Small Craft Advisory 152, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
335 PM AKST MON FEB 14 2011

.SHORT TERM...ARCTIC FRONT IS NOW ALONG FREDERICK SOUND AND WILL
SLOWLY SHIFT S TO NEAR SUMNER STRAIT AREA BY LATE TONIGHT. LOW
PRES JUST S OF THE CHARLOTTES WILL MOVE N TO DIXON ENTRANCE BY
LATE TONIGHT...THEN REMAIN NEAR DIXON ENTRANCE TUE WHILE
WEAKENING SLOWLY. HIGH PRESSURE WILL REMAIN OVER NW CANADA THRU
TUE. USED 12Z ECMWF FOR THE MOST PART FOR THE TONIGHT AND TUE
PERIODS BUT DID GET IN SOME LOCAL WRF FOR WIND DETAILS SUCH AS
OUTFLOWS.

MAIN FORECAST ISSUE OVER THE NRN HALF OF THE AREA WILL BE WINDS.
STG NLY PRES GRADIENT WILL PERSIST INTO TUE WITH A SLIGHT
WEAKENING POSSIBLE LATE TUE AFTERNOON. THIS WILL KEEP GALE TO
STORM FORCE WINDS GOING THRU THE NRN INNER CHANNELS AND OUT OF
INTERIOR PASSES INTO THE NE GULF THRU TUE. THIS WIND WILL ALSO
CAUSE SOME BLOWING SNOW OVER THE FAR NRN AREA AND WITH VERY COLD
AIR IN PLACE WIND CHILLS WILL BE AT OR COLDER THAN ADVY LEVELS
OVER THE FAR NRN AREA ESPECIALLY AT HIGHER ELEVATIONS LATER
TONIGHT AND TUE. LOCALLY...GOOD POSSIBILITY OF A MTN WAVE WITH
25-35 KT CROSS BARRIER FLOW...INVERSION AT MTN TOPS...AND CRIT
LEVEL NEAR 600 MB FROM ABOUT 03Z THIS EVENING UNTIL 00Z WED. THINK
PEAK WINDS WILL BE AROUND 55 MPH WITH THE MTN WAVE BUT THERE IS A
CHANCE OF 60+ MPH GUSTS ESPECIALLY LATE TONIGHT AND TUE MORNING.

FURTHER S...MAIN ISSUES WILL BE PRECIP POTENTIAL...AND SNOW
AMOUNTS. LOOKS LIKE PRECIP WITH THE LOW MOVING UP FROM THE S WILL
GET INTO THE SRN THIRD OF THE AREA LATE THIS AFTERNOON AND
EVENING. NRN PART OF THIS PRECIP...IN ZONE 26...SHOULD BE ALL SNOW
AS SHALLOW ARCTIC AIRMASS SHOULD SLIDE INTO THAT AREA JUST AHEAD
OF PRECIP ARRIVAL LATE THIS EVENING. MODELS ARE NOT PUTTING OUT A
LOT OF QPF IN ZONE 26 BUT SUSPECT THEY MAY BE A BIT UNDERDONE AS
SOME OVERRUNNING OF ARCTIC AIRMASS WILL CONTRIBUTE TO LIFT AND
SHOULD MAXIMIZE WHAT MOISTURE GETS UP THERE. ATTM...AM KEEPING
SNOWFALL IN ZONE 26 BELOW ADVY LEVELS BUT THERE IS POTENTIAL FOR
THAT MUCH...BUT NOT HIGH ENOUGH PROBABILITY TO ISSUE AN ADVY ATTM.
FURTHER S...PRECIP MAY BE MIXED OR RAIN TO START THEN TRANSITION
TO SNOW LATER TONIGHT. AGAIN...KEEPING SNOWFALL BELOW ADVY LEVELS
FOR THE FAR SRN AREA BUT IF PRECIP FALLS AS MORE SNOW THAN
EXPECTED...THEY MAY NEED AN ADVY IN ZONES 27 AND 28. SHOULD BE
FAIRLY SHARP CUTOFF TO PRECIP ON NRN SIDE NEAR FREDERICK SOUND.

&&

.LONG TERM...THE COLD DRY OUTFLOW PATTERN PERSISTS THROUGH MIDWEEK
BUT IS WEAKENING THROUGH WEDNESDAY AND THURSDAY. MARINE HEADLINES
WOULD BE LOWERING TO GALES OR SMALL CRAFTS BY LATE WEDNESDAY.
FREEZING SPRAY WILL DIMINISH AS WELL WITH THE LOWERING WINDS BUT
SHOULD BE SEEING SOME AROUND THE MARINE AREAS OF THE INSIDE WATERS
THROUGH WEDNESDAY NIGHT.

SNOWFALL LINGERING FOR A BIT TUESDAY NIGHT INTO EARLY WEDNESDAY
THE THEN RETREATING THE EAST OVER THE SOUTHERN PANHANDLE. THE
RIDGE OF HIGH PRESSURE KEEPING THE STRONG BERING SEA LOW AWAY FROM
NORTHWEST ALASKA GIVES WAY AND ALLOWS A LOW OR TROUGH ALOFT TO
POTENTIALLY MOVE ACROSS THE SOUTH CENTRAL PORTION OF THE STATE THE
NORTHERN GULF. THIS COULD POTENTIALLY BRING A GOOD SNOW FALL EVENT
TO THE NORTHERN PANHANDLE FRIDAY - SATURDAY TIME FRAME. IT SEEMS TO
BE SMALL PROBABILITY AT THE MOMENT BUT IT IS AN OPTION, OTHER WISE
THE OFF SHORE PATTERN WILL PERSIST. THE UPCOMING WEEKEND LOOKS AS
IF IT THERE WILL BE AN NEW INSTALLMENT OF THE COLD DRY OUTFLOW
PATTERN SETTING UP.

MODEL SOLUTION TODAY WAS FAVORING THE ECMWF BASED ON THE HOW THE
EARLY PART OF THE FORECAST WAS LOOKING. USED THE HPC GUIDANCE FOR
THE LATER PORTIONS OF THE FORECAST PACKAGE. CONFIDENCE IS FAIR IN
THE FORECAST.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 3 PM AKST TUESDAY FOR AKZ025.
         WINTER WEATHER ADVISORY UNTIL 3 PM AKST TUESDAY FOR AKZ019.
         WINTER WEATHER ADVISORY UNTIL 5 AM AKST THURSDAY FOR AKZ018.
         WIND ADVISORY UNTIL 5 AM AKST WEDNESDAY FOR AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ011-013.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031>034-043-051.
         SMALL CRAFT ADVISORY FOR PKZ035-041-042-052.

&&

RWT/BEZENEK