Small Craft Advisory 504, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
418 PM AKDT FRI SEP 7 2012

.SHORT TERM...A GALE FORCE LOW PRESSURE SYSTEM IS MOVING INTO
THE NORTHEAST GULF THIS AFTERNOON. THE LOW HAS GRADUALLY
STRENGTHENED THROUGH THE DAY WITH FAVORABLE UPPER LEVEL SUPPORT
FROM A 120 KT JET. THE LOW WILL RAPIDLY WEAKEN AS IT MAKES
LANDFALL NEAR YAKUTAT THIS EVENING AND DISSIPATES OVER THE
SOUTHWESTERN YUKON. GALE FORCE GUSTS HAVE BEEN REPORTED AT BUOY
46083 WITH MAX SMALL CRAFT WINDS OF 30 KT IN THE EASTERN PORTIONS
OF MARINE ZONE 51. AS THE LOW APPROACHES THE COAST...WINDS WILL
INCREASE ACROSS THE MARINE AND LAND AREAS IN THE NORTHERN
PANHANDLE. SMALL CRAFT CONDITIONS WILL BE FELT IN CROSS SOUND AND
NORTHERN LYNN CANAL THROUGH EARLY EVENING. WINDS ACROSS THE
OUTSIDE COASTAL LOCATIONS WILL RAPIDLY DIMINISH THIS EVENING IN
THE VICINITY OF THE LOW AND FLIP TO THE SOUTHWEST AS THE FRONTAL
BOUNDARY PUSHES THROUGH.

 SATELLITE IMAGERY SHOWS A VERY WELL DEFINED ATMOSPHERIC RIVER
AND STRONG SOUTHWESTERLY WINDS IN THE 1000-850 MB LAYER
TRANSPORTING AMPLE TROPICAL MOISTURE INTO THE REGION.
PRECIPITABLE WATER VALUES WITHIN THIS PLUME OF MOISTURE ARE
150 TO 200 PERCENT ABOVE NORMAL. THIS WILL RESULT IN HEAVY
RAINFALL AT TIMES FOR THE NORTHERN INNER CHANNELS THIS EVENING
BEFORE SHIFTING TO THE SOUTH AND EAST ON SATURDAY. RAINFALL
AMOUNTS WILL LIKELY REACH BETWEEN .75 TO 1.50 INCHES THROUGH
TOMORROW AFTERNOON WITH THE HEAVIEST AMOUNTS IN ZONE 26. AM
EXPECTING TO SEE A NOTICEABLE RISE IN RIVERS AND STREAMS WITH
THIS FIRST ROUND OF RAINFALL...HOWEVER DO NOT FOR SEE ANY HYDRO
CONCERNS AT THIS TIME THROUGH SATURDAY AFTERNOON.

 THE FRONTAL BOUNDARY WILL REMAIN NEARLY STATIONARY OVER THE
CENTRAL AND SOUTHERN PANHANDLE SATURDAY FOCUSING THE RAINFALL.
THE JUNEAU AREA AND NORTHWARD WILL SEE A BRIEF BREAK IN THE
STEADY RAIN THE FIRST HALF OF THE DAY. A SECOND LOW PRESSURE
SYSTEM MOVING EAST INTO THE SOUTH CENTRAL GULF AND A FRONTAL WAVE
LIFTING NORTH WILL ENHANCE RAINFALL OVER THE SOUTH. RAIN WILL
AGAIN BE ON THE INCREASE OVER THE NORTHERN PANHANDLE LATER
SATURDAY AFTERNOON AS THIS OCCURS. WINDS WILL ALSO INCREASE WITH
THE APPROACH OF THE WAVE IN THE SOUTHERN INNER CHANNEL SATURDAY
MORNING INTO THE AFTERNOON.

 USED MAINLY THE GFS THROUGH TONIGHT AS LIKED ITS HANDLING OF THE
LOW TRACK. DID BLEND IN A BIT OF UKMET TO LOWER THE PRESSURE A
COUPLE MILLIBARS. THE LATTER PORTION OF THE FORECAST WAS AN EQUAL
BLEND OF THE GFS/EC AS THE NEXT LOW DROPS INTO THE SOUTH CENTRAL
GULF. FORECASTER CONFIDENCE IS ABOVE AVERAGE TONIGHT BEFORE
DECREASING SLIGHTLY WITH THE HANDLING OF THE NEXT LOW.

