Small Craft Advisory 44, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
351 PM AKST MON JAN 16 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING STRONG
OFFSHORE FLOW WITH CLOUDINESS OVER THE NORTHERN AK GULF TO THE
OFFSHORE WATERS. CLOUD STREETS FROM THE OUTFLOW WINDS ARE QUITE
EVIDENT FROM VISIBLE SATELLITE IMAGERY OVER THE SOUTHERN AK GULF.
THE STRONG HIGH OVER THE YUKON AND WEAK INVERTED TROUGH OVER THE
PANHANDLE CAUSING THE OUTFLOW WINDS WILL REMAIN FAIRLY STABLE
THROUGH THE NEXT 24 HOURS. NORTHERLY WINDS WILL CONTINUE WITH
GALE FORCE WINDS OVER THE NORTHERN INNER CHANNELS AND HIGH GUSTS
OUT OF CHANNELED TERRAIN AND INTERIOR PASSES. HIGH PRESSURE DOES
BEGIN TO SLIDE SOUTHWARD DOWN BRITISH COLUMBIA WHICH INDICATES AN
INCREASE IN OUTFLOW WINDS LATE MONDAY NIGHT INTO TUESDAY.

 HIGH TEMPERATURES FOR MONDAY HAVE BEEN IN THE SINGLE DIGITS TO
MID TEENS OVER THE PANHANDLE. WITH ANOTHER CLEAR NIGHT EXPECT LOW
TEMPERATURES TO DROP TO THE SINGLE DIGITS OR BELOW ZERO TO THE
NORTH. AS STRONGEST WINDS WILL BE IN EXPOSED AREAS AND COLDEST
TEMPERATURES WILL BE IN WIND SHELTERED AREAS NOT EXPECTING WIND
CHILLS TO DROP LOWER THAN 25 BELOW ZERO FOR EXTENDED
PERIODS...WITH THE EXCEPTION OF THE KLONDIKE HIGHWAY WHERE WIND
CHILLS NEAR WHITE PASS WILL NEAR 45 BELOW ZERO. TUESDAY HIGHS
SHOULD BE SLIGHTLY COLDER THAN MONDAY AS OVERNIGHT LOWS SHOULD BE
A BIT COLDER THAN MONDAY MORNING.

 MODELS WERE IN GOOD AGREEMENT AGAIN DUE TO THE STABLE PATTERN.
GFS WAS SHOWING WEAK SHORT WAVE IN THE AK GULF A BIT FURTHER EAST
THAN THE NAM AND ECMWF. USED A BLEND OF NAM/EC AND INHERITED
GRIDS THROUGH 00Z WED. OVERALL CHANGES WERE MINOR BUT WITH THE
INCREASED EAST- WEST PRESSURE GRADIENT AS THE BRITISH COLUMBIA
HIGH DROPS SOUTH DID INCREASE INNER CHANNEL WINDS SLIGHTLY.
FORECAST CONFIDENCE IS ABOVE AVERAGE.

&&

.LONG TERM...LOOKS LIKE A BREAK IN THE VERY COLD WEATHER MAY BE ON
THE HORIZON TOWARDS THE END OF THE LONG RANGE FORECAST PERIOD BY LATE
NEXT WEEKEND WITH TEMPERATURES BEGINNING TO CREEP UP ON FRIDAY.
BETWEEN NOW AND THEN, HIGH PRESSURE IN WESTERN CANADA WILL
CONTINUE TO GENERATE STRONG OUTFLOW WINDS. THIS, COMBINED WITH
VERY COLD AIR AT THE SURFACE WILL CONTINUE TO CAUSE HAZARDOUS WIND
CHILLS OVER MANY OF THE PUBLIC ZONES AND FREEZING SPRAY OVER MOST
OF THE INNER CHANNELS AND COASTAL MARINE ZONES. CHANGE WILL COME
WHEN A DISORGANIZED AREA OF LOW PRESSURE SOUTH OF THE ALEUTIANS
GETS PICKED UP BY A DEVELOPING RETROGRADE UPPER LEVEL TROUGH THAT
WILL BEGIN FORMING IN THE SHORT TERM FORECAST PERIOD. THE TROUGH
WILL EXTEND WEST ACROSS THE SOUTHERN GULF AND BEGIN TO EXERT AN
INFLUENCE ON THE LOW PRESSURE SOUTH OF THE ALEUTIANS BY TUESDAY
NIGHT. SUPPORT FROM THE JET WILL CAUSE AT LEAST 2 WAVES TO BREAK
AWAY FROM THE LOW AND TRACK TO THE EAST BUT REMAIN SOUTH OF THE
PANHANDLE. AS THE MAIN LOW BEGINS MOVING EAST, IT WILL DEEPEN WITH
JET SUPPORT AND MERGE WITH ANOTHER DEVELOPING WAVE THAT WILL BE
MOVING QUICKLY ALONG THE FRONTAL BOUNDARY TO THE WEST. SIGNIFICANT
POP RE-ENTERS THE FORECAST LATE THURSDAY NIGHT OVER THE SOUTHERN
ZONES AND MOVES NORTH THROUGH FRIDAY NIGHT. WITH THE VERY COLD AIR
IN PLACE AT THE SURFACE AND STABLE, WARMER AIR MOVING IN ALOFT,
SOUTHEAST ALASKA MAY SEE A SIGNIFICANT SNOWFALL FROM THIS SYSTEM
OVERNIGHT FRIDAY AND THROUGH THE WEEKEND. FAR TOO EARLY TO MAKE
REALISTIC ESTIMATES ON SNOW TOTALS, BUT AS THE WEEKEND DRAWS
CLOSER, AMOUNTS WILL BE REFINED AS CONFIDENCE RISES.

BLENDED CURRENT ECMWF TO EXISTING GRIDS THROUGH THURSDAY NIGHT,
THEN NEW HPC WITH CURRENT ECMWF. FORECAST CONFIDENCE IS AVERAGE
THROUGH THE EXTENDED RANGE PERIOD.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 5 AM AKST TUESDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011>013-031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ053.
         GALE WARNING FOR PKZ011>013-022-031-043-051.
         SMALL CRAFT ADVISORY FOR PKZ021-032>036-041-042-052-053.

&&

PRB/FRITSCH