Small Craft Advisory 13, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
118 PM AKST SUN JAN 4 2009

.SHORT TERM...PREVIOUS DISCUSSION ISSUED AT 601 AM AKST SUN JAN 04
2009...HIGH PRESSURE DOMINATES THE MAINLAND ALASKA AND NORTHWEST
CANADIAN ARCTIC AREA. AN ELONGATED LOW OVER THE GULF HAS ONE LOW
SOUTH OF KODIAK ABOUT 250 NM WHILE A DEVELOPING LOW IS ABOUT
54/140 THIS MORNING WHILE THE FRONT IS BEGINNING TO APPROACH THE
COAST OF PRINCE OF WALES ISLAND.

 FORECAST REASONING: PROBLEM OF THE DAY IS ASSOCIATED WITH THE
LOW MOVING ACROSS THE SOUTHERN PANHANDLE THROUGH TONIGHT. RAIN
SNOW LINE MEANDERING ACROSS SOUTHERN PORTION OF THE AREA AND WILL
PROBABLY CREATE SOME HAVOC WITH SNOW AMOUNTS AS WELL FOR THE
WARNING ONGOING. ALSO A GOOD PUSH OF WIND HAS MOVED INTO THE AREA
AS WELL. EXPECT THE WIND THROUGH NOON OVER THE SOUTHERN PORTION
AND SNOW AND/OR RAIN TAPERING OFF AS WELL. OVER THE CENTRAL AND
NORTHERN AREAS PRECIPITATION WILL BEGIN TO DIMINISH THROUGH THE
DAY AS WELL. STRONG WINDS NORTHERLY WINDS AND OUTFLOW OVER THE
NORTHERN PANHANDLE PICKING UP THROUGH THE DAYTIME PERIODS AND
SHOULD ALSO FALL OFF THROUGH THE LATE AFTERNOON AND EVENING TIME
FRAMES.

 A FAIR 100-120 KT JET OVER THE SOUTHERN GULF IS MOVING THE LEAD
LOW QUICKLY TO THE EAST WHILE THE MAIN PARENT CENTER HANGS BACK
FURTHER WEST. SHOULD SEE THE FRONTAL BOUNDARY MOVE THE SOUTHERN
HALF THE PANHANDLE BY AFTERNOON BUT THE LOW WILL A LITTLE SLOWER.
 VERY COLD ARCTIC AIR (SURFACE TEMPERATURE THIS MORNING AS -58F
AT EAGLE, AK) REMAINS OVER ALASKAN INTERIOR AND YUKON TERRITORY
INTO TONIGHT. WIND CHILLS OVER THE WHITE PASS AREA WILL CONTINUE
TO BE IN THE MINUS 30 TO 40 RANGE THROUGH TONIGHT.

 PRECIPITATION SHOULD BE LASTING A LITTLE LONGER OVER THE MISTY
FJORDS AREA (ZONE 29) SO HAVE EXTENDED THE WARNING THERE THROUGH
MIDNIGHT. SNOW OVER THE REST OF THE AREA WILL DIMINISH BUT EXPECT
TO SEE SCATTERED AREAS OF LIGHT SNOW/SHOWERS PERSIST THROUGH
TONIGHT.

.LONG TERM...GENERAL UPPER LEVEL PATTERNS AND FEATURES VERY
SIMILAR BETWEEN GFS AND ECMWF THROUGH THE WEEK WITH GFS A LITTLE
MORE STRONGLY DEPICTING UPPER LEVEL SHORT WAVES ROUNDING THE BASE
OF AN UPPER LOW OVER BRISTOL BAY. THIS DIFFERENCE DOES NOT HAVE A
SENSIBLE IMPACT ON THE PANHANDLE UNTIL LATE NEXT WEEKEND WHEN GFS
STAMPS AN UPPER LOW THAT DEVELOPS FROM ONE OF THESE SHORTWAVES
JUST WEST OF SITKA. AT THIS SAME TIME ECMWF DEPICTS A BROAD AND
FAIRLY FLAT RIDGE OVER THE PANHANDLE WITH THE CORRESPONDING AXIS
OFFSHORE OVER THE COASTAL WATERS. WITH THIS AT THE TAIL END OF
THE EXTENDED RANGE FORECAST PERIOD...THERE WILL BE SEVERAL DAYS
TO SEE HOW IT EVOLVES.

AT THE SURFACE...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF
OCCUR AS EARLY AS TUESDAY AFTERNOON WITH REGARD TO A LOW NEAR
50N/155W.HOWEVER...BOTH MODELS TRACK THIS FEATURE AND THE
ASSOCIATED WEATHER WELL SOUTH OF THE PANHANDLE. BOTH MODELS
CONTINUE TO DEPICT A FAIRLY STRONG NORTHERLY PRESSURE GRADIENT
OVER THE NORTHERN PANHANDLE UNTIL MID WEEK. AT THIS TIME...GFS
RE-ORIENTS THE GRADIENT TO EASTERLY WHEREAS ECMWF BREAKS IT DOWN.
HIGH PRESSURE DOES REMAIN OVER BRITISH COLUMBIA AND THE YUKON AND
THE STRONG EASTERLY GRADIENT DOE RE-ESTABLISH WITH THE APPROACH
OF A STRONG LOW LATE THURSDAY NIGHT.

BY THIS TIME AT THE SURFACE...THERE ARE SOME SIGNIFICANT
POTENTIAL DIFFERENCES WITH GFS DEVELOPING A STRONG TRIPLE POINT
LOW AND TRACKING IT INTO THE NORTH CENTRAL GULF. THE 00Z ECMWF
DID NOT DEVELOP THE TRIPLE POINT. INSTEAD...A FRONT EXTENDS FROM
THE PARENT LOW SOUTH OF KODIAK CLOSE TO AND PARALLEL WITH THE
ALASKAN COASTLINE DOWN TO SITKA. RESULTANT ECMWF PRESSURE
GRADIENT WAS MORE SOUTHEASTERLY AND CONCENTRATED MORE OVER THE
SOUTHERN PANHANDLE. THE 12Z ECMWF HOWEVER LOOKS LIKE THE 12Z GFS
THOUGH SLIGHTLY WEAKER WITH BOTH THE PARENT LOW SOUTH OF DUTCH
HARBOR AND THE TRIPLE POINT IN THE NORTH CENTRAL GULF. THE 12Z
UK MO ALSO IN GOOD AGREEMENT WITH THE CURRENT GFS AND ECMWF.

UPDATES TODAY TO THE LONG RANGE FORECAST WILL BE A BLEND TO
EXISTING GRIDS AND REFLECT A PREFERENCE FOR THE CONSENSUS BEING
OFFERED BY GFS...UKMO...AND ECMWF.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 6 PM AKST THIS AFTERNOON FOR AKZ024-
     	 026.
         WIND ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ027-028.
         WINTER WEATHER ADVISORY UNTIL 6 PM AKST THIS AFTERNOON FOR
     	 AKZ021-025.
         WIND ADVISORY UNTIL 6 PM AKST THIS AFTERNOON FOR AKZ020-022.
         FLOOD ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ028.
         WINTER STORM WARNING UNTIL MIDNIGHT AKST TONIGHT FOR AKZ029.
         WINTER WEATHER ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ019.
         WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 6 AM AKST MONDAY
     	 FOR AKZ018.
         BLIZZARD WARNING UNTIL 6 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011>013-036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ021-022-031>035-051-052.

&&

MM/FRITSCH

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