Small Craft Advisory 360, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1205 PM ADT THU APR 20 2006

.DISCUSSION...
ANALYSIS - COLD AIR ALOFT IS THE MOST SIGNIFICANT FEATURE THIS
MORNING OVER SOUTHERN ALASKA. A MAJOR UPPER LOW IS N OF WRANGEL
ISLAND WITH A SHORT WAVE EXTENDING INTO S CENTRAL AK WITH -36C AT 500
MB. ANOTHER MAJOR CENTER IS NEAR PASY AND ANOTHER OFF THE PANHANDLE.
A RATHER LOW AMPLITUDE UPPER RIDGE IS ALONG 155W. SATELLITE IMAGERY
REVEALS AN EXTENSIVE FRONT AT 18Z OVER THE CENTRAL AKPENN AND JUST
OFF THE SW AK COAST. THIS FRONT IS ASSOCIATED WITH A 992 MB SFC LOW
COMPLEX OVER THE CENTRAL BERING SEA. A 1008 MB LOW IS OVER PRINCE
WILLIAM SOUND WITH A 1004 MB LOW AND COLD AIR 150 NM OFF SITKA. THERE
IS A FRAGMENTED SOMEWHAT MERIDIONAL JET AT 250 MB FROM CENTRAL ASIA
TO AN EXIT AROUND 35N 145W AT THE BASE OF A MAJOR UPPER TROF.

AER FORECASTS - THE COLD AIR ALOFT IS KICKING OUT NE TODAY BUT THERE
IS STILL SOME MOISTURE FROM THE UPPER SHORT WAVE. THE CIRRUS SHIELD
FROM THE FRONT TO THE SW HAS REACHED PAHO BY 20Z. THE DECISION FOR
TONIGHT AND TOMORROW IS IF AND HOW MUCH PRECIP TO BRING IN WITH THE
FRONT AND WHERE. WE HAVE TO BE THINKING ABOUT DOWNSLOPE EFFECTS. ALL
MODELS DEVELOP A NEW SFC LOW IN THE 990S IN BRISTOL BAY BY 12Z FRI.
THIS WILL INCREASE EASTERLY SFC PRES GRADIENTS AND GULF SE WIND WILL
BE INCREASING. LOOK FOR ANOTHER SLUG OF COLD AIR TO COME AROUND IN
THE S UPPER FLOW ALOFT BY FRI NIGHT FOR MORE OF SHOWER TYPE PRECIP.

ALU FORECASTS - WE WERE ABLE TO DROP THE BLIZZARD WARNING FOR PASN
FOR EARLIER THIS MORNING IN THAT THE SURFACE LOW AND WARM SECTOR HAD
MOVED INTO THE PRIBILOFS. SATELLITE IMAGERY SHOWS SHOWERS IN THE
COOLER AIR ALONG THE ALEUTIANS MOVING EAST. MUCH OF THE BERING SEA
WILL BE IN A NORTHERLY FETCH BEHIND THE UPPER AND SURFACE LOW BY FRI
AFTERNOON AS HIGH PRESSURE BUILDS INTO THE FAR WESTERN BERING SEA. WE
EXPECT THE SNOW TO JUST MISS PABE ON THE BACK SIDE OF THE LOW BUT THE
BRISTOL BAY AREA SHOULD GO DOWN. THE K-VALLEY WILL BE TRICKY BUT WE
TEND TO SEE IT DRIER THAN THE MODELS EXCEPT FOR THE SOUTHERN HALF
STARTING TONIGHT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 120 130 172 176 179. HVY FREZ SPRAY 185.
FIRE WEATHER...NONE.

JC APR 06