Gale Warning 365, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
106 PM AKST TUE NOV 18 2008

.SHORT TERM...A MID LEVEL RIDGE IS CURRENTLY ADVECTING OVER THE
PANHANDLE THIS MORNING. THIS IS ALLOWING FOR ONSHORE FLOW AND
SCATTERED SNOW AND RAIN SHOWERS...MAINLY NORTH OF BARNOF ISLAND.
ALONG THE INNER CHANNELS THE OVERRUNNING HAS BECOME SUFFICIENT IN
DEPTH FOR THE PRECIP IN THE FORM OF PERIODS OF LIGHT SNOW NORTH OF
ANGOON. HOWEVER MOISTURE IS NOT PLENTIFUL IN THE DENDRITE GROWTH
REGION OVER THE CENTRAL PANHANDLE THIS MORNING AND THIS WILL LIMIT
THE ABILITY OF HEAVIER SNOWFALL. INTO THIS AFTERNOON AND EARLY
EVENING THE OVERRUNNING WILL CONTINUE ACROSS THE CENTRAL AND
NORTHERN PANHANDLE WITH LIGHT SNOWFALL AMOUNTS. BUT LATE TONIGHT
THE MID LEVEL SUBSIDENCE WITHIN THE RIDGE WILL DOMINATE LEAVING
ONLY YAKUTAT WITH PERIODS OF LIGHT SNOW. WINDS ARE INCREASING
ALONG THE OUTER COAST WITH SMCR WIND GUSTS AS THE SURFACE PRESSURE
GRADIENT INCREASES OUT OF THE EAST. ALONG THE INNER CHANNELS WINDS
REMAIN STRONGEST IN EAST-WEST ORIENTED CHANNELS WITH GUSTS TO 25
KNOTS. UPDATED THE PACKAGE WITH THE 12Z GFS AS IT INITIALIZED THE
BEST WITH THE DEVELOPING FRONTAL WAVE INTO WEDNESDAY AFTERNOON
ACROSS THE NORTHERN PACIFIC. DID INCORPORATE THE 12Z NAM AND 18Z
WRF IN THE TIMING OF THE OVERRUNNING PRECIP MOVEMENT ACROSS THE
NORTHERN PANHANDLE TONIGHT.

 FOR TONIGHT PERIODS OF LIGHT SNOW WILL CONTINUE NORTH OF ICY
STRAIT AS OVERRUNNING REMAINS FAVORABLE. HOWEVER, SNOW
ACCUMULATIONS ONLY UP TO 1 INCH ARE EXPECTED AS MOISTURE IS
LACKING IN THE DENDRITE GROWTH REGION. THIS AREA OF OVERRUNNING
WILL SHIFT TO THE NORTHWEST DURING THE NIGHT AS THE MID LEVEL
RIDGE AMPLIFIES AND STRENGTHENS AHEAD OF THE UPPER LEVEL LOW IN
THE NORTHERN PACIFIC. EXPECT THE EASTERLY AND NORTHERLY FLOW TO
CONTINUE TO INCREASE INTO TONIGHT WHICH WILL DRY OUT THE MID
LEVELS, SO EXPECT PARTLY CLOUDY SKIES TO SPREAD NORTHWARD ACROSS
THE PANHANDLE BY LATE TONIGHT. THE EASTERLY SURFACE PRESSURE
GRADIENT WILL ALSO INCREASE LATE TONIGHT ACROSS THE PANHANDLE
WITH THE DEVELOPING 1040 MB SURFACE HIGH IN THE YUKON AND EXPECT
GUSTS ALONG EAST-WEST ORIENTED CHANNELS TO REACH 35 KNOTS.

