Flood Watch 4, NWS Anchorage, AK

812 
WGAK68 PAFC 151342 CCA
FFAAFC

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
536 AM AKDT SAT SEP 15 2012

AKZ125-161100-
/X.COR.PAFC.FA.A.0004.120916T0300Z-120917T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
WESTERN PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...WHITTIER...SEWARD...GIRDWOOD...
MOOSE PASS
536 AM AKDT SAT SEP 15 2012

...FLOOD WATCH IN EFFECT FROM THIS EVENING THROUGH SUNDAY
AFTERNOON...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A

* FLOOD WATCH FOR WESTERN PRINCE WILLIAM SOUND.

* FROM THIS EVENING THROUGH SUNDAY AFTERNOON

* MODELS SHOW WIDESPREAD AREAS OF 4 TO 7 INCHES OF RAINFALL WITH
  SOME AREAS IN THE MOUNTAINS SHOWING AMOUNTS GREATER THAN 9
  INCHES FOR THE 24 HOUR PERIOD ENDING SUNDAY EVENING. STREAMS AND
  RIVERS IN THE AREA DRAINING INTO PRINCE WILLIAM SOUND AND IN THE
  SEWARD AREA WILL RISE RAPIDLY TO BANK FULL LEVELS AND FLOODING IS
  POSSIBLE. RECENT COOL WEATHER HAS CAUSED GLACIAL STREAMS TO FALL
  SIGNIFICANTLY BUT SMALL STREAMS WILL RESPOND VERY RAPIDLY TO THE
  EXPECTED RAINFALL AMOUNTS.

* IMPACTS...SMALL STREAMS WILL RISE RAPIDLY AND MAY EXCEED BANK
  FULL LEVELS. MINOR FLOODING AND URBAN DRAINAGE PROBLEMS ARE
  LIKELY. IF EXPECTED PRECIPITATION AMOUNTS ARE EXCEEDED...MODERATE
  TO MAJOR FLOODING COULD OCCUR. SOME LOCATIONS MAY SEE SITUATIONS
  WHERE GRAVEL AND SEDIMENT DEPOSITS ON STREAM BEDS HAVE RAISED
  THE CHANNEL BOTTOM...LEADING TO FLOODING AS STREAM CAPACITY IS
  EXCEEDED MORE QUICKLY THAN IN THE PAST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING.

YOU ARE ENCOURAGED TO CLOSELY MONITOR THIS WEATHER SITUATION.
PREPARATION FOR THIS POTENTIALLY DANGEROUS WEATHER EVENT SHOULD
BEGIN NOW.

&&

$$

AKZ131-161100-
/X.COR.PAFC.FA.A.0004.120916T0300Z-120917T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NORTHEAST PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...VALDEZ...THOMPSON PASS
536 AM AKDT SAT SEP 15 2012

...FLOOD WATCH IN EFFECT FROM THIS EVENING THROUGH SUNDAY
AFTERNOON...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A

* FLOOD WATCH FOR NORTHEAST PRINCE WILLIAM SOUND.

* FROM THIS EVENING THROUGH SUNDAY AFTERNOON

* MODELS SHOW WIDESPREAD AREAS OF 4 TO 7 INCHES OF RAINFALL WITH
  SOME AREAS IN THE MOUNTAINS SHOWING AMOUNTS GREATER THAN 9
  INCHES FOR THE 24 HOUR PERIOD ENDING SUNDAY EVENING. STREAMS AND
  RIVERS IN THE AREA DRAINING INTO PRINCE WILLIAM SOUND AND IN THE
  SEWARD AREA WILL RISE RAPIDLY TO BANK FULL LEVELS AND FLOODING IS
  POSSIBLE. RECENT COOL WEATHER HAS CAUSED GLACIAL STREAMS TO FALL
  SIGNIFICANTLY BUT SMALL STREAMS WILL RESPOND VERY RAPIDLY TO THE
  EXPECTED RAINFALL AMOUNTS.

* IMPACTS...SMALL STREAMS WILL RISE RAPIDLY AND MAY EXCEED BANK
  FULL LEVELS. MINOR FLOODING AND URBAN DRAINAGE PROBLEMS ARE
  LIKELY. IF EXPECTED PRECIPITATION AMOUNTS ARE EXCEEDED...MODERATE
  TO MAJOR FLOODING COULD OCCUR. SOME LOCATIONS MAY SEE SITUATIONS
  WHERE GRAVEL AND SEDIMENT DEPOSITS ON STREAM BEDS HAVE RAISED
  THE CHANNEL BOTTOM...LEADING TO FLOODING AS STREAM CAPACITY IS
  EXCEEDED MORE QUICKLY THAN IN THE PAST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING.

YOU ARE ENCOURAGED TO CLOSELY MONITOR THIS WEATHER SITUATION.
PREPARATION FOR THIS POTENTIALLY DANGEROUS WEATHER EVENT SHOULD
BEGIN NOW.

