Gale Warning 266, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
256 PM AKDT THU SEP 1 2011

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS A WEAKENING LOW
OVER THE EASTERN GULF DRIFTING SE. THERE ARE SOME SCATTERED
SHOWERS MOVING OVER THE SOUTHERN HALF OF THE FORECAST AREA BUT
DECREASING CLOUDS OR PARTLY CLOUDY SKIES OVER THE NORTHERN HALF.
FURTHER WEST A DEVELOPING LOW IS LIFTING OUT OF THE NORTH PACIFIC
AND WILL DRIFT NNE THROUGH TONIGHT TO BE JUST EAST OF KODIAK
ISLAND BY FRIDAY AFTERNOON. WINDS ACROSS THE FORECAST AREA ARE ON
THE LIGHTER SIDE WITH MOST STATIONS REPORTING LESS THAN 15 KT
MAINLY FROM THE SOUTH OVER THE INNER CHANNELS AND WNW OVER THE
EASTERN GULF.

FOR TONIGHT AS THE WEAKENING LOW DISSIPATES AS IT CONTINUES TO
DRIFT SE THROUGH THIS EVENING THE SCATTERED SHOWERS WILL SLOWLY
DIMINISH AS THE UPPER LEVEL DYNAMICS MOVES INTO CANADA. BEHIND THE
LOW A UPPER RIDGE IS BUILDING OVER THE GULF AND PANHANDLE TO
INCREASE NW FLOW ALOFT ADVECTING SOME DRIER AIR AS THE CLOUDS ARE
DECREASING THIS AFTERNOON FROM PAYA THROUGH ICY STRAIT. THE SKIES
WILL REMAIN OR BECOME PARTLY CLOUDY THIS EVENING OVER THE NORTHERN
THIRD BUT AS THE RIDGE DRIFTS EAST THROUGH TONIGHT ONSHORE FLOW
WILL INCREASE AND CLOUDS WILL MOVE BACK OVER THE FORECAST AREA.
WITH PARTLY CLOUDY SKIES OVER THE NORTHERN HALF AND BREAKS IN THE
CLOUD COVER OVER THE SOUTHERN HALF AREAS OF FOG WILL DEVELOP LATE
TONIGHT AS THE GROUND AND BOUNDARY LAYER IS SATURATED FROM THE
RAIN LAST NIGHT.

AS MENTIONED ABOVE THE UPPER RIDGE WILL BEING DRIFTING EASTWARD
THROUGH TONIGHT AS A STRONG UPPER TROF DRIFTING SOUTH FROM THE
BERING WILL PHASE WITH A SHORTWAVE LIFTING OUT OF THE NORTH
PACIFIC THIS EVENING. AS THIS HAPPENS IT WILL CAUSE RAPID
CYCLOGENISIS AND DEEPEN A SURFACE LOW TO 987MB BY LATE TONIGHT AND
BE JUST EAST OF KODIAK ISLAND BY DAY BREAK. THIS LOW WILL REMAIN
NEAR KODIAK THROUGH FRIDAY AFTERNOON AND SLOWLY FILLS SOME AS IT
BECOME VERTICALLY STACKED. A STRONG FRONT ASSOCIATED WITH THE
SURFACE LOW WILL DRIFT ACROSS THE GULF THROUGH FRIDAY TO BE OVER
THE EASTERN GULF BY THE AFTERNOON. PRECIP ASSOCIATED WITH THE
FRONT WILL SPREAD ACROSS THE FORECAST AREA THROUGH THE DAY AS THE
UPPER RIDGE AXIS MOVES PAST THE PANHANDLE TO INCREASE THE ONSHORE
FLOW. ALONG WITH INCREASE ONSHORE FLOW THERE WILL BE STRONG MID-
LEVEL DYNAMICS TO INCREASE PRECIP DEVELOPMENT. BY THE LATE
AFTERNOON MOST OF THE FORECAST AREA WILL SEE RAIN FROM THE THIS
FRONT WITH THE EXCEPTION TO THE MISTY FJORDS AREA AND NEAR PAGY.

