Small Craft Advisory 27, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST WED JAN 10 2007

.SYNOPSIS...
.SHORT RANGE...LATEST SATELLITE IMAGES DEPICT A STRONG ARCTIC
HIGH OVER NORTHWESTERN CANADA.  AN UPPER LEVEL RIDGE IS SLOWLY
EDGING EASTWARD ACROSS THE CENTRAL GULF.  TO THE WEST A FRONTAL
SYSTEM IS FOLLOWING BEHIND THE RIDGE AXIS.  AN ASSOCIATED BAND OF
CLOUDS IS CREEPING INTO ZONE 17 THIS MORNING.  ACROSS THE
PANHANDLE MOSTLY SUNNY SKIES AND COLD TEMPERATURES ARE THE RULE.
STRONG OUTFLOW WINDS CONTINUE ALONG THE EASTERN INNER CHANNELS.
ADVISORY LEVEL WINDS ALSO CONTINUE IN NORTHERN LYNN CANAL. THE
ARCTIC BOUNDARY HAS DROPPED SOUTH OF THE FORECAST AREA WITH
DEWPOINTS AND TEMPERATURES TRENDING COLDER IN THE SOUTH.

MODEL DISCREPANCIES ARE SHOWING UP WITH THE LATEST 12Z RUN AS WE
HEAD INTO TONIGHT (WED NIGHT) AND TOMORROW (THU).  THE GFS AND
UKMET ARE THE MOST AGGRESSIVE SOLUTIONS IN BOTH THE STRENGTH AND
TIMING OF BRINGING THE AFOREMENTIONED FRONT INTO THE FORECAST
AREA.  THE MORE AGGRESSIVE SOLUTION PRODUCES A MORE AMPLIFIED
TROF IN THE NORTHERN GULF WHICH IT SWINGS NORTHWARD INTO THE
NORTHEASTERN GULF BEGINNING FRIDAY NIGHT.  THE NAM MEANWHILE LAGS
BEHIND THE GFS A GOOD 6 HOURS WITH A FLATTER AND MORE NORTH TO
SOUTH ORIENTED TROF. RIGHT NOW...WITH NO REAL DEFINITE SOLUTION
STANDING OUT...HAVE OPTED TO GO WITH A MODEL BLEND BETWEEN THE
GFS AND NAM IN ORDER TO STICK TO THE MIDDLE GROUND.

AS FAR PRECIPITATION IS CONCERNED...THERE WILL BE COPIOUS COLD
AND DRY AIR IN PLACE THROUGH THE SHORT TERM.  THE EASTWARD
SHIFTING UPPER RIDGE WILL START TO ADVECT A WARMER AND MORE MOIST
AIRMASS INTO THE AREA BEGINNING TOMORROW.  MODELS SUGGEST SOME
LIGHT SNOW/FLURRIES MOVING INTO PAYA TOMORROW THEN SPREADING INTO
THE NORTHERN PANHANDLE TOMORROW NIGHT (THU NIGHT).
ADDITIONALLY...A DECK OF LOW STRATUS ADVANCING ACROSS THE EASTERN
GULF THURSDAY AND MOVING INTO THE INNER CHANNELS THURSDAY SEEMS
REASONABLE GIVEN THE WARM AND MOIST AIR SPREADING EASTWARD.

.LONG RANGE...THERE CONTINUES TO BE CONSIDERABLE SPREAD IN
ENSEMBLE SOLUTIONS FOR THE WEEKEND WHICH IS ALSO EVIDENT IN THE
CYCLE TO CYCLE SWINGS OF THE OPERATIONAL MODEL RUNS. MOST OF THE
UNCERTAINTY CONCERNS THE INTENSITY AND SPEED OF SHORTWAVES THAT
FOLLOW THE UPPER LEVEL LONGWAVE RIDGE TILTING NE/SW EARLY FRI
FROM JUST EAST OF THE PANHANDLE SOUTHWESTWARD INTO THE PACIFIC.
ENSEMBLE MEAN IS STILL THE BEST CHOICE FOR SURFACE FEATURE
PROJECTS.

AFTER THE INITIAL WEAK UPPER TROUGH THU NIGHT...A SURFACE FRONT
IS EXPECTED TO MOVE THROUGH SOUTHEAST ALASKA ON SAT. THE NEXT
STRONG TROUGH DEVELOPS A LOW IN THE GULF LATE MON WITH A SURFACE
FRONT THAT REACHES THE PANHANDLE BY MON NIGHT. SOME MODERATE
REBUILDING OF THE UPPER RIDGE IN THE EASTERN GULF IS SUGGESTED
AROUND MID WEEK BUT THAT IS TOO FAR OUT FOR ANY CONFIDENCE.

THE INNER CHANNELS SHOULD REMAIN COLD ENOUGH FOR SNOW WITH THE
APPROACHING FRONT FRI NIGHT ALTHOUGH WITH COASTAL AND SOUTHERN
SECTIONS WILL PROBABLY CHANGE OVER TO RAIN. SIGNIFICANT WARMING
PRECEEDS THE NEXT SYSTEM ON MON SO PRECIPITATION WILL BE
PREDOMINATELY RAIN...HOWEVER NORTHERN LYNN CANAL MAY CONTINUE
WITH SNOW.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND CHILL ADVSRY...18 THRU NOON WIND ADVSRY...18 THRU
NOON
MARINE...GALE...11>13-31 SMCR...21-22-32-34>36-41>43-51-52  KJH/