Small Craft Advisory 171, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
215 PM AKST SAT FEB 19 2011

ONSET OF A NEW ARCTIC OUTBREAK IN A NE TO S SEQUENCE TONIGHT
AND EARLY SUN. HEAVY SNOW IS STILL TO OCCUR THIS EVENING FOR
MUCH OF THE PANHANDLE. THE ASSOCIATED WINTER STORM WARNINGS
ARE STILL IN EFFECT FOR MUCH OF THE PANHANDLE. NOTE THE LISTING
AT THE BOTTOM OF THIS PRODUCT.

GOES VIS AND IR DISPLAY THE OCFNT THAT IS XTDG SSE FM THE VCNTY
OF PAYA AT THIS TIME.  THE PARENT FEATURE FOR THIS OCFNT IS A
COMPLEX OF LOWS WI 100 NM OF PAYA HAVE CENTERS OF ABOUT 998 MB.
THE FROPA PAST A PAJN-PASI LN SHOULD OCCUR ABOUT 06Z THIS
EVENING ALBEIT SFC FNTS BECOME DIFFICULT TO LOCATE IN THE
INNER CHANNELS.

TWO DIFFERENT VERSIONS OF COLD AIR ADVECTION ARE BEGINNING
TO OCCUR, THE FIRST IS THE COLD ADVECTION FM THE W BHND THE
OCFNT. THE SECOND IS AN ARCTIC OUTBREAK FM NW CAN. SHUTOFF
IN THE SNOW WILL OCCUR ALONG WITH THE ONSET OF THE ARCTIC
OUTBREAK IN A N TO S SEQUENCE FROM 06Z TO 18Z SUN.

MODELS: THE 06Z NAM AND THE 12Z GFS HAVE HAD THE BEST FIT
WITH SEVERAL FIELDS INCLUDING THE THICKNESS GRADIENT RETRIEVED
FROM THE BIORKA RADAR WIND SHEAR. 12Z NAM WAS TOO WEAK ON
THICKNESS GRADIENTS AND THAT MODEL RUN OF SFC WINDS IS TOO WEAK.
&&

.LONG TERM...
19/12Z OPERATIONS MODELS IN GOOD AGREEMENT ON THE SYNOPTIC SCALE AND
SELECTED HPC MEAN SEA LEVEL PRESSURE GRAPHICS TO DRIVE THE WIND IN
THE LATER PERIODS. WITH AN UPR LEVEL RIDGE BUILDING FROM THE THE
WEST
A SURFACE HIGH CELL BETWEEN 1050 AND 1060 MB WILL BUILD OVER THE
SOUTHERN YUKON BY WED THEN WILL MOVE EASTWARD. EXPECT MODELS TO KICK
THIS OUT TOO RAPIDLY AS USUAL. SCREAMING MESSAGE IN GRIDS AND TEXT
WILL BE CLEAR WINDY AND COLD TUESDAY INTO THURSDAY AND PERHAPS EVEN
LONGER. CONFIDENCE HIGH SUN NITE THRU WED. THU THRU SAT MUCH LESS
CERTAIN.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 9 AM AKST SUN AKZ020-025-026.
WINTER STORM WARNING UNTIL 3 AM AKST SUN AKZ018-019-021-022-024.
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 3 AM AKST SUN AKZ023.
WINTER WEATHER ADVISORY MIDNIGHT TONIGHT TO 9 AM AKST SUN AKZ028.
WINTER STORM WARNING FROM 3 AM TO 3 PM AKST SUNDAY AKZ029.
WINTER STORM WARNING UNTIL 9 PM AKST THIS EVENING AKZ017.
MARINE...GALE WARNING FOR PKZ022-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031>036-051-052.
&&