Small Craft Advisory 176, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
355 PM AKST FRI MAR 2 2012

.SHORT TERM...MUCH QUIETER SHORT RANGE FORECAST TODAY. LAST
NIGHT'S FRONT IS WELL INTO CANADA RIGHT NOW. SNOWFALL AMOUNTS
RANGED FROM 11 TO 14 INCHES IN YAKUTAT, 5 TO 7 IN HAINES AND ON
THE HIGHWAYS, AND 3 OR LESS ELSEWHERE. PRECIP HAS MAINLY CHANGED
OVER TO SHOWERS NOW WITH MOST PLACES BEING WARM ENOUGH FOR THE
PRECIP TO FALL AS RAIN OR A MIX OF RAIN AND SNOW. THE BIGGEST
CONCERN AT THE MOMENT IS NOT THE PRECIP BUT THE WIND IN LYNN
CANAL AND SKAGWAY. LYNN CANAL IS BLOWING A SOUTHERLY GALE WITH
SKAGWAY GUSTING HIGH ENOUGH TO WARRANT A STRONG WIND HEADLINE.
THIS IS ALL DUE TO A HIGH PRESSURE GRADIENT IN THE NORTHERN
PANHANDLE.

 FOR TONIGHT AND TOMORROW, THE SHOWERS WILL CONTINUE AS W TO SW
FLOW PERSISTS. THE SHOWERS OVER THE SOUTHERN PANHANDLE WILL BE
ENHANCED TONIGHT AS A POST-FRONTAL TROUGH MOVES THROUGH. MOST OF
THESE SHOWERS SHOULD BE RAIN FOR THE SOUTH MAYBE MIXING WITH SNOW
AT TIMES IN HEAVIER SHOWERS, WHILE THE NORTH WILL BE A MIX FOR
THE MOST PART. A COLD AIR MASS ALOFT IS WHAT IS SUPPORTING THE
SNOW IN THESE SHOWERS BUT SURFACE TEMPERATURES WILL BE WARM
ENOUGH, PARTICULARLY IN THE EVENING AND TOMORROW AFTERNOON, FOR
THE SNOW TO BE RAIN BY THE TIME IT REACHES THE SURFACE OR THE
SNOW WILL MELT AS IT HITS THE GROUND. CONSEQUENTLY I AM NOT
EXPECTING MUCH IN THE WAY OF SNOW ACCUMULATION OVERNIGHT OR
TOMORROW. THOUGH THE BEST CHANCE FOR ACCUMULATING SNOW WILL BE
LATE TONIGHT AND EARLY TOMORROW WHEN THE SURFACE TEMPS ARE THE
LOWEST.

WIND WILL CONTINUE TO BE A CONCERN FOR THE NORTHERN PANHANDLE.
CURRENT PRESSURE GRADIENTS BETWEEN JUNEAU AND SKAGWAY HAVE REACHED
6 MB AND GALES AND STRONG WINDS ARE EXPECTED TO CONTINUE IN LYNN
CANAL AND SKAGWAY THROUGH THIS EVENING. WINDS ARE EXPECTED TO DROP
A LITTLE LATER TONIGHT AS THE TROUGH MENTIONED ABOVE LOWERS
SURFACE PRESSURES FARTHER SOUTH. WINDS WILL PICK UP AGAIN TOMORROW
AFTERNOON AS A VERY WEAK RIDGE REBUILDS ITSELF OVER THE SOUTH.

SHORT RANGE MODELS WERE IN GOOD AGREEMENT TODAY. DECIDED TO STICK
WITH THE NAM WITH SOME OF OUR LOCAL WRF MODEL FOR SHORT RANGE
UPDATES AS THEY SEEMED TO REPRESENT THE TIGHTER PRESSURE GRADIENT
IN THE NORTH BETTER THEN THE OTHER MODELS. FORECAST CONFIDENCE IS
A LITTLE ABOVE AVERAGE.

&&

.LONG TERM...ACTIVE PATTERN TO CONTINUE THROUGH THE LONG TERM
UNDER FAST W TO SW FLOW.

UPPER LEVEL TROUGH MOVES ACROSS SOUTHEAST ALASKA SUNDAY AND SUNDAY
NIGHT. SCATTERED SNOW SHOWERS ACROSS THE WHOLE AREA DIMINISH FROM
THE NORTH STARTING SUNDAY NIGHT. WIND BECOME NORTHERLY IN NORTHERN
INNER CHANNELS WHICH LEADS TO SOME CLEARING ACROSS THE NORTH AND
BRINGS COLDER TEMPS TO THE AREA. EXPECTING LOWS INTO THE TEEN
NORTH TO MID 20S SOUTH BY MONDAY MORNING.

BREAKS IN CLOUDS WILL BE SHORT LIVED AS NEXT SYSTEM SPREADS INTO
THE EASTERN GULF MONDAY AND ACROSS SOUTHEAST ALASKA ON TUESDAY.
SNOW WILL SPREAD ACROSS THE NORTH MONDAY NIGHT AND OVER SOUTHERN
MONDAY MORNING. THERMAL RIDGE MOVES ACROSS THE PANHANDLE ON
TUESDAY AND EXPECT SNOW TO CHANGE TO RAIN EXCEPT FOR POSSIBLY PAYA
AND THE HAINES HIGHWAYS. QPF AMOUNTS ARE MODERATE SO COULD SEE
SIGNIFICANT SNOW FOR NORTHERN HALF BEFORE CHANGING TO RAIN. RIDGE
BUILDING INTO THE PANHANDLE BEHIND THE FRONT WILL PRODUCE MAX SMCR
SLY WINDS THROUGH THE INNER CHANNELS. DO HAVE STRONG CAA ACROSS
GULF ON TUESDAY BUT THIS HAS A LONG FETCH SO MODELS PROBABLY
RUNNING A BIT COLD HERE. STARTED TO SEE A WARMING TREND IN TOADY'S EC
FOR MID WEEK.

SCATTERED RAIN AND SNOW SHOWERS WED-THU WITH MARINE PUSH
ASSOCIATED WITH BUILDING RIDGE. NEXT SYSTEM LIFTS NORTH INTO
PANHANDLE THURSDAY NIGHT AND FRIDAY.

PREFERRED THE EC TODAY WITH A STRONGER THERMAL RIDGE ON TUE-WED
SYSTEM AND IN GENERAL WARMER TEMPS THAN GFS OR NAM.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-022-031-032-034-036-041>043-
     051-052.

&&

EAL/MM