Gale Warning 3, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
512 PM AKST SUN JAN 4 2015

.SHORT TERM...PRIMARY CONCERN IS WHEN LOCALLY STRONG WINDS WILL DIE
DOWN IN JUNEAU AND DOUGLAS. OVER THE LAST 1-2 HOURS THE GENERAL
TREND IS DOWNWARD WITH PEAK GUSTS AND SUSTAINED WINDS AT ALL OF
THE AVAILABLE OBS SITES. THIS IS IN LINE WITH THE 18Z NAM WHICH ON
BUFKIT SHOWS A DISAPPEARING CRITICAL LEVEL AT ABOUT 700 MB THIS
AFTERNOON, THOUGH CROSS-BARRIER FLOW MAINTAINS 40+ KT THROUGH
ABOUT 03-04Z. THIS ALSO AGREES WITH THE 18Z NAM MTNWV SIMULATION
TRENDS. CURRENT THINKING IS THAT WE WILL LET THE HIGH WIND WARNING
EXPIRE AT 300 AKST AND THEN GO WITH STRONG WINDS IN THE HEADLINES
FOR THE FORECAST ISSUANCE. OUTSIDE OF LYNN CANAL THE TREND HAS
ALSO BEEN DOWNWARD SOMEWHAT ON WINDS. THIS IS IN LINE WITH THE CURRENT
GRIDDED FORECAST. WE HAVE N LYNN CONTINUING TONIGHT WITH STORM-
FORCE WINDS. CURRENTLY GUSTS 65-75 KT CONTINUE AT ELDRED ROCK.
GALES IN SOUTHERN LYNN, STEPHENS AND FREDERICK (DUE TO PASS WINDS
IN THE LATTER) CONTINUE THROUGH 06Z WITH OF COURSE GALE FOR
TOMORROW IN NORTHERN LYNN. WINDS AT LINCOLN ROCK AND AT FIVE
FINGERS HAVE BEEN MUCH WEAKER THAN FORECAST BUT THE THINKING IS
THAT OUTFLOW WINDS IN SIDE CHANNELS DO WARRANT THE HEADLINES SO
DID NOT CHANGE THEM. INHERITED AREAS OF FREEZING SPRAY HAZARD
(INCLUDING HEAVY IN LYNN) LOOK OK CURRENTLY PER THE FREEZING SPRAY
NOMOGRAM AND THESE CONTINUE INTO TOMORROW IN STEPHENS, GLACIER BAY
AND INTO FREDERICK. ON TO OTHER ISSUES...THE LIGHT PRECIP OVER THE
SOUTHERN REACHES HAS BEEN MOSTLY LIGHT SNOW WITH SOME HANGING ON
CURRENTLY AT KETCHIKAN, CRAIG AND HYDER...THIS SHOULD END SHORTLY AS
THE WEAK LOW PRESSURE CONTINUES MOVING EASTWARD. UPPER CLOUD ONLY
REACHED ABOUT THE SOUTHERN HALF OF THE PANHANDLE TODAY. ON THE
MODELS...LATE TOMORROW THE NEW LOW PRESSURE SLOWLY APPROACHES FROM
THE SOUTH AND A CHANCE OF RAIN AND SNOW AGAIN DEVELOPS FOR THE
SOUTHERN FRINGE WITH THE ONSET OF A WARMING TREND FOR THOSE AREAS.
REGARDING TEMPERATURES...THIS IS A TOUGH ONE AS MORE AREAS WILL
DECOUPLE THIS EVENING (EG YAKUTAT)...THUS COOLING RAPIDLY. KNOCKED A FEW
DEGREES OFF GUIDANCE FOR THOSE AREAS WE FELT THIS WOULD OCCUR. DRY
AIR SHOULD PREVENT FOG FORMATION FOR EVEN THESE AREAS EXCEPT
PERHAPS THE KETCHIKAN VICINITY AND THIS WOULD REQUIRE RAPID
CLEARING.

