Areal Flood Warning 13, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT THU SEP 20 2012

.MODEL DISCUSSION...NAM, GFS AND EC IN REASONABLE AGREEMENT.

.ANALYSIS AND UPPER LEVELS...STATIONARY BERING SEA TROUGH/WESTERN CANADIAN
RIDGE MAINTAINS MOISTURE LADEN SOUTHERLY FETCH OF MILD WINDS FROM 35N INTO
SOUTHERN ALASKA. INTERESTING STORM CENTERED NEAR 45N 170W IS ORIGINALLY FROM
THE ARCTIC AND CAME DOWN THE WEST SIDE OF THE BERING TROUGH THE LAST FEW
DAYS. THIS STORM HAS NOW MADE A TURN TO THE EAST AND FORECAST TO TEMPORARILY
DISRUPT THE WIND AND MOISTURE FLOW THAT HAS RESULTED IN THE HEAVY RAIN
SOUTHERN ALASKA. AS THE STORM BEGINS TO MOVE NORTHEAST LATE THURSDAY THE
RIDGING OUT IN ADVANCE WILL KICK THE FRONTAL BOUNDARY NORTH AND EAST LATER
THURSDAY NIGHT AND ALLOW DRIER AIR TO COME ACROSS SOUTHCENTRAL AK BY FRIDAY
MORNING. HOWEVER, AS THE SHORTWAVE RIDGE MOVES THROUGH INCREASING SOUTHEAST
FLOW FROM THE GULF WILL GRADUALLY SPREAD HEAVIER, MORE EXTENSIVE RAINFALL
BACK ACROSS SOUTHERN ALASKA FRIDAY NIGHT. AT THIS TIME IT LOOKS AS IF THE
HEAVY RAIN PATTERN WILL RETURN TO PRINCE WILLIAM SOUND FROM THE EASTERN
KENAI PENINSULA EAST TO YAKUTAT..AND TO A LESSER EXTENT OVER THE WESTERN AND
MID SUSITNA VALLEY.

RAIN WILL SPREAD NORTHWEST ACROSS BRISTOL BAY AND SOUTHERN KUSKOKWIM VALLEY
FRIDAY NIGHT, AND INTO AT LEAST THE EASTERN PART OF ZONE 155 SATURDAY
PLACING BETHEL ON THE WESTERN EDGE.

NORTHERLY GALES LIKELY FOR THE WESTERN ALASKA PENINSULA AND MARINE ZONE 171
FRIDAY NIGHT AS WELL AS SOUTHEAST GALES IN ACROSS THE GULF WHICH WILL
CONTINUE FOR 24 OR 30 HOURS OR SO. ANOTHER STORM TRACKS EASTWARD ACROSS THE
SOUTHERN BERING WHICH WILL ACT TO WEAKEN AND PUSH THE DOWNSTREAM SYSTEM
EAST.

SNOW LEVELS WILL REMAIN HIGH THROUGH SATURDAY THEN BEGIN A DOWNWARD TREND AS
THE COOLER AIR ASSOCIATED WITH THE UPPER TROUGH APPROACH FROM THE SOUTHWEST
SATURDAY NIGHT. THE LOWER SNOW LEVELS ALONG WITH A WEAKENING JET, WHICH
SHIFTS EASTWARD TO THE PANHANDLE, SHOULD HELP EASE THE FLOODING CONDITIONS
SINCE A COOLER MORE UNSETTLED PATTERN WILL HAVE DEVELOPED OVER THE AREA.

.LONG TERM FORECAST...EARLY NEXT WEEK LOOKS VERY WINDY AND WET KODIAK ISLAND
AND THE IMMEDIATE NORTH GULF COAST WITH MUCH LIGHTER AND MORE INTERMITTENT
RAIN AMOUNTS FOR INLAND AREAS SUCH AS VALDEZ AND ANCHORAGE. COLDER GALE
FORCE NORTHERLY WINDS WILL DOMINATE MUCH OF THE BERING SEA AND ALEUTIANS
THROUGH MOST OF NEXT WEEK. LESS RAIN FOR SOUTHERN ALASKA AS THE MAIN STORM
TRACK REMAINS FARTHER SOUTH AND HEADS IN OVER THE SOUTHEAST COAST.

.AER/ALU...WATCH/WARNING SUMMARY

PUBLIC...FLOOD WARNING FOR ZONES 121, 125, 131, 135
         FLOOD ADVISORY FOR ZONES 101, 111
MARINE...GALE FOR AREAS 120, 125, 130

DPERCY SEP 12