Small Craft Advisory 751, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
242 PM AKST SAT DEC 20 2008

.SHORT TERM...
MAP ANALYSIS: HIGH PRESSURE CONTINUES TO DOMINATE WESTERN CANADA
AND NORTHERN ALASKA SATURDAY MORNING. A COMPLEX AREA OF LOW
PRESSURE OVER THE WEST CENTRAL GULF HAS AT LEAST 2 SEPARATE
CENTERS IN IT. THE ASSOCIATED FRONTAL BAND OVER THE NORTHERN AND
EASTERN GULF OF ALASKA IS SHEARING OUT TO A TRIPLE POINT LOW ABOUT
400 NM SOUTHWEST OF THE QUEEN CHARLOTTE ISLANDS AND THIS FEATURE
WILL CONTINUE TO MOVE EASTWARD TO THE PACIFIC NORTHWEST. WINDY
CONDITIONS CONTINUE FROM INTERIOR PASSES DUE TO THE STRONG
PRESSURE GRADIENT. MOSTLY SUNNY TO PARTLY CLOUDY SKIES OVER
PANHANDLE AS CLOUD BANDS ARE MOSTLY OFFSHORE.

FORECAST REASONING: ANOTHER NICE BUT COLD DAY IN STORE FOR
SOUTHEAST ALASKA. THE COMPLEX LOW OVER THE GULF SHOULD
SLIDE/DUMBBELL SOUTHEAST TO MOVE INTO THE BRITISH COLUMBIA REGION
BETWEEN QUEEN CHARLOTTE AND VANCOUVER ISLANDS SUNDAY MORNING. THE
CIRRUS CLOUD DECK THAT IS SPREAD OVER THE PANHANDLE ON SATURDAY
WILL DISSIPATE OR BE PULLED BACK OFF SHORE TONIGHT WITH LOW
SLIDING SOUTH.

TEMPERATURES THE NEXT 24 HOURS SHOULD BE A COUPLE OF DEGREES
WARMER I THINK THAN LAST NIGHT AND TODAY BUT NOT MUCH CHANGE.
EXPECT TO SEE NO PRECIPITATION ACROSS THE AREA THROUGH
SUNDAY...BUT THE WINDY CONDITIONS THROUGH THE INTERIOR PASSES WILL
CONTINUE SO WILL MAINTAIN THE WIND ADVISORIES ALONG THE COAST
MOUNTAINS THROUGH SUNDAY AFTERNOON. WIND CHILL TEMPS OVER THE
NORTHERN PANHANDLE WILL BE IN THE 20 TO 25 BELOW RANGE TONIGHT
AND IN EARLY SUNDAY...JUST BELOW ADVISORY CRITERIA LOE ENOUGH FOR
FREEZING SPRAY THROUGH LYNN CANAL. THE FREEZING SPRAY COULD BE
HEAVY OVER NORTHERN LYNN CANAL SO HEADLINING THAT IN THE MARINE FCSTS.

THROUGH THE SHORT TERM MODELS IN GENERALLY GOOD AGREEMENT WITH
EACH OTHER AND MINIMAL ADJUSTMENT OVER THE LAST COUPLE OF DAYS.
USED THE GEM REGIONAL MODEL AND NAM AS THE PREFERRED SOLUTIONS.
OVERALL CONFIDENCE IN THE HIGH CATEGORY THROUGH SUNDAY. I HELD BACK
ON SOME OF THE WINDS BEING GENERATED BY THE PRESSURE FIELD AS
I THINK THEY WERE EXCESSIVE. MOST CHANGES TO THE PACKAGE WERE
MINIMAL I BELIEVE.

&&

.LONG TERM... GLOBAL MODELS SHOW A THREE WAVE PATTERN ACROSS
NORTHERN HEMISPHERE. COLD AIR TROUGHS ARE SITUATED THIS WEEKEND OVER
CENTRAL CANADA AND SIBERIA WHILE A DRY RIDGE LIES BETWEEN THEM
OVER AK. MODELS SHOW THE CANADIAN TROUGH WILL BE RETORGRADING WWD
DURING THE EXTENDED FORECAST RANGE BUT THE SIBERIAN TROUGH HOLDS
STEADY. AS A RESULT THIS RATHER FLAT TROUGH-RIDGE-TROUGH PATTERN
WILL SHARPEN AND AMPLIFY WITH THE RIDGE SHIFTING SLIGHTLY WWD FROM
AK TO OVER THE BERING SEA AND N PACIFIC JUST E OF DATELINE. HPC
DISCUSSIONS HIGHLIGHT MODEL VARIANCE THAT GROWS STARTING TUE AND I
AGREE FAVORING BLENDED ENSEMBLE SOLUTIONS OF GFS ECMWF AND GEM
MODELS FOR THE MED AND LONG RANGE FORECAST PERIODS IS WAY TO GO
FOR NOW. BUT FORECASTER CONFIDENCE IS GROWING WITH THE IDEA OF DRY
WEATHER CONTINUING OVER PANHANDLE UNTIL TUE-WED. SHORT WAVES
EJECTING OUT OF ASIAN TROUGH WILL MOVE THROUGH THE N PAC RIDGE
EARLY IN WEEK...WEAKEN...AND TURN SE ACROSS GULF OF AK MID WEEK.
THIS OVER WATER TRAJECTORY IS MUCH DIFFERENT THAN CURRENT PATTERN
AND SHOULD HELP TEMPS MODIFY UPWARD A BIT DURING THE UPCOMING
WEEK. THE JET CORE STAYS S OF OUR FORECAST AREA WHICH MEANS
PROBABLY NO DIRECT HITS FROM APPROACHING SHORT WAVES.
HOWEVER...PLUMES OF HIGHER EQUIVALENT POTENTIAL TEMP...MEANING
HIGHER MOISTURE CONTENT IN AIR... LEAD ME TO BELIEVE CLOUDY SKIES
AND INCREASED CHANCES OF PRECIP WILL SPREAD OVER THE PANHANDLE
TUE-WED AND AGAIN ABOUT FRI. IF FLOW INTO SE AK ENDS UP BEING MORE
MOIST THAN IS CURRENTLY PREDICTED THERE IS POTENTIAL FOR LOCALLY
SIGNIFICANT SNOWFALLS NORTHERN INNER CHANNELS WHERE COLD AIR MAY
BE SLOW TO SCOUR OUT. FOR NOW WE WILL STAY THE COURSE WITH
EXTENDED FORECAST TRENDING TOWARD PERIODS OF SNOW MID TO LATE NEXT
WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 4 PM AKST SUNDAY FOR AKZ018-019-025-026-029.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011-012.
         GALE WARNING FOR PKZ011-012-022-036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ013-021-031>035-043-051-052.

&&

BEZENEK/AINSWORTH