Small Craft Advisory 355, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT FRI APR 24 2009

.ANALYSIS AND UPPER LEVELS...
HIGH PRESSURE IS STILL FIRMLY ANCHORED OVER THE EASTERN NORTH
PACIFIC...WITH SURFACE RIDGING EXTENDING INTO THE GULF OF ALASKA. A
974 MB LOW IS NEAR SHEMYA...MOVING NORTHEAST INTO THE WESTERN BERING.
A FRONT ASSOCIATED WITH THIS LOW IS OVER THE EASTERN BERING AND
ALEUTIANS...AND WILL BE MOVING INTO SOUTHWEST ALASKA TONIGHT.

IN THE UPPER LEVELS...GENERALLY ZONAL FLOW STRETCHES FROM THE EASTERN
BERING THROUGH THE MAINLAND. AN UPPER TROUGH CONTINUES TO DEEPEN OVER
THE WESTERN BERING AND ALEUTIANS. AN UPPER LOW AT THE BASE OF THIS
TROUGH IS AIDING IN THE DEVELOPMENT OF THE SURFACE LOW NEAR SHEMYA.

.MODEL DISCUSSION...
MODELS ARE IN SATISFACTORY AGREEMENT THROUGH 00Z MONDAY. DIFFERENCES
ARISE AFTER THIS TIME IN HOW TO HANDLE THE LOW MOVING INTO THE BERING
SEA...AND ITS SUBSEQUENT INTERACTION WITH THE RIDGE OVER MAINLAND
ALASKA. THE GFS SOLUTION WAS ONCE AGAIN USED TO CONSTRUCT THE
AFTERNOON PACKAGE...DUE TO GOOD INITIALIZATION AND CONTINUED
CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
GENERALLY QUIET WEATHER TONIGHT WILL BE SHORT LIVED AS THE
AFOREMENTIONED FRONT MOVES INTO SOUTHCENTRAL TOMORROW AFTERNOON. WARM
AIR WITH THE FRONT WILL RESULT IN PRIMARILY RAIN...ALTHOUGH A RAIN
SNOW MIX WILL BE SEEN FOR INLAND LOCATIONS. THE FRONT IS EXPECTED TO
GRADUALLY DISSIPATE OVER THE NORTHERN GULF THROUGH THE END OF THE
WEEKEND...KEEPING CHANCES OF RAIN AND SNOW AROUND THROUGH THE END OF
THE WEEKEND.

.SOUTHWEST...
THE FRONT WILL SPREAD PRECIP OVER THE AREA TONIGHT AND TOMORROW. WARM
AIR WITH THIS SYSTEM WILL LEAD TO MAINLY RAIN...ALTHOUGH THE
KUSKOKWIM DELTA IS EXPECTED TO REMAIN COLD ENOUGH TO SEE MORE SNOW
TONIGHT. SOUTHWEST FLOW WILL TAKE OVER TOMORROW AFTERNOON THROUGH THE
END OF THE WEEKEND...KEEPING RAIN AND SNOW AROUND AS WE HEAD INTO THE
BEGINNING OF THE WEEK.

.BERING SEA AND ALEUTIANS...
RAIN AND SNOW SHOWERS WILL CONTINUE THROUGH THE WEEKEND AS THE LOW
NEAR SHEMYA MOVES INTO THE CENTRAL BERING. GALE FORCE SOUTHERLY WINDS
AHEAD OF THE LOW WILL KEEP PRECIPITATION MAINLY RAIN. ON THE BACKSIDE
OF THE LOW...COLD ADVECTION WILL TURN SOME OF THE SHOWERS BACK TO
SNOW.

.LONG TERM FORECAST...
EXPECT UPPER RIDGING TO STRENGTHEN OVER THE GULF OF ALASKA WITH AN
UPPER TROUGH OVER THE BERING SEA AND ALEUTIANS. THEREFORE
ANTICIPATING UNSETTLED WEATHER WILL CONTINUE OVER THE
ALEUTIANS...WITH QUIET AND UNSEASONABLY WARM WEATHER OVER SOME OF
SOUTHCENTRAL. MOIST SOUTHERLY FLOW WILL SET UP OVER THE SOUTHWEST
MAINLAND...KEEPING THE CHANCES OF PRECIPITATION HIGH THROUGH THE
FIRST PART OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...150 155 165 170 172 175 176 179
FIRE WEATHER...NONE

NRH APR 09