Small Craft Advisory 524, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
421 PM AKDT FRI SEP 14 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER CLOUDY SKIES WITH SOME BREAKS STARTING TO DEVELOP OVER THE
SOUTHERN AREAS. THERE IS RAIN OVER THE NORTHERN GULF COAST FROM A
WEAK SURFACE TROF MOVING OVER THE AREA. THERE IS ALSO AN UPPER
LEVEL SHORTWAVE THAT IS PRODUCING SOME SHOWERS OVER THE COAST
MOUNTAIN RANGE WITH SCATTERED SHOWERS SEEN ON CAMERAS OVER THE
REST OF THE INNER CHANNELS. WINDS ARE GENERALLY LESS THAN 15 MPH
OVER LAND WITH SOME WINDIER CONDITIONS OVER THE FAR NORTHERN INNER
CHANNELS THAT WILL PERSIST THROUGH TONIGHT. THE MARINE WATERS ARE
MOSTLY FROM THE SE 15 KT OR LESS BUT THERE IS A SMALL CRAFT ADVY
FOR NORTHERN LYNN FROM THE BUILDING RIDGE OVER THE INNER CHANNELS.
THESE SMALL CRAFT WINDS WILL PERSIST AND INCREASE SOME DUE THE
RIDGE SHARPENING UP MORE THROUGH SAT.

AS MENTIONED ABOVE A SHORTWAVE TROF WILL LIFT OVER THE NORTHERN
AREAS THIS EVENING AS THE UPPER RIDGE CONTINUES TO BUILD OVER THE
REGION THROUGH SAT AFTERNOON. AS WITH THE UPPER RIDGE THE SURFACE
RIDGE WILL ALSO STRENGTHEN TO INCREASE THE SOUTH WINDS OVER THE
MARINE WATERS TO RANGE FROM 15 TO 30 KT WITH THE STRONGEST OVER
NORTHERN LYNN FROM THE SOUTH. THE EXCEPTION TO THIS WILL BE OVER
THE FAR SOUTHERN THIRD OVER THE FORECAST AREA AS THEY WILL SEE
GENERALLY LIGHT WINDS TO 10 KT BUT WITH THE RIDGE BUILDING OVER
THE AREA THE FLOW WILL BE FROM THE NW DUE TO GRADIENT AND
CHANNELED FLOW. ONCE THAT SHORT WAVE TROF LIFTS THROUGH THE AREA
AND INTO CANADA BY LATE TONIGHT THE SHOWERS OVER THE NORTHERN
AREAS WILL DIMINISH AND BECOME MORE SCATTERED. THE SOUTHERN HALF
WILL SEE THE SCATTERED SHOWERS DIMINISH ALL TOGETHER THIS EVENING
WITH STRONGER ANTICYCLONIC FLOW. THIS SUBSIDENCE WILL ALSO HELP
TO BREAK UP THE CLOUD COVER OVER THIS AREA THROUGH SAT AND THERE
WILL BE SOME SUNNY BREAKS BY THE LATE MORNING. TEMPS OVER THE
SOUTHERN AREAS WILL CLIMB INTO THE LOWER 60S TO BE NEAR NORMAL
HIGHS FOR THIS TIME OF YEAR. THE NORTHERN HALF REMAINS TO SEE BELOW
NORMAL TEMPS DUE TO CLOUD COVER AND COOLER 850MB TEMPS.

THE NORTHERN GULF COAST WILL CONTINUE TO SEE STEADY RAIN DUE TO
PERSISTENT SW FLOW FROM ALL LEVELS.

THERE IS ABOUT AVERAGE FORECASTER CONFIDENCE THROUGH THE NEXT
24HRS AND USED A BLEND OF THE NAM/EC FOR THE SHORT TERM PERIOD.

&&

.LONG TERM...SATURDAY NIGHT A LOW PRESSURE SYSTEM OVER SW ALASKA AND
ITS ASSOC FRONT WILL MOVE INTO THE GULF. THIS WILL INCREASE
RAINFALL OVER THE YAKUTAT AREA WITH RAIN LIKELY OVER THE NORTHERN
PANHANDLE. THE TIGHT GRADIENT WITH LOW AND THE RIDGE OVER THE
PANHANDLE WILL RESULT IN STRONG WINDS OVER THE NORTHERN CENTRAL
GULF ALONG THE FRONT. A BARRIER JET WILL SET UP WITH WINDS OF
40-45KT IN OUTSIDE MARINE ZONE 52 AND 50+KT WINDS SLIGHTLY TO THE
WEST IN THE ANCHORAGE AOR. THESE STORM FORCE WINDS MAY EXTEND INTO
52 AS WELL ON SUNDAY BUT HAVE LIMITED THEM TO MAX GALE FOR NOW.

THE UPPER LEVEL LOW WILL MOVE INTO THE WESTERN GULF AND WORK TO
PUSH THE UPPER LEVEL RIDGE OVER THE PANHANDLE OFF TO THE EAST.
THIS WILL INCREASE ONSHORE FLOW AND ALLOW THE FRONT TO CONTINUE
ITS EASTWARD PROGRESSION WITH RAIN BECOMING HEAVY AT TIMES IN
THE YAKUTAT AREA SUNDAY NIGHT. UPPER LEVEL ONSHORE FLOW CONTINUES
MONDAY WITH RAIN LIKELY ALONG THE COASTAL MOUNTAINS AS THE FRONT
MOVES THROUGH THEN A BROAD RIDGE DEVELOPS OUT OF THE NORTH
PACIFIC GOING INTO TUESDAY.

THE UPPER LEVEL RIDGE BUILDS NORTH OVER THE EASTERN GULF THROUGH
WEDNESDAY AND KEEPS THE SOUTHERN PANHANDLE UNDER PARTLY CLOUDY SKIES.
OVERALL FLOW ACROSS THE NORTHERN HALF OF THE REGION WILL BE
ONSHORE...AND KEEP SOME MORE CLOUDS AROUND AND SLIGHT CHANCES OF
RAIN IN THE FORECAST.

MODELS WERE IN GOOD AGREEMENT THROUGH THE EXTENDED FORECAST. USED
MAINLY THE ECMWF AND NAM12 FOR THEIR FINER DETAILS ALONG WITH SOME
UK MET IN THE SHORTER TERM AND TRANSITIONED TO HPC FOR LATER
PERIODS. FORECASTER CONFIDENCE IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051.

&&

ABJ/HANNON