INHERITED PACKAGED LOOKED MOSTLY GOOD THROUGH ABOUT 09Z ON
PRESSURE/WIND GRIDS BUT THEN HAD TO MODIFY THE OFFSHORE FIELDS FOR
THE NEW LOW OVER THE SOUTHERN GULF WHICH TIGHTENS UP THE GULF GRADIENT
A BIT FASTER THAN PREVIOUSLY THOUGHT. WENT WITH AN ENSEMBLE
APPROACH FOR THE NEW PRESSURE USING NAM/EC/GEM/GFS FOR PRESSURE
ON OUTSIDE WATERS. UPPED THE WINDS OUTSIDE WHERE THE GRADIENT
INCREASED (SOUTHERN AND SOUTHEASTERN AREAS MOSTLY). TWEAKED SOME WIND
FIELDS OVER CROSS SOUND AND IN STEPHENS...OTHERWISE INHERITED.

.PREVIOUS LONG TERM...COMPLICATED FORECAST FOR MIDWEEK DUE TO HIGH
UNCERTAINTY IN PRECIPITATION TYPE. IN THE MEANTIME...HIGH PRESSURE
PERSISTS OVER NWRN CANADA...WHILE LOW PRESSURE EVOLVES SSE OF THE
ALEUTIANS MON AND TUE. THIS WILL SUPPORT A CONTINUATION OF STRONG
OUTFLOW WINDS...WITH GALES WIDESPREAD OVER THE INSIDE WATERS.
THESE WINDS WILL PERSIST THROUGH MIDWEEK...AND THEN WEAKEN AS
PRESSURE GRADIENT SLACKENS FRI AND SAT. COLD SURFACE TEMPERATURES
AND STRONG WINDS WILL FAVOR FREEZING SPRAY FOR THE NRN INSIDE
CHANNELS. IN ADDITION TO THE STRONG MARINE WINDS...GUSTS WILL
POTENTIALLY BE SIGNIFICANT /40-50 MPH/ FOR LOCATIONS SUCH AS
SKAGWAY...HAINES...AND JUNEAU.

FRONTAL BOUNDARY IS FORECAST TO ADVANCE NWD INTO FAR SRN PORTIONS
OF THE PANHANDLE ON TUE...AND THEN APPROACH THE CNTRL CWA BY THU.
SNOW MAY INITIALLY OCCUR FOR SRN AREAS AS THE FRONT ENTERS THE
AREA...BUT WILL TRANSITION TO MAINLY RAIN AS WARM AIR SPREADS NWD
BEHIND THE BOUNDARY. ONE EXCEPTION WILL BE HYDER...WHERE COLDER
CONTINENTAL AIR WILL SUPPORT ACCUMULATING SNOWFALL MON NIGHT
THROUGH THU. OUTFLOW WINDS OVER THE NRN HALF OF SERN AK WILL AID
IN LOCKING IN SURFACE TEMPERATURES AOB FREEZING THROUGH THU NIGHT.
HOWEVER...TEMPERATURES AT OR SLIGHTLY ABOVE FREEZING WILL SPREAD
ABOVE THE COLDER SURFACE AIRMASS. THE DEPTH OF THE FREEZING
AIRMASS NEAR THE SURFACE WILL BE SHALLOW...WHICH COMPLICATES THE
PRECIPITATION TYPE FORECAST. PERIODS OF LIGHT FREEZING
RAIN/DRIZZLE AND SNOW WILL ALL BE POSSIBLE. THE ONE CAVEAT WILL BE
DRY AIR EMANATING FROM THE COAST RANGE...WHICH WILL LIMIT COLUMN
SATURATION. IN ADDITION...ASCENT IS CURRENTLY FORECAST TO BE
MODEST. THESE FACTORS SUPPORT A FREEZING DRIZZLE SCENARIO MORE
THAN SNOW.

UPDATED PRESSURE GRIDS WITH AN ECMWF/GEM/OFFICIAL BLEND FROM 12Z
TUE THROUGH 00Z THU...THEN TRANSITIONED TO 12Z WPC. USED A
GFS/ECMWF BLEND WERE NECESSARY FOR UPDATES TO POP/QPF GRIDS. FEW
CHANGES WERE MADE TO TEMPERATURES. FORECAST CONFIDENCE IS
GENERALLY LOW DUE TO UNCERTAINTY IN PRECIPITATION TYPE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH LATE TONIGHT FOR AKZ025.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ019.
         STRONG WIND THROUGH MONDAY AFTERNOON FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ013-022-031-035.
         SMALL CRAFT ADVISORY FOR PKZ011-021-032>034-036-041>043.

&&

WESLEY/GARNER

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