Small Craft Advisory 365, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT WED APR 18 2007

.MODEL DISCUSSION...
GFS CONTINUES AS THE MODEL OF CHOICE AS INITIALIZATION PROBLEMS
CONTINUE TO PLAGUE THE WRF. SIGNIFICANT DIFFERENCES EMERGE AT H+24
WITH THE DISSIPATING LOW OVER THE SEWARD PENINSULA. CHANNEL 3 IMAGERY
INDICATES THE WRF IS HAVING A DIFFICULT TIME CHARACTERIZING THE
MOISTURE AND MOMENTUM FIELDS OF THE LOW OVER THE SEWARD PENINSULA.
THUS THE GFS IS THE MODEL OF CHOICE FOR THE WEST DOMAIN. DEEP LOW
SOUTH OF SHEMYA AROUND 45N CAPTURED WELL BY BOTH MODELS WHICH IS
SOMEWHAT SURPRISING GIVEN PROBLEM MENTIONED ABOVE. NO PHASING
DIFFERENCE WITH THE MODELS THROUGH H+60 THOUGH THE GFS IS PREDICTABLY
DEEPER. DIFFERENCES ARE SUBTLE FOR THE EAST DOMAIN MAINLY WITH THE
FILLING LOW OVER KODIAK. WRF HAS CONSISTENTLY AND INCORRECTLY TRIED
TO KEEP THE LOW IN THE GULF. EACH SUCCESSIVE RUN OF THE WRF BRINGS IT
CLOSER TO THE GFS WHICH IS IN LINE WITH THE ANALYSIS AND SHORT RANGE
PREDICTION.

.ANALYSIS AND UPPER LEVELS...
FILLING LOW OVER THE SEWARD PENINSULA AND KODIAK WITH THE ASSOCIATED
FRONTAL SYSTEM DOMINATE THE AREA. MODERATE SURFACE RIDGE EXTENDING
EAST WEST ACROSS SOUTH CENTRAL KEEPING STRONG EAST WINDS IN THE USUAL
PLACES. CHANGING DOMINANT WAVE NUMBER IN THE WESTERN HEMISPHERE AND
LONG WAVE APPARENT IN THE UPPER LEVEL WIND FIELDS AS THE JET IS
REMAINING SOUTH. HAVE EVERY REASON TO BELIEVE THIS TRANSFORMATION
WILL CONTINUE AND THE STORM TRACK WILL REMAIN SOUTH OF THE AREA FOR
THE NEXT WEEK.

.SHORT TERM FORECAST...
EAST WINDS WILL DECREASE AND THE PRECIPITATION WILL END ACROSS SOUTH
CENTRAL ALASKA OVERNIGHT. SURFACE LOW PUSHING PRECIPITATION SHIELD
OVER THE WESTERN ALEUTIANS AS PRESSURE GRADIENT INCREASES. THE SYSTEM
EXPECTED TO SLIDE EAST UNDER THE CHAIN OVER THE NEXT 36 HOURS
SPREADING ANOTHER SERIES OF NORTHEASTERLY GALES AND RAIN SNOW. RIDGE
TO BUILD INTO THE NORTH CENTRAL BERING ACROSS THE NORTHERN INTERIOR
OF ALASKA BRING DRIER AND SOMEWHAT COLDER WEATHER ALONG WITH
DIMINISHED WINDS.

.LONG TERM FORECAST...

STORM TRACK TO REMAIN SOUTH OF 55N FOR THE NEXT WEEK. ONLY
SIGNIFICANT WEATHER WILL BE ALONG THE ALEUTIANS INTO SOUTH CENTRAL
COASTAL AREAS AS THE OCCLUDED FRONTS ASSOCIATED WITH THE LOWS BRUSH
THOSE AREAS WITH MIN GALE FORCE WINDS IN THE MARINE AREAS AND
PRECIPITATION. TEMPERATURES SHOULD REMAIN WARM ENOUGH SUCH THAT THE
PRECIPITATION IS RAIN NEAR SEA LEVEL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 155 160 165 170 171 172 175 176 185.
FIRE WEATHER...NONE.

CAS APR 07