High Wind in Alaska, January 2 to 4, 2015

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
429 PM AKST FRI JAN 2 2015

.SHORT TERM...MANY FORECAST CHALLENGES LIE AHEAD IN THE NEXT 24-48
HOURS AS ARCTIC AIR MASS ENTRENCHES ITSELF THROUGH THE PANHANDLE.
FIRST, HAVE UPGRADED CROSS SOUND TO A GALE AS IT WAS REACHED ABOUT
16Z TODAY. SKIES HAVE RAPIDLY CLEARED TODAY NORTH- TO- SOUTH OVER
PANHANDLE EVEN A BIT EARLIER THAN MODEL FORECASTS. WINDS ARE
ALREADY SCREAMING OVER NORTHERN CHANNELS AND GUSTING TO 50 NEAR
JUNEAU...HIGH WINDS FOR JUNEAU/DOUGLAS WILL INCREASE TONIGHT
THROUGH TOMORROW NIGHT AS CONDITIONS LOOK GOOD FOR A MODERATE
TAKU DOWNSLOPE EVENT WITH THE INCOMING ARCTIC SURGE PROVIDING THE
BACKGROUND. MTNWV MODEL PREDICTS VERY FAVORABLE CONDITIONS
BEGINNING 06Z TONIGHT THROUGH ABOUT 06Z SUNDAY. 50KT+ CROSS-
BARRIER FLOW IS PREDICTED BY THE HIGH-RES MODELS WITH WHAT APPEARS
TO BE AN AREA OF SHEAR AND WEAK FLOW UP IN THE LEVELS ABOVE THE
CRESTS. THIS COULD ENHANCE THE WAVE. ARW MODEL PREDICTS 45KTS AT
THE SURFACE THROUGH 06Z SUNDAY. WINDS AT SOUTH DOUGLAS ISLAND HAVE
ALREADY REACHED A PEAK 50KTS. WINDS HAVE A HEAD START TODAY AS
THESE EVENTS GO...WE'LL SEE.

HAVE VARIOUS WINDS INCLUDING STORM-FORCE IN NORTHERN LYNN THROUGH
SUNDAY AND SEVERAL OTHER CHANNELS GET INTO GALE WINDS OVER THE
NEXT 30 OR SO HOURS AS GRADIENTS BECOME SIGNIFICANTLY STRONGER
THAN THOSE ANALYZED NOW. LONG-LIVED WIND EVENT BY OUR STANDARDS.
HIGH WIND WATCH POSTED FOR THE SKAGWAY ZONE FOR 03Z SUN THROUGH
03Z MON. MEANWHILE THE INCOMING ARCTIC AIR IS POISED TO CREATE
FREEZING SPRAY HAZARD ALONG WITH DANGEROUS WIND CHILLS. THE LATTER
SHOULD NOT GENERALLY GO BELOW ABOUT -20F WITH -10 TO -15F A
GENERAL MINIMUM IN MOST AREAS...SKAGWAY AREA WILL HAVE THE COLDEST
WIND CHILLS BUT WORDING WILL BE INCORPORATED IN THE HIGH WIND
WATCH. FREEZING SPRAY NOMOGRAM PUMPED OUT HEAVY CATEGORY FOR LYNN
CANAL, STEPHENS PASSAGE AND GLACIER BY AT VARIOUS TIMES DURING THE
PERIOD. MODERATE FREEZING SPRAY IS PREDICTED OVER NORTHERN
CHATHAM, FREDERICK AND SUMNER FOR SHORTER TIME PERIODS GIVEN OUR
GRIDDED WINDS AND TEMPERATURES.

FOR THE GRIDS TWEAKED SOME OF THE INNER CHANNELS FOR TONIGHT AND
TOMORROW...EG WENT WITH NORTHWESTERLY FLOW IN MUCH OF CLARENCE.
KNOCKED A FEW DEGREES OFF TEMPERATURES FOR WIND-SHELTERED
LOCATIONS AND GIVEN CLEAR SKIES THESE COULD EVEN DROP A FEW
DEGREES MORE TONIGHT. DRY CONDITIONS WILL PERSIST FOR ALL BUT THE
SOUTHERNMOST PANHANDLE THROUGH TOMORROW...SOME MODEL SCATTER ON
THAT ISSUE WITH THE EC/GFS MOVING PRECIP IN A BIT NORTH OF THE NAM
POSITION. IF IT DOES MOVE IN LATE SATURDAY ON THE SOUTHERN FRINGE
THEN SOME LIGHT SNOW IS POSSIBLE THERE AT LEAST INITIALLY.

