Small Craft Advisory 736, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKDT WED SEP 24 2008

.ANALYSIS AND UPPER LEVELS...
POSITIVELY TILTED TROUGH EXTENDING FROM THE CENTRAL INTERIOR TO SOUTH
OF THE EASTERN ALEUTIANS. THIS UPPER TROUGH IS ASSOCIATED WITH A
STRENGTHENING LOW SOUTH OF THE ALASKA PENINSULA. TO THE WEST IS A
HIGH AMPLITUDE RIDGE WITH AXIS FROM EASTERN SIBERIA TO THE CENTRAL
ALEUTIANS. NEAR THE SOUTHERN TIP OF THE KAMCHATKA PENINSULA IS A
STRONG VERTICALLY STACKED LOW WITH A FRONTAL BOUNDARY EXTENDING SOUTH
AND EAST TOWARD THE WESTERN ALEUTIANS.

.MODEL DISCUSSION...
SOME SUBTLE DIFFERENCES IN THE SHORT TERM BETWEEN THE 12Z NAM AND
GFS. THE NAM INITIALIZED POORLY ON THE DEVELOPING LOW SOUTH OF THE
ALASKA PENINSULA. OVERALL THE 12Z GFS IS THE PREFERRED SOLUTION. THE
EXTENDED FORECAST WAS UNREPRESENTATIVE OF HPCS GUIDANCE AND THE
LATEST MODEL RUNS SO DECIDED TO LOAD THE LATEST GFS WHICH WAS THE
BEST CHOICE FOR THE MEDIUM TO LONG RANGE FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
AN INVERTED TROUGH EXTENDS FROM THE DEVELOPING LOW SOUTH OF THE AKPEN
NORTHEAST TOWARD THE SUSITNA VALLEY. THIS FEATURE COUPLED WITH THE
MOIST SOUTHWESTERLY FLOW ALOFT IS RESULTING IN WIDESPREAD RAIN
SHOWERS OVER SOUTHCENTRAL ALASKA AGAIN TODAY. WHILE SEVERAL AREAS SAW
A BREAK LATE THIS MORNING...ANOTHER SHORTWAVE IS MOVING NORTHWARD
WHICH IS HELPING INITIATE MORE SHOWER ACTIVITY AS IT REACHES THE
NORTHERN KENAI PENINSULA AND PWS THIS AFTERNOON. AREAS OF LIGHT RAIN
WILL AGAIN SETTLE IN OVER THE ANCHORAGE BOWL THIS EVENING AND LAST
MOST OF THE NIGHT. THE FORECAST CHALLENGE REMAINS THE TIMING OF THE
CLEARING...IF IT HAPPENS...AS THE LOW PRESSURE SYSTEM SHIFTS
SOUTHWARD INTO THE SOUTHERN GULF OF ALASKA. STILL BELIEVE SOME
CLEARING WILL HAPPEN LATER THIS WEEK. FLOW ALOFT BRIEFLY BECOMES EAST
TO NORTHEASTERLY FRIDAY WHICH MAY ALLOW A SIGNIFICANT BREAK IN THE
CLOUDS BEFORE THE NEXT SYSTEM APPROACHES SATURDAY. COASTAL SECTIONS
WILL REMAIN CLOUDY AND WET WHILE THE INTERIOR HAS THE BEST CHANCE FOR
THE BREAKS IN THE CLOUDS.

SOUTHWEST ALASKA...

AFTER DAYS OF ONSHORE FLOW AND SOAKING RAINS...WINDS HAVE BECOME VERY
LIGHT UNDER THE BROAD AREA OF LOW PRESSURE LOCATED OVER BRISTOL BAY.
WIDESPREAD FOG AND LOW STRATUS DEVELOPED THIS MORNING WITH THESE
IDEAL CONDITIONS RESULTING IN SEVERAL AREAS REMAINING IFR DURING THE
DAY. AS THE SURFACE LOW SHIFTS SOUTH AND EAST AND THE UPPER LOW
ROTATES OVER THE EASTERN BERING SEA...CLEARING IS EXPECTED WITH
NORTHEASTERLY WINDS PREVAILING BY FRIDAY. THE PROBLEM WILL BE FOG
THAT DEVELOPS IN THE VALLEYS AS TEMPERATURES WILL COOL OFF RAPIDLY
OVERNIGHT ANYWHERE THERE IS SIGNIFICANT CLEARING. OVERALL...EXPECTING
TO SEE GRADUALLY IMPROVING WEATHER CONDITIONS ACROSS THE SOUTHWEST
INTERIOR BY THE WEEKEND WITH AREAS OF FOG LIMITED TO THE EARLY
MORNING HOURS.

BERING SEA/ALEUTIANS...NO SIGNIFICANT CHANGES TO THE FORECAST OVER
THE BERING SEA AND WESTERN ALEUTIANS. HIGH PRESSURE ANCHORED OVER
EASTERN SIBERIA WILL PREVENT AREAS OF LOW PRESSURE AND ASSOCIATED
FRONTS FROM ADVANCING NORTH. TRACKS OF DEVELOPING LOWS AND THEIR
FRONTS WILL REMAIN ALONG THE ALEUTIANS.

.EXTENDED...
WE CONTINUE TO WATCH A COOL WEATHER OUTBREAK SHAPING UP FOR THE
INTERIOR OF ALASKA LATE THIS WEEKEND. MODELS HAVE BACKED OFF A LITTLE
ON THE STRENGTH BUT STILL HAVE SOME SORT OF COOL AIR SPILLING OVER
THE ALASKA RANGE INTO SOUTHCENTRAL. WILL NOT ADVERTISE ANY SNOW FOR
SOUTHCENTRAL THIS EARLY BUT WILL WATCH VERY CLOSELY AS THIS DEVELOPS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 175 176.
FIRE WEATHER...NONE.

AB SEP 08