Gale Warning 130, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
339 PM AKDT SUN MAR 23 2014

.SHORT TERM...STRONG HIGH PRESSURE IN THE YUKON CONTINUES TO
DOMINATE THE WEATHER OVER SOUTHEAST ALASKA FOR THE NEXT 24 HOURS.
THE ONE DIFFERENCE IN THE WEATHER WILL BE A FRONT APPROACHING THE
SOUTHERN PANHANDLE THIS EVENING AND INTO MONDAY. THIS FRONT
COMBINED WITH THE HIGH TO THE NORTH WILL RESULT IN A TIGHTENING
NORTHERLY PRESSURE GRADIENT OVER THE AREA TONIGHT AND MONDAY.

 WITH THE SYNOPTIC PATTERN IN PLACE, EXPECT THE USUAL OUTFLOW
AREAS TO CONTINUE TO BE GUSTY. AS THE PRESSURE GRADIENT TIGHTENS
OVERNIGHT AND MONDAY WINDS WILL GRADUALLY STRENGTHEN. HAVE KEPT
STRONG WIND HEADLINES IN THE SKAGWAY AND HAINES AREAS BEGINNING
LATE TONIGHT AND PERSISTING THROUGH THE REMAINDER OF THE SHORT
TERM PERIOD. GUSTY WINDS WILL ALSO REDEVELOP IN THE DOWNTOWN
JUNEAU AND DOUGLAS AREA LATE TONIGHT AND GRADUALLY STRENGTHEN
THROUGH THE DAY ON MONDAY. CROSS BARRIER FLOW WILL BE IN THE
30 TO 40 KT RANGE WITH THE CRITICAL LEVEL HANGING AROUND 600 MB.
WINDS SHOULD REDEVELOP AS THE INVERSION SETS UP AGAIN LATER THIS
EVENING. CROSS BARRIER FLOW BEGINS TO STRENGTHEN LATE MONDAY
AFTERNOON REACHING 50 TO 55 KTS. THE CRITICAL LEVEL ALSO RISES
SLIGHTLY TO AROUND 500 MB WHICH IS THE IDEAL LEVEL FOR THE TAKU
WINDS. THEREFORE HAVE UPGRADED THE HIGH WIND WATCH TO A HIGH WIND
WARNING BEGINNING AT 4 PM MONDAY AFTERNOON AND CONTINUING THROUGH
TUESDAY AFTERNOON. AS FAR AS THE MARINE WINDS, EXPECT SMALL CRAFT
TO GALE WINDS IN THE INNER CHANNELS. HAVE INCLUDED SOME LIGHT
FREEZING SPRAY IN LYNN CANAL AND NEAR TAKU INLET FOR TONIGHT AND
MONDAY MORNING.

 THE APPROACHING FRONT WILL BRING INCREASING CLOUDS TO THE
SOUTHERN HALF OF THE PANHANDLE. THESE CLOUDS ARE CURRENTLY
SPREADING INTO THE FAR SOUTHERN AREAS ON VISIBLE SATELLITE
IMAGERY THIS AFTERNOON. STRONG OFFSHORE FLOW WILL PREVENT MUCH OF
THE PRECIPITATION FROM ADVANCING NORTH INTO SOUTHEAST ALASKA BUT
DO HAVE CHANCE TO LIKELY POPS BEGINNING LATE TONIGHT AND INTO
MONDAY FOR THE SOUTHERNMOST ZONES. SOME SNOW MAY MIX AT TIMES
LATE TONIGHT AND MONDAY MORNING BUT LITTLE IF ANY ACCUMULATION IS
EXPECTED AS TEMPERATURES WARM INTO THE 40S MONDAY AFTERNOON. THE
NORTHERN HALF OF THE PANHANDLE COULD SEE SOME HIGH THIN CIRRUS
FROM THE FRONT BUT EXPECT ANOTHER NICE SUNNY DAY ON MONDAY.

 USED THE ECMWF FOR UPDATES TO THE PREVIOUS FORECAST AS IT BEST
INITIALIZED THE PRESSURE PATTERN OVER THE PANHANDLE. CHANGES WERE
SMALL AND MAINLY LIMITED TO LOCAL EFFECTS. FORECASTER CONFIDENCE
IS ABOVE AVERAGE THROUGH THE NEXT 24 HOURS.

.LONG TERM...COOL, DRY, WINDS FOR THE NORTHERN AND CENTRAL
PANHANDLE. CLOUDS AND PRECIPITATION POTENTIAL FOR SOUTHERN
PANHANDLE. BLOCKY PATTERN MEANS THAT LITTLE OR NO CHANGE TO THE
WEATHER PATTERN THROUGH THE END OF THE LONG TERM FORECAST PERIOD
NEXT WEEKEND.

