Heavy Freezing Spray Warning 9, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
632 AM AKST WED JAN 18 2012

.SHORT TERM...EARLY MORNING SATELLITE IMAGERY REVEALS A
PERSISTING HIGH IN THE YUKON EXTENDING SOUTHEASTWARD INTO BRITISH
COLUMBIA AND A DEVELOPING STORM FAR SOUTHWEST IN THE NORTHERN
PACIFIC. MODERATE TO STRONG OFFSHORE FLOW ACROSS THE PANHANDLE
CONTINUES TO GENERATE OUTFLOW CLOUD PLUMES FROM THE PANHANDLE
COAST SOUTHWESTWARD OVER THE OUTER COASTAL WATERS. OFFSHORE FLOW
ACROSS THE FORECAST DOMAIN HAS BEEN WEAKENED BUT STILL STRONG
ENOUGH TO PRODUCE GALE FORCE TO SMALL CRAFT WINDS OVER THE MARINE
ZONES AND NEAR INTERIOR PASSES AND BAYS.

 AIR MASS HAS BEEN MODIFIED AND THE LOW TEMPERATURES WENT UP
SLIGHTLY LAST NIGHT INTO EARLY THIS MORNING. MENDENHALL
VALLEY...YAKUTAT AND KAKE WENT DOWN TO BELOW ZERO BUT MOST OTHER
LOCATIONS REPORTED 8 TO 15 DEGREES. AS THE PRESSURE GRADIENT
SHIFTS TO MORE NORTHEAST TO EAST...NORTHERLY LOW LEVEL WINDS HAVE
BEEN DECREASED BUT THOSE EAST-WEST ORIENTED CHANNELS HAVE SHOWN
INCREASING EASTERLY FLOW.

 MODELS ARE IN GENERAL AGREEMENT WITH THE STRONG HIGH PRESSURE
OVER THE YUKON SLOWLY WEAKENS AND CONTINUES TO EXPAND INTO
BRITISH COLUMBIA THROUGH TONIGHT. REFRESHED THE INHERITED
FORECAST PACKAGE WITH THE NAM FOR TODAY AND TONIGHT. A BIT WARMER
TEMPERATURES EARLY THIS MORNING WILL COOL A LITTLE THROUGH THE
DAY...AND CONTINUE TO DROP INTO TONIGHT AS THE COLD AIR POCKET
STILL SLOWLY DRIFTS WEST ACROSS THE AREA.

 &&

.LONG TERM...VERY GRADUAL WARM UP EXPECTED DURING MEDIUM RANGE.
COLD FLOW ALOFT OUT OF NORTH BECOMES MORE WESTERLY OVER WEEKEND
AND THE STORM TRACK THAT IS NOW CLOBBERING PAC NW SLOWLY LIFTS
NORTHWARD OVER TIME. CHANCE OF PRECIPITATION OVER PANHANDLE
INCREASES FROM SOUTH TO NORTH STARTING FRI. SOUTHERN ZONES WILL
START WITH SNOW BUT CHANGE TO RAIN AND SNOW MIXED SAT THROUGH SUN.
PRECIP IN FORM OF SNOW FORECAST TO REACH JUNEAU TO GUSTAVUS TO
YAKUTAT ABOUT SUN OR MON. LAST NIGHTS MODEL RUNS SHOWED CHANGES IN
THE STRENGTH AND TRACK OF LOW PRESSURE SYSTEMS APPROACHING
STARTING FRI. GFS WAS STORMY AND HIGHER CHANCES OF PRECIP SOONER
THAN OTHER MODELS. SLIGHT ADJUSTMENTS TO THE FORECASTS WERE MADE
BASED ON THE DRIER NAM AND EUROPEAN MODEL AT THE START OF THE
WEEKND. FORECASTER CONFIDENCE DECREASES AFTER SAT.

AS THE STORM TRACK LIFTS NORTH INDIVIDUAL SYSTEMS GET ENERGIZED
AND MAY PRODUCE VERY HIGH SE WINDS AS THEY APPROACH THE OUTER
COAST. FRI LOOKS PARTICULARLY WINDY FOR THE SOUTHERN OUTER COAST.
GIVEN THE HIGHER WINDS I INCREASED SEA STATE BY SEVERAL FEET FRI
AND THROUGH THE WEEKEND FOR THE COASTAL ZONES..MAINLY S OF CROSS
SOUND. CONDITIONS MAY BE SETTING UP FOR A SEPARATE WIND EVENT...
A JUNEAU TAKU WIND... THUR NIGHT AND FRI MORNING. THE DEPTH OF THE
COLD AIR...CURRENTLY ON THE ORDER OF 6000 FT DEEP...MAY BE TOO
THICK FOR THE TAKU WIND TO PENETRATE TO THE SURFACE BUT IT BEARS
WATCHING. WIND SPEEDS ON THE ORDER OF 60 MPH ARE POSSIBLE BOTH ALONG
THE COAST AND NEAR JUNEAU ON FRI.

