Gale Warning 426, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
150 PM AKDT MON APR 27 2009

.ANALYSIS AND UPPER LEVELS...A BLOCKING RIDGE CENTERED ALONG 140W
EXTENDS NORTHWARD OVER EASTERN ALASKA AND INTO THE YUKON. A HIGH
AMPLITUDE TROUGH EXTENDS FROM A CUT-OFF LOW OVER EASTERN SIBERIA
SOUTHWESTWARD ACROSS THE FAR WEST PACIFIC. UPPER JET HEADS NORTHEAST
OUT OF THE BOTTOM OF THIS TROUGH ACROSS THE NORTH PACIFIC (REMAINING
SOUTH OF THE ALEUTIANS) AND THEN SOUTHEASTWARD INTO A NEARLY
STATIONARY TROUGH SOUTH OF THE EASTERN ALEUTIANS. A LONG FETCH OF
SOUTHERLY FLOW UP THE WEST SIDE OF THE RIDGE IS TRANSPORTING WARM
AIR AND MOISTURE NORTHWARD ACROSS WESTERN ALASKA...RESULTING IN
A NARROW BAND OF RAIN WHICH IS TRANSLATING SLOWLY EASTWARD....BUT
WHICH WILL BE BLOCKED BY THE RIDGE FROM MAKING IT TOO FAR EAST.
A MODERATE LOW EMBEDDED WITHIN THE WESTERN TROUGH IS TRACKING
EAST-NORTHEAST TOWARD THE ALEUTIANS.

.MODEL DISCUSSION...MODELS HAVE A GOOD HANDLE ON THE RIDGE AND WITH
THE NORTHWEST PACIFIC LOW. DISAGREEMENT LIES IN BETWEEN WHERE ENERGY
MOVING THROUGH THE TROUGH SOUTH OF THE EASTERN ALEUTIANS IS FORCED
NORTHWARD UP THE WEST SIDE OF THE BLOCKING RIDGE. ALL MODELS INDICATE
A LOW MOVING UP THE STATIONARY FRONT...BUT TIMING TRACK AND STRENGTH
VARIES AMONG THE MODELS. WILL TREND TOWARD THE 12Z GFS WHICH HAS A
POSITION IN THE MIDDLE OF THE VARIOUS SOLUTIONS...AND WILL BEGIN TO
INDICATE STRONGER WINDS AS THE GRADIENT TIGHTENS UP EAST OF THIS
LOW...BUT WONT GO NEARLY AS STRONG AS THE GFS WHICH HAS THE
STRONGEST SOLUTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...EXTENSIVE CLOUD COVER CURRENTLY DOMINATES THE
CENTRAL TO WESTERN GULF AS WELL AS THE WESTERN HALF OF SOUTHCENTRAL.
THIS WILL GRADUALLY CHANGE MONDAY NIGHT AND TUESDAY AS THE RIDGE
BUILDS NORTH AND WEST AND FLOW BACKS FROM THE SOUTH TOWARD THE EAST.
THIS WILL MOVE THE CLOUDS OUT OF MOST OF SOUTHCENTRAL. HOWEVER...THE
MARINE STRATUS DECK WILL REMAIN OUT OVER THE GULF AND ALONG THE
IMMEDIATE COAST. FULL SUN WILL ALLOW TEMPERATURES TO EASILY REACH
INTO THE 50S ACROSS THE REGION. THE RIDGE WILL BECOME CUT-OFF BY
LATE WEDNESDAY AS IT BECOMES RE-CENTERED OVER THE SOUTHERN YUKON.
THIS WILL ALLOW A PACIFIC FRONT TO APPROACH KODIAK ISLAND WEDNESDAY
AND PRODUCE STRONGER WINDS...BUT THE RIDGE WILL BE STRONG ENOUGH
TO KEEP ALL OF THE RAIN WITH THE FRONT SOUTHWEST OF THE ISLAND.

SOUTHWEST ALASKA...THE BAND OF RAIN OVER SOUTHWEST ALASKA THAT HAS
BEEN PUSHING EASTWARD THIS MORNING WILL HEAD BACK WESTWARD TONIGHT
AS THE RIDGE BUILDS A BIT TOWARD SOUTHWEST ALASKA. MEANWHILE...WEAK
WAVES WILL BEGIN TO MOVE NORTHWARD FROM THE PACIFIC AND HELP TO
ENHANCE THE RAINFALL OVER THE SOUTHERN ALASKA PENINSULA TONIGHT
AND NORTHWARD TO THE KUSKOKWIM DELTA COAST BY TUESDAY. AS THE UPPER
RIDGE BECOMES CUT-OFF OVER THE YUKON WEDNESDAY FLOW WILL BACK TOWARD
THE EAST AND PUSH THE FRONT OUT INTO THE EASTERN BERING SO THAT
INLAND LOCATIONS WILL DRY OUT AND WARM UP. SOME LIGHT RAIN SHOWERS
WILL LIKELY PERSIST ALONG THE COAST UNTIL THURSDAY WHEN THE RIDGE
BUILDS EVEN FARTHER WEST. THE PACIFIC FIRE HOSE WILL REMAIN AIMED
AT THE SOUTHERN ALASKA PENINSULA THROUGH LATE IN THE WEEK...SO
STEADY RAIN WILL PERSIST.

BERING SEA/ALEUTIANS...THE NORTHWEST PACIFIC LOW WILL STALL AS IT
REACHES THE WESTERN ALEUTIANS AND BECOMES VERTICALLY STACKED. THIS
LOW WILL THEN SLOWLY TRACK EASTWARD THROUGH LATE WEEK AS ENERGY
TO THE EAST ROTATES WESTWARD OVER TOP OF IT. THUS...GENERALLY WET
UNSETTLED WEATHER WILL PERSIST THROUGH THE WEEK.

.LONG TERM FORECAST...THE ALEUTIAN LOW COMPLEX WILL MOVE DOWN
INTO THE NORTH PACIFIC AS THE RIDGE BUILDS WESTWARD ACROSS MAINLAND
ALASKA AND THE BERING. THEREFORE...EXPECT DRY AND WARM CONDITIONS
OVER MAINLAND ALASKA THROUGH NEXT WEEKEND AND A DRYING TREND ACROSS
THE BERING SEA AND ALEUTIANS BEGINNING LATE IN THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...150 155 160 172 175 176 180.
FIRE WEATHER...NONE.

SEB APR 09