Storm Warning 73, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
323 PM AKDT SAT OCT 30 2010

.SHORT TERM...STRONG SHOWERS FOR TONIGHT WILL TRANSITION TO A
STORM FORCE FRONTAL BOUNDARY SUNDAY MORNING. NOTE WINDS FOR
PUBLIC ZONE 27, AS WELL AS SEVERAL MARINE ZONES WITH GALES AND
STORMS, IN THE TABLE BELOW.

 GOES IR SHOWS CONVECTION IN CENTRAL AND ERN GLFALSK. LIGHTNING
DETECTION HAS INDICATED SEVERAL STRIKES WI 100 NM OF PAYA TODAY.
STRONG CELLS ARE MAKING LANDFALL ALONG THE ENTIRE GULF COAST FROM
PACV TO PASI. ONE LIGHTNING STRIKE WAS 60 NM NW OF PASI AT 2015Z
AND REPORTS HAVE BEEN RECEIVED THAT INDICATE STRONG CUMULUS CELLS
INLAND THAT EXTEND TO THE SRN PNHDL. THE CELLS IN THE GULF ARE
TRACKING NE AT ABT 15 KT. AN OLD FRONTAL BNDRY IS MOVG E BYD THE
COAST MTN RANGE, AND THIS EXIT HAS PERMITTED THE CELLS E OF A
PAJN-PAKT LN TO GAIN VERTICAL EXTENT.

 EXPLOSIVE CYCLOGENESIS WITH LOW 300 NM S OF PACD IS SENDING A
STRONG TRIPLE PT TO THE ENE THAT IS CURRENTLY 600 NM S OF PAWD.
ECMWF MODEL HAS A CENTRAL PRESSURE OF 937 MB FOR 00Z FOR THE
BOMB.

 THE NAM AND IN-HOUSE WRF ARE THE MODELS OF CHOICE FOR THE
CONVECTIVE ENVIRONMENT. THE ECMWF HAS BEEN THE MODEL OF CHOICE
FOR THE CYCLONE EVOLUTION OF THE EXPLOSIVE CYCLOGENESIS. THE
MODEL TRANSITION FROM NAM/WRF TO ECMWF WAS MADE DURING 06Z-12Z.

&&

.LONG TERM...ACTIVE FALL PATTERN CONTINUES THROUGH THE LONG TERM.
942 MB STORM FORCE LOW WILL ENTER THE SOUTHERN GULF SUN EVENING
THEN TRACK NORTHWARD TOWARD PRINCE WILLIAM SOUND. AS THE LOW
TRACKS NORTH IT WILL FILL WEAKENING TO NEAR 970 MB BY MON. 1ST
FRONTAL BAND WILL KEEP STORM FORCE WINDS ALONG THE OFFSHORE AND
COASTAL WATERS WITH SUSTAINED WINDS UP TO 60 KTS AND SEAS HEIGHTS
NEAR 25 FT. ALONG COASTAL ZONES WARNING LEVEL GUSTS WILL CONTINUE
SUN EVENING THROUGH MON FOR AKZ27 WITH ADVY LEVEL WINDS IN THE
SURROUNDING AREAS. THESE WINDS WILL DIMINISH LATE SUN NIGHT AS THE
FIRST FRONT PASSES THEN WILL INCREASE TO NEAR ADVY LEVELS WITH THE
SECONDARY WRAP. 850 LLJ NEAR 75 KTS FOR THE FIRST FRONTAL WRAP
THEN NEAR 55 KTS FOR THE SECONDARY WRAP.

ALONG THE HAINES AND KLONDIKE HIGHWAYS WINTER STORM WARNING REMAINS
IN EFFECT. NORTHERLY WINDS BRINGING 850 TEMPS TO -6C AS PRECIP
MOVES IN FROM THE SOUTH. MAY SEE ACCUMULATIONS OF 6 INCHES OR MORE
OF SNOW...BUT WITH WARMER AIR MOVING UP THE TRANSITION TO RAIN ALONG
THE HAINES HIGHWAY MAY OCCUR EARLIER. THAT SAID HAINES HIGHWAY
AMOUNTS MAY BE CLOSER TO ADVY WITH THE KLONDIKE NEARER TO WARNING
LEVELS.

AS THE STORM FORCE LOW DISSIPATES HIGH PRESSURE RIDGE WILL BUILD
OVER THE PANHANDLE TUE WITH INCREASED GRADIENT WINDS OVER THE
NORTHERN ZONES WILL INCREASE TO NEAR ADVY LEVEL WITH SOLID. GALES
DEVELOPING OVER N LYNN CANAL. NEXT LOW PRESSURE SYSTEM WILL
TRACKING FROM THE NORTHERN PACIFIC INTO THE SOUTH CENTRAL GULF
LATE WED THEN CONTINUE TO TRACK TOWARD PRINCE WILLIAM SOUND THU.
AMPLE MOISTURE MOVING UP WITH THIS SYSTEM MAY SEE HEAVY PRECIP OVER
THE SOUTHERN AND CENTRAL PANHANDLE AS THE FIRST FRONTAL BAND
ASSOCIATED WITH THE LOW MOVES IN.

MODELS WERE IN GOOD AGREEMENT WITH EC AND UKMET INITIALIZATION A
BIT BETTER. DIFFERENCE BETWEEN 12Z EC AND 00Z EC WAS MINOR SO
LITTLE CHANGE WAS MADE TO THE GRIDS TO DAY 3. THE 10 PM EXTENSION
OF THE WIND WARNING AND ADVY MAY BE A BIT LONG BUT WITH
UNCERTAINTY OF STRENGTH OF SECONDARY WARP DECIDED TO ERR ON THE
SIDE OF CAUTION. BY DAY 4 THE 12Z GFS AND 00Z AND 12Z EC FELL MORE
IN LINE WITH RESOLUTION OF THE MID WEEK LOW. HPC GUID ALSO SHOWED
THE NEW LOW TRACK WHICH STRONGER AND A BIT FURTHER TO THE WEST.
WITH THE NEW UPDATED MID WEEK WIND AND WAVES OVER THE AK GULF WERE
INCREASED. FORECAST CONFIDENCE IS ABOUT AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 10 AM TO 10 PM AKDT SUNDAY FOR AKZ022-023-026-
     028.
         HIGH WIND WARNING FROM 10 AM TO 10 PM AKDT SUNDAY FOR AKZ027.
 WINTER STORM WATCH FROM SUNDAY EVENING THROUGH LATE SUNDAY NIGHT
FOR AKZ018-019. MARINE...STORM WARNING FOR PKZ022-036-041>043-051.
GALE WARNING FOR PKZ021-033-035-052. SMALL CRAFT ADVISORY FOR
PKZ012-013-031-032-034.

&&

JBT/PRB