A GOOD SNOWFALL FREQUENTLY OCCURS WHEN COLD SPELLS IN SE AK
FINALLY BREAK. THE CURRENT TIMING FOR THAT TO OCCUR IS EARLY
WEEKEND IN THE SOUTH AND LATE WEEKEND FARTHER NORTH. HOWEVER
FORECAST MODELS ARE SOMETIMES TOO FAST BRINGING THIS TRANSITION
ABOUT AND THEY ARE ALREADY SHOWING VARIABILITY IN THEIR SOLUTIONS.
EASTERLY WIND DIRECTIONS AT RIDGETOP ELEVATIONS OFTEN KEEP THE
LOWER ATMOSPHERE DRY UNTIL A MORE SOUTHERLY WIND KICKS IN. HENCE,
FORECASTER CONFIDENCE IN WINDY WEATHER IS A LITTLE HIGHER THAN THE
TIMING OF ANY PRECIPITATION.

 &&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND CHILL ADVISORY UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011>013-031-053.
         GALE WARNING FOR PKZ011>013-031-051.
         SMALL CRAFT ADVISORY FOR PKZ021-022-032-034>036-041-043.

&&

AHN/TA

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JUNEAU AK
358 PM AKST WED JAN 18 2012

AKZ017>029-191300-
CAPE FAIRWEATHER TO CAPE SUCKLING COASTAL AREA-
TAIYA INLET AND KLONDIKE HIGHWAY-HAINES BOROUGH AND LYNN CANAL-
GLACIER BAY-EASTERN CHICHAGOF ISLAND-
SALISBURY SOUND TO CAPE FAIRWEATHER COASTAL AREA-
CAPE DECISION TO SALISBURY SOUND COASTAL AREA-
EASTERN BARANOF ISLAND AND SOUTHERN ADMIRALTY ISLAND-
JUNEAU BOROUGH AND NORTHERN ADMIRALTY ISLAND-
INNER CHANNELS FROM KUPREANOF ISLAND TO ETOLIN ISLAND-
DIXON ENTRANCE TO CAPE DECISION COASTAL AREA-
SOUTHERN INNER CHANNELS-MISTY FJORDS-
INCLUDING THE CITIES OF...YAKUTAT...SKAGWAY...HAINES...GUSTAVUS...
HOONAH...ELFIN COVE...PELICAN...SITKA...PORT ALEXANDER...ANGOON...
JUNEAU...PETERSBURG...WRANGELL...KAKE...CRAIG...KLAWOCK...
KETCHIKAN...METLAKATLA...HYDER
358 PM AKST WED JAN 18 2012

...A SERIES OF WINTER STORMS TO AFFECT SOUTHEAST ALASKA FRIDAY
THROUGH MONDAY...

A SERIES OF STRONG LOW PRESSURE SYSTEMS LIFTING OUT OF THE CENTRAL
PACIFIC IS FORECAST TO BATTLE A DEEP AND VERY COLD AIR MASS ACROSS
THE PANHANDLE STARTING FRIDAY AND CONTINUING INTO EARLY NEXT WEEK.
TEMPERATURES ARE EXPECTED TO SLOWLY RISE THROUGH THIS TIME PERIOD.

THE FIRST LOW IS FORECAST TO MOVE INTO THE SOUTHEAST GULF FRIDAY
AND WILL BRING SNOW TO THE SOUTHERN PANHANDLE AND STRONG
WINDS...LOW WIND CHILLS...AND HEAVY FREEZING SPRAY TO THE NORTHERN
PANHANDLE.

A SECOND STRONG LOW IS FORECAST TO MOVE INTO THE SOUTHEAST GULF
LATE SATURDAY AND INTO THE NORTH CENTRAL GULF SUNDAY. THIS WILL
BRING MORE SNOW TO THE SOUTHERN PANHANDLE THAT WILL LIKELY MIX
WITH RAIN. SNOW WILL ALSO SPREAD ACROSS THE CENTRAL PANHANDLE
SATURDAY NIGHT. STRONG NORTH WINDS AND LOW WIND CHILLS WILL
CONTINUE FOR NORTHERN SOUTHEAST ALASKA.

A THIRD SYSTEM WILL MOVE THROUGH SOUTHEAST ALASKA WITH SNOW FOR THE
NORTHERN HALF AND A MIX OF RAIN AND SNOW FOR THE SOUTHERN HALF.

PERSONS ACROSS SOUTHEAST ALASKA...ESPECIALLY THOSE WITH OUTDOOR
ACTIVITIES...SHOULD BE PREPARED FOR HARSH WINTER CONDITIONS
INCLUDING STRONG WINDS...LOW WIND CHILLS...FREEZING SPRAY...AND
HEAVY SNOW. KEEP UPDATED ON THIS DEVELOPING WINTER WEATHER EVENT
WITH THE LATEST NATIONAL WEATHER SERVICE WARNINGS AND FORECASTS
AVAILABLE FROM NOAA WEATHER RADIO OR ON THE WORLD WIDE WEB.

MM