.LONG TERM...THE LONG TERM MODELS ARE IN GOOD AGREEMENT IN THE MID
RANGE WITH THE UPPER LOW OVER THE GULF SAT AFTERNOON AND DRIFTING
EAST TO BE OVER THE FORECAST AREA BY SUNDAY. THERE IS SOME MINOR
DIFFERENCES AT THE SURFACE WITH WAVE/LOW DEVELOPMENT SAT NIGHT
INTO SUNDAY BUT THE OVER ALL MESSAGE IS THAT IT IS GOING TO RAIN.
THE RAIN WILL BE HEAVY AT TIMES OVER THE SOUTHERN HALF OF THE AREA
WITH A STRONG ATMOSPHERIC RIVER(AR) POINTED AT SE AK. THIS AR
WILL CONTINUE TO PRODUCE HEAVY RAIN INTO SUN DAY BUT AS THE COLD
FRONT DRIFTS EAST OF THE AREA AS THE UPPER LOW MOVES OVER THE AREA
SHOWERS WILL MOVE OVER THE PANHANDLE. THE UPPER LOW WILL DRIFT
INTO CANADA THROUGH SUNDAY NIGHT AND THE SHOWERS WILL SLOWLY
DIMINISH FROM NW TO SE WITH SHOWERS PERSISTING OVER THE FAR
SOUTHERN AREAS INTO MONDAY. THE NORTHERN AREAS WILL SEE THE
SHOWERS BECOME SCATTERED TO ISOLATED THROUGH MONDAY AS A FLAT
RIDGE MOVES OVER THE GULF.

WIND WISE...THE WINDS WILL INCREASE TO SMALL CRAFT OVER THE
SOUTHERN HALF SAT NIGHT AS THE WAVE MOVES INTO THE SE GULF AND
INCREASES THE PRESSURE GRADIENT. AS THE WAVE MOVES NORTH A RIDGE
WILL BUILD BEHIND THIS AND INCREASE THE WINDS FROM THE SOUTH TO
20KT FROM JUNEAU SOUTHWARD. THE NORTHERN AREAS WILL SEE LIGHT
NORTH WINDS SAT NIGHT BUT THERE MAYBE A TIME OF SOUTH WINDS 10 TO
15 MPH BUT AS THE MAIN LOW MOVES OVER THE SOUTHERN AREAS AND
SLOWLY DRIFTS NORTH THE WINDS WILL BACK AROUND TO THE NORTH SUN
INTO MON.

MID TO LATE NEXT WEEK WILL BE ON THE WET SIDE FOR SE AK AS A UPPER
AND SURFACE LOW WILL MOVE OUT OF THE BERING AND INTO THE GULF BY
WED AND DRIFT INTO THE EASTERN GULF LATE WEEK. THE UPPER LOW WILL
DIG INTO THE NORTH PACIFIC AND TAP INTO SUB TROPICAL MOISTURE THAT
WILL PRODUCE ANOTHER "AR". THIS AR MAY PRODUCE HEAVY RAIN AND
LATER SHIFTS WILL NEED TO KEEP AN EYE ON THIS AND LOCAL HYDRO
CONDITIONS. THERE IS SOME DIFFERENCES IN THE DETAILS BUT THERE IS
ABOUT AVERAGE FORECASTER CONFIDENCE.

USED A BLEND OF THE GFS/EC FOR THE MID TERM AND THEN HPC FOR THE
EXTENDED PERIODS. THE LARGEST CHANGES WAS TEMPS MID NEXT WEEK
WITH THE WARM AR.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ043.
         SMALL CRAFT ADVISORY FOR PKZ011-012-021-022-033-041-042-051-052.

&&

TPS/ABJ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
540 PM AKDT FRI SEP 07 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0447 PM     HEAVY RAIN       ELFIN COVE              58.19N 136.34W
09/07/2012  M1.30 INCH                          AK   CO-OP OBSERVER

            HEAVY RAIN IN ELFIN COVE. IN TWO HOURS 1.30 INCHES OF
            RAIN FELL. THREE UNNAMED CREEKS JUMPED BANKS BUT NO
            STRUCTURES WERE IMPACTED. NO REPORTED DAMAGE OR INJURIES.
            SPOTTER BAILED OPEN SKIFF THREE TIMES TO PREVENT SINKING.
            SPOTTER INDICATED THE BIGGEST DANGER TO HEAVY RAIN WAS
            THE POSSIBILITY OF LOSING UNATTENDED BOATS. SATELLITE
            INTERNET/TV GONE DURING STORM.

&&

JWA