.LONG TERM...HIGH PRESSURE OVER BRITISH COLUMBIA ON SUNDAY WILL
SLOWLY BEGIN TO WEAKEN THROUGH MONDAY AS A SURFACE LOW CUTS SOUTH
OF THE PANHANDLE MOVING ACROSS DIXON ENTRANCE. MODELS STILL SHOWING
A LARGE SPREAD WITH THE STRENGTH AND EXACT POSITION OF THE LOW.
THE STRONG COLD NORTHERLY OUTFLOW WINDS WILL BEGIN TO DIMINISH
SUNDAY INTO MONDAY AS THE PRESSURE GRADIENT BETWEEN THE WESTERN
CANADIAN HIGH AND SOUTHERN PANHANDLE LOW WEAKENS AND WEAK HIGH
PRESSURE BUILDS OVER THE AK GULF. ANY POTENTIAL FOR PRECIP FROM THE
WEEKEND SYSTEM WILL BE OVER THE FAR SOUTHERN PANHANDLE, BUT
HIGHER UNCERTAINTY WITH THIS DUE TO THE MODEL SPREAD. THE REST OF
THE REGION WILL REMAIN DRY WITH CLEAR SKIES AND COLD TEMPERATURES.
THE NEXT SURFACE LOW WILL MOVE INTO THE AK GULF LATE WEDNESDAY
INTO THURSDAY TRACKING UP FROM THE N PACIFIC. MEANWHILE HIGH
PRESSURE FROM THE AK INTERIOR WILL DROP INTO THE YUKON THEN DOWN
INTO BRITISH COLUMBIA. WARM MOIST AIR WILL MOVE UP ALONG FRONTAL
BOUNDARY AROUND THIS NEXT GULF LOW SPREADING PRECIP FROM SOUTH TO
NORTH WITH MOSTLY RAIN FOR THE SOUTHERN THIRD OF THE PANHANDLE.
THIS IS SETTING UP THE POTENTIAL FOR AN OVER RUNNING SNOW EVENT
FOR THE REST OF THE PANHANDLE WITH COLD AIR CURRENTLY IN PLACE
ALONG WITH MORE COLD AIR WITH THE NEXT OUTFLOW WINDS. BIGGEST
QUESTION FOR SNOW AMOUNTS WILL BE HOW MOIST THE INCOMING AIR MASS
IS AND QPF TOTALS.

COASTAL WATER WINDS WILL DROP OFF SUNDAY AS THE FIRST LOW MOVES
EAST AND THE GULF HIGH BUILDS. INNER CHANNELS WILL DIMINISH MORE
SLOWLY SINCE PRESSURE GRADIENT LAST A BIT LONGER. THIS BREAK IN
HIGHER WINDS WILL BE SHORT LIVES AS THE NEXT GULF LOW AND CANADIAN
HIGH MOVE IN. GALES WILL DEVELOP OVER THE OFFSHORE AND COASTAL
WATERS WITH OUTFLOW GUSTS OVER THE INNER CHANNELS PICKING UP TO
THE 50 TO 60 KT RANGE AT LEAST. FREEZING SPRAY AND HEAVY FREEZING
SPRAY WILL REMAIN AN ISSUE DUE TO THE ARCTIC AIR IN PLACE AND
OUTFLOW WINDS. WILL SEE A DROP OFF MONDAY TO JUST THE NORTHERN
INNER CHANNELS, BUT EXPECT MORE FREEZING SPRAY ISSUES TOWARD THE
END OF THE WEEK. THE TAKU WIND EVENT FOR JUNEAU WILL LAST INTO
EARLY SUNDAY MORNING AT LEAST. CROSS BARRIER FLOW WILL CONTINUE
AND MAY EVEN PICK UP LATE SATURDAY BUT THE CRITICAL LEVEL BREAKS
DOWN AS WIND FLOW FOR THE ENTIRE COLUMN SHIFTS MORE EASTERLY.
PRESSURE GRADIENT FOR THE FAR NORTHERN PANHANDLE LOOKS TO PEAK
SATURDAY EVENING INTO SUNDAY AFTERNOON WITH GREATEST POTENTIAL FOR
WARNING LEVEL WINDS. DECIDED TO ISSUES A HIGH WIND WATCH FOR ZONE 18 AS
WINDS WILL BE STRONGEST NEAR SKAGWAY WHILE COLDEST TEMPS WILL BE
NEAR WHITE PASS AND BLOWING SNOW POTENTIAL SHOULD BE LIMITED AS
NOT EXPECTING ANY NEW SNOW.

MODEL SPREAD WAS STILL FAIRLY HIGH FOR THE LOW OVER THE SOUTHERN
PANHANDLE. DECIDED TO LEAVE THE INHERITED GRIDS AS IS FOR THIS
SYSTEM SINCE THEY STILL DEPICTED A DECENT BLEND. AS TYPICAL
MODELS IN POOR AGREEMENT IN BETWEEN SYSTEMS, BUT THEN FALL MORE IN
LINE AS THE NEXT LOW MOVES IN LATER IN THE WEEK. WENT WITH SOME
12Z ECMWF WITH INHERITED GRIDS TO DAY 4 THEN UTILIZED NEW WPC.
MAIN CHANGE WAS NEW MODELS KEPT THE PANHANDLE ON DRY DRY SIDE
UNTIL LATE IN THE WEEK. FORECAST CONFIDENCE IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 9 PM THIS EVENING TO 5 AM AKST SUNDAY FOR
     AKZ025.
         STRONG WIND THROUGH SATURDAY EVENING FOR AKZ019.
         HIGH WIND WATCH FROM SATURDAY EVENING THROUGH SUNDAY AFTERNOON
     FOR AKZ018.
         STRONG WIND FROM 3 AM AKST SATURDAY THROUGH SATURDAY EVENING FOR
     AKZ029.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ011.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         HEAVY FREEZING SPRAY WARNING FOR PKZ013.
         STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-034-035-043.
         SMALL CRAFT ADVISORY FOR PKZ032-033-036-041-042-051>053.

&&

WESLEY/PRB

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