THE FRONT WILL INCREASE THE WINDS OVER THE GULF THROUGH FRIDAY AS
IT DRIFTS INTO THE EASTERN GULF. MAX GALES WILL DEVELOP BY MID
AFTERNOON OVER THE NORTHERN GULF AS THE WINDS WILL BE ENHANCED
FROM A BARRIER JET. THE REST OF NE GULF WILL SEE 40KT GALES WITH
SMALL CRAFTS DEVELOPING OVER THE SE GULF. OVER THE INNER CHANNELS
E/W CHANNELS WILL SEE SMALL CRAFT WINDS DEVELOP WITH A STRONG
PRESSURE GRADIENT. OVER N/S CHANNELS WINDS WILL BE LIGHT IN THE
MORNING BUT AS THE SURFACE TROF ASSOCIATED WITH THE FRONT MOVES
INTO THE EASTERN GULF IT WILL SHARPEN THE SURFACE RIDGE OVER THE
INNER CHANNELS AND WINDS WILL INCREASE TO 15-20KT BY THE
AFTERNOON. THE COASTAL LAND AREAS WILL SEE WINDS INCREASE IN THE
AFTERNOON TO BE 15 TO 20 MPH WITH SOME HIGHER GUSTS BUT THE INNER
CHANNEL LAND AREAS WILL SEE WINDS NOT AS STRONG THROUGH FRIDAY
AFTERNOON BUT WILL RANGE FROM 10 TO 15 MPH.

USED A BLEND OF THE NAM/GFS THROUGH FRIDAY AFTERNOON. WITH GOOD
MODEL AGREEMENT THERE IS ABOVE AVERAGE FORECASTER CONFIDENCE.

&&

.LONG TERM...A LONG WAVE TROUGH IS FORECAST TO SET UP ACROSS
WESTERN ALASKA AND PERSIST THROUGH THE LONG TERM. A STRONG UPPER
LEVEL RIDGE IS EXPECTED ACROSS THE PACIFIC NW AND SOUTHERN B.C
THROUGH THE LONG TERM. THIS KEEPS A MODERATE SW JET STREAM ACROSS
THE AREA. A SERIES OF WAVES IN THIS FLOW ARE FORECAST TO LIFT NE
INTO THE GULF AND DEEPEN INTO GALE TO STORM FORCE LOWS THROUGH THE
PERIOD. PRECIP IS EXPECTED TO BE HEAVY AT TIMES THROUGH THE
PERIOD.

NEXT LOW IN SW GULF SATURDAY MORNING MOVES INTO THE CENTRAL GULF
BY SATURDAY AFTERNOON WEAKENING TO AROUND 995 MB. THE ASSOCIATED
FRONT EXITS SE ALASKA SATURDAY MORNING WITH SECOND WRAP SPREADING
ACROSS THE AREA SATURDAY NIGHT. GALES AHEAD OF FRONT DIMINISH TO
SMCR LEVELS BY SATURDAY AFTERNOON AND STAY THERE THROUGH SUNDAY.

NEXT LOW MOVES INTO SW GULF MONDAY AND DEEPENS TO 955 MB JUST
SOUTH OF KODIAK MONDAY AFTERNOON. THE ASSOCIATED STRONG OCCLUSION
MOVES THROUGH EASTERN MONDAY AFTERNOON. A WAVE ALONG THE FRONT JUST
SOUTH OF THE GULF IS FORECAST TO DEEPEN INTO A 972 MB FRONTAL LOW
THAT TRACKS NORTHWARD THROUGH OUR COASTAL WATERS. THIS SHOULD
SUPPORT STORM FORCE EAST WINDS ACROSS THE NORTHERN GULF WITH SOLID
SE GALES THROUGH REMAINDER COASTAL WATERS AND MIN GALES INTO MUCH
OF INNER CHANNELS MONDAY NIGHT. WILL LIKELY NEED WIND ADVISORIES
FOR A LARGE PORTION OF THE PANHANDLE. RAIN WITH THIS SYSTEM WILL
BE HEAVY AT TIMES AND WILL BRING RIVER AND STREAMS TO SEASONABLY
HIGH LEVELS BUT DON'T THINK FLOODING WILL BE AN ISSUE...YET.

A SECOND WAVE LIFTS NORTH ALONG THE FRONT TUESDAY INTO WEDNESDAY
WITH A SECOND ROUND OF MDT-HVY RAIN.

FARTHER OUT WAVES KEEP COMING BUT THERE IS LARGE DISAGREEMENT AND
DISCONTINUITY BETWEEN MODELS ABOUT POSITION OF STRENGTHS OF
INDIVIDUAL WAVES. KEPT RAIN LIKELY AND AT MINIMUM SMCR IN MARINES
THROUGH LATER LONG TERM PERIODS.

LIKED GFS THROUGH ABOUT 120 HRS WITH PARENT LOW IN NW GULF WITH
SECOND STRONG LOW DEVELOPING ALONG FRONT IN EASTERN GULF. BEYOND THIS
PERIOD THERE WAS NO UNIFIED SOLUTION ON INDIVIDUAL WAVES BUT ALL
AGREED SE ALASKA WILL REMAIN IN AN ACTIVE AND WET PATTERN WITH JET
STREAM OVER THE AREA.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-021-022-033-036-041-042-053.

&&

ABJ/MM