAST
WITH STRONG EASTERLY DOWNSLOPE FLOW CONTINUING ACROSS THE KENAI
MOUNTAINS...ALASKA RANGE...AND ALEUTIAN RANGE. HOWEVER...SHORTWAVE
PROGGED TO ROTATE ACROSS SOUTHCENTRAL MONDAY AFTERNOON/EVENING
AND SOUTHWEST ALASKA MONDAY NIGHT LOOKS VERY IMPRESSIVE. THIS
SHOULD BE ENOUGH TO INTRODUCE CHANCE OF SHOWERS TO ALL INLAND
LOCATIONS. IF THERE ARE ANY BREAKS IN THE CLOUDS MONDAY AFTERNOON
AND EVENING...WHICH IS MOST LIKELY THE FARTHER YOU GO INLAND...THIS
SHORTWAVE WOULD HELP TRIGGER MORE NUMEROUS SHOWERS. RELATIVELY
WARM PACIFIC AIR BEING TRANSPORTED ACROSS THE REGION WILL KEEP
MOST PRECIP IN THE FORM OF RAIN. COLD AIR WILL REMAIN BACK OVER
THE CENTRAL TO WESTERN BERING WHERE WEAK FEATURES WILL BE ENOUGH
TO PRODUCE OCCASIONAL LIGHT RAIN AND SNOW SHOWERS.

THE NEXT LOW TRACKING IN FROM THE WEST WILL REMAIN SOUTH OF THE
ALEUTIANS WITH ONLY MINOR INFLUENCE ON THE WEATHER. IT WILL MERGE
WITH THE LOW COMPLEX SOUTH OF THE AKPENN ON TUESDAY.

.LONG TERM FORECAST...EXPECT LITTLE CHANGE IN THE PATTERN. THE LOW
COMPLEX DOES LOOK LIKE IT WILL GRADUALLY MOVE FARTHER NORTH TO ABOUT
KODIAK ISLAND MID WEEK AND THEN REMAIN THERE INTO NEXT WEEKEND. THIS
MEANS INFLUENCE OF THIS LOW WILL ENCOMPASS ALL OF SOUTHCENTRAL AND
SOUTHWEST ALASKA RESULTING IN CONTINUED RAIN ALONG THE GULF COAST
AND INCREASING SHOWERS INLAND. TEMPS WILL REMAIN NEAR TO SLIGHTLY
ABOVE AVERAGE. DONT EXPECT ANY MAJOR STORMS IN THE BERING...JUST
LOTS OF CLOUDS...COOL TEMPS...AND OCCASIONAL LIGHT PRECIP.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 120 130 138.
FIRE WEATHER...NONE.

SEB APR 07