Areal Flood Advisory 13, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
550 AM AKDT WED SEP 19 2012

.ANALYSIS AND UPPER LEVELS...
THE ALASKA REGION IS UNDER THE INFLUENCE OF A HIGHLY AMPLIFIED UPPER
LEVEL PATTERN THIS MORNING. A LONGWAVE TROUGH EXTENDS THROUGH THE
BERING AND WELL INTO THE NORTHERN PACIFIC...WITH A STRONG RIDGE IN
PLACE OVER THE EASTERN PACIFIC. DEEP LAYER SOUTH TO SOUTHWESTERLY
FLOW BETWEEN THESE TWO FEATURES CONTINUES TO BRING WIDESPREAD RAIN TO
MUCH OF THE SOUTHERN MAINLAND. A SURFACE LOW HAS FORMED SOUTH OF THE
AKPEN BENEATH A 140 KNOT UPPER LEVEL JET AND WILL BRING MORE RAIN AND
STRONG WINDS TO PARTS OF SOUTHCENTRAL ALASKA AS IT MOVES QUICKLY
NORTHWARD. MEANWHILE...A CLOSED UPPER LOW IS DIVING SOUTHWARD OVER
THE WESTERN BERING.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT IN THE SHORT TERM REGARDING THE LOW
APPROACHING KODIAK ISLAND THIS MORNING...AND REMAIN IN DECENT
AGREEMENT THROUGH THE END OF THE WEEK IN HANDLING THE BERING SYSTEM
AS IT DROPS INTO THE NORTHERN PACIFIC AND DEEPENS.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
RAIN WILL CONTINUE TODAY ACROSS SOUTHCENTRAL AK AS THE SURFACE LOW
CURRENTLY SOUTH OF THE AKPEN MOVES ASHORE NEAR KODIAK ISLAND. STRONG
SOUTHEASTERLY WINDS WILL CONTINUE TO DEVELOP AS THE SYSTEM
APPROACHES...PEAKING DURING THE EARLY AFTERNOON AND DIMINISHING IN
THE EVENING. WINDS WILL BE STRONGEST ALONG THE TURNAGAIN ARM AND
HIGHER ELEVATIONS BUT WILL ALSO AFFECT THE LOWER HILLSIDE AND EAST
ANCHORAGE. ADDITIONALLY...WITH THE GROUND ALREADY SATURATED AND
SEVERAL STREAMS CLOSE TO BANKFULL...LOCAL FLOODING WILL REMAIN
POSSIBLE GIVEN THE ADDITIONAL RAINFALL EXPECTED OVER THE COMING DAYS.

SOUTHWEST ALASKA...
WIDESPREAD RAIN WILL PERSIST INTO THIS EVENING ACROSS BRISTOL BAY AND
THE LOWER KUSKOKWIM VALLEY AS THE SURFACE LOW MOVES INLAND LATER THIS
MORNING JUST WEST OF KODIAK ISLAND AND TRACKS QUICKLY NORTHWARD.
GUSTY WINDS WILL ACCOMPANY THE ARRIVAL OF THE LOW IN THE BRISTOL BAY
REGION.

ALEUTIANS/BERING SEA...
THE LOW PRESSURE SYSTEM CURRENTLY OVER THE WESTERN BERING WILL BRING
RAIN AND GUSTY WINDS TO THE WESTERN AND CENTRAL ALEUTIANS TODAY AND
TONIGHT AS IT DIVES SOUTHWARD. RAIN WILL TAPER OFF TO SHOWERS ON
THURSDAY AS THE SYSTEM MOVES INTO THE NORTHERN PACIFIC.

.LONG TERM FORECAST...
ACTIVE AMPLIFIED PATTERN LOOKS TO CONTINUE THROUGH THE END OF THE
WEEK AS THE BROAD UPPER LEVEL TROUGH REMAINS OVER THE BERING...WITH
PERSISTENT DEEP LAYER SOUTHERLY FLOW KEEPING RAIN IN THE FORECAST
ACROSS MUCH OF THE SOUTHERN MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 125
         FLOOD WARNING 125 131 135
         FLOOD ADVISORY 101 145
MARINE...STORM WARNING 120 125 130
         GALE 132 138 140 150 172 175 176
FIRE WEATHER...NONE

CB SEP 12