Gale Warning 6, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
257 PM AKST SAT JAN 19 2013

.SHORT TERM...UPPER RIDGE WILL CONTINUE BUILDING NWD OVER THE
FAR ERN GULF AND SE AK TONIGHT...THEN DRIFT SLOWLY EWD SUN.
SHORTWAVE TROF WILL LIFT N FROM THE PAC INTO THE CENTRAL GULF
SUN. ARCTIC HIGH PRESSURE RIDGE OVER NW CANADA WILL SLIDE ESE
THRU SUN. A WARM FRONT WILL LIFT NWD THRU THE ERN GULF TONIGHT
AND SUN. A SLOW MOVING COLD FRONT OVER THE SW GULF WILL REACH THE
CENTRAL GULF BY LATE TONIGHT...THEN INTO THE E-CENTRAL GULF BY
LATE SUN AFTERNOON. A LOW PRESSURE WAVE WILL MOVE N ALONG THE
FRONT INTO THE CENTRAL GULF SUN. USED BLEND OF 12Z ECMWF AND
NAM...WITH THE ECMWF HAVING BEST FIT ON THE FEATURES OVER THE
GULF AND SWD WHILE THE NAM HAD BETTER HANDLE ON THE ARCTIC HIGH.

 MAIN FORECAST ISSUES WILL BE PRECIP POTENTIAL/TYPE...WINDS...AND
 TEMPS. ATTM...NO PRECIP IS BEING REPORTED OVER THE AREA WITH
MAINLY BANDS OF HIGH AND MID-LEVEL CLOUDS MOVING ACROSS THE AREA.
SOME LOWER CLOUDS ARE OVER THE SRN AREA AND THESE MAY HAVE SOME
SPRINKLES OR SPOTTY LIGHT RAIN IN THEM AS WARM FRONT CLIPS THAT
AREA THIS EVENING. WILL GO WITH LOW POPS OVER THE SRN ZONES
ESPECIALLY NEAR THE COAST FOR THE EVENING. ANOTHER AREA THAT MAY
GET INTO SOME PRECIP AHEAD OF THE MAIN COLD FRONTAL BAND IS THE
NRN INNER CHANNELS. WITH SHALLOW ARCTIC AIR IN PLACE OVER THAT
AREA...OVERRUNNING WILL DEVELOP LATER TONIGHT AND SUN MORNING AS
FLOW ABOVE THE COLD AIRMASS BECOMES SLY WELL IN ADVANCE OF WARM
FRONT. SINCE THE DEEPEST COLD AIR IS OVER THE FAR N...HAVE HIGHER
POPS THERE LATE TONIGHT AND SUN MORNING THAN OVER AREAS JUST TO
THEIR S. SUPPORT FOR THE COLD AIR WILL DIMINISH THRU SUN AS THE
ARCTIC HIGH MOVES SLOWLY AWAY FROM THE AREA...SO THE LOW LEVEL
LIFTING FROM OVERRUNNING WILL DIMINISH LATE SUN MORNING. THE MAIN
PRECIP BAND WITH THE COLD FRONT WILL REACH THE NW COASTAL AREA
TONIGHT...THEN SPREAD E TO THE NRN INNER CHANNELS BY LATE SUN
AFTERNOON. ONLY REAL THREAT FOR SNOW WILL BE OVER THE NRN INNER
CHANNELS AND PAYA AREA...WITH ONLY THE FAR NRN CHANNELS LIKELY TO
GET ANY SNOWFALL ACCUMS. WENT FOR 1 INCH THERE SUN.

 AS FOR WINDS...THE STRONG NLY WINDS IN LYNN CANAL WILL DIMINISH
TONIGHT AND SUN MORNING AS THE NLY COMPONENT OF THE PRESSURE
GRADIENT WEAKENS. HAVE GALES THERE DIMINISHING BELOW SCA LEVELS
BY DAYBREAK SUN. THE PRESSURE GRADIENT WILL BEGIN TO FAVOR THE
MORE E-W CHANNELS LATE TONIGHT INTO SUN SO THOSE CHANNELS WILL
SEE THEIR WINDS PICK UP THEN...CLOSE TO OR AT SCA
LEVELS...ALTHOUGH THE WINDS AROUND CAPE SPENCER WILL LIKELY BE
MORE PERSISTENT SCA THRU SUN. ALSO...WINDS AHEAD OF THE COLD
FRONT AND LOW PRESSURE WAVE WILL REACH GALE FORCE OVER THE WRN
AND NRN GULF MARINE AREAS FROM THE W TONIGHT...AND CONTINUE INTO
SUN ALONG THE NRN GULF AREA.