 THE START OF THE LONG TERM FORECAST PERIOD WILL FEATURE A 1040 MB
HIGH PRESSURE OVER THE MACKENZIE MOUNTAINS INTO THE NORTHERN
ROCKIES. MEANWHILE, A BROAD AREA OF SUB-1000 MB LOW PRESSURE IS
SITUATED OVER NORTH CENTRAL PACIFIC OCEAN. THE LOW CENTER IS
CURRENTLY TRAVELING SOUTHEAST, BUT SHOULD START HEADING NORTHEAST
AND HAVE A REDEVELOPED CENTER JUST OFF THE COAST FROM HAIDA GWAII
ISLAND BY MONDAY AFTERNOON. NUMERICAL MODELS ARE PROJECTING THE
CENTRAL PRESSURE OF THIS LOW TO DROP TO THE MID-980S MB. COMBINED
WITH THE 1040 MB HIGH OVER YUKON, THIS IS GOING TO CREATE VERY
STRONG PRESSURE GRADIENT ACROSS THE PANHANDLE. THIS WILL CREATE
VERY STRONG OUTFLOW WIND ACROSS THE NORTHERN AND CENTRAL PANHANDLE
FROM LATE MONDAY AFTERNOON INTO TUESDAY AFTERNOON.

 THERE ARE THREE MAIN INGREDIENTS FOR TAKU WIND EVENT TO HAPPEN IN
DOWNTOWN JUNEAU AND DOUGLAS. FIRST IS CROSS BARRIER FLOW, OR WIND
FLOWING PERPENDICULAR TO THE MOUNTAINS, DOWN THE TAKU INLET AND UP
AGAINST SALISBURY RIDGE. SECOND, INVERSION, OR A STABLE LAYER OF
AIR A LITTLE HIGHER THAN THE MOUNTAINS SUCH THAT THE COLD AIR WILL
RISE NO HIGHER. THIRD, THERE NEEDS TO BE A CRITICAL LEVEL, A
LEVEL AT WHICH THE WIND WILL REVERSE DIRECTION.

 ALL THREE FACTORS WILL BE PRESENT. THERE WILL BE CROSS BARRIER
FLOW OF AROUND 70 TO 80 MPH FROM LATE MONDAY AFTERNOON INTO
TUESDAY AFTERNOON. THE INVERSION WILL STRENGTHEN AFTER SUNSET ON
MONDAY. THE INVERSION WILL REMAIN IN PLACE DURING THE DAY ON
TUESDAY AS WARMER AIR ALOFT MOVES INTO THE AREA AND MAINTAIN THE
INVERSION. THE CRITICAL LEVEL WILL REMAIN AT 500 MB FOR THE EVENT.
USING HIGHER RESOLUTION MOUNTAIN WAVE MODEL, DECIDED TO GO WITH
WIND GUSTS OF 60 TO 70 MPH WITH PEAK WINDS UP TO 80 MPH FOR THE
EVENT. STRONGEST WINDS WILL BE NEAR DOWNTOWN JUNEAU AND DOUGLAS
AND ALSO OUT OF INTERIOR PASSES. THE HIGH WIND WATCH IS REPLACED
BY THE HIGH WIND WARNING. THE HIGH WIND WARNING WILL BE VALID FROM
4 PM MONDAY UNTIL 4 PM TUESDAY. HOWEVER, THERE ARE SOME
UNCERTAINTIES ON THE END TIME OF THE WARNING. THE TAKU WIND
INGREDIENTS MAY REMAIN FAVORABLE FOR THE TAKU WIND EVENT TO LAST
LONGER THAN THE CURRENT WARNING.

 AS STRONG OUTFLOW TRANSPORTS COLDER AIR OUT OF THE INTERIOR, THERE
WILL BE LIGHT TO MODERATE FREEZING SPRAY MONDAY NIGHT AND TUESDAY
NIGHT FOR GLACIER BAY, LYNN CANAL, AND NEAR TAKU INLET.

 DUE TO STRONG OUTFLOW WIND BRINGING IN COOL AND DRY CONTINENTAL
AIR INTO THE AREA, THE NORTHERN HALF OF THE PANHANDLE SHOULD SEE
LITTLE CLOUD COVER. DIURNAL TEMPERATURE RANGE REMAIN LARGE FOR THE CENTRAL TO
NORTHERN PANHANDLE DUE TO LITTLE SKY COVER. ON THE OTHER HAND, AS
THE LOW APPROACHES THE SOUTHERN PANHANDLE, THERE WILL BE CLOUDS
AND HIGHER PRECIPITATION POTENTIAL. HOWEVER, PRECIPITATION SHOULD
REMAIN ON THE LIGHT SIDE, AS THE CONTINENTAL AIRMASS IS WINNING
OUT THE BATTLE.

 MODEL OF CHOICE REMAINS AS ECMWF, AS THEY TEND TO BE THE FORECAST
CONFIDENCE REMAINS ABOVE AVERAGE INTO TUESDAY AFTERNOON. HIGH
CONFIDENCE ON THE GENERAL SYNOPTIC PATTERN OF OUTFLOW WINDS. THERE
ARE UNCERTAINTIES WITH THE MAGNITUDE OF LOCAL WIND EVENTS.
CONFIDENCE DROP TO BELOW AVERAGE AS MODELS DIVERGE IN OPINION ON
THE POSITION AND MAGNITUDE OF INCOMING LOW PRESSURE SYSTEMS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 4 PM MONDAY TO 4 PM AKDT TUESDAY FOR
     AKZ025.
         STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH MONDAY
     AFTERNOON FOR AKZ025.
         STRONG WIND FROM LATE TONIGHT THROUGH TUESDAY EVENING FOR AKZ018-
     019.
MARINE...GALE WARNING FOR PKZ012-013-022-031-035-041-043.
         SMALL CRAFT ADVISORY FOR PKZ011-021-032>034-036-042-051-053.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

TPS/RCL