&&

$$

AKZ135-161100-
/X.COR.PAFC.FA.A.0004.120916T0300Z-120917T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SOUTHEAST PRINCE WILLIAM SOUND-
INCLUDING THE CITY OF...CORDOVA
536 AM AKDT SAT SEP 15 2012

...FLOOD WATCH IN EFFECT FROM THIS EVENING THROUGH SUNDAY
AFTERNOON...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A

* FLOOD WATCH FOR SOUTHEAST PRINCE WILLIAM SOUND.

* FROM THIS EVENING THROUGH SUNDAY AFTERNOON

* MODELS SHOW WIDESPREAD AREAS OF 4 TO 7 INCHES OF RAINFALL WITH
  SOME AREAS IN THE MOUNTAINS SHOWING AMOUNTS GREATER THAN 9
  INCHES FOR THE 24 HOUR PERIOD ENDING SUNDAY EVENING. STREAMS AND
  RIVERS IN THE AREA DRAINING INTO PRINCE WILLIAM SOUND AND IN THE
  SEWARD AREA WILL RISE RAPIDLY TO BANK FULL LEVELS AND FLOODING IS
  POSSIBLE. RECENT COOL WEATHER HAS CAUSED GLACIAL STREAMS TO FALL
  SIGNIFICANTLY BUT SMALL STREAMS WILL RESPOND VERY RAPIDLY TO THE
  EXPECTED RAINFALL AMOUNTS.

* IMPACTS...SMALL STREAMS WILL RISE RAPIDLY AND MAY EXCEED BANK
  FULL LEVELS. MINOR FLOODING AND URBAN DRAINAGE PROBLEMS ARE
  LIKELY. IF EXPECTED PRECIPITATION AMOUNTS ARE EXCEEDED...MODERATE
  TO MAJOR FLOODING COULD OCCUR. SOME LOCATIONS MAY SEE SITUATIONS
  WHERE GRAVEL AND SEDIMENT DEPOSITS ON STREAM BEDS HAVE RAISED
  THE CHANNEL BOTTOM...LEADING TO FLOODING AS STREAM CAPACITY IS
  EXCEEDED MORE QUICKLY THAN IN THE PAST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING.

YOU ARE ENCOURAGED TO CLOSELY MONITOR THIS WEATHER SITUATION.
PREPARATION FOR THIS POTENTIALLY DANGEROUS WEATHER EVENT SHOULD
BEGIN NOW.

&&

$$

RMC

105 
WGAK68 PAFC 160003
FFAAFC

FLOOD WATCH
NATIONAL WEATHER SERVICE ANCHORAGE AK
403 PM AKDT SAT SEP 15 2012

AKZ125-131-135-160115-
/X.CAN.PAFC.FA.A.0004.120916T0300Z-120917T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
WESTERN PRINCE WILLIAM SOUND-NORTHEAST PRINCE WILLIAM SOUND-
SOUTHEAST PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...WHITTIER...SEWARD...GIRDWOOD...
MOOSE PASS...VALDEZ...THOMPSON PASS...CORDOVA
403 PM AKDT SAT SEP 15 2012

...FLOOD WATCH IS CANCELLED THROUGH SUNDAY AFTERNOON...

THE FLOOD WATCH FOR A PORTION OF AK HAS BEEN CANCELLED. 

$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT FRI SEP 14 2012

.ANALYSIS AND UPPER LEVELS...
A FAIRLY ZONAL WESTERLY FLOW EXISTS AT THE MOMENT ACROSS THE GREAT
LAND. SEVERAL EMBEDDED DISTURBANCES ARE PROPAGATING THROUGH THE FLOW.
THE FIRST WEAK TROUGH IS SPREADING MID LEVEL CLOUDS AND ISOLATED
SHOWERS OVER A GOOD PORTION OF THE SOUTH CENTRAL. THE NEXT
DISTURBANCE CURRENTLY SITS OVER THE SOUTHWEST INTERIOR WITH A WEAK
SURFACE REFLECTION. FURTHER OUT WEST A COUPLE FEATURES OF INTEREST
ARE TAKING SHAPE WITH HUGE FORECAST IMPLICATIONS. THE FIRST...A
POTENT SHORTWAVE ASSOCIATED WITH A LOW LEVEL BAROCLINIC ZONE ORIENTED
FROM WEST TO EAST OVER THE NORTH CENTRAL PACIFIC. THE SECOND...A DEEP
COLD CORE UPPER LOW DIGGING SOUTHWARD OVER THE WESTERN BERING THIS
MORNING.