 AS FOR TEMPS...HAVE MENTION OF RISING TEMPS OVERNIGHT OVER THE
FAR NRN AND PAYA AREAS AS AIRMASS SLOWLY MODERATES. MUCH OF THE
REMAINING AREA WILL SEE TEMPS BOTTOM OUT THIS EVENING THEN REMAIN
STEADY OVERNIGHT. LOOKS LIKE ALL BUT THE PAGY AREA SHOULD BE
ABOVE FREEZING BY LATE SUN AFTERNOON.

&&

.LONG TERM...MODELS ARE IN GENERAL AGREEMENT THROUGH LATE TUESDAY
NEXT WEEK WITH AN UPPER LEVEL RIDGE ACROSS THE EASTERN GULF AND
SOUTHEAST ALASKA SLOWLY DRIFTS EAST AS AN UPPER LEVEL SHORTWAVE
TROUGH MOVES INTO THE CENTRAL GULF. A SURFACE LOW ASSOCIATED WITH
THE INCOMING UPPER TROUGH WILL MOVE ACROSS THE SOUTHWESTERN GULF
EARLY NEXT WEEK INTO THE CENTRAL GULF THROUGH LATE TUESDAY. THE
GFS AND ECMWF MADE A GOOD CONSENSUS FOR SYNOPTIC PATTERN FOR THE
INCOMING LOW AND WERE USED TO REFRESH THE INHERITED FORECAST
PACKAGE THROUGH LATE TUESDAY. UNDERNEATH THE EASTWARD SHIFTING
UPPER RIDGE...SURFACE PRESSURE PATTERN REMAINS NEAR PARALLEL ALONG
SOUTHEAST ALASKA OVER THE WEEKEND WITH HIGHER PRESSURE TO THE EAST
AND LOWER PRESSURE ACROSS THE GULF.

 AN EMBEDDED WARM FRONTAL TROUGH WILL BRING CATEGORICAL POPS FROM
YAKUTAT SOUTHEAST TO THE CENTRAL PANHANDLE THROUGH EARLY MONDAY
THEN RETROGRADE TO THE NORTHWEST BY LATE MONDAY AS A WEAK RIDGE
OVER BRITISH COLUMBIA EXTENDS NORTHWEST OVER THE PANHANDLE THROUGH
LATE TUESDAY. PRECIPITATION WILL BE ALL RAIN EXCEPT NORTHERN MOST
AREA WHERE SNOW CAN CONTINUE DURING SUNDAY EVENING. THIS
SNOW...HOWEVER...WILL BECOME RAIN OVERNIGHT SUNDAY NIGHT AS WARMER
AIR ENTRAINMENT CONTINUES TO EXTEND TO THE NORTHERN PANHANDLE.
SMALL CRAFT LEVEL SOUTHEASTERLY WINDS WILL CONTINUE OVER THE OUTER
COASTAL WATERS WITH ROUGH SEAS. OCEAN ENTRANCES OF THE INNER
CHANNELS WILL ALSO SEE SMALL CRAFT WINDS.

 THE LOW OVER THE CENTRAL GULF WILL INTERACT WITH ANOTHER
DEVELOPING LOW SOUTH OF THE ALASKAN PENINSULA BY MIDDLE OF NEXT
WEEK AND MODEL DIFFERENCES BECOME LARGER. IN GENERAL...THE LOW
OVER THE CENTRAL GULF WILL WEAKEN AS IT DRIFTS NORTH TO THE
NORTHERN GULF AND THE DEVELOPING LOW INTO THE SOUTHWESTERN GULF
HAS A GREAT UNCERTAINTY. LEANED OVER THE HPC ENSEMBLE APPROACH FOR
THE REMAINING LONG TERM PERIODS. AS THE WEAKENING LOW ACROSS THE
CENTRAL GULF DRIFTS NORTHWARD TO THE NORTHERN GULF...A FRONTAL
PASSAGE WILL APPROACH THE PANHANDLE LATE TUESDAY INTO WEDNESDAY
THEN DRIFT SOUTHEASTWARD TO THE SOUTHERN PANHANDLE BY THURSDAY
THEN CONTINUE MOVE AWAY FROM THE AREA TOWARD THE WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-041-042.

&&

RWT/AHN