 FOR TOMORROW THE MID LEVEL RIDGE WILL ADVECT INTO THE YUKON
CONTINUING TO STRENGTHEN THE 1040 MB SURFACE HIGH. THIS WILL
ALLOW FOR STRONG CROSS BARRIER FLOW TO DEVELOP AND A STRONG
SURFACE PRESSURE GRADIENT IN NORTHERN LYNN CANAL. EXPECT WIND
ADVY GUSTS NEAR SKAGWAY WITH WIND CHILLS TO -20F NEAR WHITE PASS
AND GALES IN LYNN CANAL WITH FREEZING SPRAY AS WATER TEMPERATURES
CONTINUE TO COOL. THE 12Z VERTICAL MODEL SOUNDINGS NEAR JUNEAU
ALSO INDICATE STRONG CROSS BARRIER FLOW AND AN INVERSION
DEVELOPING JUST ABOVE RIDGE TOP BY THE EARLY AFTERNOON TOMORROW.
WHILE NO CRITICAL LEVEL EXIST NEAR 500MB, WILL HAVE TO WATCH FOR
WIND GUSTS TO 35 MPH TOMORROW OUT OF INTERIOR PASSES NEAR
DOWNTOWN JUNEAU. THE MID LEVEL FRONTAL BAND FROM A DEVELOPING
GALE FORCE LOW IN THE NORTHERN PACIFIC WILL APPROACH THE SOUTHERN
OUTER COAST TOMORROW AFTERNOON AND SO EXPECT LOCALLY WINDY
CONDITIONS NEAR PRINCE OF WALES ISLAND WITH GALES ALONG THE OUTER
COAST. WITH THE STRONG EASTERLY AND NORTHERLY FLOW ACROSS THE
PANHANDLE TOMORROW AND THE DRY AIR AT MID LEVELS EXPECT PARTLY TO
MOSTLY CLOUDY SKIES ACROSS THE MAJORITY OF PANHANDLE AS THERE IS
NOT ENOUGH LIFT IN THE MID AND UPPER LEVELS TO OVERCOME THE DRY
AIR FOR PRECIPITATION.

.LONG TERM...LONG WAVE PATTERN SHOWS PROGRESSIVE 4 WAVE PATTERN
WITH DEEP WAVE OVER EASTERN CHINA AND RIDGING OVER WESTERN BERING
SEA AND ANOTHER LONGWAVE OVER THE CENTRAL GULF OF ALASKA. LONG WAVE
OVER THE CENTRAL GULF OF ALASKA CONTINUES TO SHARPEN AS A
SHORTWAVE ROUNDS THE BOTTOM OF THE TROF AND MOVES ALONG THE BACK
SIDE OF A BUILDING RIDGE ALONG THE WEST COAST. SATELLITE REVEALS A
MULTIPLE LOW PRESSURE CIRCULATIONS IN THE NORTH PACIFIC NEAR 50N
155W CENTRAL GULF OF ALASKA.

MODELS CONTINUE TO HAVE A LARGE SPREAD PAST FRIDAY WITH THE 18/12Z
GFS PROVIDING A CONSOLIDATED 980MB LOW MOVING NORTH ALONG 150W.
18/12Z EC CONTINUES TO SHOW A WEAKER LOW (986MB) FURTHER WEST IN
THE CENTRAL GULF WITH A SIGNIFICANT TROF ROTATING ALONG THE
ALASKA PANHANDLE THURSDAY. THE 18/12Z EC HAS THE PARENT LOW
REMAINING NEARLY STATIONARY AND WEAKENING TO A 995MB LOW IN THE
CENTRAL GULF THROUGH FRIDAY AS A NEW LOW FORMS ALONG THE BASE OF
THE LONG WAVE TROF AND MOVES TOWARDS THE SOUTHERN PANHANDLE. THE
GFS SOLUTION IS MUCH MORE AGGRESSIVE WITH THE PARENT LOW DEEPENING
TO 978MB AND A NEW 980MB LOW APPROACHING THE SOUTHEAST PANHANDLE.
CHOSE TO USE A GFS BLEND IN THE EARLY PERIODS TO MATCH WITH SHORT
TERM GRIDS AND USED A 18/12Z EC BLEND WITH INHERITED GRIDS PAST
DAY 3 TO PRESERVE CONTINUITY IN THE LONG TERM AS CONFIDENCE IN
MODELS PAST DAY 3 IS LOW. WILL CONTINUE WIND ADVISORY FOR ZONE 18
INTO THE LONG RANGE FORECAST PERIOD, BUT HAVE NOT DECIDED FOR HOW LONG.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY AKZ018.
MARINE...GALE WARNING FOR PKZ043-051-052.
SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031-033>036-041-042.

PSS/CCC