.MODEL DISCUSSION...
GUIDANCE COMING TOGETHER ON A SOLUTION FOR THE IMPENDING STRONG LOW
THIS WEEKEND. SOME SPREAD STILL EXISTS AS FAR AS STRENGTH AND
POSITION OF THE LOW THE GENERAL CONSENSUS AMONG THE MODELS IS A
STRONG SUB-985 MB LOW DEVELOPING OVER THE ALASKAN PENINSULA LATE
SATURDAY NIGHT. THE NAM/GFS HAVE BEEN SHOWING A MORE NEGATIVELY
TILTED TROUGH AND HENCE SLOWER SOLUTION WHILE THE ECMWF/GEM A MORE
NEUTRAL TILT AND FASTER SOLUTION THAT DEEPENS AS IT MOVES INLAND.
BOTH THE 00Z RUNS OF THE ECMWF/GEM HAVE TRENDED MORE TOWARD THE
AMERICAN MODELS WITH RESPECT TO TROUGH ORIENTATION AND SUBSEQUENT
SURFACE DEVELOPMENT THOUGH BOTH ARE STILL QUICKER MOVING THE LOW INTO
THE SOUTHWEST INTERIOR. THE 12Z RUNS TODAY SHOULD BE VERY TELLING ON
THE EVOLUTION OF THE SYSTEM.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...A WEAK DISTURBANCE ALOFT IS FORCING ISOLATED
SHOWERS THIS MORNING IN THE MATANUSKA AND SUSITNA VALLEYS. AS THE
SECOND DISTURBANCE ALOFT MOVES UP COOK INLET TODAY THESE SHOWERS WILL
GIVE WAY TO A MORE WIDESPREAD RAIN IN MOST AREAS. THE BEST CHANCE FOR
STEADY RAIN LIES IN THE SUSITNA VALLEY AND NORTH GULF COAST
AREAS...THE ANCHORAGE BOWL...WESTERN KENAI PENINSULA...AND COPPER
RIVER BASIN WILL SEE PERIODS OF DOWNSLOPING OFF THE TERRAIN AND
DRYING. THIS WEEKEND A VERY STRONG LOW MOVING INTO THE SOUTHWESTERN
MAINLAND WILL BRING A SURGE OF WARM AIR AND MOISTURE TO THE SOUTH
CENTRAL ALONG WITH VERY STRONG SOUTHEASTERLY WINDS. THE EXTENT OF
THESE WINDS WILL BECOME MOVE CLEARER AS THE SITUATION
PROGRESSES...BUT TURNAGAIN ARM AND HIGHER ELEVATIONS WILL SEE THE
STRONGEST WINDS THOUGH THERE IS SOME UNCERTAINTY WHETHER THEY WILL
REACH THE LOWER ELEVATIONS OF THE ANCHORAGE BOWL AT THIS POINT.

SOUTHWEST ALASKA...SCATTERED SHOWERS EARLY THIS MORNING WILL TURN
INTO A MORE WIDESPREAD RAIN TODAY...MAINLY EAST OF THE KILBUCK
MOUNTAINS...AS A DISTURBANCE ALOFT MOVES INLAND ALONG WITH AN
OCCLUDED FRONT THAT WILL EVENTUALLY STALL AND DISSIPATE. AS THE FIRST
DISTURBANCE ROTATES TO THE NORTH AND SHEARS APART A NEW SYSTEM BEGINS
TO TAKE SHAPE JUST SOUTH OF THE ALASKAN PENINSULA THIS WEEKEND. A
COMPACT POTENT SHORTWAVE TROUGH IN THE NORTH PACIFIC LOOKS TO PHASE
WITH AN INCOMING COLD CORE UPPER LOW CURRENTLY DROPPING OVER THE
WESTERN BERING SEA. THE SYSTEM WILL BRING WIDESPREAD RAIN TO THE
WHOLE MAINLAND AS WELL AS STRONG WINDS.

BERING SEA AND ALEUTIANS...A COLD CORE UPPER LOW WILL BRING SCATTERED
TO NUMEROUS SHOWERS TO THE WESTERN AND CENTRAL CHAIN TODAY. AS THIS
LOW MERGES WITH A DISTURBANCE OVER THE NORTHERN PACIFIC MORE
WIDESPREAD RAIN AND GUSTY SOUTHERLY WINDS WILL DEVELOP...MAINLY FOR
THE EASTERN CHAIN. A FRONT WILL MOVE FROM WEST TO EAST OVER THE
WESTERN CHAIN OVER THE WEEKEND BRINGING ANOTHER ROUND OF RAIN.

.LONG TERM FORECAST...
THE EXTENDED PATTERN LOOKS TO BE VERY HIGH AMPLITUDE WITH A STOUT
NORTHEASTERN PACIFIC RIDGE BUILDING. GENERAL TROUGHING OVER THE
BERING WITH UPPER LOW CENTERS DROPPING SOUTHWARD OVER THE WESTERN
BERING WILL LEAVE MUCH OF MAINLAND ALASKA IN A DEEP LAYER SOUTHWEST
FLOW WHICH IS VERY CONDUCIVE FOR WIDESPREAD PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 101 125
MARINE...GALE 130 132 138 150 176 179
FIRE WEATHER...NONE

MTL SEP 12