Storm Warning 15, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1140 AM AST FRI FEB 15 2008

.SYNOPSIS...
.SHORT RANGE...SATELLITE LOOP SHOWS A LITTLE BREAK IN OVERCAST
OVER SOUTHERN COASTAL ZONES THIS MORNING BUT AN EXTENSIVE STRATUS
DECK EXPANDING EAST FROM THE CENTRAL GULF IS ARRIVING OVER
NORTHERN TWO THIRD OF COASTAL SECTIONS.  GUSTY WIND CONTINUES
OVER SKAGWAY AREA FOR WIND ADVISORY.  THE LATEST GFS HAS VERY
MUCH THE SAME SOLUTION FROM THE PREVIOUS RUNS.  WILL USE THE GFS
190/40 TO MAINTAIN THE CONSISTENCY.  LOW PRESSURE NORTH OF THE
PANHANDLE WILL WEAKEN AND MOVE EAST LATE THIS EVENING AS A RIDGE
OF HIGH PRESSURE BUILDING FROM THE SOUTH.  THIS WILL RELAX THE
PRESSURE GRADIENT OVER SKAGWAY AREA AND THE WIND ADVISORY SHOULD
EXPIRE AROUND 9 PM.  COLDER AIR AT THE BOUNDARY LAYER MOVING IN
THE AREA THIS AFTERNOON AND EVENING WILL SLOWLY MODIFY THE
SURFACE TEMPERATURES AND INCREASE THE CHANCE OF SNOW ACROSS THE
FORECAST AREA THROUGH TONIGHT EVEN THOUGH HUMIDITY LEVELS
DECREASE.

THE RIDGE WILL CONTINUE ACROSS THE EASTERN GULF AND SOUTHEAST
ALASKA THROUGH SATURDAY.  THIS LARGE SCALE RIDGE WILL DECREASE
THE CLOUD COVER TONIGHT ESPECIALLY ACROSS THE INTERIOR PASSAGES
FROM GUSTAVUS SOUTHEAST TO PETERSBURG AND WRANGELL AREAS FOR SOME
DEGREE OF RADIATION COOLING LATE TONIGHT THROUGH EARLY SATURDAY
MORNING.  A FRONTAL BOUNDARY ASSOCIATED WITH A LOW IN THE WESTERN
GULF WILL AFFECT THE EASTERN GULF AND THE NORTHERN HALF OF
PANHANDLE SATURDAY AFTERNOON.  PRESSURE GRADIENT WILL BECOME ONCE
AGAIN TIGHT ACROSS THE EASTERN GULF AND NORTHERN PANHANDLE IN
EAST TO WEST ORIENTATION.  MAINLY EAST OF YAKUTAT AND NORTHERN
AND CENTRAL COASTAL SECTIONS WILL SEE INCREASING WINDS LATE
SATURDAY AFTERNOON. AHN

.LONG RANGE...MILD AND WET WITH ABV AVE TEMPS THROUGH MIDDLE OF
NEXT WEEK THEN THE TREND IS FOR COOLER WEATHER TO RETURN TO SE
AK.

LONG WAVE PATTERN SETTING UP HAS COLD ANCHOR LOW NEAR DATELINE
OVER EXTEME NE RUSSIA AND DOWNSTREAM RIDGE APLIFYING OVER WRN
NORTH AMERICA. SATELLITE WATER VAPOR IMAGERY REVEALS TROPICAL
MOISTURE PLUME BLOSSOMING ALONG 160W. GLOBAL SPECTRAL MODELS ARE
IN GENERAL AGREEMENT THIS MOISTURE WILL MOVE INTO SE AK STARTING
LATE SAT AND CONTINUE INTO EARLY NEXT WEEK AND NCEP FCSTRS HAVE
HIGH DEGREE OF CONFIDENCE IN THEIR SOLUTIONS. NUMEROUS SHORT
WAVES AND UPPER LEVEL VORTICITY LOBES ARE FCST IN MODELS TO RIDE
NE ALG BAROCLNIC ZONE THROUGH THE GULF AND INTO SE AK. HENCE WE
EXPECT SLOW EASTWARD MOVEMENT OF THE MOISTURE PLUME AND PERIODIC
MODERATE TO HEAVY PCPN RATES. SATELLITE DERIVED RAINFALL RATES
ARE AS HIGH AS 0.25 TO 0.50 INCHES PER HOUR ALG THIS PLUME TODAY.
WILL BROAD BRUSH A WET SW FLOW PATTERN IN GRIDS WELL INTO NEXT
WEEK. THE DAILY DETAILS BEYOND DAY3 WILL HAVE TO BE REFINED OVER
TIME.

THERE IS POTENTIAL FOR A WINDY EPISODE AS THE FIRST SLUG OF
MOISTURE ARRIVES SAT NIGHT. GALES ARE ALREADY POSTED FOR LATE SAT
IN THE NRN OFFSHORE WATERS AND COASTAL ZONES. GALES SPREAD SOUTH
DOWN THE PANHADLE COAST SUN. WIND FCSTS ARE IN GOOD AGREEMENT
WITH ANCHORAGE AND VANCOUVER FCST TRENDS.

STARTING LATE NEXT WEEK...THU OR SO...THE MODELS SHOW THE COLD
ANCHOR LOW AND WRN NO AMERICAN RIDGE WEAKENING THEIR GRIPS AND
LIFTING EWD. THIS WOULD SHIFT THE WET BAROCLINIC BAND S AND E OF
OUR FCST AREA AND ALLOW COOLER THAN AVERAGE AIR TO MOVE IN FROM
THE NW BY NEXT WEEKEND.  TA

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WND ADVY FOR AKZ018 UNTIL 06Z TONIGHT.
MARINE...GALE WRNG FOR OFFSHORE AND ENTIRE OUTSIDE WTRS SAT.
      ...SCA FOR REST OF CSTL WTRS.