Small Craft Advisory 192, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AST MON MAR 3 2008

.ANALYSIS AND UPPER LEVELS...A DEEP ANCHOR LOW IS CENTERED JUST
SOUTH OF THE WESTERN ALEUTIANS WITH MULTIPLE WAVES EMBEDDED WITHIN
ITS CIRCULATION. A RIDGE IS BUILDING FROM THE EAST PACIFIC NORTHWARD
ACROSS THE GULF OF ALASKA AND MAINLAND ALASKA. A STRONG ZONAL JET
(ESTIMATED MAX AROUND 200 KT) EXTENDS OUT OF ASIA ALONG 30N AND
THEN CURVES NORTHWARD AROUND 160W. AT THE SURFACE THERE IS A STRONG
LOW BETWEEN THE PRIBILOFS AND EASTERN ALEUTIANS...TRACKING NORTHWARD
ALONG THE EASTERN SIDE OF THE ANCHOR LOW. OCCLUSION EXTENDS NORTHEAST
ACROSS THE PRIBILOFS TO BRISTOL BAY. BLIZZARD CONDITIONS ENDED THIS
MORNING ACROSS THE PRIBILOFS AS WINDS DIMINISHED AND TEMPERATURES
ROSE WITH THE FRONT NEARING. QUIKSCAT WINDS AND SURFACE OBSERVATIONS
SHOW A FAIRLY CONCENTRIC LOW CENTER WITH STRONG WINDS ON ALL SIDES
OF THE LOW. PRESSURE RISES BEHIND THE LOW COMBINED WITH STRONG COLD
ADVECTION IN THE LOW LEVELS ARE ENHANCING WINDS FROM THE EASTERN
ALEUTIANS TO THE ALASKA PENINSULA. GUSTS TO 64 KT HAVE BEEN OBSERVED
IN COLD BAY. RADAR IMAGERY OVER THE SOUTHERN MAINLAND SHOWS
PRECIPITATION SLOWLY SPREADING INLAND. THERE ARE STRONG EASTERLY
CHINOOKS AHEAD OF THE FRONT LIMITING PRECIPITATION IN THE USUAL
LEE SIDE LOCATIONS. HOWEVER...FLOW ALOFT IS SOUTHERLY SO SOME LIGHT
PRECIPITATION MAY MAKE IT INTO THESE AREAS AS WELL. FINALLY...IR
SATELLITE IMAGERY SHOWS MULTIPLE LOWS FORMING IN THE LEFT EXIT
REGION OF THE MAIN UPPER JET...IN THE BOX BORDERED BY 40N TO 45N
AND 160W TO 170W.

.MODEL DISCUSSION...MODELS INITIALIZED WELL WITH ANCHOR LOW AND
BERING LOW. AS WOULD BE EXPECTED THEY ARE NOT DOING VERY WELL
PICKING UP ON DEVELOPING LOWS DOWN OVER THE PACIFIC...AND THESE
PROBLEMS ARE REFLECTED IN THE VARYING MODEL SOLUTIONS. THE GFS
SHOWS GOOD RUN-TO-RUN CONSISTENCY WITH THE TRACK OF A LOW TO THE
ALASKA PENINSULA TUESDAY NIGHT. HOWEVER...PREFER THE MULTIPLE LOWS
INDICATED BY THE UKMET/ECMWF SOLUTIONS INSTEAD OF THE ONE BROAD LOW.
BEYOND THIS POINT MODEL SOLUTIONS RAPIDLY DIVERGE AND THERE IS VERY
LARGE SPREAD IN THE GFS ENSEMBLE. THE GFS/UKMET DEVELOP ANOTHER LOW
FAR TO THE SOUTH AND TRACK TO THE GULF LATE WEDNESDAY WHILE THE
ECMWF/NAM DEVELOP ONE OF THE LOWS TRACKING TO THE ALASKA PENINSULA
AND MOVE IT INTO BRISTOL BAY LATE WEDNESDAY. CURRENT FORECAST WAS
BASED OFF A LOW TRACKING TO NEAR MIDDLETON ISLAND. WITH ANCHOR LOW
SO FAR WEST AND BUILDING RIDGE PREFER SOLUTIONS THAT TRACK LOW
FARTHER WEST. THEREFORE...EVEN THOUGH THERE IS A LOT OF UNCERTAINTY
WILL TREND TOWARD THE NEW GFS SOLUTION.

.SHORT TERM FORECAST...THE BERING LOW WILL MOVE NORTHWARD AND THEN
STALL AND WEAKEN NORTH OF THE PRIBILOFS TUESDAY AS THE UPPER WAVE
ROTATES BACK WESTWARD AROUND THE TOP OF THE ANCHOR LOW. THE OCCLUSION
WILL QUICKLY MOVE INLAND AND FALL APART OVER SOUTHWEST ALASKA AND
WESTERN SOUTHCENTRAL TONIGHT. THIS WILL BRING A QUICK SHOT OF
SNOW...MAINLY IN UPSLOPE LOCATIONS SUCH AS THE WESTERN SUSITNA
VALLEY. THE COLD FRONT (EXTENDING FROM THE TRIPLE POINT OVER BRISTOL
BAY SOUTHWARD TO THE DEVELOPING PACIFIC LOWS) WILL MOVE TO SHELIKOF
STRAIT/COOK INLET TONIGHT AND THEN MOVE BACK WESTWARD AS A WARM FRONT
TUESDAY...SPREADING MORE PRECIPITATION BACK OVER SOUTHWEST ALASKA.
AS EACH SYSTEM MOVES THROUGH AIR CONTINUES TO GET WARMER. THIS ONE
WILL WARM SOME AREAS OF SOUTHWEST ALASKA ENOUGH TO MIX WITH OR CHANGE
TO RAIN. A LOW TRACK TO THE ALASKA PENINSULA WILL MAINTAIN STRONG
EAST TO SOUTHEAST LOW LEVEL FLOW ACROSS SOUTHCENTRAL ALASKA AS WELL
AS THE ALASKA AND ALEUTIAN RANGES...SO DOWNSLOPE DRYING WILL CONTINUE
IN THE USUAL PLACES. THE LOW WILL TRACK ACROSS THE SOUTHERN ALASKA
PENINSULA TUE NIGHT AND THEN STALL AS THE ANCHOR LOW BEGINS TO DROP
SOUTH AND EASTWARD UNDERNEATH THIS LOW. ALTHOUGH THERE IS GREAT
UNCERTAINTY IN WHAT WILL OCCUR AFTER THIS...IT LOOKS LIKE A GOOD
CHANCE THE NEXT SYSTEM WILL TRACK A LITTLE FARTHER NORTH AND EAST
DUE TO EASTWARD PROGRESSION OF THE ANCHOR LOW AND EAST PACIFIC RIDGE.
THEREFORE..EXPECT EVEN STRONGER DOWNSLOPE WINDS ACROSS SOUTHCENTRAL
BY MID WEEK AND AND ANOTHER SHOT OF PRECIPITATION ACROSS THE SOUTHERN
MAINLAND. TEMPERATURES WILL CONTINUE TO WARM AND CHANGE PRECIPITATION
TO ALL RAIN ALONG THE COAST WITH A GOOD POSSIBILITY OF PRECIPITATION
AT LEAST MIXING WITH RAIN IN SOME INLAND LOCATIONS AS WELL.

.LONG TERM FORECAST...GFS 500MB 5-WAVE INDICATES PATTERN WILL
CONTINUE TO PROGRESS THROUGH THE EXTENDED PERIOD. WITH SO MUCH
UNCERTAINTY IN THE SHORT-TERM DO NOT HAVE A LOT OF CONFIDENCE THAT
THIS WILL OCCUR...BUT CHANGEABLE WEATHER THIS TIME OF YEAR IS THE
NORM SO LOOKS REASONABLE THAT WE WONT STAY IN THIS SAME PATTERN
FOR A LONG TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 120 130 138 160 176 179 180 185.
         HEAVY FREEZING SPRAY WARNING 185.
FIRE WEATHER...NONE.

